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BRITISH CONCHOLOGY,

OR AN" ACCOUIfT OF

THE MOLLUSCA

WHICH NOW INHABIT THE BEITISH ISLES AND THE

SUREOUNDINO SEAS.

VOLUME L

LAND AND PEESHWATER SHELLS.

By JOHN GWYN JEFFREYS, F.R.S., F.G.S., &c.

■ O come hither, and behold the works of the Lord ! " — PsAL^i xIti. 8.

LONDON:
JOHN VA.^ VOORST, PATERNOSTER ROW.

MDCCCLXH.
[The right of Translation is reserved.]

PRINTED BY TAYLOR AND T R A N 1 1 S,
KED LION COURT, FLEET STREET.

TO THE MEMOEY

OF

MANY DISTINGUISHED NATURALISTS
AND VALUED FRIENDS,

WHO ARE NOW NO MORE,

AND IN GRATEFUL ACKNOWLEDGMENT OF THE
KIND SYMPATHY OF

THOSE WHO STILL HAPPILY SURVIVE,

FROM ALL OF WHOM I HAVE RECEIVED

MUCH ASSISTANCE

IN THESE CONCHOLOGICAL STUDIES,

I DEDICATE

THE PRESENT WORK.

PREFACE.

The question whether another book on the British
Mollusca is wanted by the scientific world, when there is
at present a complete history of the subject by the late
Professor Edward Forbes and Mr. Hanley, is answered by
the notoriety of the fact that the price of that admirable
work puts it beyond the reach of most naturalists ; and
the enterprising publisher of those, as well as the present,
volumes was so fully impressed with the necessity of
another work at a more moderate price, that he in\dted
me to undertake the task, which I fear I have inefficiently
performed. In doing this, however, I have endeavoured
to make the present work quite distinct from its
predecessor, as may be seen by comparing the two;
and those who are not fortunate enough to possess a
copy of *^A History of British Mollusca and their
Shells,^'' and who can afibrd the money for its purchase,
will not regret the expenditure.

With regard to the animals or soft parts of the
Mollusca described in this volume, I have been greatly

VI PREFACE.

indebted to the invaluable work of Moquin-Tandon,
entitled " Histoire naturelle des Mollusques terrestres
et fluviatiles de France/^ in which the physiology and
anatomy of the land and freshwater Mollusca have been
treated in a far more able and exhaustive manner than
had been previously done by any author.

My old and esteemed friend, Mr. Alder, has most
kindly promised to assist me with a notice of the Nudi-
branchsj so as to make that part of the subject as com-
plete as possible ; and the value of such cooperation will
be fully appreciated by all naturalists.

A volume of supplementary plates will probably be
published, to contain figures of every species and well-
marked variety. The figures now given illustrate the
genera ; but the cost and price of the work would have
been greatly increased by the other mode of illustration,
except by resorting to the inartistic and unsatisfactory
substitute of woodcuts.

In the prosecution of this task I have been actuated
by what I trust mil not be deemed a selfish consideration.
The study of our native Mollusca has been to me fi'om
childhood such an inexhaustible source of pleasant and
innocent occupation, it has given me so many happy
hours, and it has taken away or alleviated the sting of
so many sorrows, that I am desirous to assist in making
it more an object of general cultivation than it has
hitherto been. This field of research has by no means
been exhausted ; and whether regarded in a zoological

. PREFACE. Vll

or geological point of view^ or as tending to increase our
imperfect knowledge of tlie habits and instincts of these
humble works of our Common Creator, very much yet
remains to be done. No lover of nature need share in
Alexander's sigh, or regret that he has no more work to
do in any department to which he chooses to devote
himself. ^^ Nulla dies sine linea^' was the favourite
maxim of the great Linne ; and our days are too few for
the accomplishment of all that we propose to do, let our
aspirations be ever so modest.

A few explanatory remarks as to the scope of this
work may be here introduced.

It was at first my intention to give, in an Intro-
duction, a general outline of the subject, and to treat at
considerable length some of the principal topics which
are more especially interesting to naturalists and geolo-
gists. But the space which is necessarily occupied by
the body of the work (although the synonymy has been
compressed within the shortest limits and the descrip-
tive characters have been printed in small type) will not
admit of justice being done to this part of the subject,
without making the volume too bulky ; and I must there-
fore content myself with oflPering in the proper place a
few observations, so as to elicit further discussion.

In describing the dimensions of shells, I have taken
the measurements from average and adult specimens,
dividing inches into decimal and centesimal parts ac^
cording to the size of each species. This mode of

Vlll PREFACE.

admeasurement I have considered preferable to stating
the largest dimensions to which each species attains,
which would not give a fair idea of the usual size, or to
adopting the method used by some Continental authors
of giving the range or extreme limits of such dimensions.
Any extraordinary diflference of size presented by speci-
mens or varieties will be noticed. In giving the ad-
measurement of bivalve shells, I have considered the
length to correspond with the line of growth (viz. from
the apex or beak to the front margin), and the breadth
from one side of each valve to the other. In the case of
univalve shells I have adopted the same rule, viz. taking
the line of gi'owth for the length (the apex or point of
the spire representing each beak of the bivalve) , and the
widest part of the shell, or its greatest diameter, for the
breadth.

At the end of the work I propose to give some prac-
tical hints to collectors.

For the benefit of such of my lady readers as have not
added a knowledge of the classics to their other accom-
plishments, I have marked the accentuation of all the
names of genera and species described in this work. One
word of frequent occun^ence I have noticed to be too
often mispronounced by many who ought to know better,
and that is the specific name of our common eatable
oyster, mussel, and cockle. This word [edidis] has the
middle syllable long, as is evident by remembering one
of the various gastronomic maxims of Catius, "Vinea

PREFACE. IX

submittit capreas non semper edules." My late friend,
the Rev. Dr. Goodall, when he was Provost of Eton,
impressed on my memory a rule of pronunciation, which
it may be here useful to repeat. It is, that in words
which end in inus, .and are derived from the names of
animals, the last syllable but one is generally long (as in
Neritina and anatinus), while in those words which have
a similar termination, but are derived from vegetable or
mineral names (such as lanthina and crystallinus) , the
penultimate syllable is generally short. The first are
Latin, and the last are Greek forms. I have also
endeavoured to render as literally as possible the
English meaning of all generic and specific names,
although the barbarisms are nearly as frequent in the
nomenclature of natural history as they are in the
materia medica.

The way in which the name of the great Swedish
naturalist and founder of scientific classification ought
to be spelt has been long the subject of controversy. It
was originally Linnmus ; but on his receiving a patent
of nobility, he assumed the name of Linne. The latter
name is given in the twelfth (and most perfect) edi-
tion of the " Systema Naturse;^^ and in aU his subse-
quent works and correspondence he always used this
title of distinction. The learned Society which bears
his name in this country is Linnean and not Linnsean,
as appears by their charter and Transactions. Under
these circumstances, I have adopted the name which he

a 5

X PREFACE.

himself preferred, and which is prefixed to the work by
which he is best kno^vii as a conchologist.

A parting word to the critics ! When a mere youth,
I was encouraged by my lamented friend, Mr. Dillwyn,
to commit to print what little I then knew of the subject
comprised in the present volume ; and my first essay,
entitled " A Synopsis of the Testaceous Pneumono-
branchous MoUusca of Great Britain,^^ was honoured
by the Linnean Society by publication in their Trans-
actions. Now, in mature years, I have become still
more bold, and venture to appeal to the public. But,
although I cannot hope to be exempt from the fate of all
authors — criticism (and indeed, for the sake of science
and the elucidation of truth, I would rather in\dte it,
instead of considering it a calamity) , I cannot send forth
this little work without a mixture of the same feeling
of hope and doubt, which made the ancient poet thus
apostrophize his book : —

" Paucis ostendi gemis, et communia laudas,
Non ita nutritus. Fuge, quo descendere gestis :
Json erit emisso reditus tibi."

25 Devonshire Place, London,
24 May, 18G2.

INTKODUCTION.

CHAPTER I.

CLASSIFICATION.

DEFINITION OP THE TEEM ''CONCHOLOGY." CONFORMITY OF

SHELLS WITH THEIR INHABITANTS. CEPHALIC MOLLUSKS OR

UNIVALVES. ACEPHALA OR BIVALVES. TUNICATA. SPE-
CIES. VARIETIES. MONSTROSITIES. REVERSED SHELLS.

SYNONYMY. NOMENCLATURE.

Definition of the term " Conchology .'^ — Conchology ^,
as a branch of Natiu'al History, treats of the Molhisca
or that great division of invertebrate animals which have
soft bodies and an organization superior to that of
insects and only inferior to that of fishes. It properly
comprises the study, not only of the shell or outer cover-
ing of the moUusk, but also of the whole animal, — al-
though it has sometimes been used in a more limited
sense, in contradistinction to the term "malacology/^
which has exclusive reference to the soft parts of the
animal. Linne included the Mollusca in his great class
Vermes — some of them as Vermes Mollusca and others
as Vermes Testacea ; but as the first of these divisions
comprised a very heterogeneous assemblage of inver-
tebrate animals, and as the testaceous Annelids were
united with the latter, the classification proposed by him

* Compounded of two Greek words, Koyxri, a shellfish, and Xdyo?, a
treatise.

75032

Xii INTRODUCTION. [CH.

has not been adopted by modern naturalists. Cuvier was
the first to restrict the term " Mollusca^^ to its present
meaning. Nearly all the MoUusca have a shelly cover-
ing, which protects either the whole of their bodies or
the more important organs. Even the Nudibranchs or
Sea-slugs, in their embryonic state, are provided with
a unispiral shell; and the Limacida or Land-slugs
possess a shelly plate, which is imbedded in the shield
or mantle. The term ^^ Conchology '' may be therefore
considered sufficiently appropriate to express the nature
of this science, especially when the original meaning of
the word is taken into account. I do not profess to be
conversant with the anatomy and morphology of the
MoUusca; and I must refer those who wish to studv
this part of the subject to the admirable treatises of
Cuvier, Milne-Edwards, Quatrefages, Troschel, Von Sie-
bold, Vrolik, and other Continental writers, as well as to
those of our own equally eminent countrymen, Owen,
Gray, Huxley, and Hancock. A complete knowledge of
the MoUusca is of course unattainable mthout such
study; but I must content myself with having made
such progress as time and opportunities have permitted.

" Est quadam prodire tenus, si non datur ultra."

Conformity of shells with their inhabitants. — The im-
portance of studying all the parts of the MoUusca is
undeniable, and especially for the pui^oose of arranging
them in generic and higher groups ; but the distinctive
characters afforded by the soft parts alone, which have
been erroneously termed by some writers the " animal,"
cannot be much relied on in making out species. Phi-
hppi has completely demonstrated the insufficiency of
such characters in the case of the genus Rissoa ; and a
careful comparison of the descriptions given in the fol-
lowing pages of our Land and Freshwater MoUusca

I.] INTRODUCTION.

XUl

ought to satisfy any naturalist, who is inclined to con-
sider the question in an unprejudiced spirit, that the
body or soft parts of the moUusk, taken without re-
ference to the shell, offers an extremely shght and
variable criterion of specific difference. The shell of
itself generally enables the conchologist to distinguish
one species from another, without regard to the soft
parts ; and as the latter are seldom observable, the con-
venience of such a mode of distinction is obvious. It
would be rather difficult for a malacologist to describe
any particular kind of testaceous moUusk without no-
ticing the shell ; and for the same reason a crab or sea-
egg would not be easily recognized by the description,
if all mention of the carapace or test were omitted. The
shell of the mollusk may be in some respects considered
as a pseudo-skeleton, serving not only to protect the
soft and tender body, but also to keep the whole frame
together, like the true skeleton of any vertebrate animal.
Tliere is, besides, an intimate connexion between the
shell and the tissues of the body, which is only dissolved
by death or violence. The shell is (to use the words of
Mr. Searles Wood) "part and parcel of the animal itself."
I am aware that this opinion has been controverted by
high authority, and especially by Dr. Gray, whose valu-
able contributions to the science of zoology, in many of
its branches, are famihar to all. He, at one time, dis-
turbed the minds of geologists as well as students not a
little, by a statement that some shells which were per-
fectly ahke were inhabited by animals so extremely
dissimilar as to be referable to very different orders of
MoUusca"^. This statement, however, he afterwards quali-
fied to a considerable extent by admitting that, " in the
distinction of the larger and smaller groups of MoUusca,

* Phil. Trans. 1834, p. 302.

xiv INTRODUCTION. [CH.

the characters derived from the animal, the shell, and the
operculum, which all have a mutual relation to each
other, are of equal value and constancy;" and he ob-
served "how thoroughly they depend on each other,
and what excellent and permanent characters they afford,
both separately and in combination with each other^."
Dr. Gray seems now to be quite sensible of the value
of conchological characters, as nearly the whole of his
numerous genera of MoUusca have no other foundation
than the shell. I believe that the form and structure of
the shell will be invariably found to correspond with the
habits and wants of the animal which produces it. The
mechanical principles involved in the construction of
shells, and the adaptability of these habitations to the
uses of their builders, have been admirably explained by
the Rev. Canon Moseley, in an essay "On the Geometri-
cal Form of Turbinated and Discoid Shells," which was
published in the ^Philosophical Transactions^ for 1838,
and to which I would invite the attention of my readers.
The uniformity of the laws which are here so ably ex-
pounded, and the correlation which exists between the
mollusk and its shell, exhibit in no small degree the in-
finite wisdom of the Creator of all things, thus

"dimly seen

In these thy lowest works ; yet these declare

Thy goodness beyond thought, and power divine ! "

Cephalic Mollusks or Univalves. — The Mollusca may
be considered in a general point of view as divided into
Cephalic and Acephalous, and their shells into Univalves
and Bivalves. The former arrangement was proposed
by Lamarck, and the latter by his predecessor, Linne,
who also added a third division — viz. that of Multi valves,
which would almost be warranted by the anomalous
* Ann. & Mag. Nat. Hist. Sept. 1855, p. 425.

I.] INTRODUCTION. XV

organization of Teredo and Chiton, All these divisions,
however,, are clearly artificial. The Cephalic or Cephalo-
phorous MoUusks have a distinct head, and usually ten-
tacles or horns, with eyes at their tips or base, and a
foot or muscular disk for crawHng or floating. A few of
them have arms for swimming. Some inhabit the land,
and others the water. The Snail, Whelk, and Cuttle-
fish are instances of this kind of Mollusca.

Acephala or Bivalves. — Although the bivalve Mollusca
have no heads as a distinct part of their bodies, they are
not deficient in those organs of outward sense which cha-
racterize other Mollusca, and their brain is as largely
developed. Many of them have numerous eyes for
seeing, otolites or ear- stones for hearing, filaments for
touching, lips for tasting, a mouth for taking in their
food, and (according to some physiologists) also an organ
of smell. The fry of the Oyster, Terebratula, and other
bivalves, which, in their adult state, are permanently
attached to other substances, swim about freely, and are
provided with distinct eyes, which afterwards disappear.
All the Acephala are aquatic, and respire by means of
gills, like fishes. The Oyster, Mussel, and Cockle are
familiar examples of this kind of Mollusca.

Tunicata. — The Tunicata or Ascidians can scarcely
be said to belong to the Mollusca, from which they difi'er,
according to Milne-Edwards, in many essential par-
ticulars, especially as regards their circulation and re-
production. They appear to have a considerable afiinity
to the Polyzoa (or what are generally called " Polypes "),
and may with them constitute the great and separate
class of Molluscoidea. Each division of the animal
kingdom has so many points of resemblance to others,
and the network of organization is so closely inter-
woven, that it would be very difiicult to define any one

Xvi INTRODUCTION. [CH.

class by characters which others do not share in common
with it. Mr. Alder is at present occupied with the sub-
ject of the British Tunicata ; and it will doubtless re-
ceive from that talented and experienced naturalist the
same elucidation as was bestowed on his celebrated
Monograph of our native Nudibranchs.

Species. — I now venture to offer a few remarks on a
very diflBcult and perhaps insoluble problem, \iz. the
nature of species. The difficulty of this investigation is
greater in the study of the Mollusca and other Inver-
tebrata than in that of more highly organized animals,
because one characteristic element, from the nature of
their reproductive system, is here wanting or beyond the
reach of observation. Nearly all the land Mollusca,
the habits of which it is comparatively easy to study,
have both sexes united in the same individual ; and not
even the aquarium will enable us to make those experi-
ments as to the fertility or sterility of hybrids to which
such importance is attached in the discussion of this
question in the case of vertebrate animals.

The forms of some shells appear to be more perma-
nent or capable of being reproduced without any modi-
fication than others. The Silurian Lingula, which claims
the precedence of all Mollusca in point of antiquity, is
said to be undistinguishable from an existing species;
and its mould must therefore have been continued from
the womb of time to the present day without the slight-
est change. The secondary strata contain many well-
known instances of a similar persistence of form, espe-
cially those of Terebratula caput-serpentis and some
Foraminifera, which are considered by competent autho-
rities not to differ from species which now live in the
adjacent seas. A large proportion of the fossil shells
found in the lowermost of the Pliocene strata (or

I.] INTRODUCTION. Xvii

" Coralline Crag ^^) are precisely similar in every respect
to the recent shells of species which bear the same names
and still survive; and it is impossible for the most critical
species-maker to distinguish one from the other. Even
their varieties and monstrosities or abnormal forms are
still repeated. The opinion of the late Professor D^Or-
bigny_, which has been adopted by Agassiz_, that all tertiary
species became extinct, and that they are only repre-
sented at present by analogous forms, evidently resulted
from a preconceived theory, against which a concordance
of fossil with recent species would have militated.

Without, however, entering into an abstruse (and
perhaps useless) inquiry into the origin of species, or
how far they have been modified during any period of
time, however vast, by external circumstances or condi-
tions, it is undeniable that certain definite forms, called
" species," exist, and that they constitute more or less
extensive groups of individuals, which resemble each
other as well as their parents and offspring, to the same
extent that we observe in the case of our own kind.
These groups, to deserve the name of species, must
be distinct from others ; because if any of them are so
intimately blended together by intermediate links as to
make the line of separation too critical, the test fails, and
a subordinate group, or what is called a "variety," is
the result. For this reason it is indispensably necessary
to compare as great a number of individuals as possible,
and especially a series of different ages and sizes com-
mencing ab ovo, as well as specimens collected from
various localities. The study of abnormal or monstrous
forms is also important in order to ascertain the range
of variation in growth. By such investigations a crying
abuse of the present school of natural history (an ex-
cessive multiplication of species) would be avoided.

Xviii INTRODUCTION. [CH.

juster views would prevail as to the distinction of spe-
cies^ and the well- deserved reproach of those philo-
sophers who are confirmed in their denial that species
have any real existence in nature by the notorious dis-
agreement of naturalists as to their limits would thus
cease. There is no judge or ^' arbiter specierum ; ^^ and
every naturalist is at perfect liberty to follow the bent
of his own discretion or inclination in the extension or
reduction of species^ subject only to the opinion of his
scientific compeers. He is amenable to no other autho-
rity. Hence arises that great and continual diversity of
opinion as to the determination of certain species among
natui'alists, whose opportunities or experience are more
or less great J or whose minds are differently constituted —
the nature of some being rather analytical and of others
synthetical. The same remark of course applies to the
distribution of species into genera^ and of these, again,
into families and higher groups or sections. To a cer-
tain extent all classification is artificial and arbitrary;
but the necessity for some arrangement of the kind is
obvious, considering the immense number and variety
of objects to which some name or symbol of distinction
must be given for the sake of those who pursue or study
any branch of natural history. Systems of classification
are as indispensable to a naturalist as tools to a work-
man. This necessity of science equally applies to the
discussion of the interesting question as to the origin
and mutability of species, which in the absence of such
data could not be satisfactorily conducted.

Varieties. — Besides species, and holding a subordinate
rank to them in the great host of Nature's works, are
certain forms called " varieties,^' which are not less defi-
nite, but more difiicult to separate from the typical or
specific forms. They are offshoots of species, and origi-

I.] INTRODUCTION. xix

nate in some peculiarity of climate, situation, composition
of the soil or water which they inhabit, the nature or
supply of food, and various other conditions. The cha-
racters by which they usually differ from species consist
of size, comparative proportions of different parts, colour,
and degree of sculpture ; and the investigation of forms
thus changed or modified is often extremely perplexing.
Some species are more liable than others to variation ;
and, as might be expected, the tendency to variation is
greater in those species which most abound in individuals,
by reason of their offering a wider scope of observation
to the naturalist. Varieties are of two kinds, perma-
nent and local. The former are called "races,^^ and
have many of the characters of true or typical species,
with which they associate. Great experience and good
faith are essential to the investigation of this experi-
mentum crucis ; and the only reliable test of distinction
between species and races appears to be the discovery
of intermediate forms. In the absence of such discovery
we may proceed to classify, — although after all we must
not lose sight of the great probability that all species,
and even higher groups, may have originally descended
from races or permanent varieties, and these again from
local varieties. The latter are more readily distinguished
from species and are never found associated with them.
I believe it may be now considered a well-established
rule, that all distinct groups of individuals living toge-
ther and having a common feeding-ground, and which
are not connected or blended with each other by insen-
sible gradations, are prima facie entitled to the rank of
species. A contrary opinion used formerly to be enter-
tained by some naturalists; and it was not unusual
to found a claim to specific distinction on the fact that
the specimens thus distinguished did not occur with the

XX INTRODUCTION. [CH.

species from wliicli it was proposed to separate them.
They apparently forgot that the very difference of locality
or habitat^ with its accompanying conditions, caused the
variation in question.

Monstrosities. — These abnormal forms of shells are
frequently repeated, and even appear to be hereditary ;
and it is not easy at first to distinguish them from varie-
ties. Both are probably owing to an irregularity, or an
excessive or defective power, of secretion in. the mantle
of the animal. The monstrosity seldom, if ever, occurs
in the first stage of growth ; and the examination of the
top whorls or apex of a univalve, or of one of the beaks
of a bivalve (being in each case the nucleus of the shell) ,
offers a good criterion to distinguish monstrosities from
species. The normal or regular form becomes distorted
at a subsequent stage of growth, instead of pursuing the
usual course of formation.

Reversed shells. — Among the numerous cases of mon-
strosity to which the MoUusca are liable, by reason of
their comparatively simple organization, none is more
remarkable than the reversed turn and position which the
spire of univalve shells and the valves of some Acephala
not unfrequently assume. The twist of the spire in
univalves is, with a few exceptions, dextral or from left
to right, the shell being placed with its spire towards
the observer and its mouth downwards. If the shell is
held in this position before a mirror, the spire will of
course appear to be sinistral or turning from right to
left, which is termed "reversed.^^ This phenomenon
occurs in most species of Mollusca which have spiral
shells ; but it is more rare in some than in others. In
certain genera the shell is naturally reversed; and a
dextral spire becomes the exception or monstrosity. In
a few species the spire is as frequently sinistral as dex-

I,] INTRODUCTION. XXi

tral. The direction of the spire is attended by a corre-
sponding change in the position of those organs of the
animal which are usually placed on one particular side ;
and it may be compared to the case of a man ha\ing
his heart on the right and his lungs on the left side of
his body. The structure of a mollusk is, however, not
so complicated ; and the consequence of such a reversal
in the position of its organs is probably not very import-
ant to its economy. One curious case of this kind of
malformation is worth noticing. During the deposit of
that part of our upper tertiary strata which is called the
"Red Crag/^ nearly all the specimens of the almond
whelk (Fusus antiquus) appear to have been sinistral or
reversed, dextral specimens being comparatively very
scarce in this formation. The same species still exists
and is common in our seas ^ but the proportion of dex-
tral to sinistral specimens is at present exactly the con-
trary to what it was in the Crag epoch — the former being
now the rule and the latter the exception. A reversed spe-
cimen in a recent or fresh state is worth half a sovereign ;
while dextral specimens may be had at any street stall
(with the fish) at the rate of four for a penny. A few
bivalve species, which have one valve larger than the
other and are therefore called inequivalve, have also
their shells occasionally reversed, — their right or left
valve being the largest, contrary to the usual rule in
these species.

In the prosecution of any inquiry into the nature of
species or varieties, or as to whether there have been
any special or successive creations since this world was
called into existence by the fiat of its Great Creator, I do
not believe that it can have any irreligious or sceptical
tendency. Holy Scripture is not a work of natural his-
tory, and it is silent on the subject of this investigation.

Xxii INTRODUCTION. [cH.

As Dr. Carpenter has well observed, in his Researches
on the Foraminifera *j "The creation of any organism
seems to me just as much to require the exertion of
Divine Power when it takes place in the ordinary course
of generation, as it would do if that organism were to
be called into existence de novo ; the question being in
reality whether such exertion takes place in the way of
continuous exercise according to a settled and compre^
hensive plan, or by a series of disconnected efforts."

Synonymy. — Although the prevalent habit of multi-
plying species is much to be deprecated, an equal amount
of injury has been done to the cause of science by the
unnecessary addition, from time to time, of fresh names
for species which had been previously described; the
consequence of which is that, an overgrown mass of
nomenclature encumbers most works on natural history.
For our common Cockle and its varieties no less than
sixteen, and for the Oyster fourteen different names
have been given by British and Continental writers ; a
genus of minute shells [Odostomia] has received from
various conchologists twenty different names ; and in an
essay of M. Bourguignat on the species of Pisidium (a
small freshwater bivalve) the synonymy of P. amnicum
comprises eighty specific names and extends over more
than five octavo pages. The student may well stand
aghast at this fearful array of names, which bewilder him
and obstruct his entrance into the portals of the edifice
of natural history ! This redundancy of names for the
same object has partly arisen from the want of inter-
com'se which naturalists of this and other countries
experienced formerly, and especially during that chronic
state of international warfare which so long debarred us
from any communication with foreigners. Such an

* Phil. Trans, vol. cl. p. 570.

I.] INTRODUCTION. Xxiii

unfortunate state of things certainly retarded scientific
progress in Great Britain to a very great extent; and
the friendly sympathy which now exists between the
naturalists of all countries cannot be sufficiently ap-
preciated. In one sense the multiplication of species
and addition of synonyms are convertible terms ; and
that is^ where local varieties have been described and
raised to the rank of species. This evil it is impossible
to prevent ; but as science does not march '' pede claudOy"
but regularly and steadily, it is to be hoped that each
succeeding year will bring with further discoveries the
occasional publication of monographs by experienced na-
turalists, so as gradually to rectify this crying evil. The
introduction to the ^ Flora Indica/ by Drs. Hooker and
Thomson, contains a valuable remark which deserves the
attention of zoologists as well as botanists, viz., " The
discovery of a form uniting two others, previously thought
distinct, is much more important than that of a totally
new species, inasmuch as the coiTcction of an error is a
greater boon to science than a step in advance.^^

Nomenclature. — Very often the longest and most un-
pronounceable names have been bestowed on minute
and almost microscopic species. When the student meets
with such names as Cerithiopsis tubercularis and Omalo-
gyra nitidisslma, he is scarcely prepared to find that one
of the objects designated by these more than sesqui-
pedalian words is scarcely more than a quarter of an
inch in length, and that the other is only about one-
fifteenth of an inch in diameter ! There is, however, no
way of preventing this abuse of language for scientific
purposes, except by making a new coinage; and this
would be attended with more inconvenience to naturalists
in the substitution of new for old and familiar names,
than in the retention of a few long words.

Xxiv INTRODUCTION. [CH.

The general rule is not to alter the name which has
been first given to any species, in order to establish a con-
ventional right of priority and to prevent confusion. But
this rule is not without an exception — especially where
the original name has been accidentally misspelt, either
by the author or printer. Thus " Suediense '' has been
properly changed to Suecicum ; and " Syndosmya ^^ ought
to be replaced by Syndesmia. Such trivial corrections
are necessary in the works of our best authors ; and in
those which have largely benefited the cause of science,

" non ego paucis

Offendar maculis, quas aut incuria fudit
Aut humaua parum cavit natura."

CHAPTER II.

ORGAJ^IZATION AND HABITS.

REPEODLTTIVE system. FECUNDITY. HYBRIDISM. PROGRESSIVE

DEVELOPMENT. ORGANS OF SIGHT HEARING SMELL LOCO-
MOTION. FOOD. SIZE. HABITAT. CARE OF YOUNG. SOCIA-
BILITY. ESTIVATION AND HIBERNATION. NESTS. MODES OF

ATTACK AND DEFENCE. RENEWAL OF PARTS, PHOSPHORES-
CENCE. PERFORATING POAVERS. OCCASIONAL APPEARANCE AND

DISAPPEARANCE. TENACITY OF LIFE. AGE. RESUME.

Reproductive system. — The modes of propagation
among the Mollusca are various. In the case of uni-
valves, many of them (e. g. the Whelk tribe) have distinct
sexes, and are what botanists term " dioecious f' w^hile
most of the land-snails are nearlv " monoecious,^^ each
indiA'idual being at the same time male and female, but
incapable of fertilizing itself. Some of these even change
their sex at diff'erent periods, — the ValvatidcB being at

II.] INTRODUCTION. XXV

first male and afterwards becoming female. In the case
of the Conchifera or bivalves, they are probably all
strictly '^ monoecious '' and fertilize themselves. It was
at one time supposed that the Oyster and freshwater
Mussel were exceptions to this rule, and that some in-
dividuals were male and others female; but the re-
searches of Davaine, Moquin-Tandon, and other able
physiologists have disproved this idea*. The external
organization of the Conchifera, as well as the complete
isolation of the Teredines and many other kinds from all
intercourse with each other during the whole of their
lives, would make it very unlikely that they are of dif-
ferent sexes. Some of the MoUusca are ovoviviparous,
the eggs being hatched within the body and the fry ex-
cluded in a perfect form. This is the case not only with
" monoecious '^ kinds (such as Anodonta and Kellia) , but
also with some snails [Helix rupestris and Pupa umbili-
cata) and even with " dioecious ^^ kinds, such as Paludina
and certain species of Littorina. Some particulars will be
found in the following pages T\4th regard to the amours
of the land and freshwater snails ; and much more might
be said on this curious subject. The tender passion
seems to take up much of their time and attention. M.
Turpin has observed a pair of the common garden-snail
[Helix aspersa) engaged in love-making for the space of
more than ten hours !

Fecundity. — The extreme fertility of some moUusks is
not exceeded by that of fish. It has been estimated that
the oyster spawns annually at least three millions. Ac-
cording to C. Pfeifi*er the gills of a freshwater mussel of
moderate size contain at least 400,000 eggs ; and Jacob-
son has given a much higher figure (two millions) for the

* See also Hancock " On the Organization of the Brackiopoda,^^ Phil.
Trans, vol. cxlviii. p. 816.

b

XXvi INTRODUCTION. [CH.

product of a large individual of this kind. If this rate
of increase were unchecked, our seas and rivers would in
a comparatively short time (reckoning geologically) be
filled up with the remains of shell- fish.

Hybridism. — Although many surmises have from time
to time been hazarded as to the production of abnormal
forms of Mollusca by means of an unnatural union be-
tween individuals of different species, the only direct
experiments or observations that appear to have been
published on the subject have been made by French
naturalists. M. Gassies, in his descriptive Catalogue of
the Land and Freshwater Mollusca found near Agen,
mentioned several cases of what he called " accouple-
ments adulterins/^ which he had observed between in-
dividuals of Helioo virgata and H. Pisana, as well as
between those species and Bulimus decollatus. M. Gassies
enclosed the snails during a thunderstorm in a vessel
covered ^^At\\ metallic gauze ; and he believed that the
electricity with which the air was then charged induced
the unnatural union. Great care appears to have been
taken to prevent any error in the result, by selecting
individuals which had not been previously fertilized and
keeping them after fecundation separate from any others.
The product of these unions was as follows. The young
of H. Pisana had perfectly white shells, — their mother
li^ving the usual coloured bands ; and the young of H.
virgata had shells of a darker colour than that of their
mother. In the other case, the product of the Helices
which had been coupled with the Bulimus was various.
Many had shells which were almost scalariform ; the
shells of others were pyramidal ; but the greater part of
them had shells exactly like that of their mother. The
product of the Bulimus did not differ from their maternal
form. M. Gassies had also observed the product of a

II.] INTRODUCTION. XXvii

union between Helix nemoralis and H. hortensiSy in which
the colour of the lips of their shells in each case varied
indifferently from bro^Ti or rose-colour to milk-white.
Professor Lecoq and M. Miergue have celebrated the
voluntary nuptials between individuals of Helix nemo-
ralis and H. aspersa, as well as between Pupa cinerea
and Clausilia papillaris ; but these unions do not seem
to have been blessed with any offspring. The fact,
however^ of such unions having taken place in a state of
nature, and not under forced or accidental conditions,
is remarkable, and the more so because the individuals
belonged to what are considered different genera.

Progressive development. — The researches of geolo-
gists have established by positive evidence,, that the
organization of many animal and vegetable types has not
become more specialized or rendered more perfect since
the period to which we ascribe their creation, and that,
notwithstanding the enormous lapse of time which is
indicated by the accumulation of fossiliferous strata, the
modification or change which these types have under-
gone has been remarkably slight. There is abundant
evidence of variation, but none of what is usually under-
stood as progression*. The theory of ^'^progressive de-
velopment '^ appears to have been very hastily advanced,
and is by no means borne out by geological facts. It is
a cmious circumstance in the history of the growth of
certain land and freshwater Mollusca, that the young of
some species of Pupa resemble those of Helix, the young
of the latter those of Zonites, and the young of the last
those of Vitrina, These genera are enumerated in the
order of their organization, Pupa being the most, and
Vitrina the least perfect of them.

* See Professor Huxley's Address delivered at the Anniversary Meeting
of the Geological Society, 21st February, 1862.

62

XXviii INTRODUCTION. [CH.

Organs of sight. — The eyes of a Cuttle are more perfect
than those of many kinds of fish ; but the so-called eyes
of land-snails are supposed to be only organs of touch
and not of vision, although endued with a greater sensi-
bility than the tentacles which support them. The
coloured bulbs which fringe the mantle of a Scallop are
also called eyes; but their structure is very simple.
According to Mr. Lea, several kinds of Unto are sensi-
tive to light. These organs are entirely wanting in many
of the Mollusca, and even in some species of genera which
usually have eyes.

Hearing. — In the Pectinibranch Mollusca the contents
of the auditory capsules consist of spherical ear- stones,
which in every respect but that of form are similar to
the otolites of fishes. In the Pulmonobranch Mollusca
they are called octoconia and consist of a chalky pulp,
which is separable into minute elliptical granules. Frey
has observed organs of hearing in many of the land
and freshwater Mollusca, both univalve and bivalve. He
counted as many as 200 otolites of different sizes in one of
the auditory vessels (of which there were two) in an adult
snail. In Sphcerium (or Cyclas) each individual appears
to have never more than a single otolite. He believes
that these bodies are formed by a subcrystaUization of
the liquid contained in the auditory vessels.

Smell. — In the Helicidce, or land-snails, this sense is
supposed to lie in the bulbs which surmount their ten-
tacles. It is probable that the carnivorous or zoophagous
Mollusks have the power of scenting out their prey or
food. Quantities of the common "almond-whelk^^ of
dealers in shell-fish (Fusus antiquus) are procured on
the Cheshire coast by the fishermen placing a dead dog
on the sands at low-water mark during spring tides.
The bait is then completely covered with stones, which

II.] INTRODUCTION. xxix

f

are piled up like a cairn, partly to prevent the carcase
being carried away by the tide, and also because the
fishermen have a scruple about eating shell-fish which
have been fed on such carrion. On the next turn of
the tide the heap of stones is visited and the whelks are
found on the surface in great numbers, having been
apparently attracted by the smell of the bait, but unable
to get at it.

Locomotion. — The methods by which MoUusca move
from place to place are exceedingly varied. Most uni-
valves crawl on the lower part or disk of a large fleshy
organ, which is the homologue of a foot and supports
the body. The Melampus uses this organ in an unusual
way, by first planting the front half, like a caterpillar,
and then drawing up to it the other half, and repeating
this alternate movement in a fashion called " looping/'
The celebrated French naturalist, Adanson, gave that
genus the name of Pedipes on account of this peculiarity.
Many of the aquatic univalves can swim, or rather creep
underneath the surface of the water, the position of their
bodies being reversed, with the point of the shell down-
wards. A few of the bivalves {e. g. species of Lepton
and Galeomma) sometimes walk about with their valves
spread out like the cover of a book when left on the
table by an untidy person. The Cuttles and Pteropods
swim as rapidly as fishes, but in a different manner —
viz. by taking in and expelling by means of their mantle
successive volumes of water, so as continually to propel
th^m onwards. One kind of Cuttle is said even to pos-
sess the faculty of flying, and to dart for a considerable
distance out of the water through the air like a flying-
fish. Most of the Acephala or bivalves have a tongue-
shaped organ of progression, which is muscular and
extremely flexible. By means of this kind of foot the

XXX

INTRODUCTION. [cH.

Cockle^ Razor-fish {Solen), and other kinds burrow in
sand and mud. The Scallop and Lima fill their bodies
with water, and then, suddenly collapsing and closing
their valves, execute a series of leaps or jerks, by which
they can traverse a considerable distance, although in
an irregular course. Certain small bivalves [Sphcerium
and Kellid), while floating on the surface of the water,
spin filaments which serve to moor them and prevent
their being drifted about. Several kinds of slug secrete
glutinous threads by which they suspend themselves
from trees and either remove from one branch to another
or drop safely to the ground. Thus it will be seen that
the Mollusca partake of all the modes of locomotion pos-
sessed by other animals — that they can walk like quadru-
peds, fly like birds, crawl like serpents, swim like fishes,
and even spin threads like spiders.

The action of creeping in a snail is performed by the
close appression of its foot to the substance over which
it moves, as well as by muscular force. Any unevenness
in the surface to be traversed is filled up by folds of the
foot, which is extremely flexible. This action may be
compared to the application of one piece of flat glass to
another. Musical sounds, resembling those which are
given out by the Eolian harp, may be observed on a dry
summer evening by putting a garden-snail to crawl out-
side a window; and this phenomenon has frightened
many a timid or superstitious person, who could not
imagine whence these mysterious sounds proceeded. A
curious calculation was made by Mr. Thomas, an Ameri-
can conchologist, as to the rate of a snaiFs pace. He
found that it takes 16 days and 14 hours for a moderately
fast snail to do a mile.

Food, — By far the greater part of the MoUusca are
zoophagous or animal- eaters. The food of the Acephala

II.] INTRODUCTION. XXXi

consists of Infusoria and other animalcules^ which are
conveyed to their mouths, by an action analogous to
that of suction, through the inhalant tube or the outer
folds of their mantle. The Buccinwn or whelk tribe prey
upon other moUusks (especially bivalves) by drilling
holes in their shells with their proboscis, which is armed
with a formidable apparatus of teeth. The whelks are
also very troublesome to fishermen, being often found
sucking and sticking to the bait when the lines are taken
up. Numbers of them may be caught in lobster-pots
baited with fish or meat, if laid down on a sandy instead
of a rocky ground. Most of the littoral univalves feed
on sea- weed. The common Limpet forms by means of
its foot a shallow excavation in the rock. When the
tide returns it goes out to its pasture, browsing like an
herbivorous quadruped ; and it returns to its hole when
the tide retires. The track left by its grazing on the
submarine vegetation which clothes the adjoining rock
is very perceptible and is sometimes tortuous or maze-
like. Land and freshwater snails, as well as slugs, are
for the most part herbivorous, as gardeners know to
their cost in the former case; but some of them also
devour animal matter, and a few are cannibals. The
food of the Testacella consists almost exclusively of
living earthworms ; and a fall account of its carnivorous
and voracious propensities mil be found in this volume.
Snails have been taken with insects in their mouths,
which they were swallowing by degrees ; and, accord-
ing to M. Bonnafoux, the Helix aspersa has been known
to perforate birds^ eggs in deserted nests, in order
to feed on their contents. The number of curved si-
liceous teeth which arm the tongues or lingual plates
of snails is prodigious (amounting in some species to
many thousands), being arranged in several rows. Some

XXxii INTRODUCTION. [CH.

of the marine Mollusca are parasitic, or live upon the
secretions of other animals. Among the bivalves Mon-
tacuta substriata, and among the univalves Stylifer Tur-
toni, are instances of these parasitic habits.

Size. — This appears to depend on the supply of food ;
and it is probable that, owing to the vast shoals of mol-
lusk- eating fish which abound in the northern seas, the
shell-fish there are thinned to such an extent that the
fortunate sur\TLVors have a proportionally larger share of
food than those which inhabit southern seas, where both
species and individuals are more numerous. Northern
Mollusca are generally larger than those of the same
species from the South ■^. The same law is observable
with regard to cultivated fruits, — thinning being resorted
to for the purpose of reducing the number and in-
creasing the size of those which are allowed to remain.

Habitat. — There is probably not a square foot of land,
either in a cultivated or uncultivated state, or co-
vered with fresh, brackish, or salt water, that is not
inhabited by Mollusca of various kinds. Trees, herbage,
and sea-weeds are the chosen stations of many sorts,
for the sake of the shelter or food which they afibrd ;
and even our cellars and kitchens are not free from
them. Some live only in the ocean, and never approach
land unless when driven on shore by the winds and
waves. These are called " pelagic.^' Among them are
the lanthinaj or " blue-snaiV and a few small Ptero-
pods, which are occasionally found in our seas. The
former is provided with a cellular apparatus, by wliich

* See also Draparnaud (Tabl. Moll. p. 35) as to the comparative size
of land shells inhabiting the North and South of France. " Le cHmat
influe beaucoup sur la grandeur des individus. Chez les MoUusques,
comme chez les Mousses et un grand nombre d'autres plantes, la meme
espece acquiert un volume d'autant moindre, qu'elle habite dans un pays
plus chaud."

II.] INTRODUCTION. XXxiii

it is enabled to keep always in a floating position on the
surface of the water, with the point or spire of its shell
downwards, and which apparatus also serves as a nidus
for its spawn. A description of this curious appendage
or " float," as well as of the equally remarkable habits of
the lanthina, will be found in its proper place. The
Pteropods have feet like wings, and flutter through the
water like butterflies. They have conical, and some-
times spiral, shells as fragile and transparent as the
finest blown glass.

Care of young. — Many of the bivalve Mollusca, inha-
biting the sea as well as fresh water (e. g. Teredo and
Anodonta), retain for some time their fry, after being
excluded from the egg, in the folds of their mantle, this
being in some degree an analogous provision to that
which is possessed by the marsupial quadrupeds. The
common Limpet and some kinds of Pupa (small land-
snails) have also been observed to carry about their
young, the former within the folds of its foot, and the
latter attached to the shells of their mother. These
cases of Molluscan a-ropyrj are nearly as wonderful as
any which have been adduced in accounts of much more
highly organized animals.

Sociability. — Although many of the Mollusca are gre-
garious and assemble together on the same feeding-
grounds, it does not appear that they ever associate for
a common object, like bees or ants. Each Pholas and
Teredo makes a hole for itself; and although the com-
mon garden-snail often fastens itself to the shell of its
companion, when they hibernate and form clusters, a
smooth stone or any other object is used for the same
purpose.

Estivation and Hibernation. — Many animals in a state
of nature have their periodical seasons of repose, espe-

65

XXxiv INTRODUCTION. [CH.

cially in the winter when there is a deficiency of food.
For this reason it may be supposed that all the Mol-
Insca hibernate ; and we know that the land- snails in
this country have such a habit. Most of them bury
themselves in the ground^ or nestle in the crevices of
rocks, under the bark of trees, or even in the hollow
stems of the larger umbelliferous plants. They also
cover the mouths of their shells with a calcareous plate
of various degrees of thickness, which they secrete, in the
same way as the shells, by means of their mantle. This
plate is called an " epiphrag-m,^' and in the apple-snail
[Helisc pomatia) is of considerable thickness. But in
dry weather and during the heat of summer they form
another and slighter kind of epiphragm, in order to keep
their bodies always moist and lubricated, as without such
protection thfe tissues would soon dry up and the snails
perish. The E,ev. H. B. Tristram, in his account of the
Great Sahara, says that the snail-shells which he found
there were much thicker than those of the same species
from more temperate parts of Europe, apparently as an
additional means of preventing evaporation in so dry a
climate. The simile in the 58th Psalm (verse 8) which
is rendered in our translation for the ^ Common Praver/
" consume away like a snail,^^ may have had reference
to the inability of these Mollusca to endure exposure
to the great heat of the sun in an Eastern climate.
None of the naked Slugs occur in the lists of land
Mollusca collected by Professor Roth in Palestine,
and by Dr. Schliifli and M. Mousson in the East.
The circulation of land-snails is affected to a great
extent by the temperature. In some kinds the rate
of pulsation varies from 30 to 110 per minute during
summer ; and it ceases altogether in winter. Although
the temperature of the sea is nearly the same in summer

II.] INTRODUCTION. XXXV

and winter^ except at its surface, the circumstance that
most sea- weeds are annual would lead us to conclude
that the marine phytophagous MoUusca also retire into
winter quarters, and that, as these are preyed upon by the
zoophagous kinds, the habit of hibernating is common to
all shell-fish. In shallow seas near the land, the number
of marine animals is perceptibly diminished during cold
and inclement seasons ; and this was noticed by several
naturalists to have been the case in the wet year of 1860.
The period of hibernation differs among the MoUusca.
Some retire earlier or emerge later than others. Ac-
cording to M. Drouet the Anodontce or freshwater mus-
sels hibernate before the close of autumn, and bury
themselves deep in the mud until the middle of spring,
when the water begins to get warmer.

Nests. — A few marine bivalves, which do not spin a
byssus or bundle of threads with which they can moor
themselves to rocks, or which have not the power of exca-
vating for themselves a place of residence in stone, wood,
the tunic of Ascidians, or other substances, form a kind of
rude nest out of broken shells and zoophytes, which they
cement and line internally with a slimy exudation from
their bodies ; and thus they remain snugly ensconced
and protected from their natural enemies. Among these
nest-builders are the Modiola radiata, Lima Loscombii,
and the northern form of L. hians. So little is known
of the habits of the marine MoUusca, that I am not pre-
pared to say whether these are proper nests and used
for the protection of the young, as in the case of stickle-
backs and other small fishes, or are constructed solely
for the use of the adult shell- fish.

Modes of attack and defence. — Some aquatic moUusks
have the faculty of emitting from their bodies a purple
or dark fluids apparently for the purpose of securing

XXXvi INTRODUCTION. [CH.

their prey or concealing tliemselves from fishes or other
predaceous animals. The inky cloud which the Cuttle
ejects is of a glutinous or viscous nature, and does not
readily mix with the water. It seems to be better
adapted for entangling small fishes than to cover the
retreat of the Cuttle, which is extremely rapid in its
movements. The Aplysia, or sea-hare, gives out a
purple dye which is also glutinous and has an ofi'ensive
smell. As this mollusk crawls but slowly, it may use
the dye to obfuscate some more active animal which it
may have taken a fancy to make a meal of, all the Nudi-
branchs being said to be carnivorous. Several kinds
of Planorbis (freshwater snails) yield, on being irritated,
a quantity of their own purple blood. These are vege-
table-eaters ; and we can therefore conceive no other
object in this volmitary blood-letting than to elude ob-
servation. A few land-snails (e. g. Bulimus obscurus and
Pupa secale) in their young state, as well as some small
freshwater bivalves belonging to the genus Pisidium,
have their shells covered with mud and other extraneous
matter ; but it is difficult to say whether this is the re-
sult of design or acyident. One might suppose that the
sharp eyes of a bird or a frog would easily detect their
prey through this feeble disguis.e. Some marine bivalves
(as Lyonsia Norvegica and species of Necera) are covered
with a coat of sand, which may to some extent answer
the purpose of concealment. If the safety of these
animals is ensured by such means, how great must be
our admiration of that wonderful yet varied plan of con-
trivance which makes the humble Mollusk, as well as
Man, the object of Divine care !

Renewal of parts. — Some Mollusca, which had been
accidentally deprived of theu' feet, tentacles, eyes, and
even of their entire heads, have been known to repro-

II.] INTRODUCTION. XXXvii

duce them. Nearly a century ago, the experiment of
decapitating unfortunate slugs and snails was con-
ducted on a wholesale scale on the Continent, and every
philosopher was anxious to cut off a head. Even the
great Voltaire followed the universal fashion ; and his
experiences were pubHshed in the " Questions sur FEn-
cyclopedie.^^ In these he mentions having operated on
twenty brown slugs and a dozen snails ; and he after-
wards records with great pride and satisfaction "mes
Limaces '''' and " mes Escargots " showing their budding
heads and horns, and doing as well as might be expected
under the circumstances.

Phosphorescence. — Although a great many animals,
from the highest order of fishes to the imperfectly orga-
nized Noctiluca miliaris, as well as several of the Tuni-
cata, emit or exhibit a phosphorescent Hght, I am not
aware that any of the MoUusca possess the same property,
except some kinds of Pholas ; and it is possible that the
phenomenon in their case may be owing to animalcula
which infest them or are found in their holes. The
eggs of a common slug {Arion hortensis) are said to be
luminous for the first fifteen days after they have been
laid. But both the nature and object of this common
phenomenon requires further investigation.

Perforating powers. — Many shell-fish, and especially
bivalves, burrow in sand or mud for protection against
their natural enemies ; but some of them excavate wood,
peat, or stone of various degrees of hardness, for the
same purpose. The process of burrowing is undoubtedly
performed by the foot of the Mollusk. It is exemphfied
by the case of the common Cockle, which uses its tongue-
shaped and flexible foot in the same way as a gardener
uses his dibble, and, having thrust it into the sand and
expanded it, thus makes a hole large enough to contain

XXXviii INTRODUCTION. * [CH.

the shell. The limpet [Patella vulgata) slightly perforates
calcareous rocks by the muscular action of its sucker-
like foot or disk, which occupies all the lower part of the
body. The shell exactly fits the space thus excavated,
so as to prevent the limpet being easily dislodged by a
bird or a crab. The common garden-snail excavates
hard limestone rocks for the purpose of hibernation ; and
as its shell is covered with a delicate epidermis, which
remains on specimens having just emerged from their
winter quarters, it may be safely inferred that the shell
is not the instrument of perforation in this case. But
with respect to the Teredo or ship-worm (which tunnels
through wood), the Pholas (which pierces wood, peat,
clay, and chalk), the Gastrochcena (which penetrates
hard sandstone, chalk, and limestone, as well as old
oyster- shells), and the Saxicava (which perforates the
hardest calcareous rocks), it is not so easy to form a
definite conclusion. This volume would scarcely con-
tain all that might be said on the subject. Forbes and
Hanleyhave given an excellent account of the discussion
which had taken place up to the time of publishing their
work ; and I will content myself with stating briefly the
result of their investigation and adding a few remarks
suggested by my own inquiries.

The opinions which had been expressed on this subject
when the ^ History of the British Mollusca ' was pub-
lished, were classed by its authors, when treating of the
Pholas, under five conclusions, which are as follows : —

" 1 . That the boring Mollusca perforate by means of
the rotation of the valves of their shells, which serve as
augers. 2. That the holes are made by rasping, effected
by siliceous particles studding the substance of certain
parts of the animals. 3. That currents of water, set in
action by the motion of vibratile cilia, are the agents.

II.] INTRODUCTION. XXxix

4. Tliat the animal secretes a chemical solvent — an
acid which dissolves the substance into which it bores.

5. That the combined action of a secreted solvent and
rasping by the valves effects the perforations*.^-'

The first of these views is advocated by Forbes and
Hanley; and the other naturalists to whom they have
referred as having expressed an opinion on the subject
are as follows_, taking the several views in their order
of succession: — 1. Dr. Gray, Dr. Fleming, Mr. Osier.
2. Mr. Hancock. 3. Mr. Garner. 4. Dr. Gray, Dr.
Drummond, M. Deshayes, M. CaiUiaud. 5. Mr. Thomp-
son, M. Necker.

As I believe that all these different views, except the
first, have been successfully refuted by the arguments of
Forbes and Hanley, it only remains for me to adopt
their view, or to substitute another for it.

If we only consider the shell of PholaSy with respect
to its efficiency as an instrument of mechanical perfora-
tion, there might be sufficient reason for supposing that
it can by this mode drill a hole in peat, submerged wood,
clay, or even in chalk when softened by the continual
contact of water. The shell is certainly harder than
any of these substances j and the animal is provided with
muscles of unusual strength for efiecting the rotatory
motion which would be necessary for such an operation.
But we must also consider the cases of other perforating
mollusks whose shells are not so hard. The shell of
Gastrochcena is more fragile than that of the oyster into
which it bores, and very much more so than the lime-
stone in which it not unfrequently lodges itself. The
helmet-shaped valves of Teredo could only be used to
rasp the sides of the tube which this moUusk forms in
wood; and they are not adapted for excavating the con*
•* ' British Mollusca,' vol. i. p. 104.

xl INTRODUCTION. [CH.

cave end of the tube. The shell of Saxicava is coated
with a dehcate epidermis, which would unquestionably
be scraped away in perforating the solid limestone rock,
if the theory advocated by Forbes and Hanley is appli-
cable to this case. And, to take the case of other
marine animals which excavate rocks and shells for the
same purpose as the Mollusca, we know that the boring
Annelids or sea-worms have no hard substance in their
composition. For these reasons, I do not think that
the mechanical theory (viz. that the shell is the sole
instrument of perforation) has been established.

Since the publication of Forbes and Hanley^'s work, the
controversy has been continued with unabated ardour ;
and to the list of naturalists who have taken a part in
it, other names may be added as supporters of the under-
mentioned theories.

Mechanical. Mr. Robertson and M. Fischer.

Chemical. Dr. Mantell, M. Thorent, and Mr. Reeve.

M. Cailliaud now contends that both methods of per-
foration are adopted by the same kind of mollusk ac-
cording to the material acted upon ; and M. Bouchard-
Chantereaux, who was at first in favour of the mechani-
cal theory, is now strongly of opinion that a corrosive
secretion of the animal is the agent of perforation.

But there is another point of view in which the ques-
tion may be considered, and which does not appear to
have received any attention, although in my humble
judgment fully deserving it.

Nearly 130 years ago, a very learned but eccentric
Dutch philosopher, named Sellius, wrote and published,
for the benefit of his country, an elaborate monograph on
the Teredo. In this remarkable production he discussed
at great length, and in the most exhaustive style, all
the various theories which had been propounded up to

II.] INTRODUCTION. xU

that time as to the means by which the ship-worm bores
into wood. He showed conclusively that their shells
could not be the instruments of perforation ; and he
asked how it was possible that the extremely tender
shell of the young Teredo (in fact a mere film) could
make a hole in solid oak, a material ten times harder
than itself. Besides, as he justly remarked, the form of
the tube is evidently not the result of an auger-like in-
strument, because it is broader at the bottom than at
the top and sides. The conclusion he formed, after a
most laborious and impartial investigation, was that the
Teredo perforates by suction, aided by continual mace-
ration and softening of the wood. One of his numerous
quotations from the ancient poets, in support of his
argument, may be here appropriately repeated. It is
from his favourite, Ovid : —

" Quid magis est durum saxo? quid moUius unda?
Dura tamen molli saxa cavantur aqua."

I profess myself to be a follower of Sellius ; and I
am convinced that the sole instrument of perforation by
the Mollusca of stone, wood, and other substances, is in
every case their foot or muscular disk, which is closely
applied to the concave end of the hole and is constantly
suppHed with moisture through the glandular tissues of
the body. The strength of this organ may be easily
tested by any one who tries to remove a limpet from its
native rock, after having touched it and thus given it
due notice of his intention. By this simple, yet gradual,
process the fibres of wood or grains of sandstone may
easily be detached or disintegrated, time and patience
being allowed for the operation. When it is considered
that the hole made by an adult Pholas or Saocicava is
only a few inches deep, and that an aged Patella scarcely
penetrates a quarter of an inch into a limestone rock.

xlii INTRODUCTION. [CH.

there can scarcely be a question that these moUusks
have abundance of time to effect their purpose. It is
said that even the hardest marble is not proof against the
softest impressions, and that the big toe of St. Peter's
statue in the Vatican has been nearly worn away by the
lips of fair devotees. The osculatory process is not un-
like that of suction.

Occasional appearance and disappearance. — Both sea
and land furnish instances (some of which are difficult
to explain) of the periodical appearance and disappear-
ance of certain species of Mollusca in particular places.
Their arrival and departure are often sudden and seem-
ingly capricious. In the case of marine species, this
phenomenon is probably the result of changes in the
course of tidal and other currents, as well as of the
migratory habits of fish. These currents, by accumu-
lating or removing deposits of mud, sand, and gravel,
wliich afford shelter and food to Mollusca, conduce
greatly to their congregation or dispersal. When such
deposits are rapidly formed, the shell-bed becomes co-
vered up or silted; and the Mollusca are entombed
alive for the benefit of future geologists. When their
chief enemies, the fish, desert their former quarters and
migrate to another feeding- ground, the Mollusca then
increase and multiply, being unthinned except by the
tigers of their own kind, or occasionally by the curious
conchologist, or by all-devouring death. The destruc-
tion of shell-beds by marine currents may account for
the prevalent notion that some parts of our sea-coast
(as for example South Devon), which used to yield such
regular and plentiful harvests of shells to collectors,
are now scarcely worth searching, — -it being said that
the shells have " deserted" the coast. The unexpected
occurrence of some kinds of land and freshwater Mol-

II.] INTRODUCTION. xHu

lusca in places where they had not been previously
noticed is not nnfrequent. Many a wonderful tale of a
'' shower of snails^^ has helped to fill the pages of country
newspapers^ arising out of the sudden appearance in a
limited area of Helix virgata and Bulimus acutus, which
are abundant on most of our sandy downs and plains.
This has been sometimes caused by a mere change of
wind to the south-west^ in consequence of which the air
has become charged with moisture, and tempted all the
snails to leave their retreat at the roots of grass during
the night, and to present themselves in the morning to
the eyes of astonished rustics. It is not, however, so
easy to account for some kinds of freshwater snails (e. g.
Limn(Ba glutinosa) being found in the same spots so
abundantly some years, and scarcely at all in others, as
has been noticed by Mr. Bridgman of Norwich. This
is one of the minor, but numerous, problems in the pre-
sent branch of Natural History which still remains to be
worked out, and the solution of which will reward the
diligent and observant conchologist.

Tenacity of life. — Many of the Mollusca, as before
remarked, pass the winter in a state of torpidity, their
vital functions being apparently suspended during hiber-
nation. But some of the land-snails have been known
to live many years shut up in boxes and drawers, or
affixed to tablets as specimens. This capability of sub-
sisting for a long period without food is probably owing
to the snail being able to close its shell by an epiphragm,
which not only prevents the evaporation of its natural
moisture, but also produces a kind of protracted hiber-
nation. Miiller relates that some snails, from which he
had cut off their heads, lived more than a year in this
state without food, crawling about, and at the usual
time forming their winter epiphragms. Some marine

xliv INTRODUCTION. [CH.

Mollusca, both univalve and bivalve, possess also a cer-
tain power of endurance under altered conditions. Thus
Trochus lineatus, which inhabits rocks only uncovered
at low water, can live in a warm room for a fortnight ;
and specimens of Mya arenaria, which burrows into
muddy gravel in the sublittoral zone, have been noticed
by Mr. Rich (an intelligent collector and dealer) to sur-
vive their captivity for three weeks, being all that time
in apparently a healthy state (evidenced by the with-
drawal of their tubes when touched), at the end of which
period they were killed for commercial purposes. No
sea- water was supplied in any of the above cases. The
gills must have been kept moist by the fluid contained
within the mantle — a provision nearly similar to that by
which the camel is able to endure the heat and fatigue of
a journey across the desert after having filled its paunch
with a stock of water. M. Joly observed with respect to
some freshwater mollusca (^/iof/ow/a cygnea and Paludina
vivipara), that they maybe frozen up, and kept for some
time enclosed in ice, without being killed. Some of the
Paludincs even produced young after being thawed *.

Age. — Little or nothing is known with respect to the
duration of life in the Mollusca. According to Sir
Emerson Tennent, the pearl oysters of Ceylon only live
seven or eight years ; and it is said that snails do not
attain a greater age. This is not improbable as regards
the latter, because most of them become adult at the
end of their first year. Whether the numerous laminae
of old oyster-shells afford the same indication of an-
nual growth as the rings of a forest tree is another
question.

Resume. — In concluding this chapter, I cannot do
better than quote the resume given by M. Moquin-Tandon
* Comptes Rendus, 1843, xvi. p. 460.

III.] INTRODUCTION. xlv

of his admirable observations on the land and freshwater
Mollusca of France : —

^' Les Mollusques ont des ruses et des industries, des
sympathies et des inimities, des guerres acharnees et
des amours bizarres. Beaucoup sont a la fois male et
femelle, et par suite pere et mere .... Malgre leur
apathie apparente, les Mollusques sont des etres qui ne
manquent pas d^intelligence. Leur vie privee et leur
vie commune nous montrent des details extremement
curieux.^^

CHAPTER III.

SHELLS.

FORMATION. COMPOSITION. SHAPE. NIJCLErS. GROWTH.

COLOFR. DECOLLATION. EROSION. OPERCULUM. EPIDERMIS.

Formation. — The shells of Mollusca are formed by a
secretion from glands of the mantle or cloak. In uni-
valves this part of the body only covers the front, and in
most cases surrounds the head like a loose collar ; but
it is very flexible, and it can be withdrawn or folded
back nearly to the top of the spire to repair a fracture
of the shell in that part. In bivalves it is double, like
the cover of a book.

Composition. — Carbonate of lime is the main ingre-
dient ; and the sheUs of Mollusca difi'er from the bones
of vertebrate animals, as well as from the shells of crabs,
sea-eggs, and birds^ eggs, in the absence of phosphate of
lime. In all these cases, however, the mineral ingre-
dients are cemented together by an animal gluten.
According to M. Delacroix, the shell of a Helix pomatia

Xlvi INTRODUCTION. [CH.

is composed of the following materials, in every 100

parts : —

Organic matter 18*64

Carbonate of lime 64*96

Other mineral substances, undetermined... 16 -40/

10000

The structure of some shells is fibrous, and of others
crystalline; and they differ considerably in the degree
of compactness. Nearly all the secrets of this wonderfid
laboratory have been made known through the researches
of Mr. Hatchett, Dr. Carpenter, and others; but no
philosopher has been able to explain why this process of
formation has continued from generation to generation
in the same uniform mould, according to the nature of
each species, or how the newly-born MoUusk works out,
with unerring and undeviating instinct, the pattern
which was originally designed by its Creator. Humboldt
justly observed that there are mysteries beyond our com-
prehension ; and it might be good for us that some check
should be put on the overweening pride of intelligence
in the " audax lapeti genus.'"

Shape. — All shells assume the form of a cone. Uni-
valves are generally spiral, so as to accommodate the folds
of the body. Even the common limpet {Patella vulgata)
has a distinct spire in its embryonic state, resembling
that of Fissurella or Emarginula. The Chitons are in
some respects abnormal, having several testaceous joints,
which overlap each other, like the plates of ancient ar-
mour or the scales of a fish; but all these joints taken
together may be considered as forming a depressed cone
of greater length than that of a Patella, the lines of
growth on each side of the apex (which is compound in
Chiton) being equally symmetrical in both cases. Bi-
valves offer no exception to this conical law of growth,

III.] INTRODUCTION. xlvii

the apex or nucleus of each valve being analogous to the
same part in a spiral shell ; but in bivalves the deposit
of shelly layers is formed on both sides, in consequence
of the mantle or organ of secretion being double. Every
part of the shell, whether univalve or bivalve, enlarges by
growth in the same relative proportion.

Nucleus. — This part of the shell furnishes the concho-
logist with an important character of distinction. Odo-
stomia, Nassa, Cerithiopsis, lanthina, and many other
genera of univalve shells have the apex of their spire
differently formed. In the adult Cyprcea (or Cowry),
the whole of the spire, including the apex or nucleus,
is covered and concealed by an extraneous deposit of
shelly matter; and the same process, although to a
partial extent only, takes place with regard to the genus
Marginella. In many spiral shells the upper whorls
(which originally formed the nucleus) are deserted by
the animal, in consequence of the volume of its body
having increased so rapidly that these whorls were too
small to receive any part of it, and they therefore became
unnecessary.

Growth. — Owing to the difficulty which exists in keep-
ing and observing Mollusks in a state of confinement for
any length of time, and especially those which live in the
open sea, very little is known as to the mode and rate
of their increase. Some interesting experiments on the
growth of land-shells were, however, made by Mr. E. J.
Lowe and communicated to the Royal Society in 1854 *.
The result of his observations is as follows : — 1st, The
shells of Helicidce increase but little for a considerable
period, never arriving at maturity before the animal has
once become dormant (or hibernated). 2nd, Shells do
not grow whilst the animal remains dormant. 3rd, The

* Proceedings, vol. vii. p, 8.

Xlviii INTRODUCTION. [CH.

growth of shells is very rapid when it does take place.
4th, Most species bury themselves in the ground to
increase the dimensions of their shells. Helix pomatia
and many other shells retreat for that purpose in summer,
ha^dng their heads and the mouths of their shells down-
wards (this position being reversed during hibernation) ;
H. rotundata burrows into decayed wood for the same
purpose; while Pupa umbilicata, Clausilia nigricans [C.
ruyosa) , and Bulimus obscurus bury their heads only while
the increase takes place. With regard to marine shells
it may be observed that sea-water does not everywhere
contain the same relative proportion of mineral and
chemical ingredients, and that the admixture of fresh
water has a material effect on the substance, texture, and
composition of sea-shells. In estuaries, where the water
is brackish, oyster- shells are smaller and thinner than
usual, owing to the deficiency of calcareous salts ; while
the shells of oysters procured from considerable depths
in the open sea and at some distance from the land are
remarkably large, thick, and heavy.

Colour. — The dye by which the outer layer of shells
is stained, and which often forms bands, streaks, spots,
and other markings of the most beautiful and varied
hues, is secreted by special glands of the mantle. Owing,
however, to some defect in this organ of secretion, the
colouring-matter is occasionally wanting ; and nearly
every kind of shell, which is usually tinted, has what is
termed an " albino " or white variety. This is the case
with resrard both to land and marine Testacea.

The late Professor Forbes, in a paper which was
published in the ^ Proceedings ' of the Royal Society *,
entitled '^ Note on an indication of depth of Primseval
Seas, afforded by the remains of colour in fossil Tes-

» Vol. vii. p. 21.

III.] INTRODUCTION. xlix

tacea/^ observed that^ ^^ in our own seas, Testacea, taken
from below 100 fathoms, even when they were indivi-
duals of species vividly striped or banded in shallower
zones, were quite white or colourless ; that between 60
and 80 fathoms striping and banding were rarely pre-
sented by our own shells, especially in the northern
provinces ; but from 50 fathoms shallow-wards, colours
and patterns were well marked/'

I cannot help thinking that there must have been
some mistake as to the first and second of these obser-
vations. At least, my own experience induces me to
form a different conclusion.

Instances of depths exceeding 100 fathoms in our seas
are very rare. I only know of two. One of them is
a submarine trough off the Mull of Galloway, called
" Beaufort's Dyke,'' where the depth is 145 fathoms ; and
the other is a pit in the Sound or Sleat of Skye. The
results of dredging in Beaufort's Dyke are recorded in
the ^ Annals of Natural History"^.' Although shells
usually inhabiting comparatively shallow water, and
distinctly striped or banded [Tapes virginea and Venus
ovata), were obtained alive from this remarkable depth,
no deficiency of colour or markings is noticed in the
account of these results. In the other case, I can state
from my own knowledge that the shells were as highly
coloured and the markings quite as vivid as in specimens
found at a depth of 30 fathoms in another part of the
Sleat of Skye. Soundings were taken with Massey's
patent log, and living Testacea were brought up in the
dredge from 118 fathoms. On this occasion Captain
Otter was with me, and I had the benefit of his great ex-
perience in such matters. Last year I dredged for some
weeks off the Shetland Isles at depths between 60 and

* Vol. X., Sept. 1842, p. 21.

J INTRODUCTION. [CH.

80 fathoms ; and not only were live shells which I pro-
cured from those depths as brightly coloured and marked
with as distinct patterns as shells of the same species [e.g.
of Trochus ziziphinus), taken at low- water mark, but
colourless or white varieties of such species were found
in the same spots. The Star-fishes lately got by Dr.
Wallich in the Arctic Sea from a depth of 1260 fathoms
still retain their former colours ; and, during the recent
expedition of Torell and other Swedish naturalists to
Spitzbergen, a portion of the sea-bottom was brought up
from a depth of 1400 fathoms, when, among other ani-
mals of different types, a Crustacean of bright colours is
said to have made its appearance. The extent to which
light penetrates into the abysses of the ocean, as well as
the mode of its transmission, does not seem to be known.

Decollation, — Some univalve Mollusca, both terrestrial
and aquatic, the shells of which have a long and slowly
enlarging spire, desert the first or top whorls, and get
rid of them by a process called decollation or truncature.
The suture, or point of junction between this part of the
spire and the rest of the shell, is usually very slight ;
and the animal effects the process of decollation by
])urying itself in the earth if a land- snail, or rubbing
its shell against a stone or other hard substance if a
freshwater or marine species, in order to disengage itself
from the empty and useless whorls. Before doing this,
however, it reconstructs the top of its spire by forming
a hemispherical plate of shelly matter between that part
of the shell Avhich is to be retained and the empty top.
Among land-snails Bulimus decollatus is a well-known
instance of this peculiarity, among freshwater snails
Limnaa glabra, and among the marine univalves Trun-
catella truncatula.

Erosion. — The outer layers of the shells of aquatic

III.] INTRODUCTION. li

Mollusca, as well bivalve as univalve^ are frequently ex-
coriated or decorticated, and sometimes to a considerable
depth when the shell is thick, as in Unio margaritifer,
or the pearl-mussel. Several marine species, especially
those oiAstarte, Mytilus, and Littorina, are also affected
in the same way. Various theories have been put for-
ward to account for this erosion. In the case of fresh-
water shells, many naturalists have supposed that it is
caused by gaseous action, some have attributed it to the
attacks of Myriapodous insects, a few to excavation by
the eggs of Neritina fluviatilis, MM. de Saulcy and Fis-
cher, as well as Mr. Bland, to other Mollusca eating away
the calcareous matter for the purpose of constructing
and repairing their own shells, and MM. Cuigneau and
Lespinasse to parasitic Confervse and other hydrophytes.
But as this phenomenon is not confined to freshwater
shells, some other explanation must be sought for. It
is very probable that the former class of cases may be
attributable to chemical action, and especially that of
sulphuretted hydrogen ; but in the other, and perhaps
all the cases, the effect may be produced by another
cause. Mr. Grove suggests that it may be owing to the
want of homogeneity in the substance of the shell, and
that the slightest and almost imperceptible inequality in
the surface would result in an electrolytic action of the
water, which would gradually dissolve portions of the
shell. Sea-water is more likely to produce this effect
than fresh water, by reason of the stronger galvanic pro-
perty of the former. Corrosion of metals by water or
moisture may be due to the same cause. As the sub-
ject does not appear to have received much attention in
a chemical point of view, I trust the following remarks,
from so great an authority as Mr. Grove, wiU help to
throw some light upon it. The shells which I submitted

c2

lii INTRODUCTION. [CH.

to his examination were those of Littorina litorea, or the
common periwinkle.

" March 26, 1862.

^' Dear Jeffreys, — As you wish me to put on paper
the suggested explanation of your difficulty, viz. why
it is that substances apparently homogeneous are cor-
roded in patches or irregular hollows, I endeavour to do
so, premising that it is only theoretical and may be
found not to accord with all vour facts.

" If a plate of pure zinc be immersed in dilute sul-
phuric acid, little or no chemical action takes place ;
but keep in contact with the zinc another metal, say an
iron nail, and the zinc is rapidly oxidated and dissolved,
hydrogen being evolved from the surface of the iron. The
action is most rapid at the points most proximate to the
iron ; so that, if the nail be laid upon the zinc, both being
immersed in the liquid, the iron would seem to eat its
way into the zinc. If a few iron filings be placed upon
the zinc, the action will be similar, but Avill begin more
slowly and increase as the points of iron are exposed,
these latter Ijeing protected to a great extent by their
being negative and coated T\ith hydrogen. If an in-
finitesimal quantity of copper be dissohed in the acid, it
will be precipitated in a metallic state on the negative
points and make these permanent centres of action. So,
if no iron be made to touch the zinc, after a time some
want of absolute homogeneity is sure to determine a
chemical action ; and as any trace of metal existing in
the solution will by this chemical (or, rather, electrolytic)
action be deposited on the negative points, or those
least attacked, the action will continually increase, and,
instead of being uniform, mil be in patches around the
negative centres. Thus a piece of common zinc of com-
merce which contains small portions of iron and tin will

III.] INTRODUCTION. " liii

be corroded in pits or holes. With imperfectly con-
ducting bodies the action is similar; at very short di-
stances they conduct^ and the action spreads or extends
from a point to the surrounding points. Sometimes^, in-
stead of forming a patch, the chemical action eats its
way in a dendritic form, pursuing the ramifications of
either the more oxidable portion of the substances or
of the more accessible negative points. The slightest
superficial change will produce a corresponding corro-
sion : thus, if you were to breathe on a polished plate of
iron and wipe away the condensed moisture from half
the plate, leaving that on the other half to evaporate,
the iron would subsequently rust in a dififerent manner
on the two parts. If you electrify a plate of glass having
letters cut in paper on it, and subsequently expose it
without the paper to hydrofluoric acid, the parts pre-
viously uncovered will be attacked ; and so, if you simply
allow the paper letters to remain on the ^lass for some
time (say a day or two), and then blow them off" by
breathing on the glass, or by the vapour of hydrofluoric
acid, the letters will be made manifest. You may easily
imagine a number of other instances. The efiects all pro-
ceed from a want of perfect homogeneity, either original
or impressed by some very trifling circumstance, and
from the fact that, points of action having once been
established, the corrosion is increased by the eff'ects it
itself produces and the deposits it forms. A dentist, to
cure a carious tooth, scrapes out all the diseased parts,
&c. Another cause of localized destructive agency is that
of crystallization : if a plate of common earthenware
has been used to contain saline solutions and is then
allowed to dry and is put aside, it will efi^loresce in spots
and a sort of vegetation will sprout up here and there,
disintegrating the plate in patches. I have now in my

liv INTRODUCTION. [CH.

laboratory a piece of earthenware, which was used merely
to hold a small voltaic battery and catch the chance
spillings of sulphate of zinc from the cells, which is
here and there eaten out in deep pits, and in other places
pockmarked with small spots. If this dish had been
exposed to alternations of sea-water and air, a similar
effect would have taken place ; and yet there was no per-
ceptible want of homogeneity in the dish at first.

" The tree-like corrosions between the object-lenses of
old telescopes are probably due to the same causes, or one
of them. The old experiments of the zinc and silver
tree are instances of the same sort of action. Wet a
glass plate with nitrate of silver and hold the point of a
pin in it, the acid leaves the silver for the copper ; but
the silver is not deposited in a uniform circle, but in a
beautiful arborescent form. Old wine-bottles are fre-
quently found corroded, some in spots, others in tree-
like figures.

" I believe the above will help to solve the problem
you are investigating ; at all events, I can offer no better
solution. (' Ever yours,

"W. R. Grove /^

I may add that limestone rocks are fretted in the
same way as the shells of Purpura lapillus and a stunted
variety of Mytilus edulis which are found on these rocks,
all having the same calcareous basis. The erosion of
bivalves is greater at their beaks, where the connexion
between the animal and the shell is weaker than in other
parts. This is also the case with the points of univalves.
The action appears to be prevented by the epidermis.

Operculum. — The horny or shelly plate (" pot-lid ^^)
by which many univalve Mollusca close the mouths of
their shells is attached by a strong muscle to the back
or upper surface of the foot ; and it serves to protect the

III.] INTRODUCTION. Iv,

moUusk from the attacks or intrusion of other animals.
It is often formed on the same plan as the spire of the
shell, but it differs from the latter in being nearly always
compressed instead of tubular. The only exception to
this rule of which I am aware, as far as regards European
MoUusca, is that of Zanclea, where the operculum is
pyramidal. It has, indeed, been stated that the opercu-
lum o^Adeorbis siibcarinata is cellular ; but the supposed
operculum of this rather common shell belongs to the
Foraminifera and is the Spirillina perforata of William-
son. The mistake arose from the shells and Forami-
nifera having been found by the late Mr. William Clark
in the same parcel of dredged sand; and as the latter
exactly fitted the mouths of the former, he concluded
that the Foraminifera were the opercula of the shells.
The original specimens are now in my collection. A few
of our native MoUusca, as well land as freshwater and
marine {e. g. species of Cyclostoma, Neritina, Bythinia,
and Phasianella), have calcareous or shelly opercula.
The opercula of other kinds are horny and usually thin.
The operculum of Neritina and Jeffreysia is furnished
with an excentric process, or apophysis, which enables
it to fit more closely into the shell, like the bolt of a lock
into the box. In most cases the operculum is spiral;
but in Paludina, Phasianella, and a few other genera it
is concentric. The whorls on some of the horny opercula
nearly correspond in number with those of the shell,
being multispiral in Trochus and paucispiral in Littorina ;
but this rule is not universal. There is a difference of
opinion among physiologists as to the mode in which the
operculum is formed. Some consider the mantle as the
organ of secretion, others the foot, while according to a
few it is formed by the glands of a special organ called
the operculigerous lobe. Adanson and lately Dr. Gray

Ivi INTRODUCTION. [CH.

have likened the operculum to the second valve of bivalve
shells ; but these do not appear to be homologous organs,
although equally serving to cover the body of the mollusk.
Calcareous processes, which answer the purjDOse of oper-
cula, occur in a genus of land snails [Clausilia), as well
as in marine bivalves belonging to the genus Teredo.
In the former case this process consists of a t^Wsted plate,
which is not attached to the animal, but acts like a spring-
door in closing the interior of the shell ; and in Teredo
there are two such processes, each shaped like a spatula,
and attached to the body by strong muscles. Specimens
of Buccinum undatum and Fusus antiquus are sometimes
bioperculate ; and occasionally one of these opercula is
divided into two, or even three laminse, which are piled
upon each other, so as to give the specimen the appear-
ance of having three or four opercula. In some cases of
this malformation in Buccinum undatum, the two oper-
cula are too large to be contained within the shell, and
overlap each other ; but in others they are abortive and
widely separate from each other. They are found in
individuals of all ages ; and they appear to be congenital,
and not the result of accidental loss and renewal. In
one instance of malformation connected with this subject,
which fell under my observation, a deficiency, instead
of a redundancy, of opercular formation occurred, and
may have been caused by disease. A living specimen of
Fusus gracilis, which I procured last year in the Shetland
Isles, had no operculum or even the scar or trace of any
such process. The back of the foot, where the oper-
culum was placed in other specimens of the same kind,
was merely hardened by exposure. In Buccinum Hum-
phrey sianum the operculum is very small, and only covers
part of the aperture or mouth of the shell when the animal
withdraws itself. In some species of the genus Mangelia

III.] INTRODUCTION. Ivii

it is entirely wanting. M. nivalis has a distinct operculum ;
while M. Ginnaniana (which belongs to the same section
of this genus and is found in company with M. nivalis
in our northern sea) has not the slightest vestige of an
operculum. Exceptional instances of the same kind occur
in the tropical genera Valuta, Conus, and Oliva. But a
remarkable peculiarity is presented by some species of
lanthina. which are furnished in their embryonic state
with perfect opercula. These processes afterwards dis-
appear, being probably absorbed by the animal when the
shell becomes too large to be thus closed. Sars, Van
Beneden, and Vogt have shown tha-t the fry of many
Nudibranchs, as well as of that anomalous moliusk
Elysia viridis, have Nautiliform and operculated shells.
The fry of Dolium jjerdix, which has also an operculated
shell in this stage of grow^th only, is so unlike the adult,
that the late Professor Forbes constituted for it a new
genus of another order, under the name oi Macgillivrayia.
The fry of a curious land moUusk {Parmacella), which
partakes more of the nature of a slug than a snail, is said
to be enclosed in an operculated shell. In the adult this
shell becomes more rudimentary and only covers a small
part of the body. This is a case of retrogressive, rather
than of " progressive development.^^

Epidermis. — Most shells have an outer horny covering,
called an " epidermis '* or " periostracon," which appears
to be analogous to the periosteum of bones in vertebrate
animals. Its office is probably to protect the shell from
the chemical action of the air or water inhabited by the
moUusk. It is formed simultaneously with the shell, and
probably by the same organ of secretion. It is usually
glossy, and sometimes resembles a coat of varnish. In
Astarte (a genus of marine bivalves) it is thick and
strong. In some of the whelks and land snails it re-

c5

Ivili INTRODUCTION. [CH.

sembles the pile of cloth, and is occasionally produced
into bristles or hairs ; but in most cases it is very thin
and only forms a delicate film. It exists also in shells
which are internal, as those of Limax and Lamellaria, but
not in Cyprcea or the cowry, which is constantly being
lubricated by the mantle. In its nature it appears to
be persistent and almost indestructible, being not unfre-
quently found still adhering to shells in upper tertiary
strata.

CHAPTER IV.

EXTEENAL EELATIONS.

ENEMIES or MOLLrsCA. PARASITES. USES TO MAN : VIZ. FOOD,

MEDICINE, OENAMENT, AND ECONOMY. INJURIES TO MAN.

STUDY OE CONCHOLOGY. PLEASURES AND DRAWBACKS. INCI-
DENTS OP THE PURSUIT.

Enemies of Mollusca. — These soft creatures are the
favourite food of many animals. Man is not the only
one that finds them savoury and digestible, and that
hunts them down with insatiable voracity. The slow-
ness of their movements makes them an easy prey ; and
their shells afford them no protection against their
larger enemies. On land, hedgehogs (and it is said the
fox also), rats, thrushes, ducks and other birds, snakes,
lizards, toads, zoophagous beetles and centipedes pursue
them and greatly thin their numbers. An insect (the
Cochhoctonus vorax) lays an egg in the body of dif-
ferent species of snails, which, when hatched, eats up by
slow degrees the whole of its unwilling host, and then
curls itself up in the spire of the empty shell, until it is
turned into a chrysalis. The Mollusca which live iii
fresh water are devoured by "wild ducks and other birds
of that class, frogs, fishes, leeches, and the larvae of the

IV.] INTRODUCTION. lix

dragon-fly. The innumerable host of marine Mollusca
afford a constant supply of food to sea-fowl of various
sorts, fish (especially the cod, haddock, mullet, gurnard,
halibut, and sole), crabs and other Crustacea, star-fishes,
sea-cucumbers, and Actiniae. No less than 35,000 spe-
cimens of a small bivalve [Turtonia minuta) were esti-
mated by Mr. Hyndman to be contained in the stomach
of a single mullet which had been taken in Lame Lough.
They are not even spared by their own kind. M. Des-
hayes fed some pet snails with chopped-up morsels of
one of their companions, which appeared to be unhealthy
and not likely to survive. Many instances of such
cannibal propensities in the land and freshwater Mollusca
will be found in this volume. Bulla lignaria is a great
tyrant among the smaller marine shell-fish, and uses the
strong plates of its singular gizzard to crush them. All
the whelk-tribe, as well as the Naticce, enfold their testa-
ceous prey in their large feet, and drill holes in the shells,
as before observed, in order to feed on their contents.
The great strength of the shells possessed by some whelks
does not save them from becoming victims in their turn.
I have been informed by intelligent fishermen, that,,jf
their lobster-pots (in which the Buccinum undatum is
often caught) are left a few hours longer than usual, the
shells of the whelks are found cracked ^' like nuts,"
having been cleared out by the lobsters and crabs while
they were fellow-prisoners. Quantities of this kind of
whelk are caught on the Dogger-bank as bait for the cod-
fisheries of Iceland and Greenland. The way in which
gold-fish contrive to extract the animals from fresh-
water shells is curious. When the shell is too large to
be swallowed, the fish puts its mouth to it, and then,
sucking it for some minutes, lets it go. After a while
the snail recovers and withdraws itself from its shell,

Ix INTRODUCTION. [CH.

when the fish again seizes and sucks it, repeating this
operation for hours and sometimes for days, until its
victim is exhausted. Whether the fish kills its prey by
means of any poisonous injection is a question which
might be answered by some observant naturalist who
not only has an aquarium but makes good use of it. In
consequence of this continual and internecine warfare,
an excessive increase in the number of molkisks, both
on land and in water, is checked.

Parasites. — Very little appears to be knoAvn with re-
spect to the animal and vegetable parasites which are
nourished by the juices or excretions of living ^loUusca.
On land, several kinds of slug are infested by a small
white mite [Philodromus limacum, Jenyns), which may
often be seen in considerable numbers running actively
over their bodies, but apparently not doing the slugs any
harm, except, perhaps, in sHghtly lessening or interfering
with their secretion of slime, on which these insects pro-
bably feed. The Rev. Leonard Jenyns says that the
most striking feature in the history of this kind of para-
sitic mite is " the circumstance of its not confining its
abode to the external surface of the slug, but often re-
tiring within the body of that animal — effecting its en-
trance by means of the lateral foramen which leads to
the cavity of the lungs.^^ And he observes, " Indeed
I am inclined to think that tliis ca^dty is its principal
residence, whence it only comes forth occasionally to
ramble about the surface of the body. In one instance
I confined in a close box a slug which, to all appearance,
was free from parasites. On opening the box a day or
two afterwards, I observed very many crawling about the
slug externally, all of which would seem to have pro-
ceeded from the pulmonary cavity. On another occa-
sion I observed these insects running in and out of the

IV.] INTRODUCTION. Ixi

cavity at pleasure ; and some which I saw retire into it
never reappeared, although I watched the slug narrowly
for a considerable time. It is remarkable that the slug
appears to suffer no particular inconvenience from these
parasites, and even allows them to run in and out of the
lateral orifice without betraying the slightest symptoms
of irritation.^-' M. Barthelemy has noticed in the eggs of
one kind of slug numbers of a small Nematoid worm,
which he has named Ascarioides limacis. These worms
are present in the e^^ at the moment of its being laid,
having been previously deposited by the parent worm
while living in the ovary of the slug. The young worms
must therefore have been introduced into the q^^ while
it was being formed. They appear to adopt the same
course as the parasitic larvse of the Ichneumon when
they are deposited in the body of a grub, and to spare the
vital parts of the embryo on which they feed, until the
period has arrived for their own development. In fresh
water, the pond-mussel (Anodonta) constantly entertains
a large party of parasites, consisting of another kind of
mite {At ax ypsilophora, Buntz), which are so tenacious of
life, that after their host has been put into boiling water
and killed they survive and crawl about as if nothing
had happened to them. A kind of hair-worm [Gordius
inquilinuSy Miiller) attaches itself in clusters to Limncea
stagnalis and many other freshwater snails. In all pro-
bability, however, these are not true parasites, and only
attach themselves to the Mollusca for the sake of the
shelter afforded by their shells or mantles, obtaining
their food from the water and not from the snails, be-
cause their heads are always seen outside and in active
motion when the snails are crawling. Each genus, if
not every species, of freshwater snail may have its own
pseudoparasite. Limncea, Planoy^bis, Physa, Ancylus,

l.xii INTRODUCTION. [CH.

and Bythinia are similarly infested ; but they are of
various sizes, and some of them have different habitats.
In the sea, a small kind of pea-crab {Pinnoteres vete-
rum) is frequently found inside the mantle of Cyprina
Islandica, Modiola modiolus (or the great horse-mussel),
and Phina pectinata, taking up its abode in these snug
quarters for parasitic purposes, and not (as was imagined
by the too credulous Pliny) in order to warn the Pinna of
the approach of its foes, like a faithful friend or watch-
dog. Professor Kolliker has lately noticed in the shells
of several kinds of Mollusca, both univalve and bivalve,
certain vegetable parasites, which he regards as unicellular
^ fungi. They form minute tubes, which run straight
through the pores or fibres of the shell. He thought
it probable that these vegetable parasites dissolve the car-
bonate of lime contained in the shell by means of an acid
which they may have the power of secreting. But the pro-
cess by which shells are perforated by vegetable as well
as animal organisms does not seem to be understood, and
requires much elucidation in a chemical point of view.

Uses to Man. — {Food.) — We naturally consider our-
selves (as the " lords of the creation ^^) the sole pivot round
which all other creatures turn, without much sympathy
with them or regard for their wants and feelings. But
the countless and complicated links of the chainwork in
which all Nature is involved are so closely and wonder-
fully connected together, that not one of them can be
broken or displaced without interfering with the eco-
nomy of the whole. Much of the animal food which we
consume has been nourished at the expense of other
creatures, which in their turn have subsisted upon smaller
organisms ; and this process of destruction is repeated
until the bottom of the scale of animal life has been
reached. Then the varied and inexhaustible stores of

IV.] INTRODUCTION. Ixiii

inorganic substances are called into requisition, and
these again are supplied and renewed from decayed par-
ticles of once living matter. Thus a never-ending cycle
of waste and renewal takes place^ in accordance with the
beneficent design of the Author of all things !

The principal use which the MoUusca subserve^ so
far as man is concerned, is to supply him, directly and
indirectly, with an abundance of food. It is true that this
kind of food is not so grateful to us in a civilized as in
an uncivilized state ; but one of our most favourite lux-
uries is derived from this source, and the oyster, fortu-
nately, inhabits those regions where civilization has
attained its present height of perfection. Many other
kinds of shell-fish, such as scallops and cockles, are not
less wholesome than the king of the Mollusks, and are
by no means to be despised ; and the ormer (Haliotis
tuberculata) is reckoned a delicacy in the Channel Isles,
when properly cooked. The salt flavour which is so
much relished by a maritime population is imparted by
all the marine MoUusca. The quantity (amounting to
many hundreds of tons) of whelks, mussels, and peri-
winkles which is every year disposed of in Billingsgate
market alone is almost incredible ; and there is no
seaport or adjoining tract of country, especially in the
manufacturing and mining districts, but has a consider-
able traffic carried on within it by a numerous and in-
dustrious class of itinerant dealers in such wares. On
many parts of the Scotch and Irish coasts shell-fish form
a considerable portion of the food of the poorer inha-
bitants; and in a few of our more remote and almost
inaccessible islets (such as Fair Isle and some of the
Western Hebrides) positive starvation would ensue in
winter, if it were not for these unfailing and easy sup-
plies. In an indirect way, the MoUusca contribute still

Ixiv INTRODUCTION. [CH.

more to the sustenance of man, by supporting the innu-
merable shoals of cod, Img, haddock, halibut, and various
other sorts of fish which abound in our seas and pro\ide
a constant livelihood for a hardy race, and through them
for a great part of our population, who, both from neces-
sity and choice, are fish-eaters. Our Continental neigh-
bours, not being so well supplied as we are with sea-fish,
do not disdain any ^^frutti del mare/^ The date-shell
(Lithodomus dactylus), which is extracted with much
labour from the solid rock on the coasts of the Mediter-
ranean, is reckoned a dish fit for an emperor; and M.
Recluz says of a kind of cockle [Cardium l(svigatum)y
" Sa chair est savoureuse et prisee du gourmet/'

The Romans had their oyster-beds, as well as their
Cochlearia or snail-preserves; and Varro, in his 3rd
Book (" De viUaticis pastionibus^'), describes fully the
method adopted by his countrymen for improving the
difiierent breeds of oysters by crossing. The improve-
ment of the breed of oysters, as well as their preserva-
tion, ranks in France as a science, and has received the
name of " huitreculture,'' its professor being M. Coste.
We can, but (alas !) do not, manage these things so
well. Even land- snails are pressed into the service of
the French, and enter rather largely into their cookery.
No one can have traversed the streets of Paris, or of the
larger towns in France, without seeing dishes of Helix
pomatia temptingly displayed in the shops of restaurants,
like kidneys and white-bait in the windows of London
eating-houses. The list of eatable snails in France is
very considerable and comprises some comparatively
small species. " Chacun a son gout !"

[Medicine,) — In our pharmacopoeia of former times a
decoction of snails was much esteemed as a remedy in
pulmonary complaints ; and great numbers of them were

IV.] INTRODUCTION. IxV

unmercifully pounded alive for that purpose. Even in
the present day snail-broth is said to be serviceable as a
lenitive. In France an extract from snails, called ' He-
licine/ is used in similar cases. The spongy plate of
the common cuttle [Sepia officinalis), calcined oyster-
shells, and the Limacella of the large slug [Limax maxi-
mus), as well as "crabs^-eyes^^ (or the concretions of
calcareous matter found in the stomach of the eatable
crab), were used during the last century in the prepara-
tion of certain medicines.

[Ornament.) — When the Romans were the masters of
these islands they ransacked not only our seas and estu-
aries for oysters (those from the Mediterranean being
very scarce and inferior in quality) but also our northern
rivers for pearls, which were extracted from the Unio
margaritifer. This shell, with its accompanying product,
is represented in the Frontispiece to the present volume.
The search for native pearls continued until a compara-
tively modern period, when it was superseded by the
successful prosecution of the true pearl-fishery in Eastern
seas, the valuable and lustrous produce of which threw
into the shade our comparatively worthless and dull
jewel. Other species of freshwater mussel, as well as
the oyster, ormer, sea- mussel, and cockle, and even the
periwinkle, occasionally yield pearls, but of an unservice-
able kind. It is evident, from an examination of the
shells in which such excrescences are formed, that they
are o\ving to an irregular and partial secretion by the
mantle of the nacreous and lamellar substance which
lines the inside of the shell. In all probability the
proximate cause is some extraneous body, and not dis-
ease as was formerly supposed. In freshwater bivalves
the irritating tenacity of parasitic insects and worms
[Limnochares Anodontce and Distoma duplicatum), and

Ixvi INTRODUCTION. [CH.

in marine bivalves the attacks of perforating annelids,
would be sufficient inducements for the shell-fish endea-
vouring to smother or keep out its assailants by secre-
ting an extra quantity of nacreous matter. The nucleus
of many pearls reveals the origin of their formation. A
communication made by Signor Antonio Villa in 1860
to the Literary and Scientific Athenseum at Milan (en-
titled " SulP origine delle perle^^), and another by Mr.
Robert Garner to the Linnean Society in December 1861
(^'^Note on the formation of pearls ^''), will well repay a
perusal by those who are interested in this curious sub-
ject. The unsuccessful experiments made a century ago
by Linne for the artificial production of pearls by the
Unio margaritifer in the rivers of Sweden (and for which
he took out a patent), and the ingenious process invented
by the Chinese, of putting little josses or images of some
incorrodible metal between the mantle and shell of an-
other freshwater mussel, so as to have them coated over
with several layers of pearly matter, are now well known.
Great quantities of the Mytilus edulis are said to have
been collected a few years ago in the estuary of the
Conway, as well as in the North of Ireland, and exported
on account of the Jews, for the purpose of fabricating
mock pearls out of their nacreous linings.

Another testaceous article of commerce in this coun-
try for ornamental purposes is the ^^ ormer " or ear- shell
(Haliotis tuberculata) , which is found abundantly in the
Channel Isles. Many tons of these sheUs are annually
gathered for the Birmingham market ; and their inner
coats of mother-of-pearl are sufficiently thick to make
buttons and studs, or for inlaying.

Shells of various kinds are collected wholesale from
the famous beach of the islet of Herm, and sent to
England for fancy-work. The Romans used shells for

IV.] INTRODUCTION. Ixvii

ornamenting their dwellings. GelFs ' Pompeiana^ (vol.i.
pp. 1.95, 196) contains an interesting description of the
celebrated ^^ Fountain of Shells," which appears to have
been decorated with the Tyrian murex and pilgrim scal-
lop ; and these shells are stated to have been " neither
calcined by the heat of the eruption nor changed by the
lapse of so many centuries." Cicero is said to have also
used shells in decorating a fountain at his Formian villa.
In our own country it was once the fashion to ornament
grottos in the same way.

Among other ornamental uses may be mentioned the
purple dye which is yielded by many shell -fish. The
Greeks and Komans extracted it from Murex trun-
culus and other species which we do not possess ; and
the process of dyeing constituted one of their most
important manufactures. An excellent article on this
subject, considered in a scientific and artistic point of
view, and entitled " Natural History of the Purple of the
Ancients," by Professor Duthiers of Lille, will be found
in the '^Proceedings of the Royal Society' for 1860*.
Dr. Bizio, a distinguished chemist, has also investigated
the nature and properties of these dyes ; and a learned
Scotch divine, the Rev. James Smith, has given, in the
' Zoologist ' for 1849, a classical and elaborate disqui-
sition on the same subject. The common dog-whelk
[Purpura lapillus) of our own rocky coasts, as well as
Murex erinaceus, Scalaria communis , and lanthina com-
munis produce the same colouring-matter, but in a
smaller quantity and of a much less vivid hue -, and it
has never been turned to any account. More than a cen-
tury ago, Borlase, in his ^ Natural History of Cornwall,^
mentions "The purple-marking whelke." He says, "the
juice which marks is in a separate bag, of a yellowish-

* Vol. X. p. 579.

lx\dii INTRODUCTION. [CH.

green when first drawn npon linen, grows a little ruddy
afterwards, till it comes to a faint purple ; when diy,
and the linen washed, it is of a good purple, and rather
betters by age and frequent washing/^ A cambric
handkerchief, which I stained more than twenty years
ago ^vith the dye from the purpuriferous gland of a
dog- whelk, still retains its ^-iolet hue. The pillar lip of
this shell often exhibits the same tinge of colour.
Nearly two centuries ago Lister tried, but in yain, to
fix the purple dye which is yielded in such quantity by
the Planorbis corneus, a freshwater snail.

{Economy .) — Other uses to which the shells of Moi-
lusca are sometimes applied in this country are numerous
and varied, although not very important. The valves
of the great pond-mussel [Anodonta cygnea) make here,
as well as in the North of France, excellent ere am -
skimmers. The mussels are procured by means of a
long pointed stick, which is inserted between the gaping
valves when the animal is feeding, and these closing on
the stick allow it to be drawn up out of the water. The
shell of the almond-whelk [Fusus antiquus) serves our
northern fishermen for a lamp, being suspended from a
nail in the wall or ceiling of their hut by a piece of
string, which is fastened round the shell in a triangular
fashion. The inside is filled with fish-oil, and a wick of
cotton or tOAv is put into the canal at the extremity of
the mouth. This I have seen prepared and used in the
Shetland Isles ; and I doubt whether any antique lamp
could excel it in elegance of shape. In the palmy days
of the Italian and Flemish schools, valves of a freshwater
mussel (named for this reason Unio pictorum) were used
by the gi'cat masters to hold their colom's. Although
they have been superseded by palettes for this purpose,
they are sold by many artists^ -colourmen in London,

IV.]' INTRODUCTION. Ixix

containing a preparation of gold or silver leaf for em-
blazoning. The valves of Pecten maximus and P. oper-
cularis make an ornamental as well as a usefal little
dish for scalloped oysters. Ormers are used in Guernsey
by farmers to frighten away small birds from the standing
corn^ two or three of these shells being strung together
and suspended by a string from the end of a long stick,
so as to make a clattering noise when moved by the
wind. Among other services which the Mollusca render
to man is their indicating an approach of rain or a
change of temperature. Several interesting facts with
respect to this hygrometrical property have been recorded
by Mr. B. Thomas of Cincinnati, U.S., in Dingler^s
^ Polvtechnisches Journal : " and as I am not aware that
similar observations have been made or published in
Great Britain, I venture to direct the attention of
naturalists who live in the countrv to this curious
inquiry. Mr. Thomas states that snails are more
reliable than leaves as natural barometers ; that, in con-
sequence of their never drinking, all the moistm^e they
receive is by absorption of rain, mist, or dew through the
tissues of their bodies, and this thev afterwards exude
at regular intervals, until they obtain a fresh supply
that the colour of certain kinds of snail varies according
to the quantity of moisture retained ; that tAvo days
before rain is about to fall they climb trees, which they
never do on other occasions : and that when thev are
observed to leave the herbage and get on rocks, it is a
certain prognostication of wet weather. Not many
years ago some wonderful stories were afloat as to the
galvanic nature of snails, which it was proposed to
turn to account as a medium of communication between
distant friends ; but this mystery has been eclipsed by
that of spirit-rapping, with Which the molluscan phe-

IXX INTRODUCTION. [CH.

nomenon may perhaps be classed. I have no doubt
that both of these mysteries ^^dll in due time become
equally obsolete and superseded by some other preter-
natural manifestation.

Injuries to Man, — The sum total of the mischief in-
flicted by the Mollusca upon Man is easily told and
reckoned; and it by no means counterbalances the
benefit he derives from them. At sea^ the damage done
to the woodwork of our piers by some kinds of ship-
Avorm {Teredo)) as well as by species of an allied genus
[Xylophaga], is indeed not inconsiderable ; and, before
copper or yellow-metal sheathing was used for protect-
ing the bottoms of our outward-bound vessels, these
marine scourges used to be justly dreaded. The noble
breakwater at Plymouth has also suffered^ although not
to any extent, from the excavations made in its more
exposed parts by a small bivalve {Saa:icava rugosd) ; and,
on some parts of the coast, beds of clay, which served as
natural barriers to w^ard off the action of tidal weaves on
our harbours, have disappeared in consequence of Pho-
lades having chosen to take up their abode in them. On
land, our molluscan foes are more troublesome than
formidable. Turnips and cabbages occasionally suffer
from the partiality of slugs to such succulent food ; and
of course we cannot help sympathizing with the gentle
florist who sees her pet carnation nipped in the bud and
ruined, in consequence of its having been selected by a
hungry or dainty snail for its supper. But the wire-
worm, fly, and grub are far more formidable pests to the
farmer and gardener, and no mollusk has been known
to attach itself parasitically to Man ; so that we may
safely challenge the entomologist in favour of the com-
paratively harmless subjects of this inquiry. Various
remedies have been proposed for preventing the ravages

IV.l INTRODUCTION. Ixxi

of slugs and snails in gardens. The application of lime
has only -a temporary effect ; and it may do as much
harm as good by overstimulating the chemical ingredients
of some soils. An ingenious method has been proposed
for protecting flowers by surrounding the bed with cop-
per and zinc wire, the former being outermost. The
wire should be laid on the ground and kept clear of
dirt, or fixed in such a way that the snails and slugs
must crawl over it to reach the flower-bed. In attempt-
ing to do this, they receive an electric shock, and they find
the sensation so uncomfortable or unusual, that they
never venture to transgress the forbidden boundary. Pro-
fessor Wheatstone assures me that he has no doubt such
a galvanic battery, or " slug-shocker,^^ would answer the
desired purpose.

Study of ConcJiology. — As Wordsworth nobly says^

" Know that pride.

Howe'er disguised in its own majesty,

Is littleness ; that he who feels contempt

For any living tiling, hath faculties

Wliich he has never used ; that thought with him

Is in its infancy."

Besides the interest which belongs to the studv of anv
branch of Natural History for its own sake, Conchology
has other claims on our attention in consequence of its
important relation to Geology. The first consideration
leads us to admire (if our limited sphere of mental vision
does not enable us to fully comprehend) the infinite
wisdom, harmony, and variety of that wonderful scheme
of creation which connects us with all our fellow- creatures
in one common bond of sympathy ; and it also teaches
us a lesson of humility, by showing that all our phy-
sical, and perhaps even our mental, faculties are shared
with us by other animals, far indeed inferior to us in
organization, but equally enjoying the prescient and

Ixxii INTRODUCTION. [CH.

beneficent care of Him through whom ^' we all live and
move and have our being." The second consideration
discloses to us the ancient history of the globe which
we inhabit; and, by reason of the durable nature of
molluscous shells, which is capable of resisting the
action of many forces that destroy other organisms, we
can apply our knowledge of their living structure and
habits to the elucidation of some of those difficult pro-
blems which are necessarily involved in the study of
Geology. For this reason, shells have been aptly called
the " Medals of Creation ; " and they are as important
to this science as coins are for making us acquainted
with the history of past nations. The advantages and
pleasures of the fascinating pursuit of Natural history
have been so often and so forcibly expatiated upon by
popular writers on the subject, that I can hardly hope
to add anything to promote its interest. As a branch
of education, the benefit of such studies is incalcu-
lable. They impart and inculcate, in the most agree-
able form, the faculty of sound reasoning, the continual
exercise of memory, a love of order, habits of observation,
♦ and, above all, the necessity of truth. No one can hope
to be a naturalist who is wanting in accuracy. As a
source of intellectual gratification, no pursuit of any
other kind can excel it. It is entitled to bear equal
rank with the pleasures of " Hope," " Memory," " Ima-
gination," and " Literature," all of which have had able
poets and writers to celebrate their praises ; and, although
the great orator of ancient days had letters especially in
his view, his admirable remarks Avill apply with equal
force to the study and love of Natural science. After
premising that such pursuits are most worthy of the
dignity of a thinking being, as well as most humanizing
and li])eral in their tendency, he says, ^' Other mental

IV.] INTRODUCTION. Ixxiii

occupations are not suited either to every time, or to
every age or place : these studies, however, foster our
earlier years and impart pleasure to our declining ones ;
they adorn our prosperity, and afford a refuge and solace
in adversity ; they delight us at home, but do not hinder
us in the discharge of our public duties; they are our
companions in the evening, abroad, and in the country "^/^
We are, I fear, too prone to indulge in a patriotic
boast, that our naturalists are more painstaking and
numerous than those of other nations ; but, with regard
to conchology, I must admit that we are far excelled by
the French. Moquin-Tandon stands preeminent in the
elucidation of the anatomy, physiology, and habits of his
native land and freshwater Mollusca ; and the number
of his countrymen to whose works on the subject of con-
chology he has refen^ed in his admirable ' Histoire Natu-
relle des Mollusques terrestres et fluviatiles de France '
is no less than 168. Can we show any work at all equal
to his as regards knowledge or labour on our own land
and freshwater Mollusca, or one-half of the above num-
ber as British writers on conchology, from Lister to
the present time? It is true that the marine fauna
of France has not been studied with equal assiduity and
success ; but our superiority in this respect may be owing
to the greater extent and variety of sea-coast which we
possess, as well as to our habits as a maritime people,
evidenced by the fleet of yachts and pleasure-boats which
crowd many of our harbours. In the thinly populated
and comparatively isolated region of Scandinavia, but
where opportunities of marine investigation are peculiarly
favourable, we find a host of able and zealous concholo-
gists (such as Nilsson, Loven, Sars, Hisinger, Steen-
strup, Oersted, Moller, Morch, Asbjornsen,Malm, Torell,
* Cicero, Or. pro Arch. poet. (ed. Anth.) p. 158.

d

Ixxiv INTRODUCTION. [CH.

and Bergh), who are not far, if at all, behind us in the
race, and are worthy successors of the great Linne,
Miiller, and Fabricius. Nor are the conchologists in
Germany, Italy, and other parts of the European con-
tinent few or unknown, as may be seen by reference to
the list of authors which is appended to this volume.

Pleasures and drawbacks. — In the pursuit of this as
well as of other branches of Natural History, not the
least part of our enjoyment is derived from sympathy
with other naturalists, or from what may be, perhaps
not inappropriately, termed *^^the freemasonry of the
craft/^ In my occasional visits to the Continent, I have
invariably experienced the greatest kindness from many
who were only known to me by name; nor is such
good-fellowship less hearty at home than it is abroad.
On one occasion my hobby of snail -hunting perhaps
saved me from some trouble or annoyance. In the spring
of 1850 1 was travelling mth my wife through Lombardy,
when, during a mid-day halt at Ro\dgo to bait the horses,
I could not resist taking a walk outside the barriers,
accompanied by our courier, who had been previously
useful to me in assisting to collect shells. At the end
of an hour or so we returned, but found at the barrier-
gate an Austrian official who demanded our passports.
This was at first a poser, as I had left in the carriage at
Rovigo the document which was at that time so indis-
pensable for passing through the North of Italy. All
explanations appeared to be unavailing, when the courier
pulled out of his pocket a collecting-box full of live snails,
and at once satisfied the smiling official by allowing this
proof of our innocence with the remark, " Ecco, Signore,
i nostri passaporti \"

The reminiscences and association of ideas arising out
of the work of collection are often very pleasant, but

IV.] INTRODUCTION. IxXV

occasionally not unfranglit with sadness. A specimen
will in after days bring back to our minds many an in-
cident, which else had been forgotten, of woodland and
seaside rambles, of nautical adventure, of excursions in
foreign lands, and (above all) the companionship of be-
loved but lost friends, who have, alas ! left this fair world
and us. The bitter drop will arise from the midst of
the sweet and bubbling spring of pleasure, and give us
pain even among the encircling flowers. It is still the
same as when Lucretius wrote —

" coronse, serta parantur ;

Nequicquam : quoniam medio de fonte leporum
Surgit amari aliquid, quod in ipsis floribus angat."

Incidents of the pursuit. — It is not always easy to
enlist fishermen in the cause of science. Most of them
readily promise, but seldom keep their word ; and they
do not seem to comprehend how any sensible person can
take an interest in such pursuits, as they regard all the
products of the sea, which are not fish, as " trash." In
the Shetlands, however, I have received much assistance
from the long-line fishermen, who brought me all the
whelks (or " buckles ") which were caught sticking to
the bait on the deep-sea (or " haaf ") fishing-banks ; and
they did this regularly and for several weeks together.
M. Drouet complained bitterly of the difficulty which he
experienced in inducing the native fishermen at the
Azores to bring him any shells, even although he offered
to pay them liberally for their trouble. They told him
they did not choose to alter their habits ; and one of them,
after seeing the French conchologist very busy collecting
some small land-shells, said to his muleteer one day in
confidence, " C^est bien dommage, mais ce seigneur
frangais est pris de la!" and, while saying this, he sig-
nificantly touched his forehead. How far some persons,

^2

Ixxvi INTRODUCTION. [CH.

who affect to consider themselves as more enlightened
than the poor fisherman, may share in his remark, I will
not pretend to inquire, — although it is by no means
certain that, by their so doing, they are not themselves
gi'eater objects of pity than the crazy naturalist.

A curious question may be raised as to the right of
any person to collect and appropriate shells or other ob-
jects of Natural history. According' to the strict inter-
pretation of the law, all trespasses upon private lands
without the consent of the occupier are unjustifiable;
and it makes no difference whether the trespasser is a
naturalist in pursuit of his amusement, or whether he
is simply taking a walk for the sake of exercise. For-
tunately for scientific research, great forbearance is
almost invariably shoA\Ti to naturalists by the proprietors
or occupiers of land, even although the latter may take
no interest in such pursuits; and the instance to the
contrary, of which the gifted Hugh Miller complained,
in his " Cruise of the Betsey,^^ was probably owing to his
not having exercised the common courtesy of requesting,
from a sectarian opponent, permission to collect fossils
on his land. I could also very well imagine that the
owner of a "neat villa^^ might have a decided objection
to his favourite fish-pond being invaded by a party of
conchologists or entomologists armed with ladles or nets,
especially if they considered it quite unnecessary to go
through the ceremony of asking leave. In the case of
manorial wastes or commons, over which the lord and
his tenants have certain and well-defined rights, not ex-
tending to such things as objects of Natural history, no
question of this kind is ever likely to arise ; and the
legal maxim, "de minimis non curat lex,^^ would pro-
bably apply to this case. The majesty of the law would
iiot condescend to notice such trifles as a few shells, in-

IV.] INTRODUCTION. Ixxvii

sectSj or plants. The same rule would, in all probability,
hold good in the case of researches for Natural-history
purposes on those parts of the sea- shore which lie be-
tween high and low-water mark, and especially if they
were made exclusively in the pursuit of science and not
for commercial gain. In a seigniory or honour, com-
prising several manors, which has an extensive frontage
to the sea, on the coast of Gower in South Wales, the
lord is entitled to receive small annual sums, varying
from sixpence to half- a- crown, by way of acknowledg-
ment of his rights, for the privilege of gathering cockles,
mussels, lobsters, and crabs, as well as ore-weed or wrack
which is used as manure in that part of the country ;
and distinct licenses are granted for these privileges.
With respect to the vast tracts of the sea-bottom which
extend beyond the low-water mark of spring tides, the
right of the public to explore them with the dredge or
any other device for scientific purposes has never yet been
questioned. Even in France, where the garde-marine
have strict orders not to allow any net or similar imple-
ment to be on board of a vessel or boat on that coast
when oysters are out of season, I have found no difficulty
in obtaining the requisite permission to use my dredge, and
it was granted readily and with the utmost courtesy.

In a commercial point of view, British shells do not
fetch high prices, compared with what is given by col-
lectors for some exotic rarities. The late Dr. Turton
stated, in his useful but unsystematic little book called
' A Conchological Dictionary of the British Islands,^
that a complete collection of our native shells had
been estimated to be worth its weight in silver. This
was certainly a singular mode of valuing such property,
considering that many of our minute shells, which are so
light that hundreds of them would scarcely balance the

Ixxviii INTRODUCTION. [cH.

smallest weight used by apothecaries, are among our
greatest treasures. As is not uncommon in such cases,
beauty of form or brilliancy of colour does not always
represent the same value as rarity and the consequent
difficulty of acquisition. As much as £S has been given
for a single specimen of Panopma Norvegicay which
would be considered by all but conchologists as a very
ugly and coarse shell. Some of our scarcer kinds of
Fusus also command good prices ; and it is said that the
magnificent specimen of Buccinum acuminatum, which
once belonged to Lord Kilcoursie and is now in our
National Museum, cost the Trustees (or rather the
country) no less than £\2. Mr. Damon of Weymouth,
as well as Mr. Rich, Mr. Sowerby, and Mr. Wright, all
of Great Russell Street, London, are the principal dealers
in this line ; and a priced list of British shells may be
had of the first-named enterprising person.

CHAPTER V.

DISTRIBUTION.

EXTENT. ORIGIN OF BRITISH MOLLUSCA. FOSSILS. GULF-
STREAM.

Extent, — It has long been notorious that distinct
groups of MoUusca, as well as of other animals and of
plants, occupy more or less extensive areas of the earth^s
surface. This distribution is generally more limited with
regard to terrestrial kinds than to those which have an
aquatic habitat. The temperature of the sea at certain
depths is constantly the same everywhere, and it does not
appear to be affected by that of the surface. One species

v.] INTRODUCTION. IxXlX

of the marine Testacea [Saxicava arctica or rugosa) is said
to be almost " cosmopolite/^ being diffused over all seas
from Baffin^s Bay to that which washes the shores of
Australia. It has also a wide range of habitat in the
same seas, extending from low-water mark down to a
depth of 100 fathoms and upwards. The distribution of
Terebratula caputserpentis is nearly as extensive in re-
spect of area and depth of water. This is spread not
only over all the European seas, but also (although under
other names, viz. septentrionalis and Japonica) over a
great part of the North and South Atlantic, Pacific, and
Indian Oceans. In both of these instances the variation
of form and sculpture is very considerable, being coinci-
dent with, and probably caused by, the extent of habitat.
Philine aperta is fomid in every part of the seas of
Europe, as well as in Simon^s Bay at the Cape of Good
Hope, and in the Australian seas. Saxicava, Terebra-
tula, and Philine represent three different orders of Mol-
lusca ; and I have cited them, for that reason, as exam-
ples of the extent of what is termed " geographical distri-
bution.^^ The limits within which some other kinds of
Mollusca occur are' also very wide ; and the Gulf-stream
transports to great distances pelagic or floating kinds,
such as Hyalcea, lanthina, and Spirula. But, considering
all these to be exceptions, it may be assumed as a
general rule, that there is no specific conformity between
the marine products of the temperate and tropical
regions, especially between the Mollusca which inhabit
that part of the North Atlantic Ocean which confines
the coasts of Europe, on the one hand, and the rest of
the Atlantic Ocean, as well as the Pacific, Indian, and
great Southern Oceans, on the other hand. No authen-
ticated case has been recorded of any marine West
Indian species having been found living in the European

IXXX INTRODUCTION. [CH.

seas^ or vice versa. The most striking diflPerence appears
to be with respect to those species called '^^ littoral/''
which are more subject to climatal influence than the
inhabitants of deep "water. In the case of freshwater
shells^ the same rule and exceptions seem to prevail.
The common pond-snail {Limn(Ea peregra) is diffused
over the whole of Eui'ope, as well as over considerable
tracts of North America and Northern Asia ; and it is
only by calling them " representative " species and gi^'ing
them other names that any pretence can be made for
distinguishing certain British species of Limncea, Physttj
and Pisidium from those which are brought from very
distant parts of the world. This diffusion of freshwater
shells has been attributed to the chance transport by
birds ; but I am inclined to believe that it had a different
and very remote origin_, and that it took place long before
the present distribution of land and water. Land-shells
are much more restricted in their range ; and with the
exception of two minute species {Helios pulchella and
Cochlicopa lubrica), besides a few other snails which
have been introduced^ and as it were domesticated, by
Man, T am not aware of any kinds which are common
to both hemispheres. In Thibet and Cashmir, indeed,
many of the land-shells are said to belong to the same
species as inhabit Great Britain ; but these are probably
the descendants of ancient immigrants during the Gla-
cial epoch from more northern latitudes. The mode by
which the Mollusca have become distributed throughout
the different and remote areas in which they are now
found living or in a fossil state has in all probability
been the same from the time of their creation. Their
natural tendency is to disperse either in search of food
or from a migratory instinct ; and, although the pace
of a snail is proverbially slow, time and the action

v.] INTRODUCTION. IXXXI

of marine currents will effect for tlieir countless race
and generations that which is denied to animals of
greater locomotive powers but of less number. A small
tribe of gigantic animals would be far more easily ex-
terminated than a host of puny shell-fish. When the
Mollusca have, in the course of ages, become thus spread
over a certain space, their further progress is arrested
by some geological convulsion or change. The land or
sea-bed, which they inhabited or roamed over, is either
suddenly or gradually covered with water or dried up ;
plains are raised and converted into mountains; trees
and succulent vegetation disappear; deserts become
swamps, and rivers estuaries ; the sea-shore sinks many
fathoms deep ; the climate of the land and the tempera-
ture of the sea are altered ; and conditions unfavourable
to molluscan life succeed. By some of these means
many species are entirely destroyed within the area
which is the scene of such a convulsion or change ;
others are reduced in number and dwindle away ; while
a few of a more hardy nature survive and continue to
flourish. Frequent alterations in the relative level of
sea and land, accompanying the alternate elevation or
depression of more or less extensive districts, will doubt-
less account in a great measure for the irregular distri-
bution of some species and groups of Mollusca. But
shell-fish do not " retire " or " retreat," as has been
conjectured by some naturalists. Their instinctive im-
pulse is to advance only. When aquatic mollusks sud-
denly and unwillingly find themselves on dry land, or
snails are immersed in a sea-bath for a long time, they
have no alternative but to die at their posts like brave
soldiers ; while their comrades are starved to death, owing
to the failure of the commissariat.
With respect to the distribution of the marine Mol-

c?5

Ixxxii INTRODUCTION. [CH.

lusca in the European seas, many theories have been
from time to time advanced, each of which would divide
this great area into several distinct parts, or what are
called "provinces/' Professor Milne -Edwards, in the
' Annales des Sciences Naturelles' for 1838, proposed
the following division — 1. Scandinavian, 2. Celtic, 3.
Mediterranean. Mr. S. P. Woodward, in his verv useful
little treatise, entitled ' Manual of the Mollusca ' (the
last edition of which was published in 1856), considered
that there are four provinces, viz. 1. Arctic, 2. Boreal,
3. Celtic, 4. Lusitanian; and these, according to this
writer, were "framed upon the widest possible basis.''
In a posthumous work of the late Professor Edward
Forbes, which was most ably continued and edited by
Mr. Godwin- Austen in 1859, under the title of ' The
Natural History of the European Seas,' a fifth province
(the "Mediterranean") has been added to those above
enumerated. The latter scheme of distribution has been
recently adopted by Mr. M ^Andrew in the ^ Annals of
Natural History' for December 1861.

Now, although such a division into "provinces" or
separate areas of distribution is very plausible, and pos-
sibly may be maintainable in the same sense as the divi-
sion of Mankind into distinct races, a definite principle
seems to be wanting in their construction. If we com-
pare any one of these schemes with another, a very
material discrepancy is observable as to the relative
limits of the proAdnces. For instance (not to travel far
from home), Milne-Edwards considered that the Celtic
province had its southern boundary in the Straits of
Gibraltar ; Woodward restricted the same limit of this
province to our own coasts ; while Forbes advocated its
extension " from the Bay of Biscay to the Baltic Sea."

The principle of definition, as well as of construction.

v.] INTRODUCTION. Ixxxiii

has been also left in an unsettled and unsatisfactory
state. Woodward lays it down as a rule, that, ^' in order
to constitute a distinct province, it is considered neces-
sary that at least one-half the species should be peculiar,
a rule which applies equally to plants and animals/^
On the other hand, M ^Andrew, after admitting that a
considerable portion of the species of Mollusca inhabiting
any one zoological province may be found in other pro-
viiices, says, "It is not by a simple comparison of the
list of species that we can determine the similarity or
divergence of the fauna of separate localities, as the differ-
ence between them may consist in a few characteristic
forms, which may be especially developed in each.^^ This
wide divergence of opinion as to the rule or "law^' of
distribution, between two such able and experienced
naturalists, renders further inquiry into the facts of the
case indispensable, especially when it is considered that
so many of the " species ^^ referred to by Woodward and
of the " forms ^^ (by which it is presumed genera are
meant) indicated by M 'Andrew are questionable or still
sub judice. That genera-makers may be found who will
separate such forms as Trivia from Cyprceaf Erato from
Marginella, and Admete from Cancellaria, cannot be
helped, — although most naturalists deprecate and disavow
such trifling distinctions. But until a complete concord-
ance has been established and recognized between all the
forms, whether generic or specific, of the Mollusca which
inhabit any one area, a solid and reliable foundation
cannot be obtained for erecting the superstructure of
distribution. No conchologist, whose mind is free from
prejudice, either as regards the authority of names or of
theories on the subject in question, can detect any greater
difference between specimens of Mitra Groenlandica from
Spitzbergen and Mitra ebenus from Naples, than he can

Ixxxiv INTRODUCTION. [CH.

between recent shells of Natica clausa from the North
Cape and fossil shells of the same species from Palermo.
14; is an indisputable fact that whenever the Mollusca of
any part of the European sea-coast have been carefully
examined, the species which are there found exhibit a
greater conformity than had been previously supposed
with the species inhabiting more remote parts, the
general area being thus widened and every portion of it
brought into closer relation to the others. The former
test of percentage is in that case fallacious and no longer
to be depended upon. Thus we find that in Philippics
invaluable work on the Sicilian Mollusca, w^hich was
completed in 1844, 513 species of marine Testacea are
described. After making a small deduction for dupli-
cates [e. g. six out of eight species oi Anomia, and some
Rissoce), about 500 species may be regarded as distinct.
The treatise appended to the last volume of that work
contains a table of comparison between the Mollusca of
the Mediterranean and those of the British seas ; and
in this table 127 out of the above number of 500 are set
down as belonging to our fauna. This gives a rate of
only about 25 per cent. The result of my own exami-
nation of the marine Testacea of another part of the
Mediterranean * is very different from that of Philippi —
especially when it is taken into account that my exami-
nation only occupied three or four weeks, while Philippi
was engaged for many years in a continuous investiga-
tion. The total number of species which I found or ex-
amined on the Piedmontese coast in 1855 was 375 ; and
of this number I identified no less than 205 as British.
This gives a rate of nearly 55 per cent. ; and taking

* " On the Marine Testacea of the Piedmontese Coast," Ann. & Mag.
N.H., February 1S56, p. 155-188. An Italian translation by Professor
Capellini has been published at Genoa.

v.] INTRODUCTION. IxXXV

Philippics number of 500 as the standard of comparison
it is 41 per cent., after making some allowance on the
one hand for species unnoticed by Philippi but included
in my list, and on the other hand for species described
by him but not observed by me, although many of the
latter are unquestionably British. The discrepancy in
these results is the more remarkable when it is con-
sidered that only twelve years elapsed between the pub-
lication by Philippi and myself of our respective re-
searches. When the number and extent of similar in-
vestigations have been increased, and sufficient attention
has been paid to the discrimination of species, in order
to their identification with the names imposed upon
them by different authors, it is highly probable that a
still further correspondence will be found to exist between
the Testacea of the Mediterranean and British seas than
has been imperfectly indicated by me. One great diffi-
culty in making such a concordance has arisen from the
habit of merely collating the names given by authors, in-
stead of examining and comparing the specimens described
by them ; and I believe that many an unsuspected link
in the chain of specific identity would be detected by
pursuing the latter com'se of investigation. It was only
by mere accident, while I was lately looking over the
excellent collections of French sea-shells belonging to
M. Petit de la Saussaye at Paris and to Dr. Baudon
at Mouy, that I recognized, among some specimens
which they had received from M. Martin of Martigues,
and which he had procured by dredging in a deep part
of the Mediterranean off the coast of Provence, not only
the Buccinum Humphrey sianum of our northern sea
(under the name of B. Fusiforme, Kiener), but also the
Rissoa abyssicola of Forbes, which had hitherto been
supposed to be exclusively confined to the Hebridean

Ixxxvi INTRODUCTION. [CH.

channel. This last was called " Rissoa scabra/' although
it was not the species so named and described by Philippi.
Bulla Cranchii and other "northern " forms also occurred
among these Mediterranean shells, but under names
distinct from those which British conchologists have
given to them. If we can divest our minds of the popular
or received impression, that the diversity between species
which inhabit the extreme northern and southern por-
tions of the European seas is both general and well-
marked, we shall not be surprised at the discovery that
many species of Mollusca which at present bear different
names (such as Mitra Grcenlandica and M. ebenus) are
really the same or undistinguishable from each other, or
that even the Astarte incrassata of the Mediterranean is
only a variety of that polymorphous and northern species,
A. sulcata.

The testaceous Mollusca of our own seas have been
separated by Forbes and Hanley into no less than nine
different types — viz. Lusitanian, South British, Euro-
pean, Celtic, British, Atlantic, Oceanic, Boreal, and
Arctic. The limits of these so-called types have not
been defined mth any degree of precision ; and, although
the proposed division is highly ingenious, it can scarcely
be considered as justified by the present state of our
information on the subject. It seems to me, after a
long and careful study of the question, that no more
than tw^o groups (which are apparently distinct from
each other) can be recognized in a geographical point
of view ; and for these I would suggest the general, but
not inappropriate, names of "Northern" or North-
European, and " Southern " or South-European. It is
extremely difl&cult to fix the limits of even these com-
paratively wide areas of distribution ; but the " facies "
of each group is manifest to some extent in the lit-

v.] INTRODUCTION. IxXXvii

toral or shallow-water species, and especially in sucli
conspicuous and striking forms as those of Trichotro-
pis and Neara in our northern seas and Haliotis and
Galeomma on our southern coast. Taking the wider
basis of the European seas, I am not aware that any
species of Conus or Ringicula is found living in the
North, or that any species of Margarita or Lacuna in-
habits the South. It is, however, not unlikely that when
the sphere of our observation has been enlarged, and
a complete concordance obtained between the species of
Testacea from different parts of Europe, the exceptions
from a general distribution will become fewer and at
last disappear, and perhaps that only one common area
may be hereafter recognized. The distribution which at
present exists must be referred to a past state of things.
There can be no doubt that the area of diffusion was
formerly much more extensive than it is at present, and
that it has been restricted by subsequent causes.

Keverting, however, to the proposed scheme of distri-
bution by Forbes and Hanley, as well as to the sugges-
tion now advanced by me, our marine Testacea may be
classed as follows : — -

1. Northern;

2. Southern;

3. Oceanic, or occasional visitants.

The first of these divisions corresponds with the '^^Arctic^^
and "BoreaP^ types of Forbes and Hanley, and the
second to their '^ Atlantic " and " Lusitanian ^' types.
Their "South British," "European," "Celtic," and
" British " types indicate mixed or neutral ground, and
partake both of northern and southern characters. The
third division answers to their " oceanic " type," but it
can hardly be regarded as indigenous to the British
seas.

IxXXviii INTRODUCTION. [CH.

The same basis of classification may be adopted for our
land and freshwater shells. These have been separated
by Forbes and Hanley into only three types, viz. North
European, Central European, and South European. The
third division of the foregoing category (viz. Oceanic) is
of course inapplicable to this group ; but in other re-
spects the principles which regulate their distribution
are nearly the same as in the case of their marine ana-
logues. The difference of aspect between these and
marine species, so far as regards their distribution, is very
noticeable, although, in this point of view, many of the
land and freshwater shells exhibit a greater resem-
blance to littoral species than to those which inhabit
deeper water, by reason of their external conditions.
Temperature or climate is one of the principal agents
in regulating the diffusion of land and freshwater Mol-
lusca ; and their limits are often sharply defined by a
strait of the sea or a mountain-range. Some conspi-
cuous land-shells (as Helix fruticum and H. incarnata)
live in the North of France, although they have never
been found in this country unless in a subfossil state
and as the relics of a past state of things. Some of our
common snails do not pass the Grampian Hills. In
Zetland the Helix aspersa is a total stranger, fortunately
for the poor gardens of the natives ; and only a scanty
remnant of the tribe have succeeded in crossing the
Pentland Firth or maintaining their existence in these
barren isles. Freshwater shells are not so restricted in
their distribution, although one of our native species
(Limncea involutd) has hitherto been discovered in only
one locality — assuming that this species is distinct from
L. glutinosa, which does not appear to have been found
in the same district. A table of distribution of the
land and freshwater shells which inhabit the British

v.] ' INTRODUCTION. Ixxxix

Isles, with reference to other countries and to our upper
tertiary deposits, will be subjoined to this volume; and
I propose to give in the succeeding volumes similar
tables to show also the distribution of our marine
Testacea.

Origin of British Mollusca. — As regards the '' history"
or proximate origin of the British Mollusca, I fully agree
with Forbes and Hanley, w4io stated in the Introduction
to their work (vol. i. p. xxxv), that " the true source of
our Molluscan fauna was first manifested by the assem-
blage of Testacea preserved in the deposit called Coralline
Crag," although my investigation of the Crag shells has
not led me to form the same conclusion that they did,
viz. that most of these ancestors of our living shell-fish
are " of those forms which we regard as Southern types."
The opportunities afforded by a study of the Crag strata
are far superior to any, that we at present possess, for the
investigation of our marine Mollusca. We can explore
the ancient sea-bottom for many miles on dry land, and
as leisurely as if the bed of the present ocean were un-
covered and laid dry by some violent convulsion of
nature ; and this examination can be extended not only
superficially, but also by making sections of the bed to
a depth of thirty feet, so as to have the whole of its con-
tents exposed to view. In attempting a similar explora-
tion of the present sea-bottom, we are only able, at con-
siderable expense, with some personal discomfort, and
in such weather as we too frequently meet with in this
climate, to scrape up with the dredge a few bagfuls of
sand or mud mixed with shells ; nor can we hope to
examine in this way more than a very few inches in
depth. Many deep-burrowing shell-fish altogether escape
our observation, or are only procured by chance.

In order to ascertain the exact nature of the relations

XC INTRODUCTION. [CH.

which exist between this ancient Molluscan fauna and
that which at present inhabits our seas and coasts^ I have
not only examined the Crag strata in company with
Mr.Prestwich^ whose experience in this important branch
of geological science is so w ell known, but I have also
carefully gone over the extensive collection of Crag shells
made by Mr. Searles Wood and presented by him to
the British Museum. In pursuing the latter examina-
tion, I compared the collection with the valuable and
elaborate work of Mr. Wood, published by the Palseon-
tographical Society, in which the specimens were de-
scribed and figured, as well as with Mr. Davidson's
memoir on the Tertiary Brachiopoda in the same series
of publications ; and I afterwards collated the result of
this examination with a great many books and special
treatises on the recent conchology of Europe and the
Arctic regions. I likewise derived no small assistance
in the investigation from the opportunity I had of
consulting the large collection of recent shells in our
National Museum, and for which I would here return
my best thanks to Dr. Baird, the courteous and able
Curator of this department. This examination has satis-
fied me that, out of 386 species of marine shells belong-
ing to the Coralline Crag formation, no less than 167 are
identical with those which still live in the British seas.
Of the remaining 119 species, 7 are said to be exclusively
Northern, and 19 Southern forms, while 93 appear to
be extinct or are as yet unascertained to be existing.
This gives a proportion of very nearly 60 per cent, for
those marine species of the Coralline Crag which at pre-
sent inhabit our seas. Out of the 167 species which I
have recognized as British, 27 have been described or
recorded by different authors as Northern, and only 24
as Southern forms, — taking the Arctic circle as the

v.] INTRODUCTION. XCi

southern limit of the one^ and the Bay of Biscay as the
northern limit of the other area. The greater part are
common to the North and South. In considering the
Crag Mollusca^ the percentage of existing or recent spe-
cies would be very much larger if we were to include
the Bed Crag and the Mammaliferous or Norwich beds,
and especially if we were to add the pleistocene or post-
pliocene strata which immediately overlie those beds —
in fact the whole of our upper tertiaries. It is highly
probable that all the Mollusca which lived during the
periods represented by the newer strata still survive in
some part or other of those vast tracts of sea-bed which
lie between the North Pole and the Pillars of Hercules.
The discovery which is continually being made of missing
links, as well as the increase of experience which results
from a more extensive and perfect knowledge of the Mol-
lusca, must tend to alter the rate of percentage as between
recent and fossil forms. I am aware that the late Pro-
fessor D^Orbigny (in his ^ Paleontologie Fran9aise^), Pro-
fessor Agassiz (in his ^ Essay on Classification^), as well
as Hall, Pictet, and others, have contended that there
is no specific identity between any of the Tertiary and
recent Mollusca ; but the peculiar views which some of
those naturalists entertained and advocated, as to the
successive creation of species, may have influenced their
judgment. At all events, he must be a bold species-
maker who can pretend to distinguish Crag specimens of
the common European cowry, and of many other species,
from those which now live in the adjacent seas ; and their
varieties and monstrosities also, both in a fossil and recent
state, coincide in the most minute particulars, the only
difierence being that the latter are glossy and compara-
tively transparent, while the former are dull and opaque.
Even the lAngula of the Wenlock Silurians could not be

Xcii INTRODUCTION. [CH.

distinguished by Mr. DaAddson (who has especially and so
thoroughly studied the fossil Brachiopoda) from a living
species (L. anatina) by any characters which he could
recognize as constituting a valid specific difference.

These considerations^ however, involve the difficult
question of the origin of species ; and I will not pursue
them further, except by suggesting the very great proba-
bility that all existing species have descended by modi-
fication from primeval forms, but at the same time not
admitting the hypothesis of Mr. Darwin that such forms
were very few or perhaps unique. In those strata which
contain our earliest records of the world^s history, as
great a diversity of form is exhibited in the groups which
we call genera and species as in the existing fauna ; and
it seems evident that the plan of the Creator, so far as
we can comprehend it, has not been that of progressive
development.

Nor will I here venture to touch upon the equally
abstruse, and more speculative, hypothesis as to the
radiation of species from several centres of creation.

But I am digressing. For the reasons above stated
with regard to the connexion between the Coralline
Crag and British shells, I am inclined to regard this
formation as the starting-point, and as it were the
cradle of our moUuscan race. The fauna of Europe,
Northern Asia, the Cis- Atlantic zone of Africa, and a
great part of North America appears to have been
closely related at a comparatively recent epoch, and
to constitute only one area of origin. Many species of
Mollusca once existed at both extremities of this vast
district. Mya truncata, Cyprina Islandica, and Bucci-
num undatum live in the Arctic and North Atlantic as
well as in our own seas, and their remains or shells
are found in Sicily. Cancellaria costellifera occurs in

v.] INTRODUCTION. XCiii

our Coralline Crag beds ; and it survives in the North
Atlantic under the name of C. Couthouyi. The Cardita
senilis of the same beds is the C. sulcata of the Medi-
terranean; and the Crag C. scalaris is the C. borealis
of Conrad and inhabits the coast of Massachusetts and
the Arctic Sea. Many other instances of a similar kind
might be given. Some species appear to be more hardy
than others and have consequently resisted considerable,
and perhaps frequent, changes of temperature or climate.
Littoral or shallow- water species are of course the most
liable to be exterminated or affected by such changes,
and the instances above given are of that kind. Many
of the Thibetan and Algerian land-shells belong to
European species ; and thus the chain of relationship to
which I have referred is complete.

Our upper Tertiary fossils offer tolerable evidence that
the climate of this country was, previously to or at the
time of their being deposited, of a Glacial or Arctic
character, as will be seen by referring to the table of
distribution of our land and freshwater MoUusca at the
end of this volume. Nearly all the land-shells which
occur in the pleistocene strata, but are not now living
in Great Britain [e. g. Helix fruticum, H. incarnata, and
H. ruder ata) , are decidedly Northern species, inhabiting
Finland and Scandinavia ; and even the Alpine variety
of H, arbustorum appears to be the only form of that
species which has been found in our Tertiaries. Among
the freshwater shells in this same formation, Corbicula
(or Cyrena) flwninalis presents, however, an apparent
but remarkable exception from the above indication of
our ancient climate having been so severe, if the habits
of that species have not undergone any change. The
Corbicula is only known to live at present in Asia. But
it may be observed that a common European freshwater

XCiv INTRODUCTION. [CH.

shell [Physa acuta) inhabits the West Indies^ and that
such MoUusca seem to have a greater aptitude for dif-
fusion, or a greater capability of endui'ing different
climates, than land Mollusca, being (as some naturalists
would call it) more " mundane/^

Fossils. — It is sometimes very dif&cult, if not impos-
sible, to distinguish what are called "fossil" from "re-
cent " shells of marine species, if they are " dead " or
found in an empty state. When the shells in question
belong to species which are not known to inhabit the
locality where they occur, this difficulty may give rise to
some interesting questions. In most cases, the nature
of these shells is manifest from their dull appearance
and greater opacity, contrasted with fresh shells of the
same species ; and it does not require much experience
to determine whether single valves of Pecten Islandicus,
which are not unfrequently taken at comparatively great
depths in our northern seas, are fossil or recent, although
they occasionally retain their coloured markings. This
species is abundant in the Arctic regions, and during
the Glacial epoch appears to have been diffused over a
large tract of the European sea-bed; but I am not
aware that it is now found in a living state south of the
Bohuslan district of the Swedish coast. But a perplex-
ing case has occurred with respect to some shells which
were taken by the dredge in the Irish Sea off the coast
of Antrim. The locality is a submarine deposit called
the "Turbot bank," lying about five miles south of
Lame and having a depth of about 20 fathoms at low
water. This bank was repeatedly and diligently explored
during several successive years by Mr. Waller, Mr.
Hyndman, and other naturalists ; and I had the advan-
tage of not only examining the produce of their labours,
but of taking part in an expedition which was made in the

v.] INTRODUCTION. - XCV

autumn of 1859 for the express purpose of endeavouring
to ascertain the nature of this submarine deposit. The
result of these researches was recorded by Mr. Hyndman
in the ' Reports of the British Association^ for 1857 and
1858; and some observations on the same subject by
Mr. Waller wiU be found in the ' Journal of the Royal
Dublin Society^ for 1858 (vol. ii. p. 29-34), as well as by
myself in the ' Annals and Magazine of Natural History^
for August 1858 and February and September 1859. The
association or collection in the same spot of forms which
have been usually regarded as Northern and Southern is
one of the most peculiar features of this inquiry. Colum-
bella Holbollii, Scalaria (?) Eschrichti, Natica clausa,
Margarita cinereaj and Trophon Scalariformis (all of
which are decidedly ^' Arctic ^^ species), Crania anomala,
Trichotropis borealis, and Puncturella Noachina (which
were regarded by Forbes and Hanley as " boreal '^ types),
Terebratula caputserpentis, Lima subauriculata, and Fis-
surella reticulata (being, according to the same authors,
''^ Atlantic ^^), Argiope cistellula, Trochus Montagui, and
Pecten tigrinus C^*^ British ^^), Astarte sulcata, Buccinum
undatum, and Venus Casina (" Celtic "), Artemis lincta,
Corbula nucleus, and Trochus cinerarius {" European ^^),
together with Rissoa striatula ("Lusitanian^^), aU of
them in the same fresh and apparently recent condition
and (with the exception of those included in the first and
last categories) in a living state, were congregated to-
gether in this locality, as if on purpose to refute certain
theories of geographical distribution. With respect to
those species which were not taken there in a living
state, it was surmised that they were fossil, or had been
carried to the spot by marine currents. Some of the
specimens in question I submitted to Dr. Carpenter,
whose researches on the microscopical structure of mol-

XCvi INTRODUCTION. [CH.

luscous shells entitle his opinion to the greatest possible
weight ; and he professed that he was unable to detect
any apparent difference between the texture of these
specimens and of others (which were unquestionably
recent) belonging to the same species and placed with
them for the sake of comparison. No chemical or other
test seems to be known, by which the texture of shells
called fossil, and certainly of very remote antiquity, can
be distinguished from that of recent shells. The gloss
and the greater or less transparency of the latter, con-
trasted with the dull aspect and opacity of the former,
afford the only criteria of distinction; but it is not
known how far the continued submersion of shells for
many ages in the sea, where they are placed beyond the
reach of atmospheric influence, may have prevented any
change in their external appearance. The shells of Mol-
lusca would seem to be nearly indestructible by the
ordinary action of air and water, and especially when
their structure is crystalline and compact. The term
'^ recent '^ is, of course, comparative in point of time. But
a few of the shells from the Turbot bank, belonging as
well to some of the species in question as to other species
which are undoubtedly indigenous and exist there in a
living state, have every sign of being fossil, and are pre-
cisely similar in appearance to the shells which are found
in the Clyde and other beds of a pleistocene formation.
Some of these beds occur in the neighbourhood of the
Turbot bank, and contain Yoldia lanceolata, Leda pyg-
mcea, Hypothyris jjsittacea, and other shells of a decidedly
Arctic character ; but only one of these species (viz. Leda
pygnKBO) has been observed in the Turbot- bank dredgings,
and of this species Mr. Waller found a living specimen.
Columbella Holbollii, Scalaria (?) Eschrichti, and Mar-
garita cinerea (being three out of the five Arctic species

v.] INTRODUCTION. XCVll

which have been taken on the bank) have not^ so far as
I am aware, ever been detected in any of our Tertiary
strata. The two other Arctic species (Nalica clausa
and Trophon Scalay^iformis) inhabit the upper coasts of
Norway, as well as more northern seas. The first-named
species has a range, according to M ^Andrew and Barrett,
from the shore to 150 fathoms. It occurs in the Eed
Crag, as well as in almost every pleistocene bed which
has been examined in this country ; and I noticed it in
the collection of Dr. Van Geuns at Utrecht, among some
shells which he had found in the Subapennine deposit
of Palermo. This species is not included in Philippi's
list of Sicilian fossils. The distribution of the other
species appears to have been equally extensive; and I
have a fresh specimen, recently inhabited by a hermit
crab, which was dredged fr-om deep water oflP the Aber-
deen coast and obligingly presented to me by the late
Professor Macgillivray. It is quite possible that a plei-
stocene bed may have formerly existed in the spot which
is now occupied by the Tui-bot bank, and that the con-
tents of this bed may, by the action of the tide or marine
currents, have become mixed up with the existing pro-
ducts of the adjacent sea-bed ; and the appearance of
some of the shells to which I have refen^ed might
warrant such a conclusion. But, inasmuch as many
relics of the Glacial epoch, such as Leda pygmaa and
Area raridentata, still survive in a few and widely sepa-
rated parts of that extensive area which was once sub-
ject to Arctic conditions, it will not be surprising if all
the species I have thus mentioned as doubtful inha-
bitants of our seas should also have lingered on in their
old quarters and be really British. The conjecture that
these shells may have been accidentally transported by
sul^marine currents from the Arctic Sea to the Irish

XCviii INTRODUCTION. [CH.

coast does not rest upon any foundation. I was satisfied,
by information which I obtained on the spot and in the
course of my di'edging-operations, that no submarine
cun'ent sets in that direction, nor any which could have
brought the shells from a distance ; and the same con-
viction is entertained l)y tlie able and zealous naturalists
who have so carefully and during several years in suc-
cession explored many square leagues of this remarkable
sea-bed.

Gulf -stream. — This " deus ex machina" seems al-
ways to be called into requisition, in order to explain
any apparent anomaly in the distribution of marine
Mollusca. In the minds of many persons it ranks with
the comet in its mysterious effects. It is quite true that
the scientific world, and indeed all who take any interest
in the works of Nature, are under the greatest obliga-
tions to Commodore Maury for the lucid account he
has given, in his ^ Physical Geography of the Sea,^ of
this really wonderful phenomenon. But with regard to
the subject of the present inquiry, I cannot help express-
ing a doubt whether the effects of this great '' river in
the ocean '' have not been much overrated.

The partial glimpse which we have hitherto been able
to obtain of the results from the recent expedition of
Otto Torell and other Swedish naturalists to Spitz-
bergen shows that the Gulf-stream was found not to
exert any influence on animal life in that region, it ap-
pearing to be entirely of a glacial nature *. From careful
inquiries which I made in several parts of the eastern
coast of Zetland last year, I was satisfied that the Gulf-

* While tliis last sheet is passing through the press (22 May, 18G2),
Professor Forchhamraer has read before the Royal Society a valuable paper
on the composition and density of sea-water. His observations as to the
Gulf-stream tend to sliow that it cannot affect the distribution of animal
life in the lower zones of the sea.

VI.] INTRODUCTION.

XCIX

stream does not set upon any part of that coast. All
the driftwood that was washed ashore was of Norway
fir, and came from the opposite coast. Dr. Lukis in-
forms me that the Gulf- stream has now been ascer-
tained not to impinge on any part of the Channel Isles,
although the Sargasso weed and the seeds of tropical
plants are occasionally thrown up on those shores, after
having been deflected and drifted by marine currents.
Much evidently remains to be done in defining its exact
course in northern latitudes, and in making accurate
observations as to its influence on the fauna and flora,
as well as on the temperature, of different parts of
Europe.

CHAPTEK VI.

HABITAT.

STATIONS. ZONES. ABUNDANCE OF MOLLUSCAN LIFE. GEOLOGI-
CAL RELATIONS. CHANNEL ISLES. EXOTIC AND SPURIOUS SPE-
CIES. SEA-SIDE SKETCH.

Stations. — The subject of this chapter is closely con-
nected with that of the last ; but it seems more conve-
nient to divide it. Having considered the British Mol-
lusca with reference to their European and general
distribution, I now propose to give a short account of
their native habitats and to take a home view of the
matter.

The MoUusca may be divided into land, freshwater, and
marine. Their respiratory organization mainly results
from the nature of their habitat, or, as botanists would
term it, their " station.^^ All land-snails breathe the free

e.2

C INTRODUCTION. [CH.

air^ by means of lung-like ca\dties or pouches which they
possess. Some kinds of freshwater snails have a similar
apparatus; but they are also enabled to extract occa-
sional supplies of oxygen from the water, and are thus not
entirely dependent on their air-pouches. Others of this
kind are furnished only with gills, which they use like
iishes. In the genus Valvata the gill is external and
shaped like a feather; and the animal has also an au-
xiliaiy branchial organ, which resembles another ten-
tacle. The respiratory system of the marine Mollusca,
with the exception of a very few littoral species, is bran-
chial ; and in some kinds the gills are external. Bivalves
have usually two leaf-like gills, which are arranged sym-
metrically, one on each side of the body. In the Bra-
chiopoda, however, the brachial organs (according to
Mr. Hancock) subserve the function of gills, although
in one genus (Lingula) the lobes of the mantle may, to
a certain extent, be considered specialized breathing -
organs.

There are some peculiarities with respect to habitat that
are interesting to geologists. Some kinds of freshwater
univalves, both those called Pulmonobranch [i.e. respiring
by means of lung-like pouches), and Pectinibranch (i. e.
respiring by means of comb-like gills), have the faculty
of enduring a partial change or difference in their usual
habitat, which would be fatal to other kinds. The
Swedish naturalist Nilsson relates that two species of
JAmjKBa described by him, as well as Neritina fluviatilis,
live in the Baltic, adhering to sea-weeds, and sometimes
at a distance from the mouth of any river. With these
live certain marine Mollusca, such as the common mussel
and cockle, Mya arenaria and Tellina Balthica (or soli-
dula)^ all of which, however, are of a dwarf size. Lim-
noia is Pulmonobranch, and Neritina is Pectinibranch.

VI.] INTRODUCTION. ci

The same peculiarity _, but not of so permanent a cha-
racter, has been observed in the case of a freshwater
bivalve. The common pond-mussel [Anodonta cygnea)
is said to live in the river Trent at Bottesford in Lincoln-
shire, which is salt at high water. The fresh water,
being lighter, forms the upper stratum ; while the sea-
water covers the bed of the river inhabited by the Ano-
donta. A small Pectinibranch univalve (Hydrobia ulva)
inhabits indifferentlv salt and brackish water ; another
(H. ventrosa) frequents only the latter ; while a third
{H. similis) lives, in company with Bythinia tentaculata
and other freshwater univalves, in water which is nearly
fresh. The usual habitat of the genus Melampus (which
is Pulmonobranch) is the sea-shore ; but one species
occurs high up in estuaries, where the water is more
fresh than salt. M. Marcel de Serres is of opinion that
the habitat of Dreissena polymorpha (a kind of mussel
which abounds in many of our rivers and canals) was
originally marine, from the circumstance of the shells
being found in tertiary strata of marine formation. The
Russian traveller, Pallas, who first discovered or made
known this species, described one variety of it as marine
and the other as inhabiting fresh water. Many of the
marine Mollusca which live on the sea-shore (some of
them even beyond the reach of the tide) pass the greater
part of their time out of water ; and the same remark
applies to some freshwater snails, such as Limn^a
peregra and Ancylus fluviatilis, which are as often found
on dry land as in their natural element. Succinea putris
(a land-snail) appears to be almost amphibious. Many
genera of bivalve Mollusca contain certain species which
are marine and others which have a freshwater habitat.
Even Teredo, Pholas, and Area are in this category. The
smaller Crustaceans seem also to be very indifferent to the

cii INTRODUCTION. [CH.

nature of their habitat in this respect. Mr. Spence Bate,
who has so diligently and successfully studied our native
shrimps, informs me that Gammarus locusta, which only
inhabits the sea, is scarcely distinguishable from G. flu-
viatilis, which would be instantly killed by being put
into salt water. Professor Lilljeborg has discovered in
some of the inland freshwater lakes of Denmark several
Arctic species of marine Crustacea, which appear to have
survived the Glacial epoch, and to have adopted from
necessity a new habitat, in consequence of the gradual
elevation of the land. And the result of the researches
made by Dr. E. von Martens on the occurrence of
marine animal forms in fresh water, which was published
in ^ Wiegmann's Archiv^ for 1857, shows that 10 out of
44 divisions or groups of Crustacea, and 6 out of 52
divisions of Mollusca, are common to the sea and fresh
water. Fish have no less than 23 out of 55 divisions
similarly circumstanced as to habitat ; but some of these
are well known to migrate annually from the sea to
rivers that flow into it, for the purpose of depositing
their spawn. Such peculiarities of habitat form one of
the stumblingblocks of geology ; and it is fortunate that
the cultivators of this science are not obliged to place
their sole reliance on the palseontological contents of the
strata which they wish to investigate, as they have also
the mineral composition, as well as the relative juxtaposi-
tion, of those strata to guide them in the investigation.
Zones. — It had long been known that different parts
of the sea-bed w^ere inhabited by special forms of animal
life; but Risso, the celebrated naturalist of Nice, was
the first who proposed its distribution into zones of
depth. His theory was derived from observations on the
Mediterranean fishes. The late Professor Edward Forbes
added much to our knowledge of such distribution ; and

VI.] INTRODUCTION, ciii

his valuable researches on the Invertebrata of the ^Egean
and our own Seas enabled him to define these zones
with considerable precision. Professors Loven and
Sars, as well as Oersted, have made us acquainted with
the range and limits of marine life in the Scandinavian
seas.

In framing any scheme for dividing the sea-bed into
separate areas of molluscan habitability, according to
their depth_, it must be borne in mind that the extent
and produce of these areas vary greatly, and depend upon
the inclination and mineral nature of the coast. That
part of our sea-bed which is circumscribed by the line
of soundings may be divided into four distinct areas or
zones, of different width and depth ; and I will endeavour
to define briefly their limits, nature, and contents.

The first is the Littoral zone, or the shore, which
fringes every part of our coast and lies between tide-
marks, being laid bare when the tide retires. Wherever
the coast is steep and rocky, this zone is very narrow.
Where it shelves gradually and is sandy (each of these
conditions being probably consequent on the other), the
strand frequently extends seaward for a mile or even
further. Where it is composed of cliffs, such as chalk or
boulder- clay, the beach is pebbly, and its width is
usually intermediate between that of the two other cases
I have mentioned. The pebbles are derived from the
wearing-away of the cliffs, either in the course of their
original elevation above the sea-level (which in many
cases appears to have been slow and gradual), or else by
the combined action of the atmosphere, rain and frosty
or of the tide and waves. This pebbly beach is sometimes
succeeded by a belt of larger stones or boulders, and
that again by a strip of sand, mud, or clay, as we advance
to meet the tide. In each of these cases the nature of

civ INTRODUCTION. • [cH.

the shore^ strand, or beach depends on the composition
of the strata which form that part of the land which is
opposed to the sea. The rocks lying between tide-
marks are clothed with sea^veed, which supports a
numerous and peculiar group of Mollusca. Among
those on our OAvn coasts may be enumerated various
species of Littorina (or periwinkle), Lacuna, Trochus,
Rissoa, Chiton, Patella (or limpet), Furpura lapillus (or
dogs^-whelk), and a stunted variety or form of the com-
mon mussel. In the small rock-pools, which are left
by the receding tide, and are generally lined with Coral-
Una officinalis and other small seaweeds, as well as under
loose stones, will be found many small shells of various
sorts, including Poronia rubra, Modiola discors, Skenea
planorbis, Rissoa parva, Cerithium reticulatum, and the
fry of other species. The highest part of this zone,
which the sea does not cover for more than two or three
hours out of every twelve, is inhabited by two kinds of
Melampus (M. bidentatus and a variety of M. myosotis),
Otina otis, Assiminia littorea, Truncatella truncatula,
a variety of the common limpet, Littorina Neritoides,
and some of the numerous varieties of L. rudis. The
first three of the above species are Pulmonobranch.
That part of the littoral zone which consists of sand,
gravel, or mud is frequented by various genera of bi-
valve Mollusca, such as Mya, Solen, Tellina, Donax,
Mactra and Tapes, as well as by Mytilus edulis. Within
this zone submarine peat, chalk, and trias or new red
sandstone, harbour several kinds of Pholas ; Scrobicu-
laria piperata burrows into clay ; calcareous rocks are
perforated by Saxicava rugosa ; and fixed wood is drilled
in every direction by the destructive Teredines or ship-
worms. Wherever a river or stream empties itself into
the sea, a strong reflux is caused by the advancing tide.

VI.] INTRODUCTION. CV

which has the effect of casting on the shore a collection
of spolia marina, dislodged by the ground-swell from
considerable depths^ as well as of many land and fresh-
water shells, which have been washed down by the river
or stream and thus become mixed with those from the
sea. This phenomenon frequently occurs in some of our
upper tertiary and more recent deposits, and shows the
regularity with which such physical operations have been
repeated dui'ing periods of the duration of which we can
form no conception. In the same zone are also com-
prised estuaries, which form deep but narrow indenta-
tions of the sea- coast, and are the channels, as well as
the outlet, of tidal rivers. The water of these estuaries
is always more or less brackish. They are inhabited by
peculiar MoUusca, viz. Assiminia Grayana, Melampus
myosotis, and the several species of Hydrobia above men-
tioned. The few pelagic mollusks which occasionally, but
unwillingly, \4sit our seas, are also met with in the littoral
zone, being cast on shore generally after a continuance
of westerly gales. These consist of species oi lanthina,
Spirula Peronii, and a few Pteropods, some of which
have but a doubtful claim to be considered indigenous
productions of our seas. The present zone has been
subdivided by Forbes and Hanley into four intermediate
lines or strips, each of which is said to be inhabited by
its own peculiar set of Mollusca ; but the great variety
exhibited by our seaboard, as well as its geological for-
mation, seems scarcely to warrant such a subdivision.
For instance, Trochus umbilicatus and T. lineatus, which
are assigned by these authors to the fourth or lower-
most line, in which they usually occur on our western
and south-western coasts, inhabit the second line on the
shores of the Bristol Channel, as well as those of the
north-west of Ireland.

Cvi INTRODUCTION. [CH.

The second zone is called the Laminarian, from the
belt of that kind of seaweed which girds all the rocky
parts of our coast-line. It is seldom laid bare^ except at
very low spring-tides ; and it is generally much narrower
than the littoral zone, in consequence of the rocks, to
which the Laminaria or tangle is attached, dipping sea-
ward and being covered with sand beyond the direct and
more immediate influence of the tide. This zone may
be said to extend from low- water mark to 10 fathoms.
The mollusca which inhabit it chiefly belong to Patella,
Acmcea, Trochus, Lacuna, Rissoa, and Jeffreysia, all of
which are phytophagous or vegetable-eaters, as well as
the Nudibranchs or sea-slugs, which are mostly zoopha-
gous. Where the coast is sandy, this zone is entirely
wanting and is merged into the one above or below it,
so far as regards its zoological contents. The extent of
each zone mainly depends on its capability as a feeding-
ground; and the same species are frequently common
to every zone, when their nature is alike and they are
not prevented by an intervening barrier of sand or rock
from spreading from one zone to another. To this cause
is probably owing the great variation in the depth to
which many species attain. The common mussel, which
is usually found within tide-marks, has been recorded by
Dr. Walker as living in the North Sea at a depth of
140 fathoms or 840 feet. Cyprina Islandica, which in
most seas inhabits depths of from 30 to 140 fathoms,
occurs on the coast of South Wales at low- water mark ;
and our little cowry {CyprcBa Europcea) has a range from
low-water mark to 100 fathoms.

The third zone has received the name of ^^ Coralline,^'
from the quantity of nullipore [Melobesia polymorpha) ,
which is a stony coral-like plant, and in many places
covers large tracts of the sea-bed. Its width varies con-

VI.] INTRODUCTION. CVli

siderably ; but its vertical range may be stated as ex-
tending from 10 to 50 fathoms. As a general rule^ rocks
do not occur in this zone^ especially in the deeper part
of it — stones, gravel and sand (sometimes mixed with
mud) being its chief characteristics. These mineral
conditions to some extent regulate the nature of the
Mollusca which are here found. The whelk-tribe, as
well as many Nudibranchs, frequent the stony or, as it
is called, " hard '' ground ; and different sorts of bivalves
take up their quarters in the other, or ^' soft," ground.
Seaweeds are scarce in this zone and are generally
absent from its lower regions ; so that most of the Mol-
lusca which inhabit it are animal- eaters, — some being
sarcophagous, others zoophagous, and many of them
preying on each other.

The fourth and last is called the Deep-sea zone, and
reaches from 50 fathoms to the greatest depth comprised
within the line of soundings. Both this and the last-
mentioned zone contain our most productive fishing-
banks ; and the floor of these submarine areas is exceed-
ingly uneven, and diversified by many an unseen hill and
dale. The deep-sea zone appears to have nearly always
a soft bottom, consisting of a much finer sediment than
that which covers the bed of the coralline zone. The
only vegetable organisms which are found in it are tiny
and almost microscopic Diatoms. It is inhabited by
various kinds of Mollusca, all of which are, probably
from necessity, animal-eaters. They appear to exceed in
number, as well as in variety, the inhabitants of any of
the other zones, judging from the scanty opportunities
which occur for investigating the contents of this exten-
sive sea-bed. The point of zero in the scale of sub-
marine life has not yet been, and perhaps never will be,
found.

CVlll

INTRODUCTION. [cH.

Abundance of Molluscan life. — The whole surface of
our globe teems Avith a mass of animal and vegetable
life, to which the MoUusca contribute by no means an
inconsiderable quota. Owing to the solid and perma-
nent nature of their shells, many fossiliferous strata
are almost entirely composed of such exuviae ; and this
process of accumulation is still going on in the exist-
ing sea-bed to an enormous extent. No one can have
had any experience in exploring the bottom of our
own seas, and examining our tertiary strata, ^vith-
out noticing how closely the contents of a well-filled
dredge, taken from a submarine shell-bank, resemble
the same quantity of material dug out of a crag-pit ;
and perhaps nothing can give a more striking idea of
the incalculable lapse of time which must have taken
place in the history of the world, than the formation of
these strata which, after all, are only a few pages of
the great book. We here see layer upon layer of organic
remains heaped up and compressed, to a depth of thii^ty
feet, each layer being only a few inches deep, but repre-
senting numerous and successive generations that have
long passed away.

It has not yet been ascertained to what depths mol-
luscan life extends. The late Sir James Clark Ross,
in the interesting account of his Antarctic Voyage (vol. i.
p. 202), says, " I have no doubt that, from however
great a depth we may be enabled to bring up the mud
and stones of the bed of the ocean, we shall find them
teeming with animal life ; the extreme pressure at the
greatest depth does not appear to affect these creatures.
Hitherto we have not been able to determine this point
beyond a thousand fathoms ; but from that depth shell-
fish have been brought up with the mud.^^ Still greater
depths have been lately reached in recovering the Me-

VI,] INTRODUCTION. cix

diterranean telegraph-cable^ and with the same results ;
and the forthcoming work of Dr. Wallich on " The
North- Atlantic Sea-bed" will doubtless contain some
important observations on the existence and forms of
animal life at extreme depths in the Arctic Sea.

Although it does not come strictly within the scope
of the present treatise^ I cannot help contrasting the
fecundity of the sea with the comparative steriHty of the
land^ as regards animal life — if we consider the countless
shoals which swarm in every part of the ocean and
thickly cover its bed, and that the air_, even in its lower
zones, is almost lifeless. The lines in the 12th Canto of
the ' Faerie Queene ^ seem to corroborate this idea, al--
though not so intended by the poet : —

" O what an endlesse worke have I in hand,

To count the seas abundant progeny,
Whose fruitfull seede farre passeth those in land,

And also those which wonne in th' azure sky !

For much more eath to tell the starres on hy,
Albe they endless seeme in estimation,

Then to recount the seas posterity :
So fertile be the flouds in generation.
So huge their numbers, and so numberlesse their nation.

Witnesse th' exceeding fry which there are fed.
And wondrous sholes which may of none be red."

Geological relations. — In local lists of MoUusca, and
even in more elaborate works on this subject, it has been
the custom to state that the habitat of certain species is
restricted to " calcareous soils," ^' oolitic formations,"
"limestone," "chalk," "trap," and other strata. I believe^
however, that mineralogical conditions have very little
to do with the habitat of any of the Mollusca, nor with
their comparative abundance or scarcity in any locality,
except so far as food, moisture, or shelter, as well as the
secretion of their shells, is concerned. Such conditions

ex

INTRODUCTION. [cH.

are merely what logicians call '' accidents/^ All the earth
(even granite and felspar) is said to contain calcareous
matter, although the proportion is of course greater in
some formations than in others. The case of two com-
mon and conspicuous land-shells occurs to me with
reference to this question. Helix lapicida is directed
by Forbes and Hanley^ " to be sought for in limestone
and chalky districts." It is common, however, in the
trap formation of the Lower Harz, as well as in the
molasse of Switzerland. According to Moquin-Tan-
don the Cyclostomata " aiment surtout les terrains cal-
cairesf;" but our only species (C elegans) is tolerably
abundant in Jersey, where there are no calcareous strata.
It would be easy to adduce many similar instances to
prove that the habitat of Mollusca is not so restricted,
as has been stated, in their geological relations. But
there is no doubt that, with regard to land- shells,
both granite and peat (which are at the opposite ends
of the geological scale) are equally unfavourable to mol-
luscan Hfe; because the former is not easily disinte-
grated and converted into mould, so as to support vege-
tation, and the latter, being chiefly composed of the bog-
moss (or Sphagnum), is either innutritions or distasteful
to snails. The same observation applies to fir- woods,
which do not appear to be inhabited by the Mollusca.
With respect to the marine Mollusca, it may be ob-
served that the phytophagous kinds will be found in
abundance wherever sea-weeds flourish, and that in the
deeper zones of the sea, in which such vegetation is
absent, an ample supply of animal food is not wanting.
But the substance of molluscous shells undoubtedly de-
pends on the nature of the soil ; and carbonate of lime
seems to be as necessary to most snails for the secretion
* Brit. Moll. iv. p. 66. t Hist. Moll. Fr. t. ii. p. 492.

VI.] INTRODUCTION. Cxi

and formation of their dwellings^ as egg-shells, or lime,
are to laying-hens. The shells of our common garden-
snail (H. aspersa) in Guernsey are remarkably thin, owing
to the deficiency of calcareous material; and specimens
oiH.pomatia, from granite formations in alpine districts,
are far inferior in weight to those from our challv downs,
although they do not differ in size.

Channel Isles. — Some conchologists entertain a doubt
whether the Mollusca of Guernsey and the other Chan-
nel Isles ought to be included in the British fauna,
because of their greater proximity to the French than to
the English coast. The Sarnie fauna and flora (although
undoubtedly peculiar) have, however, been hitherto con-
sidered by our best naturahsts as belonging to Great
Britain; and our Continental neighbours have never
claimed them as their own, although they have appro-
priated Corsica, or " annexed" it to France, in a Natural-
history point of view. Some of the Mollusca, taken in
that part of the English Channel which is adjacent to
Guernsey, are peculiarly Southern forms and have not
occurred in any other part of our seas. Nearly all of
them are very conspicuous and handsome. They are
Cardium papillosum, Argiope decollata, Haliotis tuber-
culattty Murex corallinus, Triton cutaceus, and T. nodi-
ferus. Of these six species only three (viz. Haliotis tuber -
culata, Triton cutaceus, and T. nodiferus) are noticed by
either De Gerville, or CoUard des Cherres, as having been
found on the opposite coast of Brittany ; and Bouchard-
Chantereaux has not included anv of them in his list of
marine shells found on the coast of Normandy. Dr.
Bowerbank has identified some of the sponges from
Sark as northern species. In respect of geographical
position, some of the Channel Isles are not so very much
nearer France than England. Guernsey is distant about

Cxii INTRODUCTION. [CH.

sixty miles from the Bill of Portland^ and about thirty-
five miles from Cape Carteret on the coast of Brittany.
All the six species which I have above mentioned are
found on our side of the Guernsey coast.

Exotic and spurious species. — The fauna of any par-
ticular country (although isolated^ like Great Britain)
cannot be satisfactorily studied by itself and without
reference to the fauna of other parts of the same district.
The habit of observing and comparing the Mollusca of
different countries is of undeniable advantage; and it
may be favourably contrasted with the tendency of local
naturalists and collectors to exaggerate trifling differ-
ences^ which would have disappeared on a more extended
survey. The enlargement and increase of such expe-
rience have the same beneficial effect on a mind inclined
to the cultivation of science, as travelling in a foreign
land, with one's eyes open, has in expanding the intellect
and impro\4ng our social nature. By such means our
notions become in each case less contracted ; and (which
is perhaps of more importance) our ideas with regard to
the labours of other naturalists are imbued with a spirit
of greater liberality and charity than if we had pursued
the selfish course of working in our own sphere without
any intercourse or sympathy with them.

The " index expurgatorius," containing the species of
Mollusca which are termed "spurious" (being those
which have been admitted into catalogues of British
shells, but have not been proved to be indigenous to
this country), is now very small, owing to the labours of
Dr. Gray in revising the list of our land and freshwater
shells, and of the authors of the ^ British Mollusca ' in a
similar revision of our marine shells. The casual intro-
duction of tropical or foreign shells by means of ship-
wrecks or ballast is not so frequent as has been supposed.

VI.] INTRODUCTION. CXiii

— although it sometimes occurs^, and I have several times
picked up on the sea-strand, near a port resorted to by
foreign vessels, shells which had evidently come from
ballast. Strangers of this kind may, however, be de-
tected without much difficulty by the application of in-
trinsic evidence. A much more fertile and perplexing
source of error, as regards the introduction of spurious
species, consists in collectors of Mediterranean, as well
as British, shells not taking sufficient care to keep these
collections separate; and too much praise cannot be
given to Mr. M ^Andrew, whose labours and experience
in the investigation of the European MoUusca are so
well known, for his extreme accuracy in the above re-
spect.

' 'Sea-side sketch, — Having offered this imperfect view of
the British Mollusca, with regard to their structure and
habits, and their relation to other animals and ourselves,
as well as to their distribution, I cannnot refrain from add-
ing another page to this unusually long introduction, to
exhibit a charming and truthfal picture by my lamented
and highly gifted friend. Professor Edward Forbes : —
" To sit down by the sea-side at the commencement of
ebb, and watch the shore gradually uncovered by the
retiring water, is as if a great sheet of hieroglyphics —
strange picture-writing — were being unfolded before us.
Each line of the rock and strand has its peculiar cha-
racters inscribed upon it in living figures, and each figure
is a mystery, which, though we may describe the appear-
ance in precise and formal terms, has a meaning in its
life and being beyond the wisdom of man to unravel.
How many and how curious problems concern the com-
monest of the sea-snails creeping over the wet sea- weed !
In how many points of view may its history be considered !
There are its origin and development — the mvsterv of

cxiv INTRODUCTION. [CH. VI.

its generation — the phenomena of its growth — all con-
cerning each apparently insignificant individual; there
is the history of the species — the value of its distinctive
marks — the features which link it with higher and lower
creatures — the reason why it takes its stand where we
place it in the scale of creation — the course of its distri-
bution — the causes of its difiusion — its antiquity or no-
velty — the mystery (deepest of mysteries) of its first
appearance — the changes of the outline of continents and
of oceans which have taken place since its advent, and
their influence on its own wanderings. Some of these
questions may be clearly and fairly solved ; some of them
may be theoretically or hypothetically accounted for;
some are beyond all the subtlety of human intellect to
unriddle. I cannot revolve in my mind the many que-
ries which the consideration of the most insignificant of
organized creatures, whether animal or vegetable, sug-
gests, without feeling that the rejection of a mystery,
because it is a mystery, is the most besotted form of
human pride *.'^

* Nat. Hist. Eur. Seas, p. 12.

In his tarn parvis, atque tarn nullis, qujc ratio ! quanta vis ! quam
inextricabilis perfectio ! — Pliny.

AQUATIC.
Class I. CONCHIFERA, or BIVALVES.

Body of an oval form, and usually compressed at its sides :
mantle divided into two lobes which correspond with the valves
of the shell. It has no distinct head : but inside the mantle,
and within its folds, is contained a mouth ; and the edges of
the mantle in those bivalves which have it open, or of the
tubes which are formed by it in those which have it closed, are
often fringed with short filaments, which serve the purpose of
tentacles or feelers. Some kinds have also imperfect or rudi-
mentary eyes, which are set in the interstices of those fila-
ments where the mantle is open. The foot is tong*ue-shaped,
and sometimes capable of considerable extension. It is used
by the animal for creeping or attaching itself to other bodies
by a byssus or bundle of muscular threads. Reproductive
system similar to that of the monoecia among plants — both
sexes being united in the same individual, which is capable of
fertilizing itself. The whole, or most important part, of the
body is covered by a shell, formed of two valves which are
connected behind by a hinge or ligament. Respiratorij organs
consisting of gills.

Order LAMELLIBRANCHIATA

*

Gills 4, semicircular or leaf-shaped, arranged in pairs on
each side of the body.

This Order comprises all the freshwater bivalves of
Great Britain ; and they are divided into three families.

Family I. SPH^MID^.

Body subglobular : mantle open in front, and forming at the
posterior side a cylinder, which is often divided near its open-
ing into two tubes. The cylinder or tubes are contractile and

* So called from the leaf -like form of the gills.

B

2 SPH.ERIID^.

extensile, — the longer tube (when there are two) being used
for respiration and nutrition, and the shorter tube for excre-
tion. The outer edges of the mantle, as well as of the cylinder
or tubes, are simple, and not furnished with papillae or fila-
ments. The mouth consists of a slit which is placed between
the anterior adductor muscle and the base of the foot, and it has
two small triangular lips. Foot wedge-shaped, thin, and ca-
pable of great extension.

Shell composed of two thin, oval or subtriangular valves,
which are more or less inequilateral. The valves are of equal
size. The outer surface of the shell is protected by a dehcate
epidermis, and the inside is slightly lined with nacre. The
hinge is furnished with cardinal and lateral teeth, to enable the
valves to lock more closely into each other when the shell is
shut. The ligament is external, although it is sometimes seated
so far within the hinge as to be scarcely visible on the outside :
it is placed at the longer, or posterior, side of the hinge.

The animals of this family are ovoviviparous^ retaining
the fry for some time between the mantle and gills.
They are tolerably active in their habits, using their foot
for crawling like a leech ; and some of them float with
the beaks of their shell downwards, or suspend them-
selves in that position to the under surface of the water
by means of a very fine byssus which they secrete and
spin with their foot. In the winter they appear to be
torpid, and bury themselves in the mud, lil^e other fresh-
water bivalves. During this period they probably cannot
procure their food, which consists of animalcula. Speci-
mens which I had in confinement soon after Christmas
never put out their tubes, and only used their foot to
creep under some moss which was in the vessel. This
they did as often as I removed them from their place of
shelter.

The Spk(S7mdce closely resemble their marine repre-
sentatives, the Kelliadxe, which are also ovoviviparous :
])ut the mantle is more open and the ligament external in
the present family; while the ligament is internal in the

SPH^RIID^. 3

Kelliadce, and the beaks of their shell are much more
acute. This curious and distinct group of freshwater
bivalves has been carefully investigated by our country-
man, the Rev. Leonard Jenyns ; and his monograph on
the British species of Cyclas and Pisidium, which was
published in the Transactions of the Cambridge Philo-
sophical Society for 1832, is full of valuable and inter-
esting information. Since that time the labours of natu-
ralists have been divided even in this humble and com-
paratively obscure study. Several French conchologists,
especially MM. Normand and Gassies, have separately
devoted themselves to a critical examination of their
native species of the above genera; and lately M. Bour-
guignat has favoured the scientific world with an elabo-
rate essay on the recent and fossil species of Sphcerium
(or Cyclas) which have been found in France. This
essay was published in the ' Memoires de la Societe des
Sciences physiques et naturelles de Bordeaux/ tome i.
1854. The only recent species described or noticed by
him, which is not also found in this country, is the
Cyclas solida of Normand. It appears to form an inter-
mediate link between Sphcerium and Cyrena; and M.
Bourguignat has separated it from the former under the
generic name of Cyrenastrum. I mention this in con-
sequence of the Cyrena (or Corbicula) fluminalis oc-
curring so frequently as a fossil in our upper tertiary
beds, and in the hope that the Cyrenastrum solidum may
also turn up in the same deposits, and lead to an eluci-
dation of the question how the limits of the true Cijrena,
in its living state, have become so restricted since the
glacial epoch. The only other genus of this family [Fisi-
dium) has lately had an equal amount of laborious atten-
tion bestowed on it by an eminent member of the French
corps of conchologists. The ^ Essai monographique sur

B 2

4 SPH^RIID.E.

ies Pisidies Francaises/ by Dr. A. Baudon of Mouy;, may
be profitably consulted by those who take a particular
interest in this subject. It was published at Paris in
1857, and contains fifty-five pages, and five plates of ad-
mirably executed figures. All the species of Pisidium
described by Dr. Baudon, with the exception of P. co-
nicum, appear to be also common to this country ; but
one of them (the P. Recluzianum of Bourguignat), which
was at that time imperfectly known to the author of this
essay, and its generic relation to Pisidium properly ques-
tioned by him, happens to be a marine shell, viz. the
Turto7iia minuta, M. Gassies having procured specimens
from Belfast, where it is abundant.

Genus I. SPH^'EIUM>^ Scopoli. PI. I. f. 1, 2.

Body nearly equilateral : mantle having a double tube.

Shell slightly inequilateral ; beaks placed near the centre
of the dorsal margin.

This genus was founded in 1777 by Scopoli (Introd.
ad Hist. Nat. p. 397, no. 88) in sufiiciently explicit
terms, taking the Tellina cornea of Linne as the type ;
but Bruguiere (who was followed by Draparnaud and
other authors) afterwards proposed for the same genus
the name of Cyclas, by which it has been more generally
known. Owing, however, to the bibliographical re-
searches of Dr. Gray, the older and equally appropriate
name of Sphcerium was restored by him in 1847 ; and
this latter name has been since adopted by Morch, Bour-
guignat, and other continental conchologists. The Jaw
of priority seems to require the recognition and use of
this name. I am aware that in thus advocating the
substitution of another (although an older) name for that

* From its spherical shape.

SPH^RIUM. 5

of Cyclas, whicli has so long received the sanction of
naturalists^ the principle of usage may be to some extent
violated^ and that it may be urged, with great reason,
that LimrKEa and Succinea ought to give place to Nerito-
stoma and Auricula, which Klein had previously pro-
posed, as well as Physa to that of Adanson's genus
Bulin ; but I am only in the present case following the
lead of experienced naturalists, and the conflict of au-
thorities ought to be determined by the strict rules of
justice. The word being derived from cr^acptov, it ought
not to be spelt Sphmrium, as has been done by some
authors.

1. Sph^kium corneum^, Linne.

Tellina cornea, Linn. Syst. Nat. ed. xii. p. 1120. Cyclas coi-nea, Forbes &
Hanley, Brit. Moll. ii. p. 113, pi. xxvii. f.3, 4, 5, 6.

Body white, gre^dsh, brown, or yellowish : tuhes rather
long, slightly tinged with flesh-colour : foot somewhat longer
than the shell, of a faint rosy hue towards its extremity.

Shell subglobular, nearly equilateral, compressed iu front,
rather thin, glossy, yellowish horn-colour, with often paler
bands or zones which denote the periods of growth, and occa-
sionally having faint streaks of brown which radiate from the
beaks towards the front margin, shghtly but closely striate
transversely, and marked by obscure hnes in a longitudinal
direction, so as to give the surface a reticulated appearance
under a high magnifying power : ejndennis rather thin : beaks
almost central : ligament short and narrow, scarcely visible on
the outside : inside bluish-white : Tiiyige strong, having a double
cardinal tooth in each valve, besides two lateral teeth in the
right, and four in the left valve ; the cardinal teeth are very
small, but distinct ; the lateral teeth form elevated ridges or
plates, and are subtriangidar at their extremities, those on the
anterior side being the largest : ^nuscidar scars or impressions
faint, owing to the thinness of the interior hning : pallial scar
scarcely discernible. Length 0-35. Breadth 0*45.

Yar. 1. flavescens. Smaller and rounder; body and shell

* Horn-colour.

6 sphj]:rud^.

straw-colour. C. flavescens, Macgillivray, Moll. Aberd. p. 246.
S. citrinum, l^ormand, Coup d'oeil CycL p. 1.

Var. 2. nucleus. Smaller and much more globular. C. nu-
cleus, Studer, Kurz. Verzeichn. p. 93.

Var. 3. Scaldiana. Shell more oval and of a paler colour.
C. Scaldiana, Norm. Cycl. p. 5, f. 1, 2.

Yar. 4. Pisidioides. Shell subtriangular, and rather more
produced at its posterior slope ; ti^ansverse (or concentric) striae
coarser : ligament slightly perceptible on the outside. S. Pisi-
dioides, Gray in Ann. & Mag. Nat. Hist. July 1856, p. 25.

Habitat : Slow rivers, lakes,, ponds and ditches, as
well as open drains in woods, everywhere in this country ;
and it occiu's in a fossil state in the upper tertiary de-
posits at Copford in Essex and other places. Var. 1. is
from Cumberland (Gilbertson) ; Westmoreland (Glover);
Grand Canal, Dublin (Warren) ; Aberdeenshire (Mac-
gillivray & Taylor) ; in a lake near Lerwick (Norman) .
Var. 2. Crymlyn bog, near Swansea (J. G. J.) ; Barton
run, Norfolk (Gunn) ; Richmond (Choules). Var. 3.
Oxwich marsh, near Swansea, and Thames at Clifden
Hampden (J. G. J.) . The colour of the body in this variety
is yellowish- white; tubes close together, irregularly jagged
at their edges, but not fringed, the branchial tube bein":
double the breadth of the other, which is funnel-shaped ;
foot white and broad. Var. 4. Grand Junction Canal at
Paddington. The shells of this remarkable variety are
much eroded, probably on account of the water being
charged with the refuse from manufactories or sewers.
The result of a careful comparison of these shells ^Yith.
other varieties and the typical form, and the circum-
stance that no other form of this variable species has
been found associated with it, incline me to believe that
it has not sufficient claims to rank as a distinct species.
It closely resembles the Cyclas rivalis of Dupuy (Hist,
nat. Moll. terr. et fluv. France, p. 668, tab. 29. f. 5),

SPH^RIUM. 7

which is another variety of the present species. Dr.
Baudon and M. Bourguignat both agree with me in the
above opinion. This species is widely distributed in
Europe; its northern limit being (according to Von
Wallenberg) Lapland^ and its southern limit being (ac-
cording to Philippi) Sicily. Young shells are extremely
flat, and might be easily mistaken for a different species.
This common species was first made known by our
countryman, the celebrated Dr. Lister, in his Treatises
on the history of English animals, in 1678. It is the
. Tellina rivalis of O. F. Miiller, and the Cyclas rivalis of
Draparnaud, who evidently described and figured the
next species {S. rivicola) as the Tellina cornea of Linne.

2. S. Rivi'coLA*, Leach.

Cyclas rivicola, (Leach) Lamarck, An. sans Yert. vi. p. 267 ; F. & H. ii.
p. Ill, pi. xxvii. f. 1, 2, and (animal) pi. Q. f. 1.

Body yellowish-grey, or hght brown : tubes short, white,
and nearly of equal length : foot thick, and capable of great
extension, greyish-white : gills sometimes slightly tinged with
red.

Shell oval, ventricose, nearly equilateral, much compressed
in front, rather solid, glossy, yellowish horn-colour, or ohve-
green, with often darker bands or zones, deeply ridged con-
centrically, especially towards the lower or front margin, the
ridges being crossed by obscure lines which radiate from the
beaks : epidermis rather thick : anterior side rounded : pos-
terior side more produced and subtruncate : heciks central,
small, and flattened : ligament short, prominent, and distinctly
visible on the outside : inside white and nacreous, with some-
times a yellowish tinge : hinge and teeth stronger than in /S.
Gorneum, but nearly of the same form : muscular and pallial
scars distinct. L. 0*7. B. 0*9.

Habitat : Slow rivers and canals in the metropolitan,
midland, and northern counties of England, as well as

* Inhabiting brooks.

8 SPH^RIID^.

near Dublin ; and it is one of our upper tertiary fossils.
It is a local species. On the continent it ranges from
Holland to Italy.

This fine species may be distinguished from S. corneum
by its much greater size, its form being oval instead of
globular, the strong transverse ridges, and the con-
spicuous ligament. The young of this are also much
flatter in proportion to their size. Both species occur
together. >S^. rivicola was first indicated by Lister as
having been found at Doncaster.

3. S. ova'le^, Ferussac.

Cijclas ovalis, Fer. in Ess. Meth. 1807, pp. 128, 136. 8. pallidum, Gray
in Ann. N. H. ser. 2. xvii. p. 465, woodcut.

BoBY milk-white : tuhes long, united nearly all the way :
foot tongue-shaped, very extensile and flexible : gills of a
faint blush-colour.

Shell oblong, somewhat compressed, not so equilateral as
the two preceding species, owing to the greater development of
the posterior side, thin, semi transparent, not very glossy,
yellowish, with sometimes a brown tint and darker zones of
growth, with occasionally some faint rays in the direction of
the lower margin, finely striate concentrically : epidermis thin :
anterior side rounded : posterior side truncate, and sloping
towards the lower margin, which is curved and sharp : heaks
small, nearly central, and slightly prominent : ligameiit long
and narrow, distinctly visible on the outside: inside ashy-
white : hinge straight on the posterior side, and incurved on
the other side ; cardinal and lateral teeth arranged as in S.
corneum, but the former are exceedingly small and difficult to
distinguish : muscular and pallial scars very faint. L. 0-4.
13. 0-6.

Habitat: Exmouth (Clark) ; PaddingtonCanal(J.G.J.);
canals and ponds in Lancashire (Darbishire) . A speci-
men also exists in the late Dr. Turton's collection of
British shells, but without any note of the locality.

* Egg-shaped.

SPH^RIUM. 9

Mr. Daniel says that he found this species in the Grand
Surrey Canal some years before it was noticed by Dr.
Gray, but that he then considered it to be a variety of
C rivicola. It is found in company with all the other
species of Sphcerium. A living specimen, which had been
taken early in February, and kept in a vessel by itself,
gave birth about three weeks afterwards to some young
ones at intervals of two or three days. Immediately on
being excluded, they were very active, and used their long
foot as an organ of progression, by extending it to its full
length ; and, after attaching its point to the bottom of
the vessel, like a leech, they drew up their shell to it; and
by repeating this several times they contrived to travel
along for some little distance. They seemed to be fond
of nestling under their mother for the sake of shelter or
shade.

There cannot be much doubt that this elegant and
very distinct species is the same as that which Drapar-
naud, in his ^ Histoire naturelle des Mollusques ter-
restres et fluviatiles de la France ' (p. 130, pi. x. f. 6, 7),
described and figured under the name of Cyclas lacustris.
He distinguished it from S. corneum and S. rivicola by
its being " plus mince, plus transparente, plus pale et
beaucoup plus aplatie." His description of the beaks
and hinge also exactly agrees with that of our species ;
and the very difierent terms in which he cha^racterized
his C. caliculata preclude our supposing that this accu-
rate naturalist could have taken for it a variety of the
last-named species. Ferussac, being aware of the error
which Draparnaud had committed in referring the spe-
cies in question to the Tellina lacustris of Miiller, gave
it the appropriate name which I have now adopted. The
species appears, however, to have been lost in France ;
and all the continental conchologists have applied the

B 5

10 SPH^RIID^.

name given by Draparnaud to some one of tlie nume-
rous varieties of either Miiller^s species or S. corneum.
The Cyclas rhomboidea of Say_, to which Dr. Gray sup-
posed our shell to be allied, is only a fourth of an inch
long, and, according to Gould, is an obscure or doubtful
species. Its nearest congener in this country appears
to be S. rivicola ; but it may be readily distinguished
from that species by its oblong and subangular shape,
thinner texture, much paler colour and fainter striae,
and especially by its straight hinge-line. The Devon-
shire and Lancashire sj^ecimens are of a darker colour
than those from the Paddington Canal. The young
exhibit the same form as the adult ; and, like the other
species, their shells are slightly iridescent.

4. S. lacus'tre^, Miiller.

Tellina lacustris, Miill. Verm. Hist. pt. ii. p. 204. Cyclas caliculata,
F. & H. ii. p. 115, pi. xxxvii. f. 7 (as C. lacustris), and (animal) pi. O.
f.7.

Body whitish, slightly tinged with grey or rose-colour :
tuhes long ; the branchial one cylindrical and truncate at its
orifice, which is large ; the other rather conical, and having
a smaller opening : foot nearly twice the length of the shell,
obtuse at its extremity : mantle fringed with grey.

Shell nearly round, or subrhombic, equilateral, compressed,
especially towards the lower and side margins, extremely thin,
glossy and semitransparent, light horn-colour, or greyish,
with sometimes a few darker zones and an iridescent hue,
very faintly striated concentrically : epidermis very thin : an-
terior and posterior sides cut ofi' and sloping from shoulders on
the upper or dorsal side towards the front margin, which is
slightly curved and has sharp edges: heahs central, very pro-
minent, and capped with the fry or nucleus of the shell, Avhich
Ls more globular than in the subsequent stages of growth :
ligament narrow, thin, and just discernible on the outside :
inside bluish-white, with very little nacre, owing to the thin
texture of the shell : hinge rather strong ; teeth arranged as

* Inliabiting lakes.

SPHiERIUM. 11

in the other species, but the cardinal teeth are smaller and the
lateral ones shorter in proportion : muscular and pallial scars
scarcely perceptible. L. 0*3. B. 0*4.

Yar. 1. Brochoniana. SheU much larger and flatter ; leaks
smaller and less prominent. S. Broclionianum, Bourguignat,
Monogr. p. 20, pi. 3. f. 1, 2, 3.

Var. 2. rotunda. Shell rounder and flatter ; epidermis yel-
lowish-green.

Var. 3. Rycklioltii, Shell small, triangular, and globular ;
healcs very prominent. C. Bychlioltii, Norm. Cycl. p. 7, f. 5, G.

Habitat : Lakes^ ponds^ and canals, and. stagnant
water everywhere in England, Wales, and Ireland; but
I have not observed it in Scotland, nor seen any notice
of its having been found there. Yar. 1. Clumber lake,
Notts (J. G. J.). This considerably exceeds the usual
form in size, being in length 0*45, and in breadth 6,
although its depth or thickness is only 0*25. Var. 2.
Singleton, near Swansea (J. G. J.). Var. 3. Marsh be-
tween Exmouth and Budleigh Salterton (J. G. J.). In
another piece of stagnant water near Exmouth a small
globular variety occurs, in which the beaks are not pro-
minent. A monstrosity is also sometimes met with, in
which the lower or front margin is constricted or divided
by a groove. Mr. Kenyon foimd it in the North of Eng-
land ; and I have also taken it in Crymlyn bog, near
Swansea. Some shells, which Mr. Choules has found
near Richmond, partake of the characters both of this
species and S. ovale, and apparently form an interme-
diate link between them. According to Middendorft' this
species inhabits Siberia ; and Philippi and Terver have
recorded it from Sicily and North Africa. It has also a
wide range in the intermediate parts of Europe. It
often occurs in company with S. corneum; and I have
found it alive in the hardened mud of a pond which
had been drained and its bed so completely dried up

12 SPH^RIID^.

by tlie sun as scarcely to show the marks of any foot-
steps on it.

This differs from all the other species of Spharium in
the shell being rounder and of a suhquadrate form^ its
great tenuity, and especially in the singular caps or ca-
lyces which surmount the beaks.

I cannot agree with the learned authors of the ' Bri-
tish Mollusca'' in preferring Draparnaud's name of
caliculata to that which had been long before assigned
to this species by Miiller. The description given by the
illustrious Danish naturalist does not appear to me at all
deficient in that accuracy and precision which characterize
all his writings ; and if some continental authors have
erroneously confounded this species with the Cyclas la-
custris of Draparnaud, this cannot be a sufficient reason
for continuing the mistake. At any rate_, the best French
authorities (including rerussac_, Blainville, and Moquin-
Tandon), as well as nearly all the conch ologists of our
own country, have adopted Miiller^s name in preference
to that of Draparnaud.

Although Mr. Jenyns has, in his excellent Mono-
graph, given an interesting notice of the habits of this
moUusk in a state of confinement, some further details,
which have been communicated to me by my friend
Dr. Lukis, of Guernsey, of its natatory, spinning, and
other performances, may not be unacceptable. In one
of his letters to me he says, " I placed a number
in a small fish-globe in clear water taken from the
sluggish stream in which they were captured. In a
short time they commenced crawling about and actually
ascending the slippery concave glass. In a few days a
considerable number of the fry had been cast, vidiich
proved far more active than their parents, readily climb-
ing the sides of the glolie, and rarely missing their foot-

SPH^RIUM. 13

ing, while the adults made many ineffectual attempts ;
but both fry and adults^ when they reach the edge of the
water, take to the surface easily_, and creep along slowly,
and apparently with caution, as if in search of some
floating substance, near which they will rest for hours.
The exserted foot moves, during this under-surface pro-
gression, by a gentle vermicular action, the siphons being
at the same time protruded. The foot during repose
is usually retracted, and does not seem necessary for
mere floating-purposes/^ And he adds, " An inter-
esting little scene occurred in the globe the other even-
ing. Several individuals had reached a few leaves and
hanging roots of minute water-plants which floated in
the centre of the globe, down the stems of which three
or four had crept to a depth of about an inch and a half.
There they reposed : but they were not absolutely mo-
tionless ; for, to my surprise, the whole group, plants and
all, were dreamingly enjoying the delights of a slow but
long- continued rotation. At first I thought some mi-
nute water-insect had found its way unbidden into the
globe, and was thus illustrating, like some learned lec-
turer to his sleepy audience, the laws of planetary mo-
tions. But no such lecturer was there : yet, as the
revolution brought two of the little moUusks closer under
inspection, I observed their siphons to be curved exactly
in the opposite direction to the line of motion. Here
was a solution at once of the nymph-like aTp6^i\o<i,
which was evidently due to the recoil consequent upon
the circulation and expulsion of the water through the
siphons. The fortuitous position of the two individuals
and the combined action of their expulsive tubes may
not occur again ; but the whole incident was so inter-
esting and remarkable that I could not help recording
it. The fry are growing rapidly ; and I opine the

14 SPH^RIIDiE.

amount of exercise they indulge in is conducive to their
health. I have observed the Eulima distorta, Rissoa
parva and cingillus, as well as the Odostomice and Jef-
freysice, ascend to the edge of a basin and creep along
the under- surface of the water^ in the same manner as
the Jjymnceadce. But it is singular that bivalves should
imitate their less unwieldy moUuscan brethren in this
seemingly unsuitable mode of progression/^ In another
letter he says^ " Sometimes a single individual will sus-
pend itself to a little bit of the stem of a Lemna, and whirl
quite alone for hours^ even rapidly — say fifteen to twenty
revolutions in a minute/^ And in a subsequent letter
he goes on to say, " The young are far more active than
the parents. I do not perceive their siphons to be ever
exserted, while this is almost constantly the habit of the
older ones. They all continue to climb the glass globe,
and rather more so in the evening, probably preferring
to roam in the dark. I have had a fresh supply of about
half a dozen, which, soon after being immersed, began
an inspection of their new domain, and continued for a
day or two more restless than the others. On climbing
the glass, the front margin of the valves is applied to it,
and at the same time both the foot and the siphons are
exserted. The foot being extended to its full length, its
extremity is cautiously pressed against the glass, and
after a short pause the upward movement of the body
commences, which is the work of a second of time;
then another short pause, after which the front margin
of the valves and the point of the foot are again applied
cautiously to the glass, and the foot is again protruded
to repeat the same process. When the edge of the water
is reached the pauses are longer, and it is necessary for
the creature to be doubly cautious, for here is the point
of greatest difficulty. However, the foot is conveyed

SPH^RIUM. 15

horizontally along the surface of the water, which ap-
pears to recede partially from it. On examining it with
a lens, the foot is distinctly seen to have an undulating
action on the surface, as well as an irregular and im-
perfect contraction and elongation along its whole ex-
tent ; but it is never quite retracted, excepting when its
base and the front margin of the valves are in contact
with some floating weed which is capable of supporting
the whole. Thus this elegant shell traverses the still
surface. But it is most curious to see it descending the
thread-like stems of the Lemna, or some assemblage of
these delicate fibres : even a single stem is quite suffi-
cient ; and if the shell is free from any other contact, it
immediately begins its rotatory movement. A single
shell, thus suspended, revolves upon its axis in a direc-
tion which is most frequently from right to left of the
observer, or in the opposite direction from that of a
teetotum when made to spin by the fingers of the right
hand. I have suspended single threads to circular pieces
of cork in the water ; but the stems of the Lemna are
preferred. Cyclas cornea is much less active or inclined
to ascend the glass ; in fact, I have not yet seen it ac-
complish the feat of its congener. Several of the C caly-
culata (Sphcerium lacustre) will remain among the stems
of the duckweed for hours perfectly inactive, with closed
valves, as if sleeping or resting after their previous
fatigue. When the valves are pressed against the glass
while ascending, there seems to be a fulness about the
base of the foot, as if the mantle served for adhesion to
the glass.^^ Dr. Lukis afterwards informed me that he
had detected the byssal filament in S. lacustre. He
says, '^ I have this morning watched one, which had
reached the surface, spm its filament j and descend to

16 SPH^RIID^.

half an inch below the surface, where it remained sus-
pended for some time. It occupied three hours in
spinning this short thread. I think it consists of more
than a single filament ; for some minute particles, which
were floating in the water, became entangled in it. The
surface of the water was again depressed or cupped.^'
And he concluded by saying that he found the number
of filaments to vary from one to at least four, which in
one instance were far apart, the siphons or tubes and
foot being at the same time exposed ; and that the
animal had the power of raising itself by means of this
byssus again to the surface, after having been suspended
for some time below it. The filaments appeared not to
exceed half an inch in length ; and rarely could more
than a single thread be seen. M. Bouchard-Chante-
reaux has likewise, in his extremely interesting Cata-
logue of the Land and Freshwater Mollusks which in-
habit the Department of the Pas-de- Calais, noticed that
the young of S. corneum possess the same faculty of
spinning a transparent thread and attaching themselves
by means of it to water-plants.

Genus II. PISI'DIUM ^ C. Pfeifi"er. PL I. f. 3, 4.

Body inequilateral : mantle having only a single tube.

Shell inequilateral : beaks placed near the shorter or an-
terior end.

This genus was established by Carl Pfeiflfer in 1821, to
separate from Sphcerium the smaller species which have
only one tube or siphon, and whose shells are not so
equilateral. This generic distinction seems to be well
founded, in respect both of the soft parts of these mol-

* Pea -shaped.

PISIDIUM. 17

lusks and of their shells; and it has received almost
the universal assent of conchologists. The habits of the
little Pea shells are the same as those of the larger
members of the same family ; and they inhabit nearly
the same situations. One species (P. pusillum) does not
seem to require a constant, or even a frequent supply of
water, being often found living at the roots of bog-moss
which is dried up in the summer, and of grass in mea-
dows which are only irrigated in the spring ; and Nils-
son noticed, in his history of the land and river mol-
lusks of Sweden, that he had frequently found the same
species (which he erroneously referred to the P. fontinale
of C. Pfeiffer) living between the bark and wood of fallen
trees in moist places. They possess the same faculty as
the Sph(Eriaj of floating, or creeping in an inverted posi-
tion under the surface of the water. These tiny Pea
shells, or cockles, swarm in every slow river, streamlet,
lake, pool, horse-pond, ditch, and open drain ; and they
are greedily devoured by fish and ducks. In their turn,
they are fond of animal food ; and Dr. Baudon, in his
admirable Monograph, says that he has often observed
Pisidia attached to the drowned carcases of small ani-
mals, as well as to bones which had been thrown into
ditches and streams, and from which the muscular fibres
had not been removed. Perhaps, however, animalcula
fed upon the meat, and were the real objects of attrac-
tion to the Pisidia. Their shells are sometimes so
thickly encrusted with a ferruginous or mineral deposit
from the muddy sediment of the water which they in-
habit as to resemble small lumps of dirt. This deposit
appears to be partly owing to a secretion of the animal,
aided by its generally inactive habits. Water -beetles do
not allow themselves to be clogged in the same manner.
Whether this is one of the artifices by which animals

18 spHtERiid^.

escape the observation of their natural enemies is a
question which requires a molluscan mind to solve.

The critical investigation of the different species which
compose this genus is quite as difficult as it is with regard
to the large freshwater mussels. Little reliance can be
placed on the characters afforded by an examination of
the body^ or soft parts, of the animal. The form and
comparative length of the tube are especially liable to
vary even in the same individual ; and under the influ-
ence of heat and light the most Protean changes with
respect to this organ may be observed. The size of the
foot is equally a deceptive character ; and colour is al-
ways a most uncertain test. The general shape and
appearance of the shells, as w ell as the position of their
beaks, appear to offer almost the only reliable grounds
of distinction. Size, substance, sculpture, and lustre are
not of much account, as they mainly depend on the
chemical ingredients of the water inhabited by these
moUusks, as well as on their supply of food. In making
an investigation like the present, there appear to be four
courses open to the naturalist. The first, which is,
perhaps, the easiest, is to reduce all hitherto described
species to one or two, and thus to cut the Gordian knot
without further ceremony. The second, which has been
pursued to such an extent on the Continent and in the
United States of America, is to multiply the number of
species ad infinitum. The only check which can be im-
posed on this method of wholesale and indiscriminate
fabrication is the bar of scientific opinion ; and in coun-
tries where nearly all the naturalists are culprits, there
is not much likelihood of justice being so severely admi-
nistered as to prevent the repetition of such venial
offences. The third course is, to adopt the labours of
preceding writers without any inquiry. And the fourth

PISIDIUM. 19

is, honestly and to the best of one^s ability carefully to
work out the subject and to submit the result to the
free criticism of other naturalists. This last course I
have endeavoured to pursue ; and I shall not feel in the
least degree mortified or discouraged if the conclusions I
have arrived at, with much pains and great hesitation,
are not accepted by all my scientific brethren.

To give some idea of the labour involved in this in-
vestigation, I may mention that my own cabinet con-
tains no less than 274 parcels of Pisidia, which have
been, in the course of the last thirty or forty years, col-
lected from different localities and sources, and comprise
many thousands of specimens ; that I have personally
examined the types of those species which have been de-
scribed by Dr. Turton, Mr. Jenyns, Mr. Alder, Dr. Bau-
don, and other conchologists who have published on the
subject; that I have collected these tiny shells in many
parts of Holland, Germany, France, Switzerland, and
Italy, for the sake of comparison with British forms jj
and that I have had to refer to numerous works in many
languages in order to collate the descriptions of forty-
one different species which have been proposed by Euro-
pean writers within the last century. Of these, I cannot
conscientiously recognize more than six as distinct.

It will be convenient to divide the British species,
which are five in number, according to their shape, as
follows : —

A. Triangular. 1. P. anmicum. 2. P. fontinale.

B. Oval. 3. P. pusillum.

C. Bound. 4. P. nitidum.

D. Ohlong. 5. P. roseum.

20 SPH^RIIDiE.

A. Triangular.

1. PisiDiuM am'ntcum*^ Miiller.

Tellina amnica, Miill. Yerm. Hist. p. 205. P. amnieum, F. & H. ii. p. 133,
pi. xxxvii. f. 8, 9, and (animal) pi. O. f. 8.

Body greyish -white, rather transparent; tube short, sub-
conical, obliquely truncate at its orifice : foot broad at its
base, abruptly pointed, and very extensible : mantle bordered
with grey.

Shell subtriangular, rather ventricose and solid, glossy,
strongly grooved concentrically, horn-colour or yellowish-
grey : epidermis rather thick : anterior side abruptly truncate :
posterior side much produced, and sloping towards the lower
margin, which is obliquely curved : healcs rather prominent,
but obtuse : ligament short, conspicuous : inside bluish-white
and nacreous : hinge strong and curved ; teeth arranged as in
Splioerium, but the lateral teeth in this and other species of
Pisidium are exceedingly strong and developed in proportion
to the size of their shells : rnuscular and pallial scars well
marked. L. 0*3. B. 0*375.

Yarieties occur in which the striae are more numerous,
fewer, stronger or fainter than usual.

Habitat : Slow rivers, lakes_, canals, and streams in
all parts of the kingdom. It is also one of our com-
monest upper tertiary fossils. Its continental range ex-
tends from Siberia to Naples, and it is also found in
Algeria. This is the largest kind of Pisidium.

2. P. fontina'le tj, Draparnaud.

Cyclas fontinalis, Drap. Hist. Moll. p. 130, pi. x. f. 8-12. P. Henslowi-
anum (var. without appendages), Jenyns in Ann. Nat. Hist. Aug. 1858,
p. 104.

Body whitish or grey, rather transparent : tube generally
short, but capable of considerable extension and dilatation,
conical, obliquely trimcate at its orifice, where it is so flexible
that the edges are sometimes entire and at other times jagged :
foot long and curved : mantle bordered with grey.

* Inhabiting rivers. f Inhabiting fountains.

PISIDIUM. 21

Shell subtriangular, somewhat ventricose, thin, rather
glossy, finely but irregularly striate concentrically, greyish-
white : epidermis very thin : anterior side abruptly truncate :
posterior side rounded, and sloping gently towards the lower
margin ; the anterior and posterior margins are compressed,
especially towards the beaks, on each side of which they form
a kind of shoulder : heaks prominent and rather acute : liga-
ment very short and scarcely perceptible : inside white and
nacreous : hinge short, but very strong ; dentition as in P.
amnicwn, except that the cardinal teeth do not assume the
shape of an inverted Y : muscidar and pallial scars the same
as in that species. L. 0*15. B. 0'175.

Yar. 1. Henslowana. Each valve fui^nished with a plate-
Hke appendage near the beaks. Tellina Hensloiuana, Shep-
pard in Linn. Trans, xiv. p. 150. P. Henshiuianmn, F. & H.
ii. p. 131, pi. xxxvii. f. 11.

Yar. 2. pulchella. Shell more glossy, strongly and regu-
larly grooved ; heahs less acute. P. pidchellum, Jen. p. 18,
tab. xxi. f. 1-5 ; F. & H. ii. p. 128, pi. xxxvii. f. 12, 13.

Yar. 3 pallida. Shell more ventricose, irregularly striate,
and of a paler colour, with occasionally a few darker rays
which diverge from the direction of the beaks to the lower
margin.

Yar. 4. cinerea. Shell larger and flatter, with fainter striae.
P. cinereum, Alder, Suppl. Cat. Moll. Northumb. p. 4 ; F. & H.
ii. p. 125, pi. xxxvi. f. 2.

Habitat : Slow streams and standing water every-
where in these isles ; and it is one of our upper tertiary
fossils. It also ranges from Siberia to Sicily. Var. 1.
occurs in many of the northern^ eastern, home, and
south-western counties of England, as well as in South
Wales and Cork. This is also one of our tertiary fossils,
and extends from Sweden to the South of France.
Specimens from the Swansea Canal, near some tinworks,
have the beaks more or less eroded, in consequence pro-
bably of the water containing an extremely diluted por-
tion of sulphuric acid, which is used in that manufac-
tm'e. The fact, which has been noticed and considered

22 SPH^RIID^.

remarkable by some authors^ of the eave-like projection
appearing in the middle of young shells_, agrees with its
position in adult shells^ because this curious appendage
is never placed close to the beak. Var. 2. More com-
mon than the last variety^ and also inhabiting Sweden
and France. It deserves its name^ being a very pretty
object. Mr. Jenyns now considers it to be the same
species as his P. Henslowianum. Var. 3. Marshes and
pools near Swansea. It is probably the P. pallidum of
Gassies. Var. 4. Widely diffused in this country, and
also inhabiting France and Italy. The outline of some
specimens of this last variety is that of an equilateral
triangle. It is the P. australe of Philippi, and the Cyclas
lenticularis of Normand.

This species is extremely variable, and has conse-
quently received a great number of names. Out of the
41 so-called species of Pisidium which have been de-
scribed by European conchologists, no less than 21 belong
to the present form. On the Continent the type is
generally known by Polios name of Casertanum.

If the diagnosis, characters, and figures given by
Draparnaud for his Cyclas fontinalis had been more
carefully studied, it would, I think, have been obvious
that they do not apply to the Tellina pusilla of Gmelin,
with which this species has been generally (but with
doubt) allocated by so many authors. The principal
difference between these two species consists in the
former (P. fontinale) being triangular and somewhat
depressed, and having prominent beaks ; while the other
(P. pusillum) is oval and ventricose, and has obtuse
beaks. Draparnaud^s diagnosis is as follows : " C. testa
globosa, subdepressa, subina3quilaterali ; umbone sub-
acuto." Gmelin says his shell is " ovata, ventricosa ;^'
and his description of its colour as " sordide alba ^' is

PISIDIUM. 23

peculiarly appropriate to tlie P. pusillum of modern
authors. C. Pfeiffer^ in 1821;, appears to have recog-
nized Draparnaud^s shell by the same specific name of
" fontinale '" and the only distinction which he makes
between this species and his own P. obtusale (which I
regard as a variety of P. pusillum) is that the former is
described " umbone subacuto", and the latter '' umbone
obtusissimo."

It chiefly differs from P. amnicum in being very much
smaller (although the variety cinerea is nearly as large) ^
in the shell being thinner^ the posterior margin much
less produced, the i)eaks being more prominent, and the
ligament scarcely conspicuous. The cardinal teeth are
also more separate, and do not diverge from a common
base or root as in that species and Sphcerium.

B. Oval.

3. P. pusii/lum*, Gmelin.

Tellina pusilla, G-inelin, Syst. Nat. p. 3231 . P. 'pusillum, F. & H. ii.
p. 123, pi. xxxvii. f. 10, and (animal) pi. O. f. 9.

Body whitish, with occasionally a faint tinge of yellow or
red: tube short, subcorneal or cylindrical, truncate, orifice
small and its edges plain : foot longer than the shell, narrow
and slender : mantle bordered with reddish-grey.

Shell oval, compressed but swollen, thin, not so glossy as
in the other species, finely but irregularly striate concentri-
cally, a few of the striae being larger than the others and de-
noting the successive stages of growth, yellowish-white or
cinereous : epidermis very thin : anterior side rounded : poste-
rior side also rounded, and sloping very gradually below ; this
side is very httle more produced than the other, which makes
the contour of the shell more equilateral than in the foregoing
species ; both these sides are compressed, and especially above :
lower margin rounded : beaks not prominent, but blunt : liga-
ment short and inconspicuous: inside greyish-white, vrith

* Little.

24 SPH.«RIID^.

scarcely any nacreous lustre ; other internal characters the
same as in P. fontinale. L. 0-175. B. 0-2.

Var. ohtusalis. Shell smaller and much more ventricose ;
healcs prominent, very obtuse. P. ohtusale, C.Pfeiffer, Deutsch.
Land- und Sussw.-MoU. i. p. 125, t. 5. f. 21, 22 ; F. & H. ii.
p. 120, pi. xxxvi. f. ] .

Habitat : Mossy swamps, shallow ditches, drains,
grassy pools, and similar situations throughout aU the
country ; and it is one of our upper tertiary fossils. It
ranges from Lapland to Corsica, and is generally diffused
in Europe. Dr. Baudon says that it is the same species
as the P. vejitricosum of Prime ; so that it appears to be
also a native of the United States bf America. The
variety obtusalis occurs in similar situations with the
typical form ; but it is more local and not so abundant.
The intermediate gradation between the two forms is
almost infinite ; but the essential and common character
of both is the same, viz. the beaks being nearly central
and obtuse.

Having carefully studied the description and figure
given by Poli of his Cardium Casertamim, I have not
been able to arrive at the same conclusion which Moquin-
Tandon and other French conchologists have formed,
that this species is the type of the one which I have de-
scribed as P. fontinale ; and I consider that it ought
more properly to be referred to the present species. Poli
says his shell is " subrotunda f' and his figure shows
that it is much more equilateral than P. fontinale. He
also remarked the irregularity of the strise arising from
the marks of groAvth, which appears to be more cha-
racteristic of this than of the other species. As, how-
ever, he did not notice any other species, it is of course
very difficult to say precisely which species he meant ;
and under these circumstances I think it is preferable
not to revive an obscure and doubtful species, indicated

PISIDIUM* 25

by a local name, when we have at least equally good
reasons and authority for adopting a name bestowed by
an earlier writer, and which, besides, is not liable to the
same objection. This species differs from P. fontinah
in its shape being oval instead of triangular, and in its
beaks being more central, and blunt or compressed. Its
colour is also yellowish- white instead of grey ; and it has
much less lustre. It is the Cyclas fontinalis of Nilsson.

C Round.

4. P. ni'tidum*, Jenyns.

P. nitidum, Jen. p. 16, tab. xx. f. 7, 8 ; F. &H. ii. p. 126, pi. xxxvii. f. 14.

Body whitish, -^dth sometimes a faint tinge of yellow, caused
by the colour of the liver : tube short, funnel-shaped ; orifice
wdde, and its edges notched or puckered : foot rather long,
thin, slender, and finely pointed : mantle bordered with grey.

Shell suborbicular, compressed except in the upper part
where it is rather ventricose, thin, extremely glossy, iridescent
(especially in the young state and near the beaks) , finely and
regularly striated or ribbed concentrically, with from 3 to 5
separate and deeper grooves which encircle the umbonal region,
the strise or ribs being rather broad ; yellowish- white or light
horn-colour : epidermis a mere film : anterior side somewhat
truncate, but rounded: posterior side slightly produced and
sloping abruptly below : lower margin rounded : healcs nearly
central, rather prominent, but obtuse : ligament very short,
and scarcely discernible : inside w^hitish, and plainly showing
the scars of the adductor muscles and mantle : hinge and teeth
as in the two last species. L. 0*15. B. 0*15.

Var. splendens. Shell of a lemon-colour, nearly half as
large again as that of the ordinary form, stronger, less glossy,
rather more obhque, and less deeply striated, with the beaks
more swollen and the hgament stronger and perceptible.

Habitat : Lakes, ponds, and standing water in all
parts of the kingdom from Zetland to the Channel
Isles. Malm has described and figured it as a Swedish

* Glossy.

C

26 SPH^RIID^.

species ; and Moquin-Tandon has noticed it as Corsican.
I have found it also on all parts of the Continent. The
variety splendens of Baudon occurs in lakes near Lerwick,
and at Balmacarra in West Ross. A monstrosity or
distortion of this species, as well as of P. fontinale (var.
Henslowand), is sometimes met with, which has the
valves constricted or divided by a longitudinal groove.
This accidental phenomenon in the typical form of P.
fontinale induced M. Bourguignat to consider it a distinct
species, and to give it the name of P. sinuatum. It is
caused by a laceration or injury of the front margin of
the mantle.

This may be distinguished from all the preceding spe-
cies by its rounded outline, much more glossy and iri-
descent appearance, and by a few separate and deeper
grooves or lines which encircle the beak and are espe-
cially perceptible in young shells. This is also the only
kind of Pisidium which has the tube funnel-shaped and
its outer margin crenulated or plaited. For the dis-
covery of this species science is indebted to Mr. Jenyns.

D. OhJong.
5. P. Ro'sEUM^, Scholtz.

p. roseum, Scholtz, Schlesien's L.- und W.-Moll. p. 140; Jeffr. in Ann.
Nat. Hist. s. 3. vol. iii. p. 38, pi. ii. f. 3.

Body opaline white, orange -yellow, red, or rose-eoloiu- in
the upper part : tube long, slender, subconical, and truncate at
its orifice : foot long, semitransparent.

Shell subrhombic, ventricose, thin, very glossy, deeply and
regularly striated concentrically ; yellowish-white or light
horn-colour : epidermis extremely thin : anterior side truncate
and sloping abruptly below : posterior side much produced and
rounded : lovjer margin nearly straight : healcs placed con-
siderably on one side, rather prominent, but obtuse : ligament

* Eosc -colour.

PISIDIUM. 27

inconspicuous : inside nacreons-white : Tiinge-Une nearly
straight ; cardinal teeth very minute and almost impercep-
tible ; lateral teeth not well developed, except towards their
outer edges, which are strong and sharp : muscular QXid.'paUial
scars scarcely visible. L. 0*1. B. 0-15.

Habitat : Marshes, ponds, ditches, and stagnant water
from Zetland to Guernsey. It also occurs in Silesia,
Sweden, and France ; and I have found it in Prussia.
It has probably escaped notice in other parts of the Con-
tinent.

This species differs from all its congeners in its oblong
or rhomboid shape, which is principally owing to the
greater extension of the posterior side, and to the beaks
being consequently placed so much out of the centre, as
well as to the compression and nearly straight outline of
the lower or front margin. It is considerably more
ventricose than P. nitidum, which it resembles in its
gloss and sculptm^e. The umbonal strise are, besides,
not perceptible in the species under consideration ; and
the tube does not appear to have the margin of its
orifice plaited. The body has usually a rosy or reddish
hue in the upper part, which is discernible in the dried
animal.

It was not without much hesitation that I adopted the
name given by Scholtz for this species, because in a
Supplement to the second edition of his work he con-
sidered it to be a variety of P. fontinale ; but the colour
of the animal, which at first induced him to propose
this as a distinct species, appears to form a good and
constant mark of distinction, and one of the epithets
which he applied to the shell ("langlichrundlich^^) is
very appropriate. The only other species of Pisidium
besides this, which Scholtz has noticed, are fontinale,
amnicum, and obtusale. Whether it may ultimately be
united with nitidum is, however, a question which I, for

c2

28 UNIONID/E.

one^ shall not consider unreasonable, although my pre-
sent impression is that they are distinct species. The
variation of form and sculpture is undeniably very great
in all freshwater shells ; and this is probably caused not
only by the greater or less supply of food procurable
by these mollusks, but also by the chemical ingredients
of the water from which their materials are secreted or
extracted. Development of size, and of particular por-
tions of the shell (by which its shape is determined),
seems to depend on the former condition, while its
solidity and sculpture are affected by the nature of the
fluid which these moUusks inhabit. The present species
is the P. tetragonum of Normand and the P. arcceforme
of Malm.

As some test of specific distinction, I would remark
that the following species of Pisidiiim are often found
living together : viz., amnicum Sind fontinale (var. Hens-
lowana) ; fontinale and pusillum ; and fontinale (var.
pallida), nitiduyn, and roseum. Each of the above is also
sometimes found solitary, or in company with various
species of SphcBriurn,

Family II. UNIONIDtE.

Body oblong, compressed : mantle open on all sides except
at the back, but forming at the posterior side two orifices,
which correspond with the cylinder or tubes of the SpJiceriidce.
The smaller and upper, or excretal, orifice is separated from
the larger and lower, or branchial, orifice by an intermediate
fold of the mantle. The margin of the first-mentioned orifice
is plain ; but the other is fringed with several rows of cim
or tentacles. Mouth placed as in the last family. Foot large,
broad, and tongue-shaped.

Shell equivalve, oblong, inequilateral, compressed : epi-
dermis thick : becdcs (which form the nucleus or young shell)
plaited or wrinkled: ligament external, strong, and always
conspicuous : inside pearly : himje furnished with lateral teeth

UNIONID^. 29

only ; those on the anterior side being sometimes so much
developed as to resemble cardinal teeth.

Some of these mollusks^ which are often called " fresh-
water Mussels/^ are ovoviviparous^ like those of the last
family, and retain their young within the folds of the
mantle for some time before they are finally excluded ;
while others are oviparous, like the majority of mollusks.
It was for a long time supposed that they were of sepa-
rate sexes, and Von Siebold distinguished Atiodonfa
cygiiea as the male, and A. Cellensis as the female, of the
same species ; but Moquin-Tandon seems to have now
proved satisfactorily that both sexes are common to each
individual or that they are all monoecious. They in-
habit rivers and other large pieces of water. Their
habits are tolerably active in the spring, or when in
search of a suitable feeding-place ; and by means of their
large fleshy foot they are able to traverse considerable
distances, leaving a track or furrow in the soft mud.
When the water is slowly drained off", or dried up by the
heat of summer, as well as in the winter, they bury them-
selves in the mud. Their food consists of Entomostraca
and other minute animals. According to Mr. Anthony,
an American conchologist, who has especially studied
the members of this family, some species spin a byssus.
It is difficult to separate this family from their marine
analogues, the true Mussels, on merely malacological
grounds ; but I believe a good conchological distinction
(considering the shell to form an integral and important
part of the animal) is maintainable in the position of the
ligament and beaks. The former is external in the
UnionidcB, while it is internal in the MytiUdcs ; and the
beaks are nearly terminal in the latter, but in the former
they are seldom placed at a less distance than one-fourth
from the anterior end. Besides these marks of distinc-

30 UNIONIDiE.

tion^ there are no lateral teeth in Mytilida, and in My-
tilus the cardinal teeth are conspicuous. In the Unio-
nid(2, on the other hand, the lateral teeth are always,
and the cardinal teeth never, present. I am quite aware
that this last statement will be objected to by all those
conchologists who believe that, at all events, the shells of
Vnio are furnished with cardinal teeth. But I venture
to submit that these teeth are lateral, and not cardinal ;
that they are not, like the cardinal teeth in the S^jIkb-
riidcB, placed at a right angle to the hinge-line, but that
they are, on the contrary, parallel to it; and that they
are always lamellar and form more or less elevated ridges,
like the true lateral teeth in other bivalves. In the
genus Anodo7ita, indeed, the lateral teeth are not so
strongly developed as in Unio, and they may in some
cases be considered as rudimentary ; but in nearly all
the species of Anodonta these teeth form a well-defined
and often sharp crest, especially on the posterior or liga-
mental side. The unusually great length and strength
of the ligament in Anodonta seems to render the use of
lateral teeth in supporting the hinge almost unnecessary ;
and in this, as well as in many other cases of a similar
kind, the original form of such organs is retained in an
imperfect state, although their use has ceased to exist.

The study of the European members of this family
has for a long time attracted the attention of continental
naturalists ; and Carl Pfeiffer, Rossmassler, and Henri
Drouet have especially applied themselves to this diffi-
cult task. A valuable monograph has been published
by the last-named naturalist, entitled " Etudes sur les
Naiades de la France ;^^ the work being dedicated to the
late King of Portugal, whose devotion to conchology
was the more remarkable because this branch of natural
history has not been cultivated by many crowned heads.

«

UNIO. 31

In this country very little has been done to advance our
knowledge of the Unionidce ; and it would be extremely
desirable if naturalists who reside in the country would
carefully notice and record any instances of different
kinds occurring in the same waters, and whether any
intermediate forms are found in such localities.

Genus I. U'NIO^ Philippsson. PI. I. f. 5, 6.

Body elongated, rather ventricose : gills nearly straight :
labial paljps ovate.

Shell elongated, soUd : lateral teeth strong : lunide or heart-
shaped depression on the anterior side distinct.

This genus was founded by Philippsson in 1788 in an
inaugural Lecture entitled " Dissertatio historico-natu-
ralis sistens nova Testaceorum genera ;" but, owing to
the circumstance of its having been delivered at a meet-
ing of which Hetz was the president, the latter has
usually had the credit of founding the genus. From
this genus it has been since proposed to separate the
Pearl-Mussel, under the name of Margaritana, or Alas-
modon, on account of the teeth being less developed ; but
there does not appear to be sufficient reason, on con-
chological grounds, for this separation. The animals, or
bodies, of these so-called genera cannot be distinguished
from each other. All the species are, according to
Moquin-Tandon, oviparous.

Many species of Unio have been described by Conti-
nental writers ; and even Moquin-Tandon, who is by no
means addicted to this kind of manufacture, has ad-
mitted no less than eleven. Two of these (viz. U. Batavus
and U. rhomboideus [or littoralis]) , which are widely dif.
fused throughout France, have not yet been detected in

* A pearl.

32 UNIONID^.

this country, although the latter is not uncommon, in a
fossil state, in our upper freshwater tertiary beds.

That part of the shell which surrounds the beaks
(called the " umbonal region ") is sometimes eroded or
excoriated in these, as well as in other members of the
family. I believe it is caused by the chemical action of
gases which are evolved from the mud in which this por-
tion of the shell is usually imbedded. No reliance can
therefore be placed on such a feature as a mark of specific
distinction.

The word " Unio ^' is, according to Pliny, masculine.

1. Unio tu'midus^, Philippsson.

U. tumidus, Philipps. Nov. Test. Gen. p. 17 ; F. & H. ii. p. 140, pi. xl. f. 1.

Body greyish : mantle bordered with white ; the excretal
orifice being produced into a short tube, and of a brownish
colour with sometimes a few purplish streaks ; the branchial
orifice mottled with orange-brown : foot milk-white, with a
pale orange tint, thick and broad : gills pale grey : labial
palps rather broad.

Shell oval, very convex above, solid, rather glossy, yel-
lowish-brown, transversely wrinkled : epidermis rather thick :
heahs slightly incurved, and placed at a distance of about one-
fourth from the anterior side : umbonal region prominent and
strongly plaited in a wave-like manner, the folds sometimes
rising into sharp knobs or tubercles : lunule lance-shaped and
narrow : ligament short, strong, and prominent : anterior side
rounded and regularly sloping towards the front: posterior
side gradually sloping to a wedge-hke point : lower inargin
reffularlv curved: inside white and nacreous, with a faint
tinge of blue : hinge strong ; the right valve having on its
anterior side a broad, thick, and bifid tooth, Avhich is slightly
bent forwards, and irregularly grooved so as to make its crest
notched, and having on its posterior side a long and deep
channel or groove, formed by a double plate, to receive the
corresponding tooth of tlie other valve ; left valve furnished
at its anterior side yni\\ a single wedge-shaped and strong

* Swollen.

UNio. 33

tooth, which is also grooved and notched like the double tooth
of the right valve into which it locks ; this valve has also a
long, sharp and crest-like plate on the posterior side which is
morticed into the channel or groove above mentioned : muscular
2iDA pallial scars very deep and distinct. L. 1*5. B. 3.

Var. 1. radiata. Shell thinner : epidermis green, marked
with divergent yellow rays, which are interrupted by trans-
verse narrow zones of the latter colour ; posterior side more
compressed above: hinge-line nearly straight, especially in
half-grown specimens.

Var. 2. ovalis. Shell triangular-oval, or wedge-shaped,
compressed and somewhat incurved in the middle, rather
inequivalve in consequence of the right valve slightly over-
lapping the other, dark olive-brown : anterior side much
broader and abruptly truncate : lunule very broad, deep, and
oblique. Mya ovalis, Montagu, Test. Brit. pp. 34 & 563.

Habitat : Rivers, canals, and ponds in England as
far north as the Went in Yorkshire, and also in South
Wales ; and it is one of our upper tertiary fossils. Its
range extends northwards as far as Finland ; but it does
not appear to have been met with south of the Rhone.
Var. 1. R. Avon, near Bath (Clark) ; Railway lake near
Oxford (Whiteaves). Var. 2. R. Avon, Wilts (Montagu);
R. Brent (Metcalfe) ; and from Mrs. Loscombe's col-
lection of British shells. The late Mr. Clark also found
this variety near Bath, having a green epidermis which
is marked longitudinally with yellow rays, and trans-
versely with alternate zones of green and yellow. My
cabinet contains a specimen of the last variety, wliich
was sent by Col. Montagu to my late friend Mr. Dillwyn,
and by the latter presented to me with a few other
typical specimens from that excellent British zoologist.
The inside of each valve bears, in his well-known hand-
writing, the words "Mya ovalis, Wiltshire." This, there-
fore, shows what Montagues species really was ; and it
is the more interesting because the authors of the ' British

c 5

34 UNIONID^.

Mollusca ' referred it both to U. tumidus and U. picto-
rum, while Moquin-Tandon considered it to be a variety
of U. Batavus, It is more strictly a monstrosity^ or
abnormal form^ than a variety.

This species sometimes occurs in company with the
next. The Rev. A. M. Norman has recorded in the
' Zoologist' for 1857 having taken specimens at Fleck-
ney and Wistow in Leicestershire of the extraordinary
dimensions of nearly 4i inches in breadth and more
than 2 inches in lengthy the weight being over 3 ounces.
Beneath the epidermis the colour of the shell in this and
the next species is cream-white. A single individual of
U, tumidus has been known to lay 1500 eggs in two or
three days. They are deposited in small clusters, each
of which contains about 100 eggs.

2. IT. picto'rum*, Linne.

Mya pictorum, Linn. Syst. Nat. ed. xii. p. 1112. U. pictorum, F. &H.
ii. p. 142, pi. xxxix. f. 1, and (animal) pi. Q. f. 2,

Body clear red, with a more or less grej^sh tint : mantle
bordered with brown ; orifices of the same form and colour as
in the last species : foot reddish or yellowish -white, large and
tongue-shaped : gills grey : labial palps oval.

Shell oblong, compressed, not so solid as the last species,
glossy, yellow, with narrow zones of brown which denote
the marks of growth, transversely wrinkled, with stronger
furrows on the posterior side : epidermis rather thin : beaks
very httle incurved, and placed at a distance of between one-
fourth and one-fifth from the anterior side : umbonal region
not so prominent nor so strongly wrinkled as in the preceding
species : lumde long and narrow : ligament longer than in U.
tumidus : upper margin or hinge-line nearly straight : anterior
side rounded : posterior side very gradually sloping and rounded
at its extremity, compressed or pinched-up above : lower margin
nearly straight : inside cream-white or salmon-colour, highly
nacreous : Jiinge not so strong as in the last species ; the teeth

* Painters'.

uNio. 39

similarly arranged, but they are finer, sharper, and more erect :
muscular scars distinct : pallial scar faint, owing to the greater
thickness of the nacreous lining. L. 1-33. B. 3.

Var. 1. racliata. Shell having faint and narrow rays of
green which diverge from the beak.

Var. 2. curvirostris. Shell smaller, shorter, and flatter:
epidermis yellowish-green, with brown zones : posterior side
curved and wedge-shaped. U. curvirostris, Normand.

Var. 3. latior. Shell broader and shorter, yellowish-brown.

Var. 4. compressa. Shell very broad and flat ; upper margin
raised and curved : posterior side greatly compressed and at-
tenuated, assuming a beak-like form, and having a double
ridge and furrow which runs from the beak in the younger
state of growth : lower margin straight : lunule broad, and ex-
tending between the beaks, so as to separate them from each
other.

Habitat : Rivers, ponds, and canals throughout En-
gland ; but it does not appear to have been found north
of Yorkshire. It is also one of our upper tertiary fossils.
It ranges from Finland to Algeria and Sicily. Var. 1.
R. Avon, Bath (Clark). Var. 2. From Clark's and
Mrs. Loscombe's collections of British shells,, but with-
out any indication of locality. Var. 3. Canal near
Oxford (Whiteaves). Var. 4. Norwich (Bridgman).
This remarkable form might easily be raised to the
rank of a distinct species ; but I can only regard it as
abnormal, and analogous to the variety ovalis of U. tu-
midus.

This species was confounded by Lister, Linne, Miiller,
Draparnaud, and all the older writers with U. tumidus.
It differs from that species in the form of the shell, which
is oblong instead of oval ; in its much greater propor-
tionate breadth ; its thinner texture ; in the upper and
lower margins being nearly straight and parallel, instead
of being curved and wedge-shaped ; in the umbonal
region being much less prominent and swollen; and in

86 UNIONIDiE.

the hinge not being so strong, nor the teeth so thick,,
as in U. tumidus. It has been noticed by Mr. Norman
to attain, in ponds at Fleckney and Wistow in Leices-
tershire, the great size of 4^^ inches in breadth and 2\
in length, and to weigh 2 oz. 6 dr.

It is, however, by no means easy to draw a satis-
factory line of separation between this and the last
species, which are connected by several intermediate
forms, and especially by the U. Philippi of Dupuy. The
fact of their inhabiting the same spot shows, at all
events, that one of them is not a local variety of the
other ; and this ought, I think, to weigh in the scale of
specific distinction. Whether one, or both, of these now
reputed species have become in course of time permanent
varieties or " races '' of the same or some other species,
may be regarded as an antiquarian (although interesting)
question, which does not properly belong to the province
of the zoologist.

Both of these species produce pearls, though of very
small size and inferior lustre. A consolidated mass of
pearly secretion is sometimes formed inside the right
valve near the margin of the posterior side. The shells
were used by Dutch painters (from which the specific
name of pictormn originated) for holding their colours ;
and they are still to be had of any artists' -colourman in
this country, containing a preparation of ground gold
and silver leaf, for illuminating work, the other purpose
having been superseded by palettes. Bouchard-Chan-
tereaux calculated that each individual of U. piciorum
produced, in the breeding-season of May, June, and
July, no less than 220,000 eggs.

The variety curvirostris bears a strong resemblance to
some of the varieties of U. Batavus ; but there is no
satisfactory proof of that species having been found in

uNio. 37

Great Britain. A specimen named Unio Batavus in
Dr. Turton^s collection of British shells is clearly a dwarf
variety of that species^, and is the Unio nana of Lamarck,
U. amnicus of Ziegler, U. Batavus var. e. pusillus of Ross-
massler, and U. nanus of Dupuy. This specimen does
not at all agree with the description or figure given
by Turton of his My sea Batava in his ' Manual ^ ; and it
was not accompanied by any note of the locality. I do
not, however, despair of this species, as well as of U.
rhomboidezis (or littoralis), being discovered in this
country. Both of them inhabit the North of France ;
and the latter once lived in our eastern counties.

3. U. margari'tifer*, Linne.

j\fya margaritifera, Linn. Syst. Nat. ed. xii. p. 1112. JJ. margaritiferus,
F. & H. ii. p. 146, pi. xxxviii (as Alasmodonta margaritifera).

Body dirty grey, with sometimes a tint of flesh-colour :
mantle bordered below with brown, and above with white;
cirri oblong and dark brown : foot large, tongue-shaped, grey-
ish-yellow, or dirty red : gilJs greyish-brown, with whitish
streaks : labial palps broader than long, and united for two-
thirds of their length.

Shell oblong, much compressed, sohd, having a dull surface,
dark bro^vn, or nearly black, transversely and irregularly
wrinkled, especially on the posterior side, with very fine but
obscure longitudinal striae, which are interrupted by the fines
of growth : epidermis thick : heahs incurved, and placed at a
distance of about one-fourth from the anterior side : umhondl
region not prominent, always decorticated or eroded, and to
such an extent as to expose several of the inner layers : lunide
narrow and indistinct : ligament very long, and extending to the
anterior side : hinge-line curved : anterior side rounded : pos-
terior side very gradually sloping and rounded at its extremity,
pinched-up above into a blunt keel or ridge : lovjer margin
straight : inside pearly-white, with a tint of flesh-colour and
blotches of olive-green in the region of the adductor muscles,
pitted in the middle by tubercular folds of the mantle : hinge

* Pearl-bearer.

38 UNIONID.E.

strong ; the right valve having on its anterior side a very broad,
thick, and blunt double tooth, the crest of which is irregularly
tubercled, and on its posterior side a blunt and obscure ridge -
like plate, which in yoiing specimens is grooved or double ;
left valve furnished at its anterior side with a single, conical,
strong and blunt tooth which locks into the double tooth, the
posterior tooth in this valve being similar to the corresponding
one in the right valve : muscular and pallial scars very deep
and distinct. L. 2-4. B. 5.

Var. 1. sinuata. Shell rather broader in proportion to its
length than in the type, yellowish-brown : lower margin in-
curved towards the middle. U. sinuata, Lam. Hist. An. s.
V. vi. pt. i. p. 70.

Var. 2. Boissyi. Shell proportionably longer : lower mar (jin
convex, or rounded. U. Roissyi, Michaud, Compl. p. 112.
pi. xvi. f. 27, 28.

Habitat : Mountain rivers and streams throughout
the British Isles. It is found in several parts of the
Swansea Canal where the bottom is gravelly, having
been carried in by the water-courses which supply it.
It also ranges through the mountainous and hilly parts
of the Continent from Lapland to the Pyrenees. Var. 1.
West of Scotland (Bedford and J. G. J.) ; West of
Ireland (Humphreys and Barlee). A specimen of this
form from Co. Kerry measures nearly 6 inches in
breadth or width. Var. 2. Yorkshire (Sowerby). A
monstrosity also occurs having a longitudinal ridge in
the middle of the sheU.

This species differs from all the others in its shell
being much longer (measured from the beak to the lower
or front margin) as well as more depressed, in its dull
aspect and much darker colour, the extensive erosion of
its umbonal region, and especially in the posterior teeth
being scarcely developed.

The lining of mother-of-pearl is equal to half the
entire thickness of the shell, as may be seen by grinding

ANODONTA. 39.

and polishing one of the valves. The surface of the shell
is of a dull white beneath the epidermis. Pearls ob-
tained from this kind of Mussel are mostly white ; but
they are sometimes green or brown, and occasionally
(but very seldom) they are met with of a lovely pink
colour and worth being set in a brooch or ring.

In Forbes and Hanley^s work will be found a full and
interesting account of the freshwater pearl fisheries,
which have been for so many centuries, though with
little success, prosecuted in these Islands. But to amuse
my readers, and to give some idea of the state of Natural
History in Camden^s time, I will add the following
extract from his ' Britannia,^ under the head of " Cum-
berland."

" Higher up, the little river Irt runs into the sea,
in which the shell-fish having by a kind of irregular
motion {oscitatione) taken in the dew, which they are
extremely fond of, are impregnated, and produce pearls,
or to use the Poet's phrase, baccce conchea, shell-berries,
which the inhabitants, when the tide is out, search for,
and our Jewellers buy of the poor for a trifle, and seU
again at a very great price. Of these and the like Mar-
modeus seems to speak in that line,

" Gignis et insignes, antiqua Britannia, baccas."

It seems that Marmodeus wrote a Latin poem on
jewels and precious stones, which was published at
Cologne in 1539.

Genus II. ANODON'TA^, Lamarck. PI. 11. f. 1, 2.

Body oblong-oval, compressed : gills flexuous : labial palps
lanceolate.

Shell oblong-oval, thin : hinge having only rudimentary
teeth : lunule slight and indistinct.

* Toothless.

40 UNIONID^.

The habits of the Anodontce are the same as those of
the Uniones ; but they differ, according to Moquin-Tan-
don, in being ovoviviparous.

It is by no means an easy task to distinguish some of
the species of Unio ; but the difficulty is much greater
in attempting to separate the various forms of Anodonta.
Even the great Danish naturalist, Miiller, entertained
grave doubts, nearly a century ago, whether there ex-
isted more than one Scandinavian species ; although his
hesitation was not participated in by Nilsson and subse-
quent writers on the Mollusca of that country. In other
parts of the Continent, the long array of specific names,
which have been recorded by H. Drouet, shows that the
tendency of modern conchologists has been vastly to
increase the number of European species. In this
country, Montagu, with all his powers of discrimination,
evidently entertained considerable doubt as to the spe-
cific difference between A. cygnea and A. anatina ; and
Turton, more than thirty years ago, expressed his opinion
"that all our supposed species of this genus maybe
justly resolved into one, varying in their outline, con-
sistence, and colour, from age and local circumstances."
This view has been adopted by Dr. Gray and the authors
of the ' British Mollusca.^ However, as long as any di-
stinction of species is recognized, we must endeavour to
deduce from the observation of natural phenomena any
facts which may facilitate such investigation. One of
these facts seems to consist in ascertaining whether any
different forms inhabit together the same spot and under
exactly similar conditions, without any appearance of an
intermediate link or gradation. Montagu has recorded
such a fact with respect to his Mytilus avonensis and
M. anatinus ; Drouet has given other instances of the
collocation of several species of Anodonta in French

ANODONTA. 41

waters ; and Baudon has also noticed the same circum-
stance in the Departement de FOise. All these cases
would lead us to infer that there exist at least two
distinct species of Anodonta in the North of Europe ;
and I am only at present prepared to go to this extent.
At the same time, I do not dispute the claims of other
forms to specific rank. It would be unseemly, as well
as unjust, thus to depreciate the labours of those
naturalists who have so ably and carefully endeavoured
to solve this perplexing problem j and there is quite as
good reason for believing that their views as to the ex-
tension, are as correct as Ours as to the reduction, of the
specific line. Although, therefore, I only propose to
admit two old Linnean species {A. cygnea and A. ana-
Una) J some at least of the varieties hereafter indicated
may be considered distinct species by those of my readers
who from experience or choice may be inclined to take
another view of the case.

1. Anodonta cyg'nea*, Linne.

Mytilus cygneus, Linn. Syst. Nat. ed. xii. p. 1158. A. cygnea (partly),
F. & H. ii. p. 155, pi. xl. f. 2, 3, & xli, and (animal) pi. Q. f. 3.

Body grey, with a yellowish or reddish tint : mantle bor-
dered with tawny-brown : foot large, broad, dirty-yellow, with
a tinge of orange or red : gills grey, with occasionally a reddish
hue, of a gauze-like textm-e : labial palps broadly triangular.

Shell oblong, rather ventricose, thin, moderately glossy,
yellowish-green or brown, transversely and irregidarly grooved
b)'- the hues of growth, and wrinkled in the same direction on
the posterior and lower sides : epidermis thin ; heahs straight,
placed at a distance of about one-fourth from the anterior ex-
tremity : umhonal regioyi compressed, strongly plaited : liga-
ment rather long, strong, partly concealed within the over-
lapping edges of the upper margin or hinge-hne, which is
straight : anterior side not gaping, rounded, and abruptly

* Belonging to (e. g. food for) swans.

42 UNIONID^.

sloping below : posterior side gradually sloping and com-
pressed above, produced into a rounded wedge-like point, and
gaping : lower margin nearly straight : inside pearl-white and
highly iridescent : hinge slight, having a rather sharp ridge -
like plate on the posterior side in each valve : muscular and
pallial scars very slight and indistinct. L. 2*75. B. 5-35.

Var. 1. radiata. Shell larger, yellowish-green, beautifully
marked with longitudinal rays or streaks of the same colour,
which are sometimes alternate : heaJcs placed at a distance of
only one-third from the anterior side. Mytilus radiatus, Miill.
Verm. Hist, pt. ii. p. 209.

Var. 2. incrassata. Shell more swollen and solid, ohve-
brown : upper margin, or hinge-line, rather curved on the
posterior side. Mytilus incrassatus, Shepp. in Linn. Trans.
xiii. p. 85, pi. 5. f. 4.

Var. 3. Zellensis. Shell broader, yellowish-brown, having
the upper and lower sides nearly parallel ; 'posterior side much
produced. Mytilus Zellensis, Gmel. Syst. Nat. p. 3262.

Var. 4. pallida. Shell light yellow or fawn-colour : hinge-
line rather cui'ved, and raised on the posterior side, which is
produced to a long wedge-like point : lower margin rounded.

Var. 5. rostrata. Shell oblong-oval, somewhat resembhng
in shape Modiola vulgaris : upper margiyi forming a dorsal
crest, which is slightly raised and curved: anterior side
rounded : posterior side attenuated, and ending in a long
curved wedge-Hke point : lower margin nearly straight. A.
rostrata, (Kokeil) Eossmiissler, Iconogr. iv. p. 25, f. 284.

Habitat : Slow rivers, lakes, canals, and ponds
throughout the kingdom as far north as Banffshire ; and
it is one of our upper tertiary fossils. It ranges from
Siberia to the Pyrenees. Var. 1. Bog of Allen, Ireland
(Turton) ; Clumber lake, Notts (J. G. J.). This variety
is the Mytilus stagnalis of Gmelin, the M. dentatus of
Turton's Conchological Dictionary, and the M.jMludosus
of his work on the British Bivalves. Specimens of this
variety measure upwards of 6 inches in breadth. Dr.
Turton^s type (of which only one valve remains) has a
small pearly tubercle on the ridge of the laminar tooth ;

ANODONTA. 43

and I suspect that the Doctor mistook this excrescence
for a cardinal tooth, and therefore applied the specific
epithet " dentatus/^ He omitted any mention of this
character in his Dithyra, when he changed the name to
" paludosus/^ Var. 2. Scarborough (Bean) ; Otters
pool, Lancaster (Tyler) ; Oxwich marsh, near Swansea
(J. G. J.). This is the A. ponderosa of C. PfeiflPer.
Var. 3. Bog of Allen, Ireland (Humphreys) ; Clumber
lake, Notts (J. G. J.). It is the A. Cellensis of C.Pfeiffer.
Var. 4. West of Ireland (Humphreys). Var. 5. R.
Corfe, Dorset (J. G. J.) ; ponds at Wistow in Leicester-
shire, Wynyard Park, Co. Durham, and Oxford (Nor-
man). This appears to be the Mytilus Avonensis of
Montagu (Test. Brit. p. 172), judging from his descrip-
tion and the figure of that species which is given by
Maton and Rackett in the ' Linnean Transactions,^ vol.
viii. pi. 3. A. f. 4. The shell of this species is also liable
to be distorted ; and I have a specimen in which the
lower part of the left valve is deeply notched opposite
the beak, owing to an injury of the mantle on that side^
the other valve being entire.

The fry have triangular and pearly shells, which might
easily be mistaken for the valves of a Cypris or smaller
Entomostracan. The epidermis only is coloured in this,
as well as in the other species : the surface of the shell
itself, under the epidermis, is white or colourless.

2. A. anati'na*, Linne.

Mytilus anatinus, Linn. Syst. Nat. ed. xii. p. 1158. A. cygnea (partly),
F. & H. ii. p. 155, pi. xxxix. f. 3.

Body grey, of different shades of intensity : mantle bordered
with dark brown : foot yellowish-grey, or red : cjiUs, greyish-
brown.

* Belonging to {e. g. food for) ducks.

44 UNIONID^.

Shell oval, rather compressed, not so thin as in the usual
or typical form of the last species, olive-green or brown, ^vith
darker transverse bands denoting the lines of growth, and
irregularly wrinkled in the same direction : epidermis rather
thicker than in A. cygnea : heaJcs straight, placed at a distance
of about one-third from the anterior end : umhonal region
compressed, closely plaited : ligament short and prominent :
upper margin or hinge-line raised into a kind of crest, and
curved: anterior side rounded and gaping below, with an
oblique slope towards the lower edge : posterior side curved
and abruptly sloping to a wedge-like point: lower margin
gently curved : inside and hinge as in A. cygnea ; but the
lining is much thicker in the present species, and the muscular
impressions are consequently much more deep and distinct.
L.2-1. B.3o.

Yar. 1. radiata. Shell (or rather the epidermis) marked
with green and yellow rays.

Yar. 2. ventricosa. Shell larger, more solid, exceedingly
tumid, especially in the middle and towards the umbonal
region, also marked with green and yellow rays. A. ventri-
cosa, C. Pfeiffer, ii. p. 30, pi. iii.

Yar. 3. complanata. Shell oval, greatly compressed, brown:
healcs placed close to the anterior margin : upper margin raised
and curved : anterior side abruptly truncate. A. complanata,
(Ziegler) Rossmiissler, iv. p. 24, f. 283.

Habitat : Same as that of A. cygnea; but it ranges
further to the south, being a Sicilian species. It has
not been noticed in this country as a tertiary fossil.
Var. 1. The rayed markings form scarcely a varietal
character, being common to half-grown individuals of the
last, as well as of this, species. Var. 2. R. Exe (Clark).
This variety has been referred by Moquin-Tandon
to A. cygnea ; but it evidently belongs to the short
form, or what is generally called A. anatina. None of
my specimens (of which I possess a series) are as broad
as the one represented by Pfeiffer in his figure 4. This
variety attains a larger size than the typical form, being
more than 3 inches long, 5 wide, and 2 in depth. Var. 3.

DREISSENID.E. 45

Gumfrieston, near Tenby (Smith). A monstrosity, or
distortion, of this last variety is also in my cabinet,
which is flatter and has a rounded outline above in
consequence of the umbonal region not projecting. A
young specimen of the same variety is nearly round.
This appears to be analogous to the variety rostrata of
A, cygnea, and tends to confirm the idea of the two
species being distinct.

The chief points of difiference between A. cygnea and
A. anatina are, that the shells of the latter species are
smaller and comparatively longer ; the hinge-line or
crest is raised in that species, instead of being straight
or parallel to the lower margin ; and the posterior side
slopes abruptly instead of (as in A. cygnea) gradually.

Family III. DEEISSENID^.

Body nearly rhomboidal, compressed : mantle closed, except
at the posterior side, where it is folded into two orifices, one
for respiratory and nutritive, and the other for excretal purposes,
besides an opening at the lower or front margin for the passage
of the foot. The upper, or excretal, fold is the smallest, and is
not much produced : the other fold is extended into a pyra-
midal tube, which has a thickened or reflected margin and is
fringed with numerous short spine-shaped cirri or tentacles :
foot long and tongue-shaped, furnished with a byssal groove.

Shell equivalve, oblong, triangular, very inequilateral,
ventricose, covered with a thick and horny epidermis : heahs
placed at the anterior end : ligameyit internal : inside porcelain -
white : hinge furnished with minute cardinal teeth, but some-
times toothless ; below the beak in each valve is a triangular
shelf or hollow plate (as in the marine genus Crepidula) for the
reception of the anterior muscle.

These characters are also generic, as the family con-
tains but one genus. In their general aspect the Dreis-
senidce bear a closer resemblance than the last to the

46 DREISSENID>«.

Myiilidce ; but the mantle of tlie animal in the present
family is nearly closed, and the hinge of the shell is
furnished inside with a transverse plate or septum, which
is a peculiar and unmistakeable feature. Mytilus has
also several cardinal teeth; but I have failed to detect
any in the British species of Dreissena, although the
authors of the ^ British Mollusca ' and Moquin-Tandon
mention an " obscure apical elevation," or "dent cardinale
a peine saillante/' in the right valve of this species.
However, cardinal teeth certainly do exist in three species
of Dreissena from the Indian and Pacific Oceans, which
have been described by Erichson in Wiegmann^s ' Archiv
fiir Naturgeschichte ' for 1836. The same author also
incidentally remarks that the European species (which
he called Tichogonia fluviatilis) has a rudimentary tooth.
The mantle is for the most part closed and produced
into tubes on the posterior side, instead of being open
throughout as is the case in Mytilus.

Genus DBEISSE'NA *, Van Beneden. PI. II. f. 3, 4, 5.

Although the establishment of this genus is due to
Van Beneden, the probability of its separation from
Mytilus was first suggested by an equally distinguished
zoologist of our own country. Dr. Gray. The Dreissence
may be called " freshwater Mussels " with greater pro-
priety than the Uniones, or Anodontce ; and the habit and
faculty which the Dreissenca possess, in common with the
true JNIussels, of mooring or attaching themselves by a
strong byssus to extraneous substances, put us \qvj
much in mind of their marine analogues. They are also
equally gregarious and capable of living for a long time
out of water.

* N^med ftfter M. Dreissens, a druggist at Mazeylh.

DREISSENA. 47

Only one species is known in Europe ; and it was first
noticed (in 1754) by the Russian traveller and natura-
list^ Pallas, in the River Wolga, as well as in the Black
Sea. The epithets of " fluviatilis ^^ and "marinus"
which he applied to these two forms, coupled with the
circumstance that this was antecedent to the era and
usage of binomial appellations, have given rise to con-
siderable controversy as to whether these forms belong
to different species or to varieties of the same species,
one of which has a freshwater, and the other a marine,
habitat. The last supposition would be quite consistent
with the fact observed by Nilsson, that several shells,
which are usually inhabitants only of fresh water, live
in the Baltic Sea together with other shells which are
peculiarly marine.

Dreissena polymor'pha *, Pallas.

Mytilus polymor'phus, &c., Pallas, It. Euss. i. p, 478. Dreissena 'poly-
mor;pha, F. & H. ii. p. 165, pi. xlii. f. 4, 5, and (animal) pi. Q. f. 4.

Body dark- coloured : 7nantle bordered in front with greyish -
white, at the posterior side being yellowish or fawn -colour,
and striped hke the shell with zigzag marks of reddish -brown ;
cirri of the branchial orifice arranged in concentric rows, red-
dish-grey, with a tint of brown at their base : foot oblong and
cylindrical, grey, with a slight rosy hue : gills greyish : labial
palps rather large, triangular, and lanceolate : hyssus composed
of several stout and flexible threads.

Shell oblong, rising into a sharp keel in the middle of each
valve and flattened below, pointed at the end or beak, and
gradually, but obliquely, widening towards the fi'ont, rather
solid, but not glossy, yellowish-brown, and often marked trans-
versely on the upper part with undulating or zigzag streaks of
purple or dark brown, strongly but irregidarly wrinkled in the
same direction, and longitudinally but shghtly puckered at
irregular intervals : epidermis silky ; beneath the epidermis
the surface is purplish-brown ; healt's small, quite terminal, and

* Many-shaped.

48 DRETSSENID/E.

much incurved : ligament long and narrow, fitting into a groove
of the hinge in each valve : upper margin angular : anterior
side nearly straight : posterior side curved : lower margin in-
curved, and forming in the middle a large slit for the passage
of the foot and byssus : inside slightly nacreous : hinge strong,
toothless, but furnished inside each valve with a triangular
and concave plate which is placed under the beak : muscular
and j9aZZmZ scars indistinct. L. 1*4. B. 0-6.

Habitat : Slow rivers, canals, and lakes in the eastern,
home, midland, and northern counties of England, as
well as in a canal near Worcester (Reece), Bath (Hutton),
and at Edinburgh. In the North of France, Belgium,
and Germany it is also common and widely diffused.
In one respect this species may be said to be truly metro-
politan; for it has been found in the most frequented
streets of London, after they have been flushed with
water from the New Biver, where it abounds. Mr.
Norman informs me that he saw immense numbers of
the Dreissena in a living state, lining some of the iron
water-pipes which had been taken up in Oxford Street,
and that the colouring of the shells was as vivid as if the
animal had lived in the light of day.

It is difficult to believe, in the absence of some proof
to the contrary, that this species is not indigenous to
the whole of the North of Europe, as well as to Bussia.
The circumstance of its not having been noticed in this
country before 1824, and then only in a metropolitan
locality, does not preclude the possibility of its having
previously existed in some other part of Great Britain ;
and its not having been previously recorded as British
rather proves a want of observation or opportunity than
its non-existence. Helix Cartusiana, H. obvoluta, and
Clausilia Rolphii, all of which are conspicuous land shells,
were not known to the observant Montagu, although
they are not uncommon in some parts of this country

DREISSENA. 49

and are clearly indigenous species; and many other
similar instances_, both at home and abroad, might be
cited on this point, as well as with respect to the sudden
and unaccountable appearance and disappearance of cer-
tain species in particular spots. With regard to the
period at which the Dreissena first made its appearance
or was noticed on the Continent, M. Moerch has lately
investigated its geographical history and has ascertained
that it was common in the interior of Germany before
1780, and that it then inhabited streams which flowed
into the Rhine. In a work by H. Sander of Carlsruhe,
published in that year, and entitled " Vaterlandische
Bemerkungen fiir alle Theile der Naturgeschichte,^^ he
described in unscientific, but intelligible, terms a fresh-
water Mussel which was not uncommon in that district,
and to which he gave the name of Pinna fluviatilis. This
description clearly applies to our Dreissena. In draining
the Haarlem See, the Dreissena was found in abundance ;
and it appears that no communication ever existed be-
tween that great lake and any port or harbour. It has
also been found in an inland lake near Copenhagen. It
was at one period thought (and even by the unimagi-
native Linne) that the Teredo^ or ship-worm, had been
imported into Europe from India; but that idea has
been quite dispelled, as much for the reason that some
species of Teredo which are found in Europe also occur
there in tertiary formations, as because they are different
from oriental or tropical kinds. The first of these reasons
may again, and with the like success, be urged in favour
of the Dreissena being a native of the North of France ;
for, in a recent article by M. Charles D^Orbigny, pub-
lished in the ^ Bulletin de la Societe Geologique de
France ^ (2^ ser. t. xvii. p. 66), and entitled " Sur le
diluvium a coquilles lacustres de Joinville," Dreissena

50 DREISSENID^.

polymorpha is enumerated as one of the fossils. Mr.
Prestwicli informs me that this deposit was in all pro-
bability contemporaneous with those of St. Acheul and
Amiens^ and that at all events it belongs to what is
termed by modern geologists the upper tertiary forma-
tion. I am therefore not without hope that this remark-
able shell may be discovered in the corresponding strata
in this country. It is frequently founds in a recent or
li\dng state_, with the Anacharis alsinastrurrij an aquatic
plant which chokes up our canals and is said to have been
imported from North America. Respecting \\\.q Anacharis,
Messrs. Hooker and Arnott. in their excellent work on
the British Flora, remark that '^\i seems inexplicable how
this plant should have occurred in so many different
places at the same time.^^ Perhaps if the Eriocaulon
septangularey or Naias flexilis, both of which are also
North-American water-plants, and are at present con-
fined to a very few stations in the Hebrides and West of
Ireland, had been placed in conditions which were more
favourable to their growth and propagation, each of them
might have spread with as great rapidity as the Ana-
charis. If, as I believe, the indigenousness of the
Dreissena as regards this country should hereafter be
established, the ingenious theories which have been pro-
posed to account for the mode of its transport across the
seas will not require further discussion.

PECTINIBRANCHIATA. 51

Class II.
GASTEROPODA*, or UNIVALVES.

Body of a conical shape : mantle tormmg a single lobe, which
only covers the front: head usually distinct, and furnished
with tentacles, of which the upper pair (in those kinds which
have four), or the single pair, have in most cases two eyes,
placed either at their tips or base, or on separate stalks : foot
a muscular disk, by means of which the animal generally
crawls, or sometimes floats in an inverted position on the
under surface of the water : reproductive system various ; some
kinds being hermaphrodite, and ha\ing both sexes united in
the same individual, but requiring impregnation by another
individual ; while in other kinds the sexes are separate, each
individual being either male or female : resphxitory system con-
sisting of gills, or lung-like organs ; the former, and some of
the latter, being possessed by aquatic kinds ; while the terres-
trial kinds are only furnished with the lung-like organ : those
kinds which are aquatic, and have this last organ, eliminate
oxygen from the water and also respire atmospheric air ; but
the terrestrial kinds, or Snails, breathe only the pure air, like
vertebrated land animals.

Shell usually present, conical or spiral, and covering the
whole, or most important parts, of the body.

The only two Orders which we have to deal with in
this division of the subject are as follows : —

I. Pectinibranchiata.

II. Pulmonobranchiata.

Order I. PECTINIBRANCHIATA

J,

Body spiral : respiratory apparatus consisting of a single
comb-like gill, which is placed within the mantle, on the upper
side of the head.

Shell external and spu^al.

* Foot forming the belly. f Having comb-like gills.

D 2

52 NERITID^.

Only three families of this Order inhabit the fresh
waters of this country. They are, —

I. Neritid^.

II. PaLUDINIDyE.

III. Valvatid^.

All these freshwater Snails have two tentacles, and the
same number of eyes, which are placed at the base of the
tentacles. Their shells are furnished with an epidermis
and operculum.

Family I. NEEITID^.

Body oval, having a short spiral turn at the end : eyes
placed outside the tentacles at their base : gill inside the
mantle : sexes separate.

Shell semiglobose, with an excentric spire and a semicircu-
lar mouth : operculum having an excentric and short spire,
and furnished imderneath with an apophysis or projecting pro-
cess which locks into the columellar or piUar lip.

Although the members of this family are very
numerous and widely dispersed beyond the limits of our
seas, we have only a solitary representative, forming the
single species of one genus.

NERITI'NA*, Lamarck. PI. III. f. 1, 2, 3, 4.

Body furnished with a strong and prominent snout or
muzzle : tentacles long : eyes placed on footstalks : foot broad.

Shell triangular-oblong : ojperculum calcareous and sohd.

The mollusks of this genus inhabit waters which have
a stony or gravelly bottom. Their habits are sluggish ;
raising their shell but little dming their march, and then
only showing their tentacles, eyes, and the front of their

* Diminutive of Nerita, a genus of marine shells.

NERITINA. 53

mantle. They have not been observed to float_, or creep
on the under surface of the water^ which may account
for the shells being so often found encrusted with cal-
careous matter. Their tentacles_, however^ appear to be
extremely sensitive and always in motion. They are
vegetable feeders. Their eggs are generally deposited
and carried on the shell until they are hatched or de-
veloped. These are rounded, of a yellow colour, and
provided with a thick and leathery covering, which splits
in two when the fry are excluded, the upper half being
detached and the other part left adhering to the parent
shell. Moquin-Tandon says the eggs are deposited in
a cluster of from 50 to 60.

Valuable notices of the genera Nerita and Neritina
by M. Recluz will be found in the 1st volume of the
'Journal de Conchyliologie;' and M. Pouchet has pub-
lished an elaborate monograph on the Nerita fluviatilis,
considered in an anatomical and physiological point of
view. Neritina is very closely allied to Nerita, and pro-
bably only forms a section of the latter genus. There are
marine, as well as freshwater, species of Neritina.

Neritina fluvia'tilis*, Linne.

Nerita fluviatilis, Linn. Syst. Nat. ed, xii. p. 1253. N. fluviatilis, F. &
H. iii. p. 3, pi. Ixxi. f. 1,2, and (animal) pi. H. H. f. 1.

Body of a clear jellowish-grey, speckled with black above,
white below : head and snout black : mouth very large, fur-
nished with cartilaginous jaws and a Ungual plate or riband,
which is very complicated : tentacles clear greyish-white, darker
at the sides, and more or less streaked with black transversely ;
they diverge widely from their base, and are very slender,
ending in a fine point : eyes very large and black : foot obtusely
rounded in front, and having its extremity or tail covered by
the operculum when the animal is crawling.

Shell convex above, slightly compressed towards the spire,

* Inhabiting rivers.

54 NERITID^.

and almost concave below, solid, moderately glossy, j'ellowish
or brown, with often bro^vn or white zigzag streaks, spots, or
bands, which run lengthwise or in a spiral direction, and
marked with fine but distinct transverse strise or plaits, which
are more conspicuous towards the suture : epidermis thin :
wliorls 3, rather convex, the last or lowermost exceeding two-
thirds of the whole shell, increasing veiy rapidly and dispro-
portionately in size : spire very short and oblique : suture
rather deep : mouth, or aperture, semilunar : outer lip sharp :
j)illar-lip exceedingly broad, polished and flat, with a sharp
and plain edge : operculum semilunar, glossy, of an orange or
yellowish colour, marked spirally with two or three slight
grooves, and ti'ansversely with numerous and flexuous striae ;
its external edge is thin and has a border (sometimes two) of
black or yellowish-red, both above and below ; its internal
edge is thick ; the spire of the operculum is placed at the
lower side, and formed of 1| or 2 whorls ; attached to the
under side of the opercular spire is a singular process, re-
sembling a second but much smaller operculum, which has
also a thickened edge on the inside, and projects obliquely so
as to act as a bolt in fastening the operculum to the pillar-lip.
L. 0-35. E. 0-25.

Habitat : Slow rivers^ streams, and lakes through or
into which Avater flows, or having a stony or gravelly
bed, in all parts of the kingdom, from the Orkneys to
Cornwall. It has been found in the peat-bed at New-
bury ; but this is not, I believe, recognized as belonging
to the upper tertiary formation. This species ranges
from rinmark to Algeria and Sicily, where the form or
variety called by Lamarck N. Batica prevails. A dwarf
variety has been described by Nilsson, which inhabits the
shores of the Baltic Sea, adhering to seaweeds and
stones, sometimes at a distance from the mouth of any
river, and living in company with the common Mussel
and a few other decidedly marine shells. He also noticed
that these last are similarly dwarf forms. A variety in
which the shell is quite black has been found l^y Mr.
North in the Ouse. Many other varieties have been

PALUDINA. 55

described by European authors as distinct species; but
they appear only to differ from the typical kind in size
and colour^ as well as in the spire being more or less
excentric. In adult specimens, the septa or internal
walls of the spire are wanting, and appear to have been
absorbed, as stated by Dr. Gray. This is also the case
in Melampus or Conovulus,

Family 11. PALUDINIDiE.

Body elongated, spiral, and having a prominent snout : eyes
placed outside the tentacles at their base : gill inside the
mantle : sexes separate.

Skell having a long symmetrical sjnre and an oval mouth :
operculum also oval, irregularly concentric or paucispiral.

These mollusks are, as well as those of the last family,
herbivorous ; but they differ in being ovoviviparous, in-
stead of oviparous. Their habits are much more active
than those of the Neritidce. They sometimes, but rarely,
float. The fry are furnished with opercula before they
are excluded by the mother. According to Bouchard-
Chantereaux, the young remain in the ovary, to the num-
ber of 20 or 30, for two months, at the end of which time
only 2, 3, or 4 are born, the period of accouchement ex-
tending over several days.

Genus I. PALUDI'NA*, Lamarck. PI. III. f. 5, 6.

Eyes placed on short pedicles or footstalks : operculum horny,
irregularly concentric, and having its nucleus on the inner
side.

Lister and Cuvier have investigated, although at very
distant intervals, the anatomy of these mollusks, which

* Inliabitina: marshes.

56 PALUDINID.E.

are the largest of our freshwater Pectinibranchs. Lister
says he was indebted to Dr. Plot^ the historian^ for the
discovery that they were viviparous ; and he says that the
males are smaller than the females and their shells have
less-swollen whorls. They inhabit slow rivers^ ponds and
canals ; and one species lives within the influx of the tide
in the Thames. The epidermis of the last-formed whorl
in the young shell, when it leaves its mother, has three
transverse rows of recurved bristles, which in after- growth
are replaced by the coloured bands that encircle adult
shells, the formation of these bands, as well as of the
bristles, being caused by difierent organs which are suc-
cessively developed in the same part of the mantle. It
has been stated in that useful periodical 'The Zoologist'
(p. 7402) that our native Pahidince are not always vivi-
parous, and that a specimen of P. vivipara deposited in
an aquarium some eggs from which the fry were subse-
quently excluded. This was in the winter, and after the
Paludina had been kept for many months in a state of
confinement. It is hoped that further observations will
be made on this point, as the ovoviviparous character of
this genus constitutes one of the grounds of distinction
from the next genus, Bythinia.

1. Paludina contec'ta*. Millet.

Cyclosfoma contectum, Millet, Moll. Maine et Loire (1813), p. 5. P. Lis-
ten, F. & H. iii. p. 8, pi. Ixxi. f. 16.

Body dark grey or brown, with yellow specks : head small,
but globular : snout prominent and bilobed : tentacles long and
widely spread out, blacldsh, with grey tips ; the right tentacle
of the male shorter and thicker at its point than the left : eyes
round and black : foot cloven or bilobed in front, and rounded
behind ; its tail or extremity nearly covered by the operculum
when the animal is crawling.

* Covered (?". e. by the operculum).

PALtDINA. 57

Shell conical, moderately solid and glossy, yellowish, with
sometimes a green or brown tinge ; the last whorl having 3,
and each of the two preceding whorls 2, spiral brown bands,
the uppermost of which is usually the broadest ; there are also
numerous and very fine spiral striae, besides faint and irregular
lines of growth : epidermis rather thick : whorls 7, extremely
convex ; the last being equal to about one-half of the shell ;
they increase gradually in size, except the two first, which
are disproportionately small and twisted, resembling those of
Succinea : suture remarkably deep : mouth oval, or approaching
to a circular shape : outer Up sharp and slightly reflected : inner
lip separate from the columella ; both lips forming a complete
peristome : umbilicus small, oblique, but very distinct and deep,
exposLug part of the internal spire : operculum rather thin,
compressed towards the nucleus, which causes the under side
to project, like the boss of a shield ; it is marked with nume-
rous concentric striae and more distant lines of growth. L. 1-5.
B. 1-25.

Habitat : Slow rivers^ canals, and large pieces oi
standing water^ throughout the greater part of England,
as far north as Yorksliire. It is, however, rather local.
This is a Finland species, and ranges south to the
Pyrenees.

This mollusk, when at rest, adheres firmly to stones
and wood ; but on being touched, it immediatelly falls oft'.
It sometimes attains to a large size, one of my specimens
being more than 2 inches long and If broad.

The Linnean description of Helix vivipara accords
more properly with that of the next species, w^hich has
only an umbilical chink (^^imperforata'^), and is pecu-
liarly "subovata^^ and ^^obtusa.^^ The name given by
Millet to the present species, which does not appear to
have been known to the authors of the ' British Moliusca,^
must of course be adopted in preference to the very
modern one of '' Listeri" which was proposed by them.
Miiller considered this species to be that of Linne ; and
he described the other as Neritafasciata.

D 5

58 PALUDINID^.

2. P. viYi'pARA^, Linne.

Helix mvipara, Linn. Svst. Nat. ed. xii. p. 1247. P vivipara, F. & H.
iii. p. 11, pi. Ixxi. f. 14, 15, and (animal) pi. H. H. f. 2.

Body of a darker colour than that of P. contecta : snout
broad: tentacles bluish-black, with bright yello^y spots; the
difference of their size in the male being very perceptible : eyes
rather large : foot very broad, and slightly truncate in front.

Shell oval, rather solid, but not so glossy as that of P. con-
tecta, yellowish -green, with bands and striae as in that spe-
cies ; the surface of the two last whorls is often iiTCgularly
indented or pitted: epidermis rather thin: whorls G|, rather
convex, the last exceeding one-half of the shell, gradually in-
creasing in size, except the first, which is extremely small and
twisted, but much less prominent than in the last species,
making the point of the spire to appear blunt : suture rather
deep : mouth oval, and less inclined to a circular shape than in
P. contecta : outer li/p rather thick and slightly reflected : inner
lip united above to the columella, but both lips form a com-
plete peristome : there is no umbilicus, but instead of it there
is a small and narrow chink behind the inner lip : operculum
rather thick, comj)ressed transversely, and marked with strong
lines of increase and finer intermediate striae. L. 1*5. B. 1*2.

Var. iinicolor. Without bands.

Habitat : The same as that of the last species (with
which it is often found living)^ except that the Rev. Dr.
Gordon has found it at Findhorn in the Moray Firth
district. Sir Charles Lyell has recorded its occurrence
in the lacustrine deposit at Mundesley in Norfolk. Its
northern range abroad is also the same ; but it extends
southwards to Naples, and (according to Philippi) pro-
bably also to Sicily. The variety has been found by
Mr. Pickering in Hertfordshire_, and by myself in the
Thames at Richmond. I have also a monstrosity in
which the last whorl has a keel occupying the place of
the upper band.

This species differs from P. contecta in its shell being

* Bringing forth its young alive and perfect.

BYTHINIA. 59

thicker and longer, the whorls being much less swollen,
the suture not so deep, the apex or point of the spire
more blunt, and the mouth being less circular. Its size
is not quite equal to that of the other species, the largest
British specimen which I have of this being 1 1 inch
long and 1^ broad.

The animal is rather active. M. Millet counted in a
female 82 young ones of different sizes. Mr. Clark has
remarked that, in all the specimens which he procured
from the River Exe, the point of the spire is eroded.
This is probably owing to the influx and admixture of
sea-water in that part of the river, because there are few,
if any, manufactories on the banks of the Exe. In the
Paddington Canal and parts of the Thames near London,
the erosion is evidently owing to the last-mentioned cause.
Draparnaud named this species Cyclostoma achatinum.

Genus II. BYTHI'NIA *, [Bithinia] Gray.
PI. III. f. 7, 8, 9.

Eyes sessile: opercuhim testaceous and solid, irregularly
concentric, and having its nucleus nearly in the middle.

This was first indicated by Dr. Gray as a subgenus of
Paludina; and the name which he proposed has been
adopted by almost all conchologists. The chief differ-
ence between this and Paludina consists in the animal
of Bythinia being oviparous, instead of ovoviviparous, —
its eyes being sessile, instead of placed on stalks or tu-
bercles as in the other genera of this family, — and in the
operculum being testaceous and concentric, with its
nucleus placed almost in the middle. The tentacles of
the male are of equal size in the present genus. Although
the derivation of the word Bythinia would imply that

* Inhabiting deep water.

60 PALUDINID^

these mollusks inhabit deeper water than others of the
same family, such is not the case. They generally fre-
quent small streams, canals, shallow ponds and ditches.
They lay their eggs in three long rows on stones, as well
as on the stalks and leaves of water-plants.

1. Bythinia tentacula'ta *, Linne.

Helix tentaculata, Linn. Syst. Nat. ed. xii. p. 1249. Bithinia tcntaculafa,
F. & H. iii. p. 14, pi. 1^. f. 5, 6, and (animal) pi. H. H. f. 3.

Body dark bro^Ti or almost black above, dirty grey beneath,
covered with small and irregular specks of yellow : head small
and semioval : snout long and deeply cleft in front : tentacles
very long and slender, greatly diverging : eyes large, oval, and
black : foot much broader than the snout, rounded in front,
with a blunt and rounded tail which is half concealed by the
operculum when the animal is crawling.

Shell subconical or oval, rather sohd and glossy, nearly
opaque, of an amber colour, with often more or less of a brown-
ish tint, very finely and closely striate in a spiral direction and
crossed transversely by the marks of growth ; the spii'al striae
are sometimes confluent and form white lines : epidermis very
thin : whorls 6, convex ; the last exceeding one-half of the
shell, and the rest diminishing in proportion and ending in
rather a sharp point : suture rather oblique and deep. : mouth
oval, angular above : outer lip thick, and sometimes strength-
ened by a white, rather strong, internal rib, which when re-
peated gives the shell a slightly varicose appearance ; this hp
is very little reflected : inner Up united to the columella, but
forming with the other hp a complete peristome : umhilical
chink small and narrow : operculum obhquely oval, very thick,
angular at the top, compressed or indented in the middle of
the upper half; it is marked with exquisitely fine concentric
stria} and a few coarser ridges, denoting the marks of periodical
increase, which form raised platforms or layers, the smallest
or first-formed being uppermost. L. 0-5. B. 0-25.

Var. 1. ventricosa. Shell white: whorls more swollen.
Paludina ventricosa, Menke.

Var. 2. decoUata. Upper whorls wanting in half-grown and

* Having tentaclea.

BYTHINIA. 61

adult specimens ; their place being supplied by a nearly flat
and semispiral plate, as in Bulimus decoUatus.

Var. 3. eoccavata. Whorls more rounded, and suture much
deeper.

Habitat : Slow rivers^ ponds^ and still waters every-
where in England_, Wales^ and Ireland^ as well as at
Frazerbiirg in Aberdeenshire ; and it is perhaps the
most abundant fossil in the lacnstrine beds of our upper
tertiaries. Var. 1. Devonshire (Mus. Turton) ; Bristol
and Wandsworth (J. Gr. J.) ; Richmond^ Surrey (Choules) .
Var. 2. Woolwich and Cardifi* (J. G. J.) ; Co. Armagh
(Waller). Var. 3. Cardiff (J. G. J.). This last variety
seems to connect the present species with B. Leachii ; but
it differs from the last-mentioned species in its greater
size, as well as the oval shape of the mouth. B. tenta-
culata ranges from Siberia to Sicily. The animal is
sluggish, but irritable. It sometimes floats, or creeps
on the under surface of the water. Draparnaud says
that it feeds on animal as well as vegetable substances.
The shell is often encrusted with a ferruginous or mineral
deposit. From this circumstance Draparnaud derived
the name of impura which he gave this species, having
needlessly changed the prior one assigned to it by Linne.
The epidermis in young specimens is slightly hispid and
resembles a fine velvety pile.

This species was first made known and admirably
described by our countryman. Lister.

2. B. Leach'ii"^, Sheppard.

Turbo Leachii, Sliepp. in Linn. Trans, xiv. p. 152. Bithinia Leachii, F.
& H. iii. p. 16, pi. Ixxi. f. 7, 8, and (animal) pi. H. H. f. 4.

Body greyish-white, with black and yellow specks : tentacles
very flexible : foot slender.

* Named afteii Dr. Leach, a celebrated English zoologist.

62 PALUDINIDJi:.

Shell conical, rather thin, glossy, and semitransparent,
greyish horn- colour or amber, microscopically striate in a
spii'al direction, and irregularly marked by the lines of growth :
epidermis extremely thin : whorls 5, very convex and rounded,
but narrow, the last occupying about one-half of the shell :
spire rather abruptly pointed : suture nearly straight, ex-
tremely deep : mouth nearly round, very slightly angular above,
where the outer lip meets the columella : outer lip rather thick,
and strengthened by a slight internal rib, scarcely reflected,
except below : inner lip forming with the other lip a com-
plete peristome : umbilicus small and narrow, but distinct :
operculum almost circular and flat, otherwise like that of the
last species. L. 0*25. B. 0-2.

Var. elongata. Shell smaller ; spire more produced.

Habitat : Nearly the same as that of B. tentaculata ;
but the present species does not extend so far norths
and it is more local and much less abundant. It is
also equally rare as a tertiary fossil. The variety is
from Woolwich marshes and Northampton. Malm has
recorded this species as Swedish; and Morelet has
noticed it as inhabiting Algeria.

This species is distinguishable from the last, in com-
pany with which it is sometimes found living, by its
much smaller size, the whorls being more swollen and
narrower (giving the shell a scalariform appearance), the
very deep suture and distinct umbilicus, as well as by
the shape of the mouth and operculum. It is sometimes
known by the specific name of ventricosa, which was origi-
nally given to it by Dr. Gray, but without any description.
The Cyclostoma simile of Draparnaud, to which the pre-
sent species has been referred by some authors, is very
different, as will be seen presently. Specimens in Dr.
Turton^s collection, named respectively "Paludina simi-
lis/' " P. viridis/' and " P. anafmaj" all belong to B.
Leachii, being merely difterent stages of growth. The
late M. D^Orbigny gave me, at llochdle, in 1830 some

HYDROBIA. 63

shells which he had received from Draparnaud under the
name of " Cyclostoma anafinum.'^ These appear to be
a small variety of the present species, and are probably
the B. humilis of M. Boubee.

Genus III. HYDRO'BIA *, Hartmann.
PL III. f. 10, 11, 12.

Ei/es placed on tubercles : operculum horny and thin, pauci-
spiral.

The little mollusks which are comprised in this genus,

although very closely related to the true and marine

RissocBy appear to have as much right to be generically

separated from the latter as Neritina has to form a

distinct genus from Nerita. Nearly all the Hydrobice

are inhabitants of fresh and pure water; but one of

them [H. ventrosa) frequents estuaries, as well as pools

and ditches close to the sea-shore which are liable to be

occasionally overflowed by the tide, and the water of

which is more or less brackish. Those species which

inhabit fresh water have been arranged by Moquin-

Tandon in a subgenus of Bythinia, named by him Bythi-

nella. With Bythinia, as well as with Rissoa, this genus

has undoubted relations. It differs, however, from the

former in the eyes not being sessile, but placed on short

tubercles, and from the latter in wanting the caudal

filament which is appended to the foot. The shell of

Hydrobia has besides an umbilical cleft which does not

exist in Rissoa ; while its operculum is decidedly not

Bythinian, but Rissoan, or rather Littorinan. It may

therefore be considered as in many respects forming an

intermediate link between those two genera, but having

a greater affinity to Rissoa. The ' genus Hydrobia was

* Living in water.

64 PALIJDINID^.

founded by Hartmann in 1821. An objection has been
made to the name on the ground that it had been pre-
viously used for a genus of small water-beetles ; but it
does not seem that any confusion or inconvenience is
likely to result from the use of the same name in such
different departments of zoology, and precedents are not
wanting for such a double application. We have only
two species of Hydrobia-, but on the Continent there
are four or five times that number, including Hydrobia
marginata which existed duiing the Glacial epoch in our
eastern counties and Bedfordshire, but appears not to
have survived that period.

The estuarine or brackish -water species of Hydrobia
were formed by Professor D^Orbigny into another genus,
which he called Paludestrina ; and these also constitute
the genus Paludinella of Pfeiffer and Loven.

1. Hydrobia si'milis *, Draparnaud.

Cyclostoma simile, Drap. Moll. Terr, et Fluv.Fr. p. 34, pi. i. f. 15. Bissoa
anatina, F. & H. iii. p. 134, pi. Ixxxvii. f. 3, 4.

Body dark grey, with a yellow or brown tint and white
flaky specks : head rather large and prominent : snout broad,
long, and ridged transversely: tentacles long, slender, and
diverging : eyes large and rather protuberant : foot short, very
broad, and expanded on each side in front, rounded behind,
and extending considerably beyond the operculum when the
animal is crawling.

Shell subconical or oval, rather thin, glossy, semitrans-
parent, yellowish horn-colour, or sometimes clear white, ob-
scurely and slightly marked by the lines of growth : ejnderiiiis
a mere film : whorls 5-6, rounded, but compressed ; the last
exceeding one-half of the shell : spire rather pointed : suture
somewhat oblique and deep, forming a narrow canal : mouth
oval : outer Z//> thin, shghtly reflected : inner lip united to the
columella, but continuous with the outer hp : umhilical chinh
obhque, small, but distinct : opercidum oval, obtusely angular

* KesembHng another species.

HYDROBIA. 65

above, thin and flat, having a lateral and indistinct spire of
only 2 whorls, and resembling that of the marine genus Lit-
torina ; it is marked with strong, but remote, irregular and
flexuous lines of increase. L. 0'15. B. 0*1.

Habitat : Muddy ditches which are occasionally, but
seldom, overflowed by the tide, by the side of the Thames
from Greenwich to below Woolwich. These ditches are
separated from the river by a high and broad embank-
ment, which is provided at distant intervals with sluices
to drain off the surface water. It lives there in company
with Bythinia tentaculata and other freshwater shells,
as well as with the more marine and peculiar moUusk,
Assiminia Gray ana; and it is gregarious. Its food
appears to consist of decaying vegetable matter ; and its
habits are rather active, creeping and floating with tole-
rable rapidity. Mr. Prestwich and Mr. Pickering found
specimens of it in peat, in the main-drainage-cutting
between Woolwich Arsenal and the exit to the Thames,
through Plumstead Marshes ; but it can scarcely be con-
sidered one of our upper tertiary fossils. This species is
widely diffused in France, and extends south to Corsica.
The Paludina meridionalis of Risso appears to be only a
rather longer and stouter form of this species, judging
from typical specimens in the Museum at the Jardin des
Plantes.

No one can, I think, take the trouble of carefully
comparing specimens of this shell with the description
and figure given by Draparnaud of his Cyclostoma simile,
without being satisfied of their specific identity ; and the
general consent of continental conchologists is in favour
of this view. In France H. similis inhabits fr^esh water.
Morelet states that in the South of Portugal it is found
both in running water and marshes, and that the shells
of the males have a longer spire than those of the other

66 PALUDINID^.

sex. British authors have referred this species to the
Cyclostoma anatinum of Draparnaud, but_, as I believe,
erroneously. The Bulimus anatinus of Poiret, from which
Draparnaud seems to have taken the specific name of
his species, is in all probability the Turbo ulvce of Pennant.
That species is universally known in France by the name
which Poiret gave. Michaud, in his Supplement to
Draparnaud's last work, mentions Cyclostoma anatinum
as inhabiting " les eaux saumatres ; ^^ although Drapar-
naud gives a difPerent habitat (" les eaux donees") for the
same species. It is not impossible that the latter meant
Bythinia Leachii. The contour of the shell of H. similis
is not unlike that of a dwarf Bythinia Leachii ; but the
channeled suture, as well as the very different operculum,
will readily serve to distinguish them, irrespectively of
size.

2. H. VENTRo'sA *, Montagu.

Turbo ventrosus, Mont. Test. Brit. ii. p. 317, pi. 12. f. 13. Rissoa vetiirosa,
F. & H. iii. p. 138, pi. Ixxsvii. 11,5, 6, 7.

Body dark grey, almost black in front: head rather pro-
tuberant: snout long and ridged transversely: tentacles fili-
form, with black and grey rings : eyes on very short stalks,
placed a httle behind the outer base of the tentacles : foot
cleft in front and rounded behind.

Shell forming a lengthened cone, rather thin, glossy, semi-
transparent, yellowish horn-colour, obscurely but closely
striate by the lines of growth : epidermis very delicate : luhorls
6-7, rounded and swollen ; the last not being equal to half
the length of the shell : spire pointed : suture rather obhque
and deep : mouth oval : outer lip thin, shghtly reflected : inner
lip in adult specimens separate from the columella and forming
with the other lip a complete peristome : umhilical chink very
small : operculum like that of II. similis, but having a smaller
spire and closer lines of increase. L. 0*2. B. 0-125.

* Swollen.

HYDROBIA. 67

Yar. 1. minor. Shell much smaller : spire shorter.

Var. 2. decollata. Shell slightly eroded : sjnre truncate.

Yar. 3. ovata. Shell having a much shorter spire, consist-
ing* of only 4 whorls, which are more swollen than usual, and
the last considerably exceeds one-half of the shell.

Yar. 4. elongata. Shell having its spire proportionally
longer, with sometimes as many as 8 wliorls.

Yar. 5. pellucida. Shell clear white, and nearly transpa-
rent.

Habitat : Abundantly in many estuaries and in track-
ish water in which the admixture of fresh predominates
over salt, throughout England and Y^^ales; and I have
also taken it in Larne Lough, Ireland. It occurs in
the upper tertiary bed at Clacton, and elsewhere in the
estuary of the Thames. Var. 1. Burry River, South
YYales (J. G. J.). Var. 2. Burry River, but not in the
same part of the estuary where the first variety is found,
and Guernsey (J. G. J.). Var. 3. Oxwich marsh, near
Swansea (J. G. J.). Var. 4. ArnokVs pond, Guernsey
(J. G. J.). Var. 5. Manorbeer, Pembrokeshire (J. G. J.) ;
Scarborough (Bean) : very rare. This species inhabits
similar situations along the sea-coasts of Sweden, France,
and Portugal, as well as of Algeria.

H. ventrosa is gregarious, and sometimes lives in com-
pany with H. ulvcBy which however is more of a marine
than a freshwater species. The latter is never found
out of the reach of the tide, and inhabits the mud flats
and ooze ; while the present species usually lives in ponds
and ditches into which the sea only flows at high water
or in spring tides. The habits of this species are more
active than those of H. ulvce ; and I have observed that
when they are found together the latter may be seen
crawling slowly over the mud and Ulva at the bottom of
shallow pools, while the other seems to disport itself by

68 PALUDINID^.

floating with tolerable rapidity along the under surface
of the water. The shell is often encrusted with a mineral
deposit or covered with an algoid or confervoid growth.
The variety 5 resembles the Cyclostoma viti^eum of Dra-
parnaud and the Paludina diaphana of Michaud. Some-
times the shell is distorted by having the upper part of
the spire twisted to one side, or by the last whorl having
a few obscure spiral ridges.

This small, but abundant, species has received a great
number of names from modern conchologists, in conse-
quence of their referring it to ill-defined species of ancient
authors. I do not believe that it is the Turbo stagnorum
of Baster, because he describes the habitat to be "in
aquis dulcibus," and the aperture or mouth to be mar-
gined. Nor can I identify it with the Helix octona of
Linne, which is said to have eight whorls and a round
aperture. Nor is it, in my opinion, the Turbo theriyialis
of Gmelin, because he gives an inland habitat (Pisa) and
says that the shell is white and has only four whorls.
There can, however, be no doubt of its being the Cy-
clostoma acutum of Draparnaud ; and this specific name
has been adopted by almost every continental naturalist.
The Paludina muriatica of Lamarck is evidently H. ulv(S.

This species differs from H. similis in its long spire,
the suture not being channeled, and in the umbilical
chink being very much smaller. From H. ulvca it may
be known by its being less than half the size of that
species, its much deeper suture, the body or last whorl
not being keeled (as is the case in H. ulvce), as well as in
the inner lip being disconnected from the columella.

The shells which Mr. Pickering found some years ago,
about two miles below Gravesend, together with a spe-
cimen of Litiopa bombyx, and which Forbes and Hanley
considered (but with some doubt) to be a variety of

HYDROBIA. 69

H. ventrosa, bear siicli a close and suspicious resem-
blance to a Cape of Good Hope species of Hydrobia,
that I cannot venture to include it among the British
MoUusca. It does not appear to have been described by
any author ; but Mr. G. B. Sowerby has named it Rissoa
castanea, on my authority, in his ^ Illustrations of British
Conchology.' Both Mr. Pickering and myself have
failed to rediscover this species in the spot where he
originally found it, although we have at different times
carefully searched for it. The fact of Litiopa bombyoo,
which is peculiar to the Gulf- weed, having been taken
with it, leads to the supposition that both of these shells
might have been accidentally brought into the Thames,
attached to the keel, rudder, or anchor of an inward-
bound vessel, and carried by the tide into the ditch where
they were discovered by Mr. Pickering. Many other
modes of introduction will doubtless occur to my readers.

I received some years ago from the late Mr. G.B. Sow-
erby two specimens of Hydrobia Ferussina, which he said
had been found in Hampshire. I do not propose to add
this species to the British list on such slight and insuffi-
cient grounds ; but as Helix obvoluta has only been found
in the same county, as a British shell, and both these
species inhabit the greater part of Prance, I merely call
the attention of conchologists to the circumstance, it
being not improbable that the H. Ferussina may also
turn up in the South of England.

The Hydrobia marginata [Paludina marginata of Mi-
chaud) inhabited this country a Iqng time ago, but ap-
pears to have become extinct as a British species. Sir
Charles Lyell first, I believe, recorded it as occurring in
the Mundesley bed, where I have since found it ; it also
occurs in the weU-known upper tertiary strata at Grays,
Stutton, Clacton, and Cropthorn ; and I lately detected it

70 VALVATID.E.

among some shells collected by Mr. Wyatt from a similar
deposit at Biddenham near Bedford. This species now
inhabits the South and South-west of France, as well as
the Jura and Switzerland ; and it has been found in a
fossil state in the lacustrine beds at Amiens.

The Natica Kingii of Forbes and Hanley (iii. p. 343,
pi. ci. f. 1, 2) belongs to this family, and not to the
Naticidce. It is the LWioglyphus Naticoicles of Ferussac,
and inhabits the Danube. Professor King is said to
have found the specimen (which is now in my collection)
in the bottom of a fishing-boat at Cullercoats. How this
Austrian and freshwater species could have got to the
Northumberland coast, is very difficult to say. Professor
King informs me that he never received any shells from
the Danube, and that his statement as to the Northum-
brian locality is perfectly correct. The question of the
indigenousness and unaccountable habitat of this speci-
men must therefore remain a mystery.

Family III. VALVATID^.

Body elongated, spiral : eyes placed within the tentacles at
their base : gill protruding beyond the edge of the mantle, the
respiration being aided by a tentacular filament : sexes united,
or common to each individual.

Shell having a short but symmetrical spire and a circular
mouth : operculum regularly multispiral.

This family comprises only one genus {Valvata), which
was founded by the Danish naturalist, Miiller. It is
remarkable for its branchial apparatus, which is external
or protruded when the animal is moving. In this posi-
tion it resembles a feather, and caused Geoftroy to give
to these elegant little creatures the expressive name of
" porte-plumet." Besides this branchial plume, the ani-

VALVATIDiE. 71

mal has another peculiar organ to facilitate its respira-
tion^ consisting of a filament or appendage to the mantle^
which might be mistaken for a third tentacle or a para-
sitic worm, and is placed on the right side of the body.
The form of the shell and operculum is very graceful^
and is somewhat like that of Trochus or Margarita.

The members of this family and genus are vegetable
feeders. They are very shy. Miiller relates that he
was tantalized by watching them for several hours, in
the hope that they would show themselves and enable
his draughtsman to make a sketch of the animal and
its curious plume, but that he was disappointed. He
appears to have consoled himself by the idea that the
little snails acted on the proverbial principle that you
were not to put any trust in man ! The reproductive
system of these mollusks is peculiar, and resembles
that of Ancylus, or the freshwater Limpet. Although
each individual is of both sexes, it is at first only male
or female, and afterwards changes its sex. They are
gregarious, and inhabit slow rivers, streams, canals, and
nearly stagnant water. The shells may often be seen
attached to the cases of the Phryganea, or May-fly, and
thus collected form a very pretty object.

The shells of some of the Valvatidce closely resemble
in shape the cases made by the larvse of certain insects ;
and their similarity is so great that Mr. Swainson pro-
posed a new genus of Mollusca for these insect-cases,
under the name of Thelidoinus. Such instances of mi-
metic analogy occur in other branches of the animal king-
dom. The valves of some Entomostraca, belonging to
the genus Estheria, are not unlike those of a young Ano-
donta in appearance, although their structure and compo-
sition are very diflPerent.

72

VALVATID^.

VALVA'TA^, Miiller. PI. III. f. 13, 14, 15.

Eyes nearly sessile : operculum horny and thin.

1. Valvata piscina^'lis t, Miiller.

Nerita 2>isci7ialis, Miill. Verm. Hist. pt. ii. p. 172. V. piscinalis, F. & H.
iii. p. 19, pl.lxxi. f.9, 10.

Body of a clear yellomsh'gTey, with small and indistinct
milk-white specks : snout long, narrow, and transversely
wrinkled : tentacles long, cylindiical, rather close together, and
slightly recurved at the point : eyes large and round, but not
prominent: foot separate from the snout and six times as
broad, deeply cleft in front and rounded behind; its tail
nearly covered by the operculum : hrancliial plume transparent,
bearing on each side fourteen slender offsets, which are placed
at right angles to the stalk : branchial appendage of the same
size and length as the tentacles.

Shell forming a depressed cone, subglobular, rather solid
and opaque, brownish-yellow, closely and regularly striate
transversely, and more or less distinctly ridged in a spiral
direction, which often gives the surface an elegantly reticu-
lated appearance : whorls 6, rounded and convex, the last being
rather less than one-half of the shell : spire compressed and
blunt : suture nearly straight and very deejD : mouth circular :
outer lip rather thick and reflected : inner lip quite separate
from the columella and continuous with the outer lip, so as to
form a complete peristome : umbilicus round, not large, but
very deep, exposing nearly all the interior of the spire : oper-
culum circular, slightly compressed in the middle, forming a
concentric spire of from 10 to 12 whorls, the outer edges of
which are thickened and raised so as to project over and
partly overlap the succeeding whorl of the operculum. L.0-25.
B. 0-275.

Yar. 1. clepressa. Shell having the spire more depressed and
the umbilicus consequently larger. V. depressa, C. Pfeiffer,
Deutsch. Moll. i. p. 100, pi. ii. f. 33.

Yar. 2. subcylindrica. Shell having the spire more produced,
and flattened at the top : imibilicus small.

* Closed by a valve, or operculum.

f Inhabiting fish-ponds.

VALVATA. 73

Var. 3. acuminata. Shell having the sjjire still more pro-
duced, and ending in rather a sharp point.

Habitat : Slow and still waters throughout the Bri-
tish Isles ; common in our upper tertiary beds. Var. 1
occurs also in various parts of the kingdom ; but it is
more local, and not found with the typical form. The
young of both these forms have invariably the spire pro-
portionably more depressed than in the adult. Var. 2.
Grassmere (J. G. J.). This somewhat resembles the well-
known form called " antiqua '^ by Professor Morris, from
the upper tertiary deposit at Grays. Var. 3. Avon E/.,
Bristol (J. G. J.) j Northof Ireland (Mrs. Puxley). Spe-
cimens of the typical form, which Mr. Bridgman pro-
cured and kindly sent me, from brackish water at Lynn,
are much thicker and of a darker colour than usual, and
have stronger striae ; and the opercula have fewer whorls
and slighter ridges. In another variety which I have
received from my valued friend and correspondent, Mr.
Waller, and which he found at Finnoe, Co. Tipperary,
the shell is more conic and. the spiral ridges form irre-
gular white lines. A monstrosity has also occurred to
me, in which the spire is twisted to one side. This spe-
cies ranges from Siberia to Naples.

In May, June, July and August the eggs of this mol-
lusk are deposited on various substances, and sometimes
on the shell of a Planorbis. They are united in a gela-
tinous mass, and enclosed in a globular capsule having a
short stalk, by which it is attached. The eggs contained
in each capsule number, according to Bouchard-Chante-
reaux, from 60 to 80 ; but Moquin-Tandon, who appears
to have observed many cases of such egg-laying and
-hatching in an aquarium, states that out of 19 capsules
the number of eggs in each varied from 4 to 24 only.
When the eggs have come to maturity, which is about the

E

74i VALVATID^E.

twelfth day after they have been laid^ the capsule^ being
distended^ bursts^ and abont two -thirds of the fry emerge
and enter on their career of life. The capsule then re-
sumes its former shape, and retains the rest of the fry
for four days longer, w hen they are, in their turn, hatched
or emancipated.

Both Draparnaud and Montagu were aware that this
species was furnished with the branchial plume ; but the
former included it in the heterogeneous assemblage of
species which he called Cyclostoma, assigning the next
species to Valvata; and our countryman referred one
species to Helix and the other to Turbo. The present
species is the Nerita obtusa of Studer ; and Draparnaud
adopted his specific name.

2. V. crista'ta"^, Miiller.

V. cristata, Miill. Verm. Hist. pt. ii. p. 198 ; F. & H. iii. p. 21, pi. Ixxi.
f. 11, 12, 13.

Body dark grey or brown, with a few small black specks on
the upper part, slate- colour underneath : snout prominent,
rather narrow and curved, faintly wrinkled : tentacles long,
slender, close together but recurved at their points : eyes small
and round : foot quite separate from the snout, and resembling,
in proportion to its size, that of the last species : hranchial
jilume transparent, bearing about 15 offsets on each side of the
stalk : hranchial ap^endaye rather shorter than the tentacles.

Shell forming a flat coil, concave beneath, rather solid,
semitransparent, yellowish or greyish-horncolour, closely and
regularly striate transversely : epidermis very thin : whorls 5,
the last exceeding in breadth all the rest put together : spire
flat, or slightly concave omng to the convexity of the whorls :
mouth circular ; outer lip thin and slightly reflected : inner lip
separate from the columella and continuous with the outer lip :
umhilicus very large and open, fully exjiosing the interior of
the spire : operculum circular, concave like an inverted pot-
lid, forming a concentric spire of about a dozen whorls, the

* Crested ; so called from its brancldal plume.

VALVATA. 75

outer edges of which are membranous and project in front so
as to make slight ridges. L. 0*025. B. 0*125.

Habitat : Lakes, canals, ponds and ditches, with the
last species. It has an equally extensive range both
here and abroad, except that the present species does
not appear to have been found south of Corsica. It is
also one of our upper tertiary fossils. A monstrosity is
in my collection, which has the last whorl detached and
coiled upwards, as is not unfrequently the case with
several species of Planorbis.

The branchial plume is not always protruded, even
when the animal is crawling.

Although the spire in some specimens is a trifle more
depressed or sunk than usual, I am not aware that the
Valvata spirorbis of Draparnaud (which Moquin-Tandon
regards as a variety of the present species) has ever been
found in this country. The V. minuta of that author is
a totally different species, having a globular shell, with a
produced spire, and resembling a miniature V.piscinalis.
The present species is the V. planorbis of Draparnaud.

There is no difficulty in distinguishing V. cristata
from the fry of V. piscinalis, much less from the adult,
where the great difference of size affords a sufficient
criterion. The shell of the present species in all stages
of growth is quite flat, and resembles that of a Planorbis,
constituting apparently a passage into that genus ; while
the other is trochoid or subglobose, and has a prominent
spire. Their bodies, or the soft parts of the animal, do not
present such a decided difference. The tentacles of V.
piscinalis are, however, rather more slender, and the
snout is proportionably larger than in this species.

E 2

76 * PULMONOBRANCHIATA.

Order II. PULMONOBEANCHIATA*.

Body spiral : respiratory apparatus principally consisting of
an internal cavity or sac, formed by a fold of the mantle, and
lined with a network of vessels, which serves the purpose of
lungs.

Shell usually external and spiral, but sometimes internal
and rudimentary or wanting. In the two latter cases the
mantle is external and forms a shield on the back.

With respect to the reproductive system of the Mol-
lusca comprised in this Order, it may be observed that
each individual of those kinds which do not possess an
operculum has both sexes united in itself, but requires
to be fertilized b}^ another individual, while those which
have an operculum are of different sexes. The former
are androgynous, answering in some respects to the
botanical term " monoecious ;^^ and the latter are strictly
" dioecious.^'

The Pulmonobranchs, Pulmobranchs, Pulmonifers, Pul-
monates, or Pneumonobranchs, by all of which various
names these mollusks have been called, on account of the
analogy which their organ of breathing bears to the
lungs of vertebrate animals, respire for the most part
atmospheric air. The aquatic kinds obtain also some air
from the water by means of auxiliary branchial organs.
All the land mollusks, or Snails, belong to this Order.
The other members of it are aquatic ; but none of them
inhabit the open sea, although a few, belonging to the
genera Melampus or Conovulus and Otina, are amphi-
bious. These last I propose to include in the marine
Mollusca, as they live in the sea for many hours out of
the twenty-four, and are only met with on dry land

* Having a lung-like gill.

LIMN^lDiE. 77

when the tide has retired. One species of Melampus is
found in brackish, but never in fresh, water.

In this country, about three-fourths of the Pulmono-
branchs are terrestrial; the remaining fourth live in
fresh and shallow water, occasionally rising to the sur-
face or crawling out of their native element to renew
the supply of air. They are nearly all herbivorous ; but
the Testacella, or Shell- Slug, feeds exclusively on the
earthworm, and the Slugs and many kinds of Snail (both
terrestrial and aquatic) eat animal as well as vegetable
substances, and are occasionally cannibals. It has been
proposed to call the tentacles of the aquatic kinds by
another name (viz. vibracles), in consequence of their
being contractile, instead of retractile like the tentacles
or horns of land-snails, and also because they do not
bear the eyes on their tips or extremities, as in the last-
mentioned kinds. This distinction seems, however, to be
unnecessary ; and much confusion might result from such
an innovation, as the word ' tentacles ^ has been so long
and universally applied to the feelers of all the Gastero-
poda or univalve MoUusca.

They may be conveniently divided according to their
different habitats ; and the freshwater kinds will be de-
scribed first, so as to complete this branch of the subject.
These are aU covered or protected by a shell, and are
comprised in the undermentioned family.

Family LIMN^ID^.

Body generally long and spirally coiled, but in one genus
short and hood-shaped : mantle covering the upper part in front:
head short : tentacles 2, contractile : eyes placed on the inner
base of the tentacles, a little towards the front : foot oval, used
for crawling or floating.

Shell spiral, or hood-shaped.

78 LlMNiEIDiE.

Genus I. PLANOR'BIS^ Guettard. PL IV. f. 1, 2, 3.

Body long, twisted in a flat coil : tentacles very long and
slender : foot short and narrow, attached to the upper part of
the body by a stalk, which is shaped like the lower half of an
honi'glass.

Shell quoit-shaped, or flat : whorls cylindrical : spire dex-
tral, or turning from left to right, and visible on each side.

This genus has some remarkable peculiarities. One
of them consists in the habit of the animal emitting its
purple-coloured blood, or a fluid like that which is se-
creted by the Aplysia, on being irritated, apparently as a
means of defence against its enemies. Another is, having
several of its vital organs placed on the left side of its
body, instead of on the right (as is the case with nearly all
the other Gasteropoda), while the spire of its body and
shell is coiled the other way, viz. from left to right. And
a third peculiar feature consists in the form of its shell,
wliicb is flat or concave on one or both of its sides, re-
sembling that of an Ammonite, The body of these mol-
lusks is too small for its shell ; and when crawling, the
animal leaves part of the shell empty, putting one in
mind of loose and ill-fitting clothes. O. F. Miiller, nearly
a century ago, seems to have satisfactorily settled the
question that was then raised as to whether the shells
were right- or left-handed ; but the discussion has lately
been renewed. The shell being viewed in its natural
position, there can be no doubt of its being dextral.
Some of the smaller species of Planorbis, inhabiting
marshes and very shallow water which are dried up in
summer, close the mouth of their shell with an epi-
phragm, or filmy covering, like that of some land-snails.
The animal then retires into the interior of its coil and

* Flat-coil.

PLANORBIS. 79

awaits the return of moist and more congenial weather.
All of them frequent stagnant or slowly-running water,
and are herbivorous. Their eggs are enclosed in a
globular bag, which is fixed to stones and the stalks or
leaves of submerged water-plants. Owing to the sluggish
habits of most of the species, as well as to the nature
of their habitat, the surface of their shells is apt to
become encrusted with a mineral or vegetable deposit.
The genus seems to have been originally indicated by
Petiver in his ' Gazophylacion.''

There being several species, it may be more con-
venient to divide them, as before, into sections.

A. Shell glossy ; last whorl very large in proportion to the
rest, and partly covering the preceding one.

1. Planorbis linea'tus*, Walker.

Helix lineata, Walker, Test. Min. Ear, p. 8, pi. 1 . f. 28. P. laacstris, F. & H.
iv. p. 162, pi. cxxviii. f. 1-3.

JioDY reddish-brown, tinged with violet, dark purple in
front with a few black specks : head strongly bilobed : ten-
tacles filiform, diverging at their base : eyes small, but distinct,
scarcely prominent : foot broad and rounded in front, gradu-
ally narrowing and pointed behind.

Shell quoit-shaped, the upper being rather more convex
than the lower side, both sides depressed or almost concave in
the middle, rather thin, very glossy, semitransparcnt, reddish
or yellowish-horncolour, or grey, closely striate in a trans-
verso direction, the striae becoming curved towards the mouth :
epidermis very slight : periphery (or circumference of the
outer whorl) bluntly keeled: luhorls 4, compressed on all
sides ; the last exceeding in size the rest of the shell, and con-
cealing nearly two-thirds of the preceding whorl in its clasp :
suture distinct, but not deep : mouth obliquely heart-shaped :
outer lip thin and flexuous, obtusely angulated above : um-
hilicus small and rather deep : inside the last whorl are from

* Streaked.

80 LIMN^ID.^.

2 to 5 rows of curved plates, which are arranged on each side
across the spire, opposite to each other and at nearly equi-
distant intervals. L. 0-065. B. 0-2.

Habita-T : Slow streams and ditches in the home and
eastern counties, as well as in Guernsey (Lukis), Notts
(Lowe), and Co. Tipperary (Humphreys) ; but it is a
local species. It is found in our upper tertiary strata.
According to Malm it occurs in Sweden ; and it appears
to have a wide range over the more temperate parts of
Europe, as far south as Toulouse.

This pretty and curious little mollusk is rather active,
and is usually found on duck-weed and other aquatic
plants. It lays only from 3 to 8 eggs, which come to
maturity in ten or twelve days. The internal plates,
which are observable outside the last whorl of the shell,
form half-closed chambers ; and the animal retreats into
the front one for safety. These plates appear to answer
the same purpose as the teeth or folds which barricade
the apertures of many of the small land-snails. They are
also only formed in adult individuals. The peculiarity
of this structure induced one of its earliest discoverers,
Lightfoot, to call the present sheU a Nautilus ; and the
late Professor Fleming proposed for it on the same grounds
a new genus {Segmentind) , which has been adopted by
Capt. Brown and Dr. Gray ; but, even as a test of concho-
logical distinction, this character does not seem to be of
any value. Miiller noticed, in his description of the next
species, that a few of the specimens which he had exa-
mined had two streaks, like ligaments, in the upper part
of the last whorl, apparently indicating the marks of
fracture and mending of the shell, by which he may
possibly have meant this species ; but he only described
one species of this form, which still bears the name he
gave it, Planorbis nitidus. The present species was first

PLANORBIS. 81

made known by Mr. Walker, an intelligent bookseller at
Faversliam in Kent, tbe description of it having been
supplied to bim by Mr. Jacob. The only share which
Mr. Boys appears to have had in the discovery is his
having sent parcels of shell-sand to Walker; but the credit
of the publication entirely belongs to the latter. Two
years afterwards Lightfoot described and published this
species in the ^Philosophical Transactions/ under the
name of Nautilus lacustris.

2. P. n/tidus*, Miiller.

P. nitidus, Miill. Verm. Hist. pt. ii. p. 163 ; F. & H. iv. p. 161, pi. cxxvii.
f.11,12.

Body reddish-grey, with sometimes a yellowish tinge, and
marked with extremely fine dark-grey specks : tentacles very
long and slender : eyes rather large : foot short, very broad in
front, and sHghtly narrowing behind to an abrupt but not a
fine point.

Shell shaped like the last, but flatter and with much more
of the spire visible above, in consequence of the last whorl
not clasping such a large part of the preceding one, very thin,
glossy and prismatic, hght-j^ellowish-horncolour or grey, with
sometimes a reddish tinge, faintly striate by the lines of growth,
with occasionally a few spiral microscopical hues, which are
more distinct on the under side, giving an appearance of the
sculptui'e pecuhar to the shells of Limncea : epidermis ex-
tremely dehcate : periphery rather sharply keeled : whorls 4-5,
the last covering about one -half of the preceding whorl : su-
ture rather deep : mouth and outer lip formed as in P. lineatus,
but larger : umbilicus small, not deep. L. 0-06. B. 0*225.

Habitat: Ponds, marshes, and stagnant water through-
out Great Britain, from the Moray Firth district south-
wards. It is also one of our upper tertiary fossils.
MiddendorflP has included it in his list of Siberian shells ;
and it is extensively distributed over the European con-
tinent, having apparently its most southern limit in

* Shining.

E 5

82 LIMNvEID^.

Corsica. Although it is much less local than the last spe-
cies^ I am not aware of their having been found together.

Its habits are slower and more timid than those of P.
lineahis ; and it is not so fertile, never laying more than 6
eggs. The shell is often infested by the minute egg-cases
of a water-insect, or coated with the spores of Confervce.

The shell differs chiefly from that of the last species in
being of a lighter colour, flatter, and thinner, in the
whorls being more visible above, the keel being much
sharper, and especially in the absence of the internal
septa or partitions.

B. Whoi'ls few.

3. P. Nauti'leus"^, Linne.

Tm^bo Nautileus, Linn. Syst. Nat. ed. xii. p. 1241. P. Nautileus, F. & H.
iv. p. 152, pi. cxxyi. f. G, 7.

Body greyish- brown, with sometimes a faint reddish tinge,
minutely speclded with black : head very large and thick :
tentacles long and cylindrical, greatly diverging : eyes distinct,
scarcely prominent : foot broad, rounded in front, and ending
in a blunt point behind.

Shell quoit-shaped, having the upper side flat and the
lower side rather convex, thin, not glossy, light-brown or grey,
sometimes white, closely striate by the lines of growth, which
at distant but regular intervals form strong curved ridges and
frequently rise into projections like the rowels of a spiu* on the
outside : epidermis rather thick : periphery bluntly and in-
distinctly keeled : whorls 3, depressed above, the last exceed-
ing in size the rest of the shell : suture rather deep : mouth
oblique, and either oval or nearly circular, according to the
greater or less depression of the whorls : outer Up thin, form-
ing with the inner lip in the adult a complete peristome : iim-
hilicus very large and exposing all the spire. L. 0*035. B. 0-1.

Var. cristata. Shell having the transverse ridges stronger,
and the periphery deeply notched or crested by them. P. cris-
tatusy Drap. Hist. Moll. p. 44, pi. ii. f. 1-3.

* Shaped like a Nautilus.

PLANORBIS. . 83

Habitat : On aquatic plants in marshes, lakes, ponds,
and ditches, from the northernmost extremity of Zetland
to the Channel Isles. It is also one of our upper tertiary-
fossils. The variety is not uncommon, and merges in-
sensibly into the ordinary form. The degree of sculpture
appears to depend much on age, as it is usually stronger
in half-grown individuals and disappears in the adult.
A monstrosity also occurs in which the whorls are more
or less twisted and separate from each other, sometimes
being raised like a snake lying on its coil. The range of
this species abroad extends from Finland to the Pyre-
nees and even to Algeria.

This pretty little mollusk is slow in its movements,
and may be noticed feeding on the decaying leaves of the
Iris pseudacorus and water-plants. According to Bou-
chard -Chantereaux, it lays only from 3 to 6 eggs, which
leave the capsule in ten or twelve days. The sculpture
of the shell is extremely elegant ; and it is by far the
smallest of its kind. The minuteness of its size, dull
appearance, and comparatively large umbilicus will at
once serve to distinguish it from either of the foregoing
species. If the rings which encircle each whorl are
marks of annual growth, it must attain a very respectable
old age for a mollusk, as I have counted as many as 20
rings in one specimen. In all probability, however, these
marks do not indicate the annual, but only the periodical
growth, several of them being formed in the first year.

4. P. al'bus^ Miiller.

P. alhus, Miill. Yerm. Hist. pt. ii. p. 164; F. & H. iv. p. 149, pi. cxxvi.
f.1,2.

Body grey or dirty-brown, sometimes inclined to a reddish
hue, with fine but indistinct black specks : head thick, rounded

* White.

in front : tentacles widely spread at their base, long, slender,
and pointed : eyes small and rather of an oval shape : foot
narrow, rounded in front and narrowing gradually behind to
a blunt point.

Shell flat above, with a depression in the centre, slightly
concave below, rather thin, not glossy, greyish-white, closely
striate in the line of growth, and more strongly striate or
ridged spirally : epidermis thick, sometimes hispid or bristly :
'periphery slightly compressed on each side, but not keeled :
whorls 5, the last exceeding the rest in size : suture rather
deep : mouth obliquely oval : outer lip slightly reflected ; the
upper part projecting considerably: inner lip spread on the
columella, but continuous with the outer lip : umhilicus very
large, but not deep. L. 0-08. B. 0-275.

Var. Draparnaldi. Shell more closely and sharply striate
in the line of growth : periphey^y distinctly keeled : umbilicus
deeper. P. sjnrorbis, Drap. Hist. Moll. p. 45, pi. ii. f. 8-10.
Helix Draparnaudi, Sheppard, in Linn. Tr. xiv. p. 158. P.
Draparncddi, Jeffr. in Linn. Tr. xvi. p. 386.

Habitat : Same as that of the last species^ but more
generally diffused. The most northern limit in these
islands appears to be Aberdeenshire. It is also an upper
tertiary fossil. The variety has been found at Holbrook
in Suffolk (Sheppard) ; Cardiff, Bristol^ and Church
Stretton in Shropshire (J. G. J.). It has been referred
by the authors of the ' British MoUusca ' to the P. margi-
natus of Draparnaud. This common species ranges from
Siberia to Portugal and Algeria.

The spire is often twisted or distorted in this, as well
as in the other species of Planorbis. The spiral strise
are always visible, even in dead and water- worn speci-
mens which have lost their epidermis. The finest spe-
cimens I have seen were kindly sent to me by my friend
Mr. Norman, who found them at Kibworth, Co. Durham,
their diameter being rather more than a third of an
inch.

In all probability this was the Helix spirorbis of Linne.

PLANORBIS. 85

The description of its colour {" alba^^), as well as all the
other characters given of this species in the ^ Fauna
Suecica/ are peculiarly appropriate to P. albus. The
present species being common in Sweden, and not likely
to be confounded with any other, could scarcely have
escaped the keen observation of the great naturalist;
and it was not otherwise noticed by him. However, as
the confusion has already been too great in the specific
names of this genus, I will not venture to increase it by
restoring Linnets name.

5. P. gla'ber*, Jeffreys.

P. (/later, Jeffr. in Linn. Tr. xvi. p. 387 ; F. & H. iv. p, 150, pi. cxxvi. f.8,9,

Body yellowish-grej : tentacles rather short, cylindi-ical, and
ending in a blunt point : foot rather broad, especially in front,
with a yellowish edge.

Shell rather convex above and depressed in the centre,
concave below, rather thin, glossy and sometimes iridescent,
greyish -horncolour and occasionally marked with white curved
streaks in the line of growth, finely but irregularly striate
transversely, and very faintly and obscurely striate in the op-
posite or spiral direction ; the spiral stride are only visible in
some lights and by the aid of a strong magnifying power :
epidermis thin and smooth : j;eripAer?/ rounded : whorls 5, con-
vex, but somewhat angular, the last scarcely exceeding one-
half of the shell : suture very deep : mouth rather more circular
than oval : outer lip shghtly reflected, the upper edge project-
ing a httle beyond the lower one : inner lip united to the colu-
mella, but continuous with the outer Hp : umbilicus large and
rather deep. L. 0'05. B. 0-15.

Habitat : On aquatic plants in marshes, lakes, and
ponds, from Burra fiord in Unst to Penzance ; but it is
not generally diffused. It is an upper tertiary fossil. I
only know of about twenty localities. The largest speci-
mens I have seen were found by Mr. Bridgman near

* Polished.

86 LIMN^ID^.

Norwich, and measure nearly a quarter of an inch in
diameter. It is distributed throughout the greater part
of the Continent, and ranges from Sweden to Corsica
and Algeria. According to the Rev. R. T. Lowe, it also
inhabits Madeira.

This species differs from P. albus in its smaller size
and glossy aspect ; in the upper side being rather convex,
instead of flat (owing to the rotundity of the whorls) ;
in its deeper suture and umbilicus ; in the upper part of
the outer lip not projecting so much, in consequence of
which the mouth appears to be more circular; and,
especially, in not having the strong and regular spiral
striae which characterize the last species. The mouth is
also not nearly so large; and the periphery is never keeled
or compressed. The present species is equally abundant
where it occurs ; but I am not aware that both species
have been found living together.

It is the P. Icevis of Alder, and probably also the
P. cornit of Ehrenberg from the Nile. The P. Ross-
mcBSsleri of Auerswald appears to be only a large variety
of the same species, having the peristome thickened by
an inner rib (as in the next species), judging from Ross-
massler's description and figure, as well as from an ex-
amination of typical specimens in the Museum at the
Jardin des Plantes. Yon Martens has published, in the
^ Malakozoologische Blatter' for 1859, some excellent
dissertations on the synonymy of a few of the European
land and freshwater shells, and is of opinion that this
species is also the P. gyrorbis of v. Seckendorf and has
five other aliases.

PLANORBIS. 87

C. Whorls many, keeled.
6. P. spiror'bis^_, Miiller.

P. spirorhis, Miill. Verm. Hist, pt.ii. p. 161 ; F. & H. iv. p. 159, pi. crxvii.
f.9, 10.

Body purplish-grey or redclish-brown, with minute black
specks on the foot : tentacles rather long, slender and pointed :
foot short and narrow, obtusely rounded in front and angular
behind.

Shell slightly concave above and flat below, or vice versa,
slightly wider at the base, rather solid, glossy, brownish horn-
colour, closely striate in the line of growth, and marked spirally
with very faint and minute striog : epidermis thin : periphery
angular, and sometimes bluntly keeled on the lower side :
whorls b~Q, gradually increasing in size, the last not exceeding
in diameter one-sixth of the whole spire ; they are rounded,
but angular : suture deep : mouth nearly circular, often thick-
ened or strengthened inside by a rib : outer lip very slightly
reflected : inner lip continuous with the other lip, but spread
over the columella : umbilicus very large and shallow. L. 0*04.
B. 0-25.

Yar. ecarinata. Shell smaller, light grey, having one whorl
less than usual and no trace of a keel. P. spirorhis, Moq.-
Tand. Hist. MoU. Fr. p. 437, pi. xxxi. f. 1-5.

Habitat : On plants and grass in shallow and stag-
nant water everywhere from the Moray Firth district to
the Channel Isles. It is also a fossil of our upper ter-
tiary beds. The variety appears to be very rare in this
country. I have only found it once ; and that was in
Oxwich marsh, near Swansea. A monstrosity not un-
frequently occurs, in which the whorls are more or less
twisted and separated. Some specimens which my late
friend Mr. Barlee found at Penzance resemble a minute
corkscrew; and in another form of the same kind of
distortion which I found in Bishopston Valley, near

* Round-spired.

88 LIMNiEIDiE.

Swansea, the last whorl only is separated from the rest
and curled upwards. In the last-mentioned locality
there was a great deal of mud which had been brought
down by a stream and deposited in the grassy pool where
I found the shells. This mud must have inconvenienced
the mollusk and prevented its completing the spire of
its shell on the usual plane ; so that it gave the last whorl
an outward twist, apparently in order to get clear of the
incumbrance. When the drains and splashy pools in
which this kind of Planorbis lives are dried up by the
heat of summer, it retires far within its shell and closes
the mouth or opening with a yellowish- white and rather
solid lid, patiently waiting for the next shower of rain
and fasting in the mean time. This species inhabits
Siberia, and ranges as far south as Algeria and Sicily.

It differs from P. glaber in the whorls being much
narrower and consequently more compact, and in usually
having a blunt keel on the periphery.

The typical or ordinary form is the P. rotundatus of
Poiret, P. vortex var. ^. of Draparnaud, and P. leuco-
stoma of Michaud, besides having other specific names
for several of the varieties.

7. P. vor'tex"^, Linne.

Helix vortex, Linn. Sjst. Nat. ed. xii. p. 1243. P. vortex, F. & H. iv. p. 157,
pi. cxxvii. f. 6-8.

Body reddish-brown, with a slight tint of violet, rather
distinctly marked with minute black specks : tentacles very
long, slender and finely pointed : foot evenly rounded in front
and keeled behind.

Shell much compressed, concave above and flat below, thin,
glossy, yellowish or greyish-horncolour, finely and closely
striate in the line of growth, and occasionally having a few
obscure and extremely minute spiral stria3 : epidermis thin :

* Whirlpool.

PLANORBIS. 89

periphery slightly keeled towards the lower side, and always
angular in consequence of the outward compression of the
shell : wliorls 6-8, gradually enlarging, the last not exceeding
in diameter one-fifth of the whole spire, angular on both sides
and sloping gently towards the outer edge : suture well de-
fined, but not deep : mouth obliquely oval, ending above in
rather an acute angle, and having the inside sometimes thick-
ened by a slight rib : outer lip not reflected : inner lip much
spread on the columella, but continuous with the outer lip :
umbilicus very large and shallow. L. 0-05. B. 0-3.

Yar. compressa. Shell thinner and much flatter, with the
keel more distinct and sharp and placed nearly in the middle
of the periphery. P. compressus, Mich. Compl. p. 81, pi. xvi.
f. 6-8.

Habitat : The same as that of P. spirorbis, and having
a similar range at hoAie and abroad as far southward as
Algeria. It is, however, not so generally diffused as
that species. They are sometimes found together. The
present species is also one of our upper tertiary fossils.
The variety is not uncommon. I have a distortion from
Clumber lake, Notts, in which the spire is displaced on
the lower side, and the first whorls are set at an acute
angle to those which succeed.

This mollusk is sluggish, but fond of floating. It lays
from 10 to 12 eggs. The epiphragm is thin and mem-
branous.

The shell diff'ers from that of P. spirorbis in being
thinner, flatter, and rather longer, and in having a distinct
and prominent keel. This species was first described
and figured by Lister.

8. P. CARINA Tus *, Miiller.

P. carinatus, Mlill. Yerm. Hist, pt, ii. p. 175 ; F. & H. iv. p. 153, pi. cxxvii.
f. 4, 5.

Body deep -reddish brown with a yellowish tint, and of a

* Keeled.

90 LIMNiEIDiE.

lighter colour underneath, finely and rather distinctly marked
with black specks : tentacles long, slender, bluntly pointed :
foot acutely rounded in front and obtusely so behind.

Shell compressed, concave above and flat or very slightly
convex below, rather thin and glossy, yellowish-horncolour,
finely and closely striate in the line of growth, with a few
slight spiral strife : ej)idermis thin : pgr^p7iery strongly keeled
towards the middle : whorls 5-6, the diameter of the last being
rather less than a third of the whole spire, moderately con-
vex above, but much less so beneath, sloping gradually on
both sides to the periphery : suture deep : mouth obliquely
oval, sharply angulated above, the inside sometimes thickened:
outer lip slightly reflected : inner lijp continuous with it, much
spread on the columella : umbilicus very indistinct, owing to
the lower side being nearly flat. L. 0-1. B. 0-5.

Yar. disciformis. Shell flatter and thinner, of a yellowish
colour, having the last whorl larger in proportion to the others,
and the keel more prominent and sharp and placed exactly in
the middle. P. lutescens (afterwards altered to disciformis),
Jeffr. in Linn. Tr. xvi. pp. 385 & 521.

Habitat : Marshes and stagnant water in our home
and eastern counties, as well as in those of Dorset, Somer-
set, Northampton, York, Glamorgan, and many parts of
Ireland. Dr. Leach says that it also occurs near Edin-
burgh. It is, however, local, and never plentiful. It is
an upper tertiary fossil. The variety is found in Bucks,
Oxford, Cambridge, Glamorgan, Cork, and Tipperary, and
is somewhat rare. This variety bears the same relation
to the typical form as the P. compressus of Michaud does
to P. vortex. The monstrosity, so common in this genus,
in which the last whorl is disjoined from the rest, also
occurs, but very seldom. It is a Swedish species, and
ranges southward to Portugal and Corsica.

This mollusk is very slow in its movements, but ap-
pears to be fond of floating. It lays from 10 to 20 eggs,
which quit the capsule in from ten to fifteen days. It is
occasionally met with in company with the next species.

PLANORBIS. 91

This is in all probability the Helix i:tlanorhis of the
^ Fauna Suecica/ which is described as " plana" and
" margine prominulo;" but as the description and figure
given by Lister^ to which Linne there refers, sipply to the
Helix complanata of the latter, more confusion will be
avoided by the adoption of Miiller^s name.

9. P. complana'tus "^^ Linne.

Helix complanata, Linn. Syst. Nat. ed. x. p. 769. P. marginatus, F. & H.
iv. p. 165, pi. cxxvii. f. 1-3.

Body of a deep violet-red, with very fine black specks, espe-
cially on the edges of the foot : tentacles very long and slender,
bluntly pointed : foot rounded in front, convex behind, and
ending in an obtuse tail.

Shell concave above and slightly convex below, rather
soHd and opaque, not glossy, yellowish-horncolour with some-
times a tinge of brown, closely but irregularly striate in the
line of growth and more or less distinctly striate in a spiral
direction : epidermis rather thick : 'periphery strongly keeled
on the under side : ivhorls 6, the diameter of the last being
about one-fourth of the whole spire, convex above and slightly
so beneath, sloping abruptly on the upper, and gradually on
the lower side to the peripher}^ : suture moderately deep :
mouth roundish-oval, slightly angulated above by the keel, the
inside being sometimes strengthened by a rib : outer lip a little
reflected : inner lip continuous with it and affixed throughout
to the columella : umbilicus broad and very shallow. L. 0-125.
B. 0-6.

Yar. 1. rhomhea. Shell smaller, more soHd, rather more
convex above and deeply umbihcated below ; keel blunt and
almost obsolete. Helix rhomhea, Turton, Conch. Diet. p. 47.

Var. 2. alhida. Shell whitish or colourless.

Habitat : Marshes, ponds, canals, ditches and stand-
ing water everywhere in England, Wales, and Ireland ;
but I am not aware of any Scotch locality. It is one of
our upper tertiary fossils. The variety 1. is from Dublin

* Flattened. '

93 LIM^MIBM.

and the South of Ireland ; and the other variety has
been found by Mr. Choules at Eltham in Surrey. A
monstrosity, having the whorls dislocated and more or
less separate from each other, sometimes corkscrew-
shape, has been found by Mr. Bean near Scarborough,
and by myself on Crymlyn Burrows, near Swansea. It
is the Heliw Cochlea of Brown (Mem. Wern. Soc. pi. xxiv.
f. 10) and H. terebra of Turton's ' Conchological Dictio-
nary.' This common species is widely distributed in Eu-
rope from Finland (according to Nordenskiold and Ny-
lander) to Algeria and Sicily.

It is a sluggish and slimy as well as a very irritable
mollusk, and often indulges itself in floating lazily along
the under surface of the water. It lays from 8 to 10
capsules, each of which contains from 6 to 21 eggs ; so
that it appears to be more prolific than many of its con-
geners.

Its shell may be distinguished from that of P. cari-
natus by its narrower and more rounded whorls, as well
as by the keel being placed below, instead of in or to-
wards the middle of, the periphery. It is usually larger
and thicker than that species and is much more gene-
rally diffused and plentiful.

There can be no doubt that this is the Helix compla-
nata of Linne, whose epithet "deorsum carinata^' is
peculiarly appropriate; but both MUller and Drapar-
naud have substituted other names (viz. umbilicatus and
marginatus) on w^hat I cannot help considering as very
insufficient grounds. If Linne's name was prior to what
is termed " the binomial epoch," and therefore inadmis-
sible (which is a very questionable objection), still Gme-
lin's adoption of that name, as well as Miiller's, take
precedence of the one proposed by Draparnaud. It must
also be borne in mind that this species and P. carinatus

PLANORBIS. 93

are connected together through the P. submarginatus of
Cristofori and Jan, alias the P. intermedins of Char-
pentier. Some of the aberrant forms are as difficult to
separate as those of P. spirorbis and P. vortex. The
present species was first made known by Lister.

The P. turgidus described by me in the ' Linnean
Transactions ' is not a British species ; and I was mis-
informed as to the locality. Its nearest ally is, as I
stated, P. corneus ; but it has been erroneously referred
by subsequent writers to the present species.

D. Wliorh roimded and not keeled.

10. P. cor'neus^, Linne.

Helix cornea, Linn. Syst. Nat. ed. xii. p. 1243. P. corneus, F. & H. iv.
p. 147, pi. cxxvii. f. 1-3.

Body dark red or nearly black, of a greyish hue beneath,
with black and grey specks on the upper part : tentacles long
and curved, with rather blunt tips : eyes of a moderate size
and not prominent : foot slightly tubercled, narrow and angu-
lated in front, rounded and convex behind.

Shell rather deeply concave above and nearly flat below,
somewhat solid and opaque, glossy, whitish-horncolour with
a reddish-brown tinge, closely but irregularly striate by the
curved hnes of growth and marked with fine and close -set
spiral striae, which are more perceptible in the first whorls ;
the upper surface is also sometimes pitted or impressed in an
irregularly quadrangular form like cut-glass : epidermis rather
thin: periphery rounded and quite destitute of any keel or
angularity : wliorls b-Q, more perceptible on the umbilical or
lower side, in consequence of that part of the spire being
intorted ; diameter of the last whorl rather less than a third
of the whole shell ; they are very convex above and rather
compressed beneath : suture deep : mouth forming a segment of
two-thirds of a circle : outer lip a little reflected, the upper
side not projecting much beyond the lower one : inner lip con-

*■ Horn-coloured.

94 LIMN^ID^.

tinuoiis, but closely attached to the columella and widely
spread on it: umhilicus broad and shallow. L. 0-35. B. 1.

Yar. albina. Shell perfectly white.

Habitat : Marshes^ ponds^ and ditches in many parts
of England and Ireland ; but, although gregarious, it is
very local. It occurs in a fossil state in the mammalian
crag of Suffolk, as well as in the upper tertiary beds of
Suffolk, Essex, and Worcestershire. The variety is found
in Surrey. It is a Siberian species, and diffused over the
Continent as far south as Corsica. M. Terver has found
a thin variety of it in Algeria.

This far exceeds in size any other European species of
Planorbis. Its anatomy, embryology, and habits were
accurately described by Lister nearly two centuries ago ;
and he seems to have made several experiments, but in
vain, with the hope of being able to fix and render useful
the purple dye which this moUusk so plentifully yields.
It is a sluggish and extremely sensitive animal ; and
when irritated it emits the fluid or secretion in con-
siderable quantity from a gland at the sides of its neck.
It may often be seen floating on a warm and still summer
day. It lays only two or three capsules, each containing
from 20 to 40 eggs, which are excluded at the end of
fifteen or sixteen days. The epidermis of the young shell
is covered with fine down, its surface resembling velvet
pile. In this state it is the P. similis of Miiller.

11. P. contor'tus*, Linne.

Helix contorta, Linn. Syst. Nat. ed. xii. p. 1244. P. contortus, F. & H. iv.
p. 160, pi. cxxvi. f.3.

Body black, with a slight tinge of red : tentacles remarkably
slender : eyes very small : foot broad and rounded in front,
narrowing behind to a blunt tail.

* Twisted.

PHYSA. 95

Shell flat above, with a deep depression or concavity in the
middle, very concave below, rather solid for its size, and opaque,
yellowish-brown or horn-colour, closely and deeply striate in
the line of growth, but not otherwise sculptured : ejpidei^mis
rather thick : periphery rounded : ivJiorls 8, extremely compact
and much compressed, angular above and slightly so beneath:
suture deep : mouth semilunar, occasionally strengthened in-
side by a rib : outer lip not reflected, the upper side scarcely
projecting beyond the lower one : inner lip thin, not con-
tinuous but attached to the columella : umbilicus large and
deep. L. 0-075. B. 0-175.

Yar. alhida. Shell nearly white.

Habitat : On water-plants in lakes, ponds, and ditches
throughout the greater part of Britain, and reaching as
far north as the Shetland Isles ; but it is local. It is also
an upper tertiary fossil. The variety was found by me
in a lake near Lerwick, with specimens of the ordinary
colour. The usual monstrosity occurs in which the spire
is dislocated. Abroad it ranges from Siberia to Portugal
and Corsica.

This curious little moUusk is slow, irritable, and fond
of floating. It is not very prolific ; for each capsule (of
which it lays from 5 to 9 during the breeding-season)
contains only from 6 to 8 eggs, giving an annual average
of about 50 for an individual.

The shell of this, as well as of the last species, is so
diflPerent from any other which I have described, that it
is unnecessary to make any comparison. Their forms
are, however, represented by many analogous species in
North America. "*

Genus II. PHY'SA*, Lamarck. PL IV. f. 4, 5, 6, 7.

Body rather long, and twisted in a spiral coil : tentacles long
and slender -.foot rather long, rounded in front and pointed

* A bladder.

96 limn.^idtE.

behind, attached to the upper part of the body by a very short
and broad stalk or pedicle.

Shell conic -oval or oblong : spzVe produced, sinistral or
turning from right to left.

This peculiar and characteristic genus has intermediate
relations with Plano7^bis and Litmicea. It resembles the
first in its long tentacles, as well as in some of the organs
being placed on the left, instead of on the right side of
the body ; and it agrees with the latter in the form of
its shell : but it differs from 1)oth in the spire being
sinistral, although that is not a very important cha-
racter. The shells of Physa have a remarkably polished
appearance, caused in some cases by their being more
or less enveloped by an expansion or lobe of the mantle,
the lubricating friction of which always keeps the surface
smooth and bright. These little mollusks frequent shal-
low, and generally clear water, and are gregarious. Their
eggs are deposited in strips of a gelatinous consistency,
which are fixed to submerged stones as well as to the
stalks and leaves of aquatic plants.

A. Mantle having plain edges and not expanded over the shell,
which is covered with an epidermis and has a long spire.

1. Physa hypno'rum*, Linne.

Bulla hypnorum, Linn. Syst, Nat. ed. xii, p. 1182. P. hi/pnorum, F. & H.
iv. p. 143, pi. cxxii. f. 6, 7.

Boj^Y lustrous, dark grey, dusky bro^Ti, or almost black, with
sometimes a faint tint of blue, covered ^vith very minute black
or dark-grey specks : tentacles long, slender, and pointed, di-
verging considerably at their base : eyes very small and not
very distinct : foot lance-shaped, narrow, blunt and truncate in
front, compressed and rather pointed behind.

Shell oblong, spindle-shaped, thin, highly pohshed, semi-
* Frequenting the Hypnurn, a kind of moss.

PHYSA. 97

transparent, yellowish or reddisli-horncolour, faintly striate by
the lines of growth, and marked spirally with a few very in-
distinct striae, which are only perceptible by means of a high
magnifying power : epidermis very thin : ivhorls 6-7, convex,
but slightly compressed at the sides, the last exceeding in size
all the rest put together : spire tapering, but blunt at its ex-
tremity : suture distinct, though not deep : movjJi oval, con-
tracted on the inner side by the periphery of the penultimate
wborl, acutely angulated above and rounded below: outer Up
thin and fiexuous : inner lip spread on the columella, which
has a strong and broad fold on its lower side. L. 0'5. B. 0-2.

Habitat : Ponds, ditches, and among grass in pools
which are quite dried up in summer, throughout these
isles from the Moray Firth district to Guernsey; but
it is rather local. It is also an upper tertiary fossil.
A variety occurs in which the shell is smaller and of a
dark copper-colour; and I also possess a specimen in
which the spire is eroded and truncate, the opening
having been filled up by a shelly plate. Miiller recorded
a specimen which had only the right eye, the other being
wanting. It is a native of Siberia, and ranges southward
to Nice and the Eastern Pyrenees. According to Gould
and Philippi, it is the same species as the P. elongata of
Say, which inhabits the northern and western parts of
the United States.

This mollusk is rather active in its habits, and may be
seen in fine weather floating with tolerable rapidity. It
is rather prolific ; and the young attain their full size at
the end of the second year. The largest specimens I
have ever seen of this species were found by me more
than a quarter of a century ago, in fish-ponds at Fre-
mington, in the north of Devon, some of which are
three-quarters of an inch in length.

Gmelin supposed that the Bulla hypnorum of Linne
might be a variety of the next species ; and Miiller, for
nearly the same reasons, called the present species Plaii-

F

98 LIMN^ID^.

orbis turritus. But the Linnean epithets ^'^spira pro-
minente ^' and '' spira obsoleta " appear unmistakeably
to distinguish the two species; and, at all events, it
would now be very inconvenient to make any change of
name by adopting that given by Miiller, instead of the
one by which this species is so universally known. The
late Dr. Fleming proposed to separate it generically from
the next under the name of Aplexa -, but this separation
has only been adopted by a very few conchologists. A
well-known European species, P. acuta, seems to con-
nect the two British forms, both as regards the soft parts
of the animal and the shell.

B. MantU having lobes or digitated processes which expand
over the shell ; the latter being destitute of an epidermis
and having a short spire.

2. P. fontina'lis"^, Linne.

Bulla fontinalis, Linn. Syst. Nat. ed. xii. p. 1185. P. fontinalis, F. & H.
iv. p. 140, pi. cxxii. f. 8, 9.

Body lustrous, dark grey with sometimes a sHght tint of
yellow or violet : mantle fringed with about a dozen lobes or
digitations of imequal size : tentacles rather slender, hght grey :
eyes conspicuous: foot obtusely rounded in front, and con-
tracted behind to a somewhat fine point.

Shell oval, extremely thin, glossy, semitransparentjgrej-ish-
horncolour with a slight tinge of yellow or brown, faintly
striate by the Hues of growth and microscopically striate in a
spiral direction : vjhorJs 4-5, swollen, the last occupying con-
siderably more than three-fourths of the shell : spire not much
produced, blunt at its point : suture moderately deep : 7nouth
nearly of the same form as that of the preceding species, but
much larger and wider in proportion : o^lfer lip very thin and
flexuous : i7i7ier lip much spread on the columella, which has a
slight and narrow fold on its lower side. L. 0-35. B. 0-25.

Yar. 1. injiata. Shell half as large again as the usual size :

* Frequenting fountains.

PHYSA. 99

ivhorls angular towards the suture, the middle one rather
more prominent than the penultimate whorl, causing the
summit of the spire to appear abruptly terminated.

Yar. 2. curta. Spire extremely short. Bulla Jluviatilis,
Turt. Conch. Diet. p. 27.

Yar. 3. ohlonga. Spire considerably produced.

Yar. 4. albina. Shell of a milk-white colour.

Habitat : On water-cresses and other aquatic plants
in running brooks, as well as in slow rivers, canals^ and
ditches everywhere in Great Britain, as far north as
Aberdeenshire. Var. 1. Dublin (Humphreys and War-
ren). Var. 2. Clonoony Barracks, Ireland (Brown) ;
Bramerton, Norfolk (J. G. J.). Var. 3. Anglesea, on
Chara aspera (J. de C. Sowerby) ; Naas, Ireland (Hum-
phreys). Var. 4. Birkenhead. (Webster). This species
is widely diflPused on the Continent, and ranges from
Finland to Sicily.

This common and pretty little moUusk is rather lively,
creeping and floating by jerks. A considerable por-
tion of the shell (especially the back of the spire) in its
living state is often covered with the spores of Con-
fervae or some of the freshwater Algae, which shows
that the mantle does not envelope all the surface. When
the fry are excluded from their gelatinous case, they are
about the size of a pin's head, and are very active. The
jerking motion which this animal has, is said to be owing
to its being infested by a small kind of parasitic worm
which causes it some uneasiness. I should rather be in-
clined to attribute this motion to the length and narrow-
ness of the foot, which has to support a comparatively
bulky shell. According to Montagu, the P. fontinalis
spins a filament by which it lets itself down to the bottom
after floating, if there is no leaf or stalk near it. Leach
says that when it is annoyed by the approach of wander-

f2

100 LIMN.^ID^.

ing animals, it repulses them with repeated blows, in-
flicted by a rapid movement of the shell ; the foot being
the point of fixture. This species was first described
and figured by Lister.

The shell is more ventricose than that of the last spe-
cies ; and it has a much shorter spire and a larger
mouth.

The Bulla rivalis of Maton and E-ackett, which was
supposed to have been found in Hampshire, is a common
West- Indian species, which now bears that name. It is
the P. Sowerbyana of D^Orbigny.

Mr. Choules has described in the 'Zoologist' a species
of Physa which he found in a water-tank in Kew Gar-
dens, and which Mr. Norman (being misinformed as to
the precise locality) has proposed to admit into our
native Fauna. It appears to be a variety of the P. acuta
of Draparnaud, but it is undistinguishable from speci-
mens in the British Museum which were collected in
Cuba, St. Thomas, and St. Croix ; and it has probably
])een introduced with some aquatic tropical plant. Dr.
Hooker informs me that many West-Indian plants have
])een imported and cultivated in the Gardens. P. acuta
has never (so far as I am aware) been found in this
country ; and although it is abundant in the middle
and South of France, it has not been recorded as inha-
biting any of the northern Departments. The P. sub-
opaca of Lamarck is a variety of that species.

The P. alba of Turton, who stated that he had received
it from Capt. Blomer as a native of Towyn in North
Wales, is the P. contorta of Michaud, and is only known
to inhabit the Eastern Pjrrenees, Corsica, Sicily, and
Algeria.

LIMN.EA. ^ 101

Genus III. LIMNiE'A *, {Lymnea) Bmguiere.
PL IV. f. 8, 9, 10.

Body rather long and twisted in a spiral coil: 7?^a(i pro-
minent : tentacles short, triangular and flattened : foot oblong,
bilobed or notched in front and obtusely rounded behind, at-
tached to the upper part of the body as in Physa.

Shell conic-oval or elongated : spii^e usually produced,
dextral or turning from the left to right.

As in Physa, some of the species of Limncea, which
appear to form a transitional link between the two
genera, have their shells enveloped by an outer fold or
lobe of the mantle. These species have been generically
separated by some authors under the several names of
A^nphipeplea, Lutea, and Myxas. The difference be-
tween such and the typical species is, however, not greater
than between the two forms of Physa which I have above
noticed. All the species of Limnaa frequent shallow
and still waters ; and they are very prolific and grega-
rious. Their mode of propagation is very singular — three
or more individuals being united in a chain for that
purpose. Leach has remarked that, in consequence of
the sexual parts being distant fi'om each other, one in-
dividual is able, at the same time, to perform the function
of each sex with two others, as was first observed by
Geoffroy about the middle of the last century. The
spawn resembles that of the last genus.

The generic name has been spelt by authors in no less
than nine different ways ; but the correct orthography is
undoubtedly LimrKsa (from Xifivalos:), as proposed by
Rang.

* Inhabiting marshes.

102' LIMN^ID^.

A. Shell extremely thin and fragile, and almost enveloped by

an outer lobe or membranous expansion of the mantle :
sjpire very short.

1. LiMNiEA GLUTiNo'sA*, Mliller.

Biiccinum glutinosum, Miill. Verm. Hist. pt. ii. p. 129. Lhnn<2U8 gluti-
nosus, F. & H. iv. p. 182, pi. cxxiv. f. 6, 7.

Body dark grey, with a greenish-yellow tinge and bright-
yellow or whitish specks : tentacles very short, rather triangular,
with blunt tips : eyes placed on tubercles on ttie inner side of
the tentacles, very black and distinct : foot exceedingly large,
broad in front and obtusely rounded before and behind.

Shell globosely-oval, so excessively thin as to be almost
membranous, highly polished, transparent, yellowish or greyish-
horncolour, with a few indistinct darker spiral zones, remotely
and irregularly striate by the lines of growth, which are stronger
towards the suture, and closely but microscopically striate in
a spiral direction : epidermis extremely thin : whorls 3-4,
globular, the last forming nearly the whole of the shell : spire
slightly produced : suture rather deep : mouth oval, a little con-
tracted above by the projection of the penultimate whorl :
outer lip very thin : inner Up much spread on the columella
and thickened at its edges : columellar /o^tZ (forming the lower
part of the pillar of the spire) curved and sharp. L. 0-55.

B. 0-45.

Yar. mucronata. Shell not quite so globular : sp>ire more
produced.

Habitat : Lakes and ponds in the home and eastern
counties, as well as in a ditch near Dunster Castle in
Somersetshire (Leach) ; Bala Lake (Gibbs) and a pond
near Windermere (Bulwer) ; but it is a local species^
although abundant where it occurs. Its periodical re-
appearance in the same spots has been remarked both
by Mr. Bridgman and Mr. Whiteaves to be very uncer-
tain and unaccountable. Specimens have been kindly
sent to me by Mr. Bridgman, in which the spire is more

* SKmy.

LIMN^A. 103

or less intorted^ resembliug in this respect tlie form of
L. involuta. Tiie present species ranges from Finland,
througli Sweden, Germany, and France, as far south as
the Pyrenees.

It is rather an active mollusk, and nearly always in
motion. Bouchard-Chantereaux.says that each of its
capsules contains from 30 to 40 eggs. In the young the
shell is entirely covered by the pallial fold.

2. L. involu'ta*, Thompson.

Limnetis invohctus, (Harvey) Thomps. in Ann. Nat. Hist. v. p. 22. Lim-.
TUBUS involutus, F. & H. iv. p. 184, pi. cxxii. f. 11.

Body unknown as to its external parts, except that the
greater part of the shell is covered by the mantle.

Shell oval, rather glossy, semitransparent, yellowish -horn-
colour with a tinge of brown, closely but irregularly striate by
the lines of growth, which are stronger towards the suture,
often impressed and sometimes constricted by a few spiral
grooves in different parts of the shell : ejndermis thin : luhorls
3-4, convex, the last covering all the rest except the point of
the spire or nucleus : spire flat or slightly concave, with the
point upraised and twisted : suture distinct, but not deep :
nioutJi pear-shaped : oiiter li}:) thin, slightly reflected : inner Vp
much spread on the columella : fold narrow and sharp. L. 0*4.
B. 0-275.

Habitat : A small mountain-lake, and a stream which
flows into it, at Cromaglaun near Killarney ; not rare.
In one of my specimens, which has the mouth some-
what contracted below, a tendency to an umbilical cleft
is observable.

It is strange that no other locality but the one above
mentioned has ever been discovered, here or abroad, for
this remarkable species. It has some affinity to L. glu-
tinosa, and may ultimately prove to be an aberrant form
of that species, corresponding with the variety Burnetti

* Having the spire intorted or sunk.

104 LIMNiEID^.

of L. peregra. Very little is known with respect to the
external parts of the body; but Professor Goodsir has
given some valuable details of its internal organization,
which are published in an appendix to Mr. Thompson's
paper in the ^Annals of Natural History/ He says,
'' In structure the Limnaus involutus resembles the other
species of the genus ;^' from wliich remark it might be
inferred that the mantle has not the expanded lobe
which is peculiar to the subgenus Amphipeplea. Dr.
Perceval Wright, however, informs me that the greater
part of the shell in this species is covered by the mantle,
as in L. glutinosa. The form and substance of the shell
are also similar in both of these species.

B. Exterior of the shell never covered by the mantle : spire

produced.

3. L. PER EGRA*, Miiller.

Buccinum 'peregrum, Miill. Verm. Hist. pt. ii. p. 130. Limnmcs fcreger,
F. & H. iv. p. 168, pi. cxxiii. f. 3-7.

Body yellowish-grey, with a brown or olive-green tinge,
mottled with black and covered with small yellow or milk-
white, and black .specks : tentacles diverging from each other
at nearly a right angle : eyes distinct : foot oblong, very broad,
nearly truncate in front, and obtusely rounded behind.

Shell obliquely ovate, thin, moderately glossy, semitrans-
parent, yellowish-horncolour, irregularly striate by the lines
of growth, and closely and microscopically striate in a spiral
direction, with occasionally a few indistinct spiral ridges and
pitmarks : epidermis rather thin : ivhorls 5, convex, the last
occupying three-fourths of the shell : spire produced and
pointed : suture rather deep : mouth large, oval, very Httle
contracted above by the projection of the penultimate whorl :
outer lip thin, slightly reflected : inner lip folded on the colu-
mella and thickened, forming behind it a slight umbihcal cleft :
fold rather prominent and curved. L. 0-75. B. 0*425.

* Traveller.

LIMN^A.

105

Var. 1. Burnetti. Body a little broader than that of the
typical form, dark olive, spotted with opaque yellow : mantU
nearly black, with a few paler spots. Shell rather globular
and solid, of a dull aspect, yellowish-brown, closely and
strongly striate in the line of growth : epidermis rather thick :
the last whorl nearly covering all the others : spire exceed-
ingly short, nearly truncate and almost intorted. L. 0*725.
B. 0-65. Limncea Burnetti, Alder in Ann. Nat. Hist. n. s. ii.
p. 396, pi. ii., top figures. Limnceus Burnetti, T. & H. iv.
p. 172, pi. cxxiii. f. 8, 9.

Var. 2. lacustris. Body of a darker colour than usual.
SheU resembling that of the last variety ; but it is much
smaller and more glossy, and has strong and regular transverse
grooves, and the spire is not quite so short nor inclined to be
intorted. The shell is often eroded. Oulnaria lacustris, Leach,
MoU. Brit. Syn. p. 107.

Yar. 3. liitea. Shell remarkably solid, having a very short
spire of from 3 to 4 whorls. Helix lutea, Mont. Test. Brit,
p. 380, tab. 16. f. 6.

Var. 4. ovata. Body of a paler colour. Shell ampuUaceous
and rather thinner than usual : whorls exceedingly convex,
the last being larger in proportion to the rest : sp)ire very
short : suture deep : mouth very large. Limneus ovatus, Drap.
Hist. Moll. p. 50, pi. ii. f. 30, 31.

Var. 5. acuminata. Shell resembling the last variety in all
respects, except in having a more produced spii'e and a smaller
mouth.

Var. 6. intermedia. Shell rather compressed towards the
front margin and thinner than usual : sj)ire more produced :
mouth expanded. Limnea intermedia, Per. in Lam. An. s. V.
vi. pt. ii. p. 162.

Var. 7. ohlonga. Shell oblong and compressed in front.

Var. 8. lahiosa. Shell smaller, having the outer lip remark-
ably expanded and reflected. L. 0*5. B. 0-35.

Var. 9. picta. Shell rather smaller than the last, and beau-
tifully marked by alternate bands of brown and white, which
are sometimes confluent.

Var. 10. maritima. Shell dwarfed, rather solid : spire pro-
duced : suture deep. L. 0*4. B. 0*225.

f5

106 LIMN^ID^.

Yar. 11. Succineceformis, Shell shaped like a Succinea, and
very thin : whorls 4 : spire small and oblique.

Yar. 12. decollata. Shell more or less eroded : spire trun-
cate.

Yar. 13. sinistrorsa. Shell resembling that of a Pliysa in
having the spire sinistral or reversed, rather solid ; the spiral
ridges distinct and prominent. Limnceus lineatus, Bean, MS. ;
E. & H. iv. p. 168, pi. cxxiii. f. 7.

Yar. 14. scalar if or mis. Shell oblong, with deep and regular
transverse striae: ivhorls more or less disjoined: suture con-
sequently very deep.

Habitat : Still and slowly running waters every-
where. Var. 1. Loch Shene^ Dumfriesshire (Burnett) ;
Breconshire (Moggridge) . Var. 2. Mountain-lakes in
Zetland^ Scotland, Ireland, and the North of England.
Var. 3. South Devon (Montagu) ; South Wales (J.G.J.):
thrown up by the tide at the mouths of rivers. Var. 4.
Lakes, canals, and large ponds ; attaining sometimes a
considerable size. Var. 5. With the last. Var. 6. Ponds.
Var. 7. Lewes, Suffolk ; Church Stretton, Salop ; Bear-
haven, Co. Cork (J. G. J.). Var. 8. Appin, Argyleshire
(Bedford). Var. 9. Ulva L, Hebrides (same). Var. 10.
Marshes on the sea- coasts of Glamorganshire and North
Devon (J. G. J.). Var. 11. Kensal Green (J. G. J.).
Var. 12. Church Stretton ; Oxwich, near Swansea
(J. G. J.). Var. 13. Scarborough (Bean). Var. 14.
Warminster (J. G. J.). This and the two last forms are
rather monstrous than varietal. This species is fre-
quently met with in our upper tertiary beds. The typical
form and several of its varieties extend from Siberia to
Sicily. It is a very ubiquitous species ; and Capt. Hut-
ton found a variety of it in Afghanistan.

The variability of this common and abundant species
is equal to the extent of its geographical distribution. I
was at first inclined to consider that the Limneus ovatus

LIMN^A. 107

of Draparnaud, and its allied forms^ would legitimately
constitute a distinct species ; but, after a very careful
and protracted comparison of many hundred specimens,
I could not satisfactorily separate them from interme-
diate varieties. The difference in the colour of the body,
as well as in the consistency and even the shape of the
shell, appears to depend on the nature and quantity of
the food, the chemical ingredients of the water, and the
degree of stagnation or rapidity of its current. M. Mo-
relet, in his description of the Portuguese land and fresh-
water Mollusca, says, with much naivete, of the L. inter-
media, "aussi reconnaissable que puisse Tetre une espece
dont le caractere principal est de n^en point avoir.^^ The
difficulty of admitting or rejecting such forms as specific
is quite as great as in the case of Anodonta. I have
merely noticed some of the more peculiar varieties of the
present species.

L. peregra is not very slow in its movements. It is
nearly amphibious ; and, as its name imports, it is fond
of wandering and seeing a little of the world, being
occasionally met with at some distance from its native
element in a damp meadow or climbing up the trunk of
a willow-tree. This habit reminds one of the inland
travels of the Perca scandens. An interesting account
of the floating voyages made by our moUuscan traveller
on an old canal near Inchbroom will be found in the
Rev. Dr. Gordon^s Contributions to the ^ Zoologist.' He
says that when the shoal of L. peregra had fairly started,
they resembled a fleet of herring-boats in miniature.
This moUusk is very proliflc and lays about 1300 e^g^
in a season, contained in clusters of from 12 to 180. It
is zoophagous, as well as phytophagous ; and a writer in
the ^ Zoologist^ lately stated (p. 7400) that it ate min-
nows when they were confined together in an aquarium.

108 LIMNiEIDiE.

I have seen these pond-snails attack and devour their
own brothers and sisters under the same circumstances,
when they had no other supply of food ; and this was
done by piercing the spire of the shell near its point,
which was thinner and somewhat eroded bv the action
of the water. Their shells are often coated with mud.

It is probable that Linne considered this species to be
a variety of his Helix auricularia. What his H. limosa
was, it is now impossible to say with any certainty. His
epithet ^^ oblongiuscula " for that species appears to be
more appropriate to L. palustris ; while the term "ovata "
which he uses for " auricularia ^' is applicable both to
this last species and L. jjeregra. In the first edition of
the ' Fauna Suecica/ H. limosa is described as having an
operculum like Paludina or Bythinia ; but in the second
edition this character is omitted. Nearly a centmy be-
fore Linnets time the present species had been distin-
guished by Lister, although not by any specific name.
At least 30 species have been made by Continental au-
thors out of some of its countless varieties.

4. L. auricula'ria *, Linne.

Helix miricularia, Linn. Syst. Nat, ed. xii. p. 1249. Limnaus uuricula-
rius, F. & H. iv. p. 169, pi. cxxxiii. f. 1.

Body dull greenish-brown or yellow, mottled with black,
and covered with veiy small bright-yellow or mill{:-white, and
black specks : tentacles broad, flat and conic, diverging as in
the last species : eyes small and indistinct : foot bordered with
yellow, prominent and obtusely rounded in front, keeled and
rounded behind.

Shell obliquely globose-oval, thin, glossy, semitransparent,
yellowish-horncolour, deeply but irregularly striate by the
lines of growth, with very much finer and closer intermediate
striae, which are arranged in rows, and regularly but indi-
stinctly ridged in a sphal direction : epidermis thin : ivhorls

* Ear-shaped.

LIMN^A. 109

4-5, veiy much -swollen and expanded in front, the last occu-
pying at least five-sixths of the shell : spire oblique, exceed-
ingly small, but produced and ending in a sharp point : suture
very deep : mouth extremely large, roundish oval, a little con-
tracted and nearly tnmcate on the inner side both by the
penultimate whorl and the columellar fold : outer lip thin, con-
siderably reflected : inner lip slightly thickened on the colu-
mella and forming behind it a slight umbilical cleft : fold
prominent, strongly curved and sharp. L. V12d. B. 0-825.

Yar. 1. acuta. Body of a greyish colour and closely covered
with black spots. Shell smaller than the typical form, more
oblong, and having the last whorl and mouth proportionably
narrower. Limneus acutus, Jeffi'. in Linn. Tr. xvi. p. 373. Lim-
noius auricularius, var., F. & H. iv. p. 171, pi. cxxiii. f. 2.

Yar. 2. albida. SheU smaller and thinner, white, with a
shorter spire and less distinct striae. L. 0'675. B. 0*55.

Habitat : Lakes^ marshes, slow rivers, canals,, deep
ditches and large ponds in most parts of Great Britain ;
but it is locals and does not satisfactorily appear to have
been found in Scotland. Y'ar. 1. Marshes on the sea-
coast of Glamorganshire ; Church Stretton, Salop ; Kent;
Co. Tyrone (J. G. J.) : Yoxford, Suffolk (Barlee). This
variety is intermediate between L. peregra and the pre-
sent species ; but being found only with the former spe-
cies, I am inclined to think it belongs to L. auricularia,
A monstrosity of this form in my collection has a second
or inner mouth formed by a plate on the columellar
side. Var. 2. Bath (Clark) ; Blenheim lake (Mrs. Richard
Smith). The variety acuta is one of our upper tertiary
fossils. This species ranges from Siberia to Portugal.

Its habits are inactive ; and when it crawls, only the
front edge of its mantle and the tentacles are perceptible.
It occasionally may be seen floating on the surface of
the water. It is apt to be infested, as well as its con-
geners, by an annelid allied to the Nai's vermicularis of
Miiller, which usually takes up its abode between the

110 LIMN^ID^.

neck and mantle and over the tentacles of the moUusk,
incessantly vibrating, and apparently not parasitic but
feeding on animalcules. Possibly, however, these worms
may have the same truly parasitic propensities which are
attributed to the Nereid, that often takes up its abode
with the Hermit-crab in the same empty shell, and of
which my friend Mr. S pence Bate has given in the ' Zoo-
logist' (1859, p. 6687) an amusing account, as follows :
— " The soft and serpent-like Annelide smells the repast
that the master of the house is enjoying, and, like a wily
guest, takes care to be present at the meal, even though
unbidden. See ! beneath the Crab the beautiful head
glides out. While the self-confident owner is devouring
one piece, and in his full enjoyment looking round and,
perhaps, admiring the submarine scenery, the worm at-
tacks that which is in the other hand, and by little and
little the Crab feels it going, and makes an effort to stop
it on the way ; but it evidently can be seen, by his man-
ner, that he cannot believe that any one would be so
rude as to steal his dinner out of his very mouth, and
does not think much about the undevoured food, but
which, nevertheless, is slowly, gradually and surely taken
away."

Draparnaud noticed, besides the parasitic worms, four
long and very minute filaments or tubes, which he
thought were auxiliary organs of respiration; but sub-
sequent naturalists have not confirmed this discovery.
Muller states that he kept a specimen of L. auricularia
alive from June to October in the clearest water, which
was never renewed, and that it appeared to have no
other nourishment than Cryptogamia or Confervoid
spores.

This species chiefly difi'ers from some of the varieties
of the last, with which it is connected by the form acuta,

LIMNiEA. Ill

in the shell being much more swollen, and having the
last whorl and mouth excessively large in proportion
and the spire consequently smaller. The rows of very
minute longitudinal striae may also be regarded as an-
other test of distinction. Young shells are more slender
than those of L. peregra. The present species was first
described by Lister.

5. L. stagna'lis*, Linne.

Helix stagnalis, Linn. Syst. Nat. ed. xii. p. 1249. LimncBUS stagnalis,
F. & H. iv. p. 174, pi. cxxiv. f. 4, 5.

Body fawn-colour or yellowish- grey with a reddish tint,
covered with very small brown and milk-white specks : ten-
tacles rather long and pointed : foot having a narrow edge of
yellow, very broad at its sides, swollen and keeled behind.

Shell elongated, of a moderate thickness, semitransparent,
yellowish-horncolour or greyish-white with sometimes a
sHght tinge of red, irregularly striate by the lines of growth,
with extremely fine and close-set interstitial striae, which are
curved and arranged in rows, and regularly but indistinctly
ridged in a spiral direction, so as to form, by intersecting the
longitudinal striae, quadrangular facets, resembling those of
cut glass : epidermis thin : luhorls 7-8, rather convex and
bulging out in the middle, the last occupying nearly three-
fourths of the shell : spire oblique, much produced and taper-
ing to a fine point : suture moderately deep, margined above
by a narrow white line, which is formed by the upper edge of
the preceding whorl : mouth oval, interrupted on its inner side
by the periphery of the penultimate whorl and the columellar
fold : outer lip rather thin and slightly reflected : imier lip
spread on the columella and thickened in adult specimens :
fold prominent and very strongly curved. L. 2. B. 1.

Var. 1. fragilis. Shell smaller, more slender and tapering.
Helix fragilis, Linn. Fn. Suec. 2187 ; Mont. Test. Brit. p. 369,
tab. 16. f. 7.

Yar. 2. cdhida. Shell of the last-mentioned form, but of a
white colour.

* Inhabiting ponds.

112 LIMNiEID^.

Var. 3. lahiata. Shell dwarfed and more solid, with the
outer lip much reflected and thickened. L. 0*9. B. 0*55.

Var. 4. sinistrorsa. Spire reversed.

Habitat : Slow rivers, marshes, and standing water
throughout the kingdom; but it is more local than L.
peregra. Var. 1. Kennet and Avon Junction Canal,
Wilts (Montagu) ; Surrey and Croydon Canal (Leach) ;
R. Cam at Cambridge (Granger) ; Grand Canal, Dublin
(Warren). This variety is the Stagnicola elegans of
Leach. Var. 2. From the last-mentioned locality. Var. 3.
Lough Neagh, Ireland (Moggridge). Var. 4. Kenn Moor,
Somerset (Norman). This species is one of our upper
tertiary fossils. It ranges from Siberia to Naples.

This mollusk is sluggish, but fond of floating. Before
descending to the bottom it withdraws its body into the
shell, and in so doing disengages the air from its pouch,
which escapes with a perceptible noise. The shell is
remarkably handsome ; but it is often disfigured by a
coating of vegetable or calcareous matter. The outer
lip sometimes becomes thickened in consequence of a
temporary cessation of growth ; and in such cases vari-
cose marks are observable on the spire at intervals.
Young shells are extremely slender, and the mouth is
not expanded as in adult specimens. In this state they
somewhat resemble L. glabra in form, and might be
mistaken for a new species. Miiller tried the experi-
ment of cutting oflP the heads of some of this kind of
mollusk to see if they would be reproduced ; but he tells
us that the poor animals did not long sur^dve the opera-
tion. Menke supposed that the shell of this species was
the helmet of the Frogs in Homer^s ^ Batrachomyo-
machia^; but, in opposition to this ingenious idea, it may
be remarked that the L, stagnalis does not appear to

LIMN^A. 113

have ever existed in Greece. From the description of
the armour of the Frogs, it does not appear that any
species in particular was intended : —

" Form'd of the varied shells the waters yield,
Their glossy helmets glisten'd o'er the field."

It is not likely that Homer was a conchologist, or distin-
guished one shell from another for poetical purposes.
The kind of shell in question must have made cumber-
some helmets for the valiant Frogs.

L. stagnalis is a large and favourite object for the
aquarium ; and Mr. Lloyd has recorded in the ^ Zoologist^
some interesting observations as to the mode of its
respiration.

The shell is so much larger and longer than that of
any other LimncBa, that it is unnecessary to make any
further comparison between them.

C. Spire of the shell much produced, and whorls gradually

enlarging.

6. L. palus'tris*, Miiller.

Buccinu7n palustre, Mllll. Yerm. Hist. pt. ii. p. 131. Limnceus palustris,
F. & H iv. p. 180, pi. exxiv. f. 2.

Body dark grey, with a tinge of violet-brown, covered with
fine black and yellowish-white specks : tentacles conic, curved
and pointed : eyes placed on small tubercles : foot oblong,
truncate and slightly notched in front, narrowing behind and
ending in a blunt tail.

Shell oblong, rather solid, of a somewhat duU hue, yellowish-
brown with sometimes a violet tint, sculptured as in L. stag-
nalis, but the spiral ridges are generally more prominent and
numerous : e/pidermis rather thin : wliorJs 6-7, rounded and
moderately convex, the last occupying about two-thirds of the
shell : spire produced and tapering to a somewhat fine point :
siitwre rather deep, often margined above by a narrow white

* Inhabiting bogs.

114 LIMN.EID^.

line, which is caused by the appearance through the shell of
the upper edge of the preceding whorl : mouth obliquely oval,
but contracted on the inner or columellar side : outer lip rather
thick, scarcely reflected, but expanded below : inner lip spread
on the columella : fold extremely prominent and sharp. L. 1.
B. 0-4.

Yar. 1. Corvus. Shell much larger and more swollen, of a
purplish -brown colour. L. 1-35. B. 0-65. HeliM Corvus,
Gmel. Syst. Nat. p. 3665.

Var. 2. elongata. Spire elongated.

Var. 3. tincta. Shell shorter and broader, Hght brown
with a purplish mouth. Limneus tinctus, JefFr. in Linn. Tr.
xvi. p. 378.

Yar. 4. conica. Shell conic, greyish -white, with a deep
suture and an umbihcal cleft. L. Q-o. B. 0*25.

Yar. 5. rosea -lahia'ta. Mouth of the shell furnished inside
with a rose-coloured or white rib.

Yar. 6. decoUata. Spire truncate.

Habitat : Marshes, ditches, and shallow pools every-
where from Aberdeenshire to the Channel Isles. Var. 1.
Suffolk (Barlee). Var. 3. Falmouth (J. G. J.). Var. 3.
Swansea and Dorsetshire (J. G. J.) ; Anglesea (Gibbs).
This last variety resembles a Bulimus in form. Var. 4.
Banks of the Thames from Hammersmith to Woolwich
(J. G. J.) ; Cork (Humphreys) . This is a peculiar variety;
but as it is connected with the typical form by the variety
tincta, and it is not found in company with any other
form, I do not consider it to be specifically distinct. Some
specimens have a longer spire and resemble L. truncatula.
Var. 5. Belfast (Thompson); Cork (Humphreys). Var.6.
Preston (Gilbertson) ; Guernsey (Lukis) ; Ballinahinch,
Co. Gal way (J. G. J.). This species is also one of our
upper tertiary fossils. Abroad it ranges from Siberia to
Algeria and Sicily.

It has the character of being a slow, irritable, and very

LIMN^A. 115

greedy animal — none of which are amiable qualities in
our own species ! Owing to the nature of its habitat^
the shell is apt to have a coat of hardened mud. The
whorls are sometimes more or less distorted or scalari-
form. Draparnaud says that the animal has only two
aeriferous tubes, instead of four as in L. auricularia ; but
this remarkable and anomalous organization does not
appear to have been observed by other naturalists.

This species differs from all the preceding in the shell
being thicker and the whorls much more narrow. It
was first (and well) described by Lister.

Mr. Bean was kind enough to give me specimens of
L. cornea (a native of the North- American lakes) which
his son was said to have collected in the West of Ireland.
It is allied to the present species, through the variety
tincta ; but I suspect there must have been some mistake
as to the alleged Irish locality.

7. L. trunca'tula*, Miiller.

Buccinum truncatulum, Miill. Verm. Hist. pt. ii. p. 130. Limnmis trun-
catulus, F. & H. iv. p. 177, pi. cxxiv. £ 3.

Body dark brown or grey, of a lighter colour on the lower
side, covered with fine black specks : tentacles short, but slender,
rounded at their tips : eyes nearly sessile : foot rather short,
marked with milk-white spots, which are scattered and larger
than the black specks, nearly truncate in front, gradually
narrowing and abruptly rounded behind.

Shell oblong-conic, turreted, rather solid for its si^e,
glossy, yellowish-brown or horncolour ; sculpture the same as
in the two last species : epidermis thin : whorls 5-6, rounded
and convex, but compressed in the middle, so as to make the
top of each appear somewhat truncate ; the last whorl occu-
pying about three-fifths of the shell : spire abruptly tapering
to a rather fine point : suture extremely deep : mouth oval,
scarcely contracted on the inner side : outer lip sharp : inner
lip continuous with it and reflected on the columella, behind

* Slightly truncate.

116 LIMN^IDyE.

which is a distinct umbilical chink : fold rather slight but
thick. L. 0-4. B. 0-2.

Var. 1. major. Shell larger : whorls more swollen and the
last considerably exceeding the usual proportion of size.

Yar. 2. elegans. Shell much larger, more solid and slender,
greyish-white, marked with coarse spiral ridges : S2)lre much
produced : suture oblique : outer lip thickened. L. 0-6. B.
0-225.

Var. 3. minor. Shell much smaller, thinner and semi-
transparent, dark horncolour, marked with stronger and closer
longitudinal striae. L. 0-285. B. 0-165.

Var. 4. alhida. Shell smaller, milk-white.

Var. 5. scalariformis. Shell smaller : whorls nearly dis-
united.

Var. 6. microstoma^ Shell smaller and narrower : ivhork
more swollen : mouth contracted.

Habitat : Banks of slow and muddy rivers and
streams, marshes, ditches, grassy pools, waterfalls, and
moist places everywhere from the northernmost point of
Zetland to Jersey. Var. 1 . Penzance (Millet and Barlee) ;
Newton Nottage, Glamorganshire (J. G. J.). Var. 2.
Hants (Mus. Loscombe). Var. 3. Momitainous tracts
and sea-side marshes. Var. 4. Battersea (J. G. J.) :
Crymlin Burrows, Swansea, (Moggridge). Var. 5. War-
minster (J. G. J.). Var. 6. Southampton (J. G. J..
Besides these varieties, my cabinet contains specimens
in which the spire is more produced, or shorter with
the whorls partly intorted, and some have interrupted
spiral bands of white lines. This species occurs in our
upper tertiary beds. Its foreign distribution extends
from Siberia to Algeria and Sicily; and, according to
Captain Hutton, it is a native of Afghanistan.

This abundant but pretty little mollusk is nearly
amphibious, being more frequently met with out of the
water than in it. It is also found in very elevated spots.

LIMNJLA. 117

Moquin-Tandon states that lie had observed it in the
Pyrenees at a height of 1200 metres (nearly 4000 feet) ;
and instances of its occurring at a tolerable elevation in
this country might doubtless be also given, as I have
found it living at the sides of all our mountain tarns,
but no other animal in company with it. It deposits its
spawn on the mud, which is its usual habitat, and not,
like its congeners, on the stalks and underneath the leaves
of water-plants.

The form of its shell somewhat resembles that of L.
peregra, var. maritima ; but its minute size and turricu-
lated spire will serve to distinguish the present from
any other species. This is the Limneus minutus of Dra-
parnaud and Helix fossaria of Montagu. The name it
now bears seems to have been derived, not from the
truncature or decollation of the spire, but from the
truncate or turreted form of the whorls.

8. L. gla'bra^, Miiller.

Buccinum glahrum, Miill. Yerm. Hist. pt. ii. p. 135. Limnaus glaher,
F. & H. iv. p. 178, pi. cxxiv. f. 1.

Body dusky-grey with a tinge of slate-colour, covered with
minute, but distinct, black specks : tentacles rather long : eyes
placed on prominent tubercles : foot truncate in front, from
which it spreads a little towards the rear, ending in a thick
and narrow tail.

Shell cyHndrical, rather thin and glossy, greyish-horn-
colour or brownish, sculptured as in the three preceding species :
epidermis very thin : whorls 7-8, rounded but not very convex,
the last occupying not much more than half the shell : spire
produced and ending in a somewhat blunt point : suture slight,
but distinct, margined as in the two foregoing species : mouth
pear-shaped, contracted above at an acute angle, and furnished
inside with a thick broad white rib, which is placed at a httle
distance from the opening : outer lij) thin, scarcely reflected :

* Smooth.

118 LIMN^ID^.

inner Up rather thick : fold somewhat prominent and sharp.
L. 0-6. B. 0-2.

Yar. elongata. Spire more produced, so as to alter the
relative proportions of length and breadth.

Habitat : Ditches and shallow pools, but sparingly-
distributed in this country. It appears, however, to have
been found in the following counties and places, — viz.
Northumberland, Durham, York, Salop, Norfolk, Suffolk,
Essex, Oxon, Wilts, Dorset, Cornwall, Guernsey, Jersey,
Cork and Belfast. Although local, it is plentiful where
it occurs. It ranges from Scandinavia to France as far
south as the lower Pyrenees,

It is an exceedingly sluggish and timid mollusk, but
ventures occasionally on a very short floating excursion.
It often retires considerably within its shell, when it
forms the inside lip or rib. The repetition at intervals of
this lip, which is seen through the semitransparent shell,
gives the latter a varicose appearance. The shell is also
liable to lose its first or apical whorls, and consequently
to become decollated.

This species is the Bulimus leucostoma of Poiret, Helix
octanfracta of Montagu, and lAmneus elongatus of Dra-
parnaud.

Genus IV. AN'CYLUS*, Geoffroy.
PL IV. f. 11, 12, 13, 14.

Body oval, conic, slightly twisted behind ; head very large :

tentacles short, nearly cylindrical but thicker at their base :

foot oval, or oblong, obtusely rounded in front and behind,

closely attached to the upper part of the body : respiratory

pouch or sac forming a short tube.

Shell hood-shaped, with an incomplete or rudimentary spire,
which is in some species dextral and in others sinistral.

* Hooked.

ANCYLUS. 119

This is in some respects an anomalous genus^ although
undoubtedly related to Limncea, Menke and other con-
chologists have proposed to separate it from the LimnceidiB
and to make it a distinct family by itself. The resem-
blance of its shell to the marine Limpet, or Patella^ has
caused this to receive the not inappropriate name of the
" freshwater Limpet," — showing that the sea and land
have their respective representatives or analogues in the
system of Nature. It was for a long time supposed,
even by the great Cuvier, that the Ancyli were branchi-
ferous ; but it has now been satisfactorily ascertained,
by the careful investigations of Mr. Berkeley and other
able physiologists, that they are truly pulmoniferous,
although they are also capable (like other aquatic Pul-
monobranchs) of extracting air from the water for the
purpose of respiration. They inhabit both rapid and still
waters, attached to stones and the leaves of plants. They
are not inactive in their habits, but have never been
observed in a floating position. One of our native species
(A. fluviatilis) is nearly as amphibious as the Limncea
peregra and L. truncatula ; and it may often be seen on
rocks at the side of waterfalls, having no other moisture
than the spray which occasionally falls on it. When it
crawls, only the tips of its tentacles, and sometimes the
front edge of its mantle, are visible. The only two
British species of Ancylus are apt to be infested with a
number of quasi-parasitic worms, as is also the case with
many kinds of Limncea. The food of the Ancyli consists
of freshwater Alga3 or Confervse, as well as of decayed
vegetable matter. They are said also to eat or swallow
a certain quantity of very fine gravel or sand, apparently
to assist their digestion, which is very slow. They can
live a long time without any nourishment.

120 LIMNiEID.^.

A. Body sinistral. Shell dextral.

1. Ancylus fluvia'tilis*, Miiller.

Ancylus fluviatilis, Miill. Verm. Hist. pt. ii. p. 201 ; F. & H. iv. p. 18G,
pi. cxxii. f. 4.

Body slate-colour or dark grey, with fine black specks :
tentacles somewhat triangular at the base, becoming slender
towards their tips, which are blunt : eijes not very prominent,
but distinct : foot oval, nearly equal in circumference to the
mouth of the shell.

Shell semi-oval, incurved towards the front like a helmet
of the ancients, rather thin, not glossy, yellowish -grey or horn-
colour, strongly and regularly striate longitudinally in a radi-
ating direction from the crown to the margin or outer edge of
the mouth (some of the striae often forming remote ridges) and
very finely striate transversely or in the line of growth : anterior
margin somewhat narrower than the other : epidermis rather
thin : spire forming the beak and being equal to about half a
whorl, with a compressed and blunt top, which turns a little
to the right, bending down towards and nearly reaching the
posterior margin : mouth oval : outer lip membranous, slightly
reflected. L. 0-3. B. 0-233.

Yar. 1. Capuloides. Shell larger and higher, with the beak
not placed so near the posterior margin. L. 0*415. B. 0*3.
A. Capuloides, (Jan) Porro, Mai. Com. p. 87, pi. 1. f. 7.

Yar. 2. gihhosa. Shell smaller, more swoUen, with the
beak reaching or overhanging the posterior margin. A. gih-
bosus, Bourguignat in Journ. de Conch, iii. (1853) p. 186.

Yar. 3. alhida. Shell milk-white and more finely striated.

Habitat : Abundantly on stones and rocks in shallow
rivers and streams everywhere from Aberdeenshire to
the Channel Isles. I once found it of a dwarf size on
the leaves of the white water-lily in a stagnant pond
near Swansea, into which no stream had flowed within
the memory of man, living in company with A. lacustris,
and coated with a confervoid growth. Yar. 1. R. Corfe,

^ Inhabiting rivers.

ANCYLUS. 121

Dorset : very rare (J. G. J.). Var. 2. Sark ; Osmington
mills^ near Ringstead^ Dorset ; Dunboy, near Bearhaven,
Co. Cork (J. G. J.). This last variety is the A. deper-
ditus of Ziegler and Dupuy ; but (according to Bour-
guignat) not of Desmarest, who first used that name
for another species. Intermediate forms in respect of
the position of the beak incline me to consider this only
a variety. Var. 3. Wokey hole^ near Wells (Beevor) ;
Scarborough (Bean) ; near Torquay (Norman) ; Arish
mill^ near Lul worthy Dorset (J. G. J.). Specimens
from different places vary in colour from white to dark-
horncolour or reddish-brown. This species is also one
of our upper tertiary fossils. Abroad it ranges from
Finland to Algeria and Sicily ; and the Rev. R. T. Lowe
has incladed it in his list of Madeiran land-shells.

M. Bouchard- Chantereaux published, nearly thirty
years ago, an extremely interesting account of the em-
bryogeny of A. fluviatilis, illustrated by a plate showing
the successive development of the spawn into the fry.
He says, each individual lays, in the course of the breed-
ing-season, about 80 eggs, which are enclosed in from
7 to 10 capsules and arrive at maturity in from twenty-
four to twenty-seven days, according to the temperature.
The animal seems to be more fond of Fontinalis antipy-
retica than of any other plant.

Many species have been carved out of this variable
kind by Continental authors. In very young shells may
be detected faint traces of a more complete spire, which
is intorted so as to cause a concavity in the beak, called
by M. Bourguignat the " depression apicale.^^ This
species was first made known by Lister, and described
by him under the name of Patella fluviatilis, but ac-
companied by other epithets. It has by some authors
been considered to be the Patella lacustris of Linne ;

G

122 LIMN^ID/E.

but I will defer my remarks as to this name until I have
to treat of the next species.

E. Body dextral. Shell sinistral.
2. A. lacus'tris *_, Linne.

Patella lacustris, Linn. Syst. Nat. ed. x. i. p. 783. A. ohlovgus, F. & H. iv.
p. 188, pi. cxxii. f, 5.

Body yellowish-grey with a greenish tinge, covered with
minute and indistinct dark specks : tentacles thick, pointed at
the tips : eyes as in the last species : foot truncate in front and
very round behind, having a few yellow specks interspersed
among the black ones.

Shell oblong, obUquely twisted to the left, thin, glossy
greyish -horncolour, very finely but indistinctly striate as in
A. fiuviatilis, but without the intermediate ridges : anterior
margin very little narrower than the other : e/pidermis thick :
heak sharp and ridge-like, turning obliquely to the left, but
placed close to the margin : month oblong : outer lip membra-
nous, reflected. L. 0-25. B. 0-1.

Yar. ].. compressa. Shell rather larger, and considerably
broader and flatter, than usual.

Yar. 2. alhida. Shell milk-white, with a light-grey epi-
dermis.

Habitat : On the under side of the leaves of water-lilies
and other aquatic plants^ as well as on fallen leaves of
trees_, in slow rivers^ lakes, canals, marshes, and ponds
throughout the greater part of the kingdom as far north
as Aberdeenshire. It is, however, a local species.
Y^ar. 1. Dunstall, StaflTordshire (J. G. J.). Y^ar. 2.
Grand Canal, Dublin (Y^arren). It is also one of our
upper tertiary fossils. Its foreign distribution is the
same as that of the last species.

Miiller states that this is not only a freshwater but a
marine shell, having taken it alive and adhering to marine

* Inhabiting lakes.

ANCYLUS. 123

species of Conferva, in the Baltic Sea. According to
Mr. WhiteaveSj it hibernates between the sheathing
leaves of Sparganium ramosum.

This species is easily recognizable from A. fluviatilu-
by its different habitat and the oblong shape of its shell,
as well as by the form of the beak, which is twisted
decidedly to the left, instead of being (as in the other
species) nearly central or inclined to the right.

It has been called by some authors A. oblongus, being
the specific name given to it by Lightfoot under the im-
pression that this was not the Patella lacustris of Linne.
There can, however, be scarcely any doubt that Linne
meant this species, and not A. fluviatilis, because in his
^ Fauna Suecica ' he mentions its being rather common
in lakes and attached to the submerged leaves of aquatic
plants, especially of Stratiotes. His description of the
shell is applicable to either species.

Nearly half a century ago, a curious instance of false
analogy occurred with respect to an organism which
Draparnaud described and figured (in his admirable
History of the Land and Freshwater MoUusca of France)
as " Ancylus spina-rosce'^ from specimens sent him by
Ferussac. These specimens were afterwards discovered
not to be testaceous; and many conjectures were from
time to time made as to their nature. It was supposed
by some that they were parts of a small pod or capsule,
by others that they were the bracts of a flower-stalk, and
by not a few naturalists that they were scales of a fish.
The puzzle, however, was at last solved by the discovery
that these nondescripts were the valves of a Cyjjris, and
therefore belonged to the Crustacea.

TERRESTRIAL.

The Slugs and Land-Snails^ which (as I before observed)
constitute about three-fourths of the British Pulmono-
branch Mollusca^ may be conveniently divided into two
sections. The first section agrees in all essential particu-
lars^ except that of having retractile (instead of contrac-
tile) tentacles^ with the aquatic family of Limnmd^E, which
have been above described. The second corresponds with
the Pectinibranch Mollusca in having separate sexes,
their eyes at the base of the tentacles, and univalve spiral
shells which are furnished with opercula ; and the main
point in which it differs from that great Order consists
in the organs of respiration, resulting from the nature
of their respective habitats. All the land Pulmono-
branchs are more slimy than their aquatic representa-
tives ; and they appear to be less inactive in their habits.

The first section comprises four families, viz., —

* Tentacles, almost in every case, 4 : eyes placed on the tips of
the upper, or single, pair : shell rudimentary, shield-like,
or complete and spiral.

I. LlMACID^.

II, Testacellid^.
III. Helicid^.

** Tentacles 2, besides rudiments of a second or lower pair : eyes
placed at the internal base of the developed pair : shell
spiral, elongated.

lY. Carychud.'e.

LIMACID.^. 125

Family I. LIMACID.E.

Body long, straight, and flexible : mantle covering only the
upper part of the back, and forming a shield : head prominent :
tentacles 4, cylindrical, arranged in pairs, the upper pair being
the longest : eyes 2, placed on bulbs at the tojD of the upper
tentacles : foot united to the body and coextensive with it.

Shell either rudimentary and of an indefinite form, or
shield- shaped, placed underneath the mantle.

I do not propose to treat of this family aud its com-
ponent members to the same extent as my opportmiities
have enabled me to do with respect to the testaceous
members of the same Order ; and I must admit that I
have not paid equal attention to this part of the subject.
The aspect^ and much less the handling, of these slimy
creatures cannot be considered as especially inviting ;
and as I believe the majority of my readers share in this
opinion, I may with greater confidence ask their indul-
gence for any shortcomings on this point. At the same
time I would observe that the subject offers, to those
who are inclined to pursue it, a wide field of research
and a greater prospect of novelty than can be expected
from the study of the testaceous Mollusca. The ana-
tomy, physiology, and habits of the Slugs were described
nearly two centuries ago by our countryman, Dr. Lister,
in his admirable treatises on British animals ; and Mr.
Nunneley and the Rev. B. J. Clarke have lately done
much to increase our knowledge of these mollusks. Some
of their remains have been detected in our upper ter-
tiary beds at Copford, as well as in similar deposits in
the South-west of France.

126 LIMACID^.

Genus I. ARI'ON *, Ferussac. PI. V. f. 1, 2.

Body nearly cylindrical, with a strongly wrinkled skin :
sJmld oblong, shagreened: respiratory orijice placed near the
front edge of the shield : foot furnished at its posterior extre-
mity or tail with a mucus- or sKme-gland.

Shell amorphous, consisting of loose calcareous grains
which are covered by the hinder part of the shield.

The Arions, or black slugs, frequent damp and shady
woods, as well as hedge-banks and gardens. During
the daytime they lurk under stones and logs of wood,
or bury themselves in the earth, where they excavate a
sort of tunnel ; but at night, and after rain, they sally
forth to feed. They are great pests in gardens, gene-
rally selecting the best cabbages and most succulent
vegetables. They are, however, not very particular
about their food, and act the part of land-scavengers,
devouring animal matter of all kinds in every state of
decomposition, and even each other^s slime. They may
be frequently met with in garden-walks, after a shower,
in search of food. During the season of reproduction
they deposit their eggs, which are very numerous, sepa-
rately underground. When at rest, they contract their
bodies into a lump. In this state they offer a dainty
prize to ducks. They differ from the Limaces, or com-
mon slugs, in their respiratory orifice being placed in
front, instead of near the hinder part, of the shield, in
having a slime-gland at the tail, and in the arrangement
of the teeth.

* The name of an ancient musician and poet : scarcely appropriate to
this genus.

ARION. 127

1. Arion a'ter*_, Linne.

Limax afer, Linn. Syst. Nat. ed. x. p. 652. A. Em])iricorum, F. & H. iv.
p. 7, pi. D. D. D. f. 4.

Body rather contracted and rounded in front, pointed behind,
varying greatly in colour, from black to brown, red, yellow,
greenish, and even white, with all the intermediate shades,
covered with prominent and large tubercles : shield, or mantle,
finely shagreened, of a lighter colour than the rest of the
body: tentacles coarsely shagreened, much swollen at their
tips, especially the lower pair : foot generally having a yellow
border, which is crossed at the sides by close and curved dark
lines: slime of a yellowish colour. L. 4. B. 0-5.

Shell consisting of small separate calcareous grains of
unequal size.

Habitat : Woods, hedges, fields, and all sorts of damp
places in the country tliroughout these Isles. Abroad
it ranges from Siberia to Portugal and Corsica, as well
as to Madeira ; and a variety of it was found as far north
as Jan Mayens Isle by the naturalist who accompanied
Prince Louis Napoleon^ s expedition.

This species has had an infinity of names given to it,
on account of its extreme variability of colour. It is
the A. Empiricorum of Ferussac, so called from the cal-
careous substance which is found under the shield having
been formerly used in the preparation of medicine.

The A.flavus of Ferussac {Limax flavus, Miiller), which
has been found in the North of England by Mr. Alder
and Mr. Blacklock, as well as by Mr. Norman and Mr.
Whiteaves in Somersetshire and Oxfordshire, appears,
according to Moquin-Tandon, to be a doubtful species.
MM. Bouchard-Chantereaux and Normand state that
this last-mentioned species or variety inhabits woods and
moist places in the North of France.

* Black.

128 LIMACID/E.

2. A. horten'sis"^^ Ferussac.

A. hortensis, Fer. Hist. Moll. p. 65, pi. ii. f. 4-6 ; F. & H. iv. p. 10,
pi. E.F.F. f. 1.

Body longer than that of the last species in proportion to
its size, and of nearly an equal breadth throughout, brown,
red, yellow, grey, greenish, or black, usually more or less di-
stinctly marked on the back and sides with stripes or longitu-
dinal bands, and covered with coarse oblong tubercles : shield
having usually a dark stripe down the middle and another on
each side : tentacles not much swollen at their tips • foot nar-
I'owly bordered with grey, yellow, reddish, or orange : slkne
yellowish or whitish. L. 1-5. B. 0-35.

Shell of an ii-regular shape, composed of grains like those
in the last species, but cemented together by a calcareous
matrix, so as to resemble tiny lumps of the conglomerate
which is called by geologists " breccia."

Habitat : Under stones and dead leaves in gardens,
fields, and damp spots everywhere. Its foreign distri-
bution is also perhaps equally extensive with that of
A. ater.

According to Bouchard-Chantereaux, the eggs of A.
hortensis are phosphorescent during the first fifteen days
after they have been laid. They take from twenty to
forty days to arrive at maturity, and the young become
adult towards the end of the first year.

This species differs from A. ater in being much smaller
and more slender, as well as in usually having longitu-
dinal lines or stripes. The substitute for a shell is also
more compact, and making some approach to a definite
form, in the present species. Dr. Gray describes the
shell to be '^ distinct, oval, concave ;" but tliis description
does not agree with the generic character of this part of
the animal.

It is the A. fasciatus of Nilsson. Miiller described

* Frequenting gardens.

GEOMALACtJS. 129

two slugs [Limaoo cinctus and L.fuscus) as having longi-
tudinal stripes; and although it is most probable that
one or both of them may be identical with the present
species^ the name given by Ferussac has been adopted
to prevent confusion.

Genus II. GEOMA'LACUS f- PL V. f. 3.

Body resembhng that of Arion, but more extensile and
keeled on the back, besides having the reproductive oriliee
placed near the base of the right lower tentacle, in which
respect it differs both from that genus and Lhnax.

Shell unguiform, imbedded in the shield.

This genus, of which only one species is known, appears
to be intermediate between Arion and Lhnax. I suspect
that the Lhnax anguiformis of Morelet (Moll. Port. p. 3G,
pi. iii. f. 1) also belongs to the present genus, if indeed
it is not the same species as ours.

Geomalacus maculo'sus J, AUman.

G. nmculosus, Allm. in Ann. N. H., new series, xvii. p. 297, pi. 9 ; F. & H.
iv. p. 12, pi. F. F. F*. f. 5.

No detailed account of this curious slug has been
published ; but it is described to be an exceedingly beau-
tiful animal, measuring, when creeping about, two inches
in length ; the colour of the shield and upper part of the
body is black, elegantly spotted with yellow ; the under
surface of the foot light yellow, and divided into three
nearly equal bands; the edge of the foot brown, with
transverse sulci. A white-spotted variety also occurred.
It can elongate itself, so as to assume the appearance of
a worm and thus enter exceedingly small apertures. It
was discovered by an active and indefatigable Irish
naturalist, Mr. William iVndrews of Dublin, during the

t Earth-mollusk. | Spotted.

G 5

130 LIMACIDvE.

autumn of 1842^ ^^on rocks around Lough Carrough,
to the south of Castlemain Bay, Co. Kerry, in the West
of Ireland." Mr. Andrews informs me that it is im-
possible to appreciate the extreme beauty of this slug
without observing it in the living state. The surmise
offered by the authors of the ' British Mollusca/ that
this may be an Asturian, as well as an Irish, slug, is pro-
bably well founded. Morelet^s description, in 1845, of
his Limax anguiformis appears to have escaped their
notice. He especially mentions the peculiar form of
the slug and the position of the respiratory organ.

Genus III. LI'MAX^ Linne. PL V. f. 4, 5.

Body nearly cyhndrical, with a wrinkled skin, and more or
less keeled on the back : sliield sometimes shagreened, but in
most cases concentrically striate : respiratory orifice near the
hinder edge of the shield : reproductive orifice close to and
behind the right upper tentacle : foot not furnished with a
mucus -gland.

Shell oval or shaped hke a finger-nail, formed of concentric
layers, and covered by the hinder part of the shield (Limacella,
Brard).

The habits of this kind of slug are nearly the same as
those of Avion; but some of them appear to like the
company of man more than he desii'cs, being often
found in kitchens and domestic offices. They are, how-
ever, sometimes useful in eating that kind of fungus
which causes dry rot, and another kind which infests
cellars and makes choice Port wine what is termed
^'^ corked." Among themselves they are also sociable,
and are often found clustered together in the same spot.
Gardeners have great cause to complain of their voracity^
and especially when they see the finest strawberries have
been selected for their supper or early repast.

* Slug.

LIMAX. 131

A. Shield shagreened

I

1. LiMAX GAGATES*, Drapamaud.

L. gagates, Drap. Hist. Moll. p. 122, tab. ix. f . 1 ; F. & H. iv. p. 24,
pi. D. D. D. f. 3.

Body very slightly contracted and nearly cylindrical in front,
gradually tapering to a point behind, varying from slate-colour
to dark-red or even black, covered "with small oblong inter-
laced tubercles : shield oblong, somewhat truncate in front
and rounded behind, apparently divided into two lobes, finely
shagreened or grained: tentacles very short and thick, not
much swollen at their tips : hack sharply keeled its whole
length, bordered with white or a lighter colour than the rest
of the body : sUme nearly colourless. L. 2-5. B. 0-85.

Shell oval, rather thick (especially in the middle), and
slightly wrinkled.

Habitat : Hedges and at the roots of grass and the
foot of old walls in many parts of Great Britain from
the Clyde district to Guernsey; but it appears to be a
local species. It also occurs in the north, east, west, and
south of France, ranging to Corsica and Algeria, and
probably also to Naples. Mr. Norman has given an
excellent description of this species in the ^ Zoologist^
for 1853, and remarked that when at rest this slug as-
sumes a more rounded form than any other British
kind, contracting and squeezing itself into so small
a compass that its height is but little exceeded by its
length. Its slime is thick and glutinous, resembling
varnish. The apparent division of the shield into two
lobes, as noticed by Draparnaud, is owing to its being
indented behind by the keel.

* Jet.

132 LIMACID/E.

2. L. MARGiNA Tus *^ Miiller.

L. marginatus, Miill. Verm. Hist. pt. ii. p. 10. L. Sowerbii, P. & H. iv.
p. 22, pi. E. E. E. f. 3.

Body nearly cylindiical, truncate and slightly tumid in front,
gradually tapering to a point behind, yellowish or reddish-
browTi speckled with black, irregularly wrinkled : shield oblong,
obtusely rounded at both ends, wider and slightly truncate
behind, partly bordered with a dark band on each side and
occasionally streaked down the middle, veiy irregularly granu-
lated : tentacles thick, not much swollen at their tips : hack
having a prominent keel or ridge, which extends the whole
length from the hinder edge of the shield to the tail, and is of
a lighter colour than the rest of the body : foot pale-margined :
slime colourless. Dimensions same as in the last species,

SuELL oval, thickened, with conspicuous lines of growth :
boss or nucleus near one end, rather prominent. L. 0-2.
B. 0-125.

Habitat : Under stones, among dead leaves, and at
the foot of old walls everywhere. The shell or Limacella
has been fonnd in our upper tertiary beds. Although
this must be a widely diflused species, it does not appear
to have been noticed by any Continental writers except
Miiller, Moquin-Tandon, and the Abbe Stabile, accord-
ing to whom it inhabits Denmark and the mountainous
districts of France and Lugano.

This slug is inactive in its habits and secretes a thick
and tenacious slime. Stabile says that it is much preyed
upon by the Silphce, Carabi, and other large carnivorous
beetles. L. marginatus is said in its turn to attack and
eat other animals, and especially live worms and smaller
slugs.

Miiller' s description seems to be sufficient for the
identification of this species with that of Draparnaud
and subsequent authors, who have adopted the name first
given to it. He particularly mentions its having a white

* Bordered.

LIMAX. 133

keel, as well as marginal streaks on the shield, — although
he says it inhabits the beech, which character is more
applicable to L. arborum. Draparnaud doubted whether
his species was that of Midler because of this difference
in the habitat. It is the L. Sowerbii of Ferussac and
L. carinatus of Risso and Leach. The shell is the
Limacella unguiculus of Brard.

The shield in this species is much smaller in proportion
to its body than in L. g agates ; and the respiratory orifice
is in the last-named species placed more towards the
middle of the shield-area. The colouring is also dif-
ferent.

B. Shield concentrically wrinkled.

3. L. fla'vus *, Linne.

L.flavus, Linn. Syst. Nat. ed. x. i. p. 652; F. & H. iv. p. 19, pi. E. E. E.
f. 1.

Body slightly contracted in front, rather broad in the middle,
and tapering gradually to a point behind, yellowish, speckled
with white and black so as to form a kind of network, covered
with coarse oval tubercles : head of a bluish colour : shield
oblong, larger and more rounded behind, elegantly grooved by
concentric and rather undulating Hues : tentacles bluish ; the
upper pair rather short, the lower ones remarkably so : foot
keeled towards the tail, margined with yellowish- white ; sole
milk-white : sli7ne yellow. L. 4. B. 0*75.

Shell obliquely oval or quadrangular, rather concave on the
under side, thin, crystalhne and nacreous, with distinct lines
of growth : boss shghtly projecting behind : margin membra-
nous. L. 0-3. B. 0-125.

Habitat : Cellars, wells, sculleries, and other damp
places, as well as in moist woods, everywhere. It is
also common in the northern and central parts of
Europe.

* Yellow.

134 IIMACIDJE.

This kind of slug is nocturnal, but very active. Its
slime is abundant and stains linen of a yellow colour.
It appears to be fond of bread, cooked vegetables, and all
sorts of kitchen refuse.

It is probable that the L. flavus of Miiller may be a
variety of Avion ater, because he describes the shield as
not having any concentric wrinkles, although in the
same description he also notices a yellow slug which
seems to belong to the present species. This is the
L. variegatus of Draparnaud ; and its shell is probably
the Limacella concava of Brard.

4. L. agres'tis *, Linne.

L. agrestis, Linn. Syst. Nat. ed. x. i. p. 652 ; F. & H. iv. p. 13, pi. D. D. D.
f. 3.

Body spindle-shaped, slender, ash-grey with a reddish or
yellowish tinge and sometimes mottled, nearlj^ smooth : shield
rather large, more tumid behind, the concentric striae more
remote and indistinct than in any of the other species : tentacles
dark grey : hack obhquely, but not strongly, keeled towards
the tail: foot having very pale sides: slhne milky. L. 1*5.
B. 0-4.

Shell obliquely oval or inclined to oblong, concave on the
under side, rather thin, with indistinct hues of growth, and
marked obliquely by exceedingly minute striae which cross
each other: boss very small, slightly projecting behind on one
side : margin membranous, rather broad, and obliquely striate.
L. 0-2. B. 0-1.

Habitat : Fields, gardens, and woods throughout the
British Isles. The shell is also one of our upper tertiary
fossils. Its foreign distribution extends from Siberia to
Corsica and Algeria, and (according to Lowe) Madeira.

This slug is a great pest in the kitchen garden, and
does not even spare succulent leaves and roots of flower-
plants. Mr. Whiteaves says that it also feeds on earth-

* Inhabiting fields.

LIMAX.

135

worms. Its slime is abundant and viscous, feeling like
a lump of sticky fat. Miiller states that when it is
touched it draws in its horns and remains all day as if it
were dead, but in the evening it recovers itself. It is
extremely prolific, producing several families, averaging
fifty each, in the course of the breeding-season, viz. from
April to November. According to Leuch, a German
naturalist, a pair of these slugs have been known to lay
776 eggs. These eggs have retained their vitality and
the young have been developed from them after having
been dried eight times successively in a furnace. It has
the same faculty as L. arborwn of letting itself down
from one branch of a tree to another or to the ground,
by means of a slimy thread. Mr. Norman informs me
that in the earlier part of the year this slug is usually
creamy- white or light-drab ; that as the summer passes
away it assumes a darker hue, and brown flakes are
more or less thickly scattered over the surface; and
that during the autumn it is frequently of a rich brown
colour. A monstrosity of L. agrestis was found by Mr.
Gibbs, having the upper tentacles united into one.

Lister first distinguished the field-slug from other
kinds bv its smaller size and the nature of its slime :
and he also described its shell by appropriate characters.
This shell is the Limacella obliqua of Brard.

5. L. ARBORUM *, Bouchard-Chantereaux.

L. arborum, Bouch.-Chant. Moll. Pas-de-Cal. p. 28 ; F. & H. iv. p. 17,
pi. E. E. E. f. 2 (as L. arboreus).

Body rather slender, gelatinous, sea-green or bluish-grey
with irregular yellowish -white spots, indistinctly streaked with
a darker colour down the sides, leaving a lighter stripe in the
middle from the shield to the tail, finely wrinkled : shield

* Inhabiting trees.

136 LIMACID,?:.

rounded in front and obtusely angulated behind, the concentric
or transverse striae rather fine, streaked lengthwise, the middle
stripe being usually darker : tentacles short, yellowish-grey :
hacTc distinctly keeled towards the tail : foot having its edges
nearly white : slime colourless. L. 3. B. 0-4.

Shell squarish-oval, nearly flat, very thin, glossy, and iri-
descent, with minute nacreous tubercles ; lines of growth in-
distinct, obliquely striate as in the last species : boss nearly
inconspicuous and subterminal : margin broad, thin and mem-
branous. L. 0-2. B. 0-125.

Habitat: Trees (especially the beech) ^ as well as among
rocks and under stones^ both inland and on the sea-coast,
in most parts of Great Britain, from the north of Zetland
to the Channel Isles. According to Von Martens, it is
the L. Livonicus of Schrenck, and inhabits Russia ; it
occurs in several parts of Norway; Bouchard-Chan-
tereaux and Norm and have instanced localities in the
North of Erance, and 1 have found it in the Lower Harz :
but it has not been noticed further south. It has been
probably mistaken for the young of the next species.

M. Bouchard- Chantereaux^ who first described the
tree- slug, says that it prefers old trees, feeding on de-
cayed wood and not touching the leaves ; and he adds
that it is not prolific. He has often seen the young
(which he believes to be the L. filans or spinning-slug of
Hoy and some other English authors of the last century)
spin its slimy thread and descend from one branch to
another, but not plunging into air (or taking what bathers
would call " a header '') without apparent fear and
hesitation, the sole of its foot exhibiting during the
descent a similar movement to that which is observable,
while it is crawling on the sides of a glass vessel. In a
remote cluster of the Shetland Isles, called the Out-
Skerries, where I have taken this slug, with my friend
Mr. Norman, no trees exist ; but perhaps it found de-

LIMAX. 137

caying seaweed to be equally palatable. Its slime is
abundant ; and the animal, on being touched, yields a
fluid like clear water. Professor E. Forbes found it
plentifully, creeping on bare stones and rocks, at an
elevation of above 1500 feet, near Connor Cliffs, above
Dingle, in Kerry. Mr. Lowe observes that it prefers
walnut-trees. Mr. Daniel informs me that he has seen
this slug in couples during the pairing- season suspended
by slimy threads from the branch of a tree.

6. L. MAx'iMUS^, Linne.

L. yymximus, Linn. Syst. Nat. ed. xii. p. 108. L. cinereus, F. & H. iv.
p. 15, pi. D. D. D. f. 1.

Body rather slender, yeUo wish-grey, but varying in intensity
of colour and being sometimes quite black, with occasionally
streaks or spots of black or white, covered with numerous and
elongated tubercles, so as to appear strongly wrinkled : shield
oblong, very tumid, somewhat contracted or even pointed
behind, distinctly and regularly striate : tentacles (especially
the upper pair) long in comparison with those of other species,
yeUowish-brown : bacJc rounded, except close to the tail, where
there is a shght keel : foot edged with white : slime whitish.
L. 4-5. B. 0-75.

Shell squarish-oblong, rather convex above and nearly flat
beneath, solid, irregularly crystalline, rather glossy and na-
creous, with distinct lines of growth, obhquely striate as in
the two last species : boss very small, placed near one end : mar-
gin thin and membranous. L. 0*5. B. 0*325.

Habitat : Woods, gardens, hedges, under old logs of
wood, and nearly everywhere in town and country. Its
foreign range extends from Finland to Corsica and
Algeria, and (according to Mr. Lowe) Madeira.

This is the largest species of LimaXy and sometimes
exceeds six inches in length. It is inactive in its habits,
not very prolific, and exudes a thick and glutinous slime,

* Largest.

138 LIMACID^.

which is iridescent when dried. Its eggs are deposited
in a cluster and slightly attached to each other. When
alarmed, or at rest_, this slug merely draws its head within
the shield, but does not otherwise contract its body.
When irritated, it is said to expand its shield. It is
liable to be infested, as well as some of the other slugs,
by a white parasitic mite, called Philodromus (or Acarus)
limacum, which swarms about its body and, according
to Mr. Jenyns, dwells in its respiratory cavity, but which
does not seem to cause the slug any harm or incon-
venience, except perhaps in feeding on its slime and
slightly lessening the secretion. Mr. Daniel informs me
that these slugs suspend themselves in pairs during the
breeding- season by threads of slime, and that they always
feed by night, but that the variety cinereo-niger of
Nilsson prefers terra firma to mid-air and keeps much
more respectable hours. Like all other slugs and snails,
it will soon eat its way out of a large pill-box, or even a
stouter one made of cardboard, if confined in it. The
shell or ossicle which is contained under the shield was
known to Pliny ; and it was used by the ancient phy-
sicians for the sake of its carbonate of lime. The sub-
stratum of this shell is membranous ; and a layer of the
same filmy material covers the upper surface, having the
appearance and character rather of a periosteum than of
a Molluscan epidermis.

The young of this species- may be distinguished from
L. arhorum, among other respects, by its upper tentacles
being proportionally much longer, as well as by the pos-
terior margin of its shell being more pointed. The shell
of L. maximus is also longer, more convex, and thicker.

Miiller gave this species the name of cinereus, on the
supposition that the L. maxi7nus of Linne might be a
variety of Avion ater ; but the diagnosis of the great

LIMAX. 139

Swedish naturalist is couched in the same terms as that
of his predecessor, Lister, who accurately distinguished
the present species from the black slug. It is the L.
antiquorum of Ferussac ; and the shell is the Limacella
parma of Brard.

The L. brunneus of Bouchard-Chantereaux (F. & H.
iv. p. 20, pi. F. F. F. f. 4) is, according to Moquin-Tan-
don, a doubtful species ; and it is probably only one of
the numerous varieties of L, agrestis. It is rather local,
but appears to be widely distributed in this country, from
Zetland to Cornwall. In France its range extends
from Boulogne to the Pyrenees. In Dr. Gordon^s ex-
cellent contributions to the ^ Zoologist ^ it is stated that
this little slug, which is not uncommon in the Moray
Firth district, is the most lively and fearless of its tribe,
and that when disturbed, instead of contracting itself
into a lump, like most of its congeners, it makes bold
and repeated efforts to escape from the annoyance and
crawl away. The only essential diff"erence that I can
detect between it and L. agrestis is, that this slug is
smaller (scarcely an inch in length when crawling), and
of a uniform brown colour; and M. Bouchard-Chan-
tereaux admits that it is closely allied to the latter species.
The original L. brunneus of Draparnaud differs somewhat
in colour. The British species so called appears to be
the L. parvulus of Normand (Descr. Lim. Valencienues,
p. 8j, judging from his description.

The L. tenellus of Forbes and Hanley (iv. p. 21, pi.
F. F. F. f. 3), which they refer to Miiller^s species of that
name, can scarcely be considered as more than provi-
sionally introduced into the list of British slugs. Moquin-
Tandon reckons this also to be a doubtful species.
Miiller describes his L. tenellus as being ten inches long
(although this is evidently a typographical error) ; and

140 TESTACELLIDiE.

Nilsson describes his species of the same name as being
equal in size to L, flavus ; while the authors of the
^British Mollusca' state that the dimensions of their
slug do not exceed an inch and a quarter in length.
Miiller, Draparnaud, and Nilsson also mention its
having a greenish hue, which the British slug does
not appear to have possessed, M. Drouet says this
species belongs to Avion. A single specimen was found
by Mr. Blacklock in a wood at Allansford, near Shortly
Bridge, in Northumberland, and by him communicated
to Mr. Alder, who published the discovery in the ' Trans-
actions of the Northumberland and Newcastle-upon-
Tyne Natural History Society.^ It may possibly have
been the young or a variety of L. flavus. As, however,
this tribe is gregarious or at any rate individually
numerous, it is to be hoped that further researches will
be made, so as to settle the question as regards not only
the specific distinction of this slug, but also the pro-
priety of its admission into the British fauna.

Family II. TESTACELLID.^.

Body cyhndrical, exceedingly long and flexible : mantle ru-
dimentary, but capable of being occasionally expanded, gene-
rally covered by the shell : other characters similar to those of
Limacidoe, except in a few anatomical particulars.

Shell ear-shaped, with a very small terminal spire, ex-
ternal, and occupying the same place as the mantle in the last
family.

This family comprises only one genus, viz., —

TESTACEL'LA*, Cuvier. PL V. f. 6-9.

Body of a firm texture, with a nearly smooth skin : tentacles
cylindrical: labial j^alps extensible: foot margined.

* Diminutive shell.

TESTACELLA. 141

Shell solid : spire consisting of half a whorl : columellar fold
internal, very broad.

This peculiar genus appears to form a natural family
of itself, when viewed with respect to the British Mol-
lusca only ; but it is connected with the Slugs on the
one hand through the genus Parmacella, which has no
representative in this country, and on the other hand
with the Snails through the Vitrina semilunar of Fe-
russac (also a Continental mollusk), which Oken called a
Testacella. The Testacella partake in some degree of
the nature both of a Slug and a Snail, having a long
naked body and a small shell placed near its tail. The
shell serves to protect the heart, liver, and other vital
organs. The Snail-slug was first made known by the
celebrated Reaumur in 1740 through the Academy of
Sciences at Paris, in consequence of a communication
made to him by M. Dugue from Dieppe, and which con-
tains an excellent account of the shape, habits, and mode
of reproduction of this curious mollusk. From that
period down to 1800, many observations were made and
recorded in France on the same subject ; but it was only
in the last-mentioned year that Cuvier, being struck by
the remarkable aspect of the shell, constituted for it, in
his ' Lessons on Comparative Anatomy,' the genus Tes-
tacella. This name was adopted both by Lamarck and
Draparnaud in 1801 ; but in the following year it was
erroneously altered by Faure-Biguet to Testacellus. This
slight history of the name is given to prevent a con-
tinuance of this mistake, which was adopted by Fe-
russac, Sowerby, Gray, and other naturalists. By far
the most complete and valuable account, considered in a
conchological as well as a palseontological point of view,
which has been given of this genus, is contained in a

142 TESTACELLID.E.

monograpli by MM. Gassies and Fisclier, publislied at
Paris in 1856.

The Testacella appears to be the only land-mollusk
which has truly predaceous habits ; its marine representa-
tives in this respect being the Cuttle and the Whelk. It
is scarcely inferior to the tiger_, snake, or shark in its
cunning and ferocity. Its prey chiefly consists of earth-
worms, which it hunts underground and pursues through
their galleries, crouching occasionally and making a
spring on its \ictim. It is said that when the poor worm
has had the start of its pursuer, the Snail-slug intercepts
it by tunnelling across the line of its retreat. It will
devour a lob-worm much longer than itself, seizing it in
the middle; and when the writhings have been succeeded
bv exhaustion, it detaches and swallows one half of the
worm; and after that has been digested, it finishes its
long meal with the other portion. For this purpose its
mouth is furnished with an apparatus of sharp recurved
teeth, which enables the Testacella to retain a firm hold
of its victim and swallow it more easily. The worm is
provided with some means of defence, in the rows of stiff
bristles which encircle its rings ; and by contracting its
body a short respite is occasionally gained. But the
chance of ultimate escape or safety is very slight. When
the Testacella sees or scents its prey, it glides softly and
cautiously towards it ; and, apparently without taking any
notice of the worm, it seems to feel its way, and usually
succeeds in fastening itself on an unprotected part of
the body between the rings. The attack, if unsuccessful
at first, is renewed ; but if the worm resists too long, the
Testacella gets impatient, and by pressing or doubling
its victim into the earth, by which means the rings are
forced open, its purpose is effected and the meal secured.

TESTACELLA. 143

Although it also feeds on slugs and snails^ and even on its
own species (the shells of which have been found in its
stomach) J it will not eat dead animals, and even refuses
pieces of a fresh worm which has been chopped up to
feed it. It only sallies out at night in search of its prey,
burying itself deep in the ground during the daytime.
After having gorged itself with a worm, it rests many
hours in a half-torpid state until the meal has been di-
gested ; and it can remain fasting a long time (as much as
fourteen or fifteen nights) until hunger impels it to make
a fresh hunt. It does not fear the cold, or appear to
suffer any inconvenience from it except when the ground
is hardened by frost ; and in this respect it resembles the
Slugs, the Vitrince, and some of the Zonites, all of which
are nearly as carnivorous and hardy as the Testacella.

Gassies and Fischer are of opinion that the holes which
may be sometimes remarked in the shields of the Limax
gagates and other Slugs have been made by the Testa-
cella, for the sake of extracting the calcareous matter
from the internal shells or Limacella of the Slugs to
form its own more complete shell ; and they have noticed
that the Slugs which have been thus attacked soon die.
If the Testacella is taken fresh from the ground and kept
a short time in the hand, the warmth seems to revive it
and induce it to crawl away ; but if its retreat is op-
posed, it will violently bite the skin and oblige the ex-
perimentalist to let it go, from an instinctive feeling' of
disgust. During cold northerly and easterly winds these
creatures enclose their bodies in a kind of cocoon, like
that of the silkworm, which is secreted from their skin
and often mixed with earthy and extraneous particles.
Mr. Norman has informed me that in this state their
mantle is expanded to such an extent as to cover all the
upper part of the body. Ferussac appears to have been

144 TESTACELLID.E.

mistaken in supposing that the whole gf the body was
enveloped by the mantle. If this slimy pellicle be sud-
denly removed, the Snail-slug is liable to be attacked by
a disease which usually ends in its death. Heavy rains
destroy a number of them. The average length of life in
the Testacellce appears to be five or six years. Their
smell is like that of worms, but even more nauseous.
They chiefly frequent gardens, where they are sure of
finding their proper food; but they may occasionally be
met with in woods near inhabited places, as well as at the
foot of old walls. In winter they bury themselves very
deep in the ground ; and my gardener once brought me
living specimens of T. Maugei which he had dug up in
trenching some celery-roots at a depth of about two feet.
The eggs are laid separately, and are very large in pro-
portion to the size of the body. These somewhat re-
semble hen^s eggs both in shape and consistency, and
are covered with a rather thick and tough skin. If they
are taken out of the earth and exposed to a cold air, they
frequently crack and burst in pieces which fly ofi" to some
little distance. Faure-Biguet appears to have succeeded
in preserving the eggs under such circumstances by
plunging them as soon as taken into boiling water. It
is believed that the Testacella never come to the surface,
except occasionally during the breeding-season, but that
at all other times they live underground. Their eyes,
however, are perfect ; and their horns, or tentacles, are
rather long and extremely sensitive. '

TE STAGE LLA. 145

Testacella Halioti'dea*^, Draparnaud.

T. haliotidea, Drap. Hist. Moll. p. 121, tab. ix. f. 12-14. T. haliotoidea,
F. & H. iv. p. 2d, pi. G. G. a. f. 1.

Body contracted towards the front and somewhat pointed at
the head, rather smaller in the middle, a little broader behind,
capable of extending itself like a worm, with a thick and
tough skin, which is smooth when the animal is crawling at its
full length, but transversely wrinkled when it is at rest, yel-
lowish-brown, sometimes mottled or speckled with black, red,
or white : lips or labial lobes flexible and extensible, resembling
a third (but much shorter and thicker) pair of tentacles : mantle
very small and thin, not much larger than the shell : tentacles
rather short, smooth, brown, very little swollen at their ex-
tremities : eyes placed on the upper side of the tentacular ex-
tremities, but not quite at the end : hack convex, divided into
three nearly equal parts by two longitudinal grooves which
extend on each side of it from the front edge of the shell to
within a very short distance of the tentacles ; these grooves
have parallel offsets above and below, which are finely rami-
fied: foot bordered with distinct and prominent edges. L. 3.
B. 0-4.

Shell oblong, compressed, especially in the middle and to-
wards the front margin, solid, not glossy, closely striate by
the lines of growth, and sometimes also marked by a few in-
distinct lines which radiate from the spiral point : epidermis
rather thick : spire terminal, sharp, and very small : anterior
margin rounded : posterior margin obliquely truncate : lateral
margins obtusely curved : mouth exceedingly large : pillar lip
thickened and slightly reflected : fold flat and sharp-edged.
L. 0-25. B. 0-15.

Yar. scutulnm. Body yellowish, speckled with brown. Shell
narrower : spire more produced and pointed. Testacella scu-
tidum, Sowerby, Gen. Sh. f. 3-6.

Habitat : Gardens at Norwich, Plymouth, Bideford,
Youghal, andBandoii. The variety, which was first dis-
covered by the late Mr. Sowerby in his garden at Lam-
beth, is not uncommon in many parts of the metropolitan

* EesembUng a Hcdiotis or ear shell.

H

116 TESTACELLID/E.

district^ as well as in Guernsey. This species has been
noticed by Continental writers as occurring throughout
a great part of France (principally in the South and
South-west^ but also, according to Collard des Cherres
and De PHopital, in the Department of Finisterre and at
Caen), Spain, Algeria, Corsica, Sicily, Madeira, and the
Canary Isles. It has also been found in a fossil state
near Clermont and in the South of France.

Whether this singular and somewhat anomalous mol-
lusk is really indigenous to this country, or has been in-
troduced and acclimatized, it is almost impossible to say.
The means by which MoUusca become spread are various ;
and Man is one of the unconscious agents of such diffu-
sion. A usual habitat of this kind of Testacella is at the
roots of flower-plants, or under heaps of dead leaves in
gardens ; and if a plant were imported into this country
from the botanic garden at Montpellier with the native
soil or a compost made of leaf-mould, either the Snail-
slug or its eggs would perhaps accompany it.

The European Snail-slug is by no means prolific, lay-
ing only 6 or 7 eggs from April to July. During this
operation its head and tentacles are drawn in. The eggs,
when new-laid, are pointed at each end. The young are
excluded at the end of from twenty-five to thirty days.
The slime is abundant and colourless.

Mr. Tapping described in the * Zoologist' for 1856
(p. 5105) what he considered a new species of British
Testacella, under the name of Medii'Templi. It was
found in only one part of the Middle-Temple Gardens,
under the shelter of a south-west waU. But his descrip-
tion scarcely differs from that of the variety scutulum ;
and Mr. Norman, who has examined typical specimens of
the supposed species, informs me that they belong to
that variety. The colour of the body, as well as the form

TESTACSLLA. 147

of the s}iell_, are exceedingly variable characters in this

genus.

It is the Testacella Europcea of De Roissy, who pro-
posed a change of name in consequence of Lamarck
havings a few months previous to the publication of the
* Histoire ^ of Draparnaud, described what was then sup-
posed to be the same species under the somewhat similar
name of Haliotoides ; but it now appears that Lamarck^s
species is the one which I am next about to notice.

The T. Maugei of Ferussac was observed by the late
Mr. J. S. Miller, the Curator of the Philosophical Insti-
tution of Bristol, between forty and fifty years ago, in
the nursery-gardens of Messrs. Miller and Sweety near
that city, where it is still to be found in considerable
numbers. It has been since, to a certain extent, natu-
ralized or acclimatized in this country, having been ob-
served in other parts of Somersetshire, as well as at Ply-
mouth and Cork. I may add to this list of localities my
own garden at Norton near Swansea, which was occa-
sionally supplied with plants from Miller and Sweet^s
nurseries. It was originally (in 1801) noticed as a native
of Teneriffe; and it appears to be also indigenous to
Madeira, the Canary Isles, Portugal, and the South-west
of France. A variety of it (called T, Deshayesii or
Alta-ripce) occurs in a fossil state at Haute-Rive in
France. This species has a smaller head, as weU as a
much larger and more convex (almost semicylindrical)
shell, than T. Haliotidea. The present spedles is more
prolific and gregarious than its congeners. Mr. Norman
has kept specimens of T. Maugei y as well as of T. Halio-
tidea and its variety scutulum, alive for some time, and
has carefully watched their habits in a state of confine-
ment. He says that the nest of earth which T, Maugei
makes for itself in times of drought reminded him not a

H 2

118 TESTACELLIDtE.

little of the cocoon of the Puss-moth. "VYithin this co-
coon the Testacella lies encysted until nioisture_, working
its way through the walls of its dwelling, rouses it again
into activity and sends it forth in quest of food. While
in the encysted state, a thin white membrane (a deve-
lopment of the mantle) is extended from beneath the
shell and stretched over the back and sides of the ani-
mal. An admirably-designed protective shield is thus
formed, which checks evaporation from the surface of
the body, and enables the flow of mucus, which is so
essential to the life of the animal, still to course along
the lateral canals and thence be distributed through the
branching channels over the entire surface of the body.
When T. Maugei is removed from its cyst and the body
moistened with water, the extended membrane is gradu-
ally retracted until it is entirely withdrawn beneath the
shell. Mr. Norman also remarks that the habits of this
species resemble in many respects those of the earth-
worm, which (like the Testacella) may in times of drought
be found coiled up in as compact a mass as possible
within a chamber of the baked soil. The T. Maugei
has also the power of greatly elongating and extending
the body, which very much facilitates its passage through
the earth. The Testacella and its prey are both noc-
turnal animals; and those who wish to procure speci-
mens should look for them at daybreak, especially after
a warm dewy night in the months of July and August.
Mr. Normal has had as many as five dozen living
T. Maugei sent to him from Clifton, which were taken
in this way. The eggs of this species are large, oval,
opaque, and covered with a cream-coloured tough skin.
The shell is developed upon the young, while still in the
embryo state.

HELICID.E. 149

Family III. HELICIDJE.

Body long and spirally coiled : mantle covering the front or
anterior part : tentacles nearly always 4 (rarely 2 only), re-
tractile : eyes placed on the tips of the upper or single pair :
foot oblong, distinct from the rest of the body.

Shell spiral, and in almost every case capable of containing
the whole body.

This family comprises the true Snails, and abounds in
species as well as individuals. L. Pfeiffer described no
less than 1149 species of the typical genus, Helix, in
1848, when his very serviceable Monograph on this
family was published ; and if we add to this list the re-
sult of subsequent discoveries or reputed novelties, as
well as all the species of Bulimus and other allied genera
(which scarcely differ fi'om Helix, and are only considered
distinct for the sake of more easy classification), we can
form some idea how exceedingly numerous this family
is. Strictly speaking, it only consists of one genus, like
TestacellidcB ; and there is rather a generic than a family
resemblance among its members. The chief points of
difference between the genera of the present family are,
that in Succinea the body is ordinarily a trifle larger
than the shell ; in Vertigo the two lower or smaller ten-
tacles are wanting ; in Clausilia the shell has a reversed
spire, and is furnished inside with a small moveable pro-
cess ; in Bulimus, Pupa, and Balia the spire is longer,
and in the last-mentioned genus reversed; while in
Cochlicopa and Achatina the spire is more produced and
the mouth of the shell is channeled or notched at its base.
But without some artificial classification of this kind the
genus Helix would be too unwieldy; and the division
into subgenera is generally considered inconvenient, be-
cause it occasions additional and unnecessary nomen-

150 HELICID^.

clature. The genera into whicli this family may be
divided_, as regards the British species, are as foUows : —

* Shell oval, usually not quite covered by the body. 1. Src-

CIKEA.

** Shell globular or round, glassy, sometimes covered in
part by a lobe or expansion of the mantle. 2. YixRCifA.

3. ZONITES.

*** Shell shaped like the last, but not glassy, nor any part of
it covered by the mantle. 4. Helix.

**** Shell cylindrical: mouth often furnished inside with
teeth, and in one genus also with a moveable plate. 5. Bu-
LiMus. 6. Pupa. 7. Vertigo. 8. Balia. 9. Clausilia.

***** Shell shaped Hke the last : mouth more or less notched
at the base, and sometimes also toothed. 10. Cochlicopa.

11. ACHATLNA.

Genus I. SUCCrNEA *, Drapamaud.
PI. VI. f. 1-3.

Body gelatinous, usually incapable of being quite contained
within the shell : tentacles 4 ; upper pair conic, lower pair very
short : foot large, oblong-.

Shell oval or oblong, thin, amber-colour : S2nre short :
raoutJi large.

The Amber Snails are allied to the Limncea in form
and habits, as well as in some respects to the Slugs and
the true Snails, or Helices — showing that the order of
Nature is not like the steps of a ladder, but bears a
greater resemblance to chain- or net-work, every link or
mesh of which is connected with the other. These snails
are in a great measure amphibious. Mr. Benson men-
tions his having found our common species (>S^. putins)
creeping on stones under water in an Irish lough, in
company with species of Planorbis, Bythinia, and Physa,

* Amber-colour.

SUCCINEA. 151

althougli he had also observed that an Indian species of
Succinea frequented dry places where no water ever
lodged. Miiller says, however, that they are no more
amphibious than Helix nemoralis, a variety of which he
had seen living many days in a brook. Although the
Succinece inhabit the banks of lakes and marshy places,
and may even, after a flood of heavy or continued rain,
be seen under water, I have noticed that they do not
like remaining in it, but crawl out on comparatively
dry land, or climb up the stalks of aquatic plants and
willows. When they are under water they draw in their
tentacles. They can float on the water in a reversed
position ; and in dry weather they withdraw themselves
far into the shell, covering up the mouth with a mem-
branous epiphragm like the Planorbis spirorbiSj var. lea-
costoma. They are vegetable feeders. Their eggs are
agglutinated together and deposited on the stalks and
leaves of aquatic plants, as well as upon stones at the
water's edge. Succinea are found in all parts of the
world ; and the extent of their variation is equally great.
Their shells may be distinguished from those of Limnceu
by the absence of any fold on the columella or pillar.

1. Succinea pu'tris ^, Linne.

Helix ptctn's, Linn. Syst. Nat. ed. xii. p. 1249. S. putris, F, & H. It.
p. 132, pi. cxxxi. f. 4, 5.

Body rather thick, reddish-yeUow, closely covered with
small, flat and irregularly- shaped tubercles : tentacles short ;
upper pair not much swollen at their tips, and marked with
minute and indistinct black specks : snout, or front of the head,
large and very tumid : foot broad, nearly triuicate in front,
triangular and slightly pointed behind.

Shell oval, very thin, semitransparent, glossy, of an amber-

* Frequenting putridity.

152 HELICID.E.

colour with often a greenish or reddish hue, finely but irregu-
larly striate by the lines of growth, otherwise quite smooth :
epidermis rather thick : whorls 3-4, convex, the last occupy-
ing at least four-fifths of the shell : spire short, abrupt and
blunt at the point : suture rather oblique and deep : mouth
oval : outer lip slightly thickened, contracted above, where it
joins the columella: pillar lip sharp. L. 0*6. B. 0-3.

Var. 1. suhglohosa. Shell shorter and broader in proportion
to its length, usually much smaller and more soUd.

Yar. 2. vitrea. Shell extremely thin : spire smaller.

Var. 3. soUdula, Shell much thicker, reddish-yeUow.

Habitat : On water-plants and other herbage, as well
as on mud, in all sorts of moist places, from the extreme
north of Zetland to the Channel Isles. Var. 1 . Marshes
and by the side of lakes, on the sea-coast and in moun-
tainous districts. Var. 2. Carmarthenshire (J. G. J.) ;
Cork (Humphreys). Var. 3. Deptford, Wilts (J. G. J.).
This species is one of our upper tertiary fossils. Abroad
it ranges from Siberia to Naples ; and Captain Hutton
has found it in Afghanistan. Probably some exotic
species are mere varieties of this widely-diffused shell.

It is a sluggish mollusk, and secretes a quantity of
slime. The clusters of eggs are oblong. It hibernates
early, and passes the winter attached to stones by means
of its epipliragm, which resembles silver-paper. The
shell sometimes attains the length of an inch.

xVccording to the strict rules of priority, Klein^s spe-
cific name of vetula ought to be adopted ; but it is now
obsolete. This name may possibly have been derived
from an account which was given by Tulpius, an ancient
and very learned physician, in his medical observations,
of a wonderful cure performed on an old woman of
eighty-nine by a dose of two of these snails pounded up
alive !

SUCCINEA. 153

2. S. e'legans^, Kisso.

S. elegans, Eisso, Moll. Alp. Marit. p. 59, no. 128. S.putris, var., F. & H,
iv. p. 135, pi. cxxxi. f. 1-3.

Body thick, yellowish-brown, sometimes nearly black, co-
vered with minute round tubercles and clusters of black
specks : tentacles very short, yellowish- white and transparent,
streaked down the middle with lines of black specks ; upper
pair rounded at their tips : snout round and somewhat tumid :
foot broad, rounded in front and behind, narrower at the tail.

Shell oblong, not very thin, glossy, scarcely semitrans-
parent, amber-colour with a brownish or reddish hue, sculp-
tured like the last species : epidermis rather thin : whorls 3-4,
moderately convex but compressed towards the suture, the
last occupying about three-fourths of the shell : spire rather
short and pointed : suture remarkably oblique, not very deep :
mouth oval: outer lip slightly tliickened and considerably in-
flected above : pillar lip sharp. L. 0*6. B. 0-25.

Yar. 1. minor. Shell smaller and thinner, of a reddish-
brown colour, with a shorter spire and more expanded mouth,

Yar. 2. ochracea. Shell smaller and thicker, also reddish-
brown, with a larger spire and smaller mouth.

Habitat : Similar situations and as extensively distri-
buted as >S^. /?w^m. Var, 1. Falmouth; Hammersmith
(J. G. J.). Var. 2. Scarborough (Bean); Newcastle
(Alder) ; Tenby ; Tingwall lake, Zetland (J. G. J.). The
last variety is often mistaken for S. oblong a. This spe-
cies is also one of our upper tertiary fossils. Abroad it
is found everywhere between Finland and Sicily. Ac-
cording to Deshayes, it inhabits the Morea ; and Captain
Hutton notices it as an Afghanistan shell.

The present species sometimes occurs living with ;S^.
putris, of which, on account of the great variability of
form which prevails in all the species of this genus,
S. elegans has been considered by some authors as a
variety. Each of these species has, however, its own

* Graceful.

H 5

154 HELICID^.

corresponding variety ; and I am inclined to consider
them distinct. The species now under consideration
differs from S. putris in the darker colour of its body
and the more slender shape of the shell, as well as in
its longer and more pointed spire. It forms a passage
through its second variety from the last to the next
species.

It is the S. Pfeijferi of Rossmassler, as well as the
>S^. gracilis of Alder, but not of Lea. M. Bourguignat
has ascertained, by a recent examination of Risso^s col-
lection, that it is the present species which the celebrated
naturalist of Nice described as S. elegans ; and his de-
scription sufficiently corresponds with that of Ross-
massler.

3. S. oblon'ga*, Draparnaud.

S. oblonga, Drap. Hist. Moll. p. 59, pi. iii. f. 24, 2.5 ; F. & H. iv. p. 137,
pi. cxxxi f. 6, 7.

Body short, brown or grey of different shades, with some-
times minute black spots, finely shagreened : tentacles rather
short ; upper pair scarcely inflated at their tips : foot short and
rather broad, bluntly pointed behind.

Shell oblong- oval, rather solid, moderately glossy, brownish
or reddish-yellow, with sometimes a greenish hue, rather
strongly but irregularly striate by the hnes of growth, but
devoid of any other scidpture : epidermis thick : ivhorls 3-4,
convex, the last occupying about two-thirds of the shell : sjnre
prominent, but abrupt and blunt at the point : suture oblique
and very deep : mouth roundish-oval: outer Zi^j rather thick,
considerably inciu'ved on the columella : Inner lip sUghtly re-
flected. L. 0-25. B. 0-175.

Habitat : Dry ditches, chiefly near the sea-coast. It
is a very local species in this country. I have found it
among the sand-hills on Crymlyn Burrows near Swan-
sea, and in a similar situation on Braunton Burrows

* Oblong.

VITRINA. 155

near Bideford in North Devon. Mr. Kenyon is said to
have found it near Glasgow^ Mr. M'^ Andrew at Balti-
more^ Mr. Wright and Mr. Carroll near Cork, and
Mr. Waller discovered it among turf-bogs at Finnoe,
Co. Tipperary. The last appears to be the only inland
locality. It is not uncommon in our upper tertiaries.
This species is widely diffused on the Continent from
Sweden to Lugano ; and the S. ahbreviata of Morelet,
from Braganza in Portugal, appears to be only a variety
of it.

S. oblonga is unmistakeably different from either of
the foregoing species, being invariably so very much
smaller and having such a large spire in proportion to
the size of the shell, with a deeper suture and a rounder
mouth. I can scarcely regard the S. arenaria of Bou-
chard-Chantereaux as even a well-marked variety of this
species. Most, if not all, of the British specimens belong
to this form. The greater solidity of its shell and the
comparatively shorter spire are probably owing to the
nature of its habitat. According to Bouchard-Chan-
tereaux this variety buries itself in the sand and makes
a rather solid epiphragm. The shell is usually covered
with a viscous slime or exudation from the animal, by
which a slight coating of dirt is sometimes formed.

Genus II. VITRlNA*, Draparnaud. PL VI. f. 4-6.

Body short, usually incapable of being quite contained within
the shell : mantle furnished with a supplementary lobe, which
is extended over the front of the shell when the animal crawls ?
tentacles 4, cylindrical, the lower pair very short : foot rather
narrow.

Shell somewhat globular, extremely thin and transparent :
spire short : mouth obUquely semilunar : outer lip thin : no
umbilicus.

* From vitrum, glass.

156

HELICIDiE.

These little Glass-Snails are allied to the Slugs in
some of their habits^ and to the true Snails in the form of
their shells, leading to the former tlirough Succinea and
to the latter through Zonites. Their food is partly vege-
table, consisting of Jungermannice. and decayed leaves,
and partly animal. They are said to attack earth-worms,
although not in the same way as Testacella. I once saw
no less than seven individuals of V. pellucida busily en-
gaged in feeding on a scarcely dead worm, which was
faintly writhing about and endeavouring in vain to get
rid of its tiny assailants. They have also been noticed
eating horsedung. They live in moist and shady places,
but are seldom met with until late in the autumn. Their
eggs are deposited in small heaps and have a membranous
covering. The whole of the body can be withdrawn into
the shell. They are very hardy, and capable of enduring
an extreme degree of cold. I have found a variety of
the V. diaphana on the Rifelberg near Monte Rosa, at a
height of between 7000 and 8000 feet above the level of
the sea, living among perpetual snows and on ground
that never thaws. Only one species now inhabits this
country, although another {V. diaphana) formerly did
so, as is proved by its occurrence in our upper tertiary
strata. This last species has a wide range over the Con-
tinent, and, according to Potiez and Michaud, inhabits
the North of France. It has been observed on the
Vosges Mountains at a height of upwards of 4000 feet.
Several other species are found on the Continent.

VlTRINA PELLU'CIDA*, Miillcr.

V. pellucida, Miill. Verm. Hist. pt. ii. p. 15 ; F. & H. iv. p. 30, pi. cxxxi.
f. 8-10, and (animal) pi. I. I. I. f. 2.

Body rather slender, grey with more or less of a reddish

* Transparent.

VITRINA. 157

tinge, and having some minute black specks on the anterior
part : foot yellowish underneath, pointed behind.

Shell convex above, rather depressed below, exceedingly
thin and brittle, remarkably glossy and almost iridescent,
nearly transparent, marked indistinctly by the lines of growth,
as well as by close-set and very minute striae in a spiral di-
rection : eindermis thin : whorls 3-4, convex, the last occu-
pying more than two-thirds of the shell : sj^ire extremely short,
rising gradually to a blunt point : suture very slight, forming
a narrow groove, which is striate across : mouth nearly round,
except where it is interrupted by the periphery of the penul-
timate whorl : outer Up not very thin, nor inflected above :
pillar lip sharp. L. 0'125. B. 0*25.

Yar. 1. depressiuscida. Shell rather oval and flatter on
both sides : spire scarcely raised above the level of the last
whorl. V. Draparnaldi and V. depressa, Jeffr. in Linn. Trans,
xvi. pp. 326, 327.

Var. 2. Dillwynii. Shell nearly globular, with the last
whorl very convex : spire more prominent. V. Dillwynii,
Jeffr. I. G. p. 506.

Habitat : Under stones and logs of wood, as well as
among moss and dead leaves, in woods and shady places
throughout Great Britain. Var. 1. Neighbourhood of
Swansea and Plymouth (J. G. J.). It approaches very
near to V. major of the elder Ferussac and V. Drapar-
naldi of Cuvier, with which I at one time considered it
to be identical. Var. 2. Sand-hills near Swansea, at
the roots of Rosa spinosissima. The foreign range of
this common species extends from Siberia to Sicily.

This is an active and hardy creature, and, whether
crawling or at rest, it seems always to keep the outer
lobe of its mantle in motion, so as to polish the shell.
Bouchard-Chantereaux says that it does not begin laying
its eggs until September, October, or November, and that
the young attain their full growth in from eight to ten
months. He believes it does not live longer than from
twelve to fifteen months, having always found a number

158 HELICID.^.

«

of dead individuals in January, after tlie close of the
breeding-season. Miiller lias noticed that it is most
lively during rain, and that it does not soon die if put in
water. He added that while it was under water it ex-
tended all its body except the tentacles, which were
drawn in, and feigned death; that after the lapse of
some hours it crept out of the water cautiously and by
degrees, and if it was not alarmed by the observer it
stretched out its horns, and after crawling into some
place of shelter withdrew its body into the shell. Mr.
Daniel, having collected both of these species in Ger-
many, informs me that V. pellucida is much more gre-
garious than V. diaphana.

Genus III. ZONI'TES*, De Montfort. PI. VI. f. 7-9.

Body long, rather bulky, but always capable of being con-
tained within the shell : mantle thick and slightly reflected :
tentacles 4, cylindrical, swollen or bulbous at the tips : foot
narrow.

Shell conical, usually depressed, thin and semitransparent,
extremely glossy : sjyire composed of several whorls : mouth
obliquely semilunar : outer lip thin : umbilicus more or less
distinct.

These pretty little snails resemble the Vitrince in the
bulkiness of their bodies and the glassy appearance of
their shells, as well as in the structure and arrangement
of their dental apparatus or lingual riband. The edge
teeth are hooked in the present genus and Vitrina, but
serrated or notched in Helios. Their habits also are
nearly the same as those of the VitrincBj being rather
zoophagous than phytophagous. They greedily devour
all kinds of animal food, whether fresh or putrid ; and

* From zona, a girdle.

ZONITES.

159

they are said even to attack the larger snails and to enter
their shells for that purpose. They frequent dark and
damp places, heing generally met with under stones, old
bricks, and logs of wood which are partly buried in the
earth, as well as under and among dead leaves and moss
in woods ; and one kind inhabits cellars, vaults, and wells.
Some of them give out when touched or disturbed a fetid
smell like that of garlic, which may be perceived at a
considerable distance. Their eggs are laid in the earth
and joined together in small clusters.

A. Spire depressed : umbilicus open.
1. ZoNiTEs cella'rius^, Miillcr.

Helix cellaria, Miill. Verm. Hist. pt. ii. p. 38. Z. cellarhcs, F. & H. ir.
p. 33, pi. cxx. f. 1-3, and (animal) pi. H. H. H. f. 3.

Body obtusely rounded in front and narrowing gradually
behind, nearly covered with small and rounded but very flat
tubercles, rather transparent, slate-colour or bluish-grey, with
a faint tinge of yellow : tentacles long and slender, with very
large bulbs surmounting the upper pair, bluish or yellowish-
grey, finely speckled with black: foot very narrow, pointed
and somewhat keeled behind.

Shell compressed, nearly as convex above as below, thin
and brittle, very glossy, semitransparent, yellowish or brown -
ish-horncolour above, and whitish with often a greenish tinge
underneath, irregularly striate by the curved lines of growth,
which are stronger near the suture, and microscopically stri-
ate, like Vitrhia, in a spiral direction : epidermis rather thick :
whorls 5-6, dilated, regularly increasing in size, the last occu-
pying about one-half of the shell : spire extremely short and
nearly flat, almost central : suture slight, forming a narrow
groove or chanuel : mouth obliquely and deeply semilunar :
outer lip shghtly reflected : wnhilicus broad and deep, ex-
posing nearly all the interior of the spire. L. 0*2. E. 0*5.

Yar. 1. Gomplanata. Shell rather smaller : spire very flat.

* Frequenting cellars.

160 HELICID^.

Var. 2. albida. Shell white or colourless.

Yar. 3. compacta. Shell not so white underneath : whorls
more convex and compact, the last not being so much dilated :
spire more prominent.

Habitat : Cellars, vaults, drains and sculleries, under
stones, loose bricks, tiles and logs of wood about houses,
as well as under stones and fallen trees which have lain
long on the ground in woods, everywhere from Zet-
land to Guernsey, The varieties are occasionally found.
Var. 3 approaches the next species in form. Z. cellarius
occurs in a semifossil state at Copford, Clacton, and
Maidstone. Its foreign distribution extends from Fin-
land to Algeria and Sicily ; and Mr. Lowe has recorded
it from Madeira and the Canaries. Gould has described
it as a North- American species, and says it is the Helix
glapjhyra of Say ; but he adds that it was probably im-
ported from Europe about water-casks or greenhouse
plants.

Miiller has noticed the shy habits of this snail, and
says that, when crawling, it alternately withdraws one
of its horns half-way, although there is no obstacle in
front of it, and immediately puts it out again. Mr.
Sheppard remarked that it had a very fetid smell, much
resembling that of the urine voided by the common
snake se defendendo, and by which one might frequently
be guided to the spot where it lies concealed. He also
noticed that in some instances this odour was not per-
ceptible until the snail had been immersed in boiling
water. The organ of smell must be very acute in this,
as well as all the other species of Zonites, judging from
the size of their tentacular bulbs, in which this sense is
supposed to be placed. Its slime is watery and abun-
dant. The dark band which often encircles the suture
in dead shells is owing to the dried remains of part of

ZONITES. 161

the body appearing through the shell. A specimen in
my collection has the outer or last whorl marked by a
rufous band between the suture and the periphery.

Linne does not appear to have known this common
species. Much confusion has been caused by the post-
humous editor of his ' Systema Naturae ' (Gmelin) care-
lessly changing the name which Miiller gave to a differ-
ent species of Helix from nitida to nitens, and applying
the latter name to the present species. This is the
Helix lucida of Pulteney^ but not of Draparnaud^ and
the H. nitida of the last-named author.

2. Z. allia'rius "^^ Miller.

Helix alliaria, Mill, in Ann. Phil, new ser. iii. p. 379. Z. alUarius, F.& H.
iv. p. 34, pi. cxx. f. 5, 6.

Body resembling that of Z. cellarius ; but it is of a much
darker colour, and the tentacles are shorter in proportion.

Shell more convex above and less so below than in the
last species, rather more solid and glossy, of a darker colour
on the upper side and not so white underneath, sometimes
marked with a few indistinct spiral lines : whorls 5, rather
convex, often irregularly coiled, the last not so large in pro-
portion to the others as in Z. cellarius : spire somewhat pro-
duced : suture moderately deep, but not channeled : mouth
narrow : outer Up sharp, slightly reflected near the pillar :
umbilicus open and deep. L. 0"1. B. 0'275.

Yar. viridula. Shell greenish- wbite.

Habitat : Under stones on hills and open spots, as
well as among sand-hills ; having an equally wide distri-
bution with the last species, but more local. The variety
is from Northumberland (Alder) ; Kent (Smith) ; So-
merset (Norman) ; Cork (Humphreys) ; Belfast (Thomp-
son) ; Lincolnshire, Salop, Zetland, and Co. Tyrone
(J. G. J.). This species is one of our upper tertiary

* Garlicky.

162 HELICIDiE.

fossils. It has been recorded by M. Grateloup as occur-
ring at Dax in the Department of the Landes, and
by M. Terver at Lyons ; but it has probably been passed
over in other parts of Europe as a variety of Z. glaber,
which is not uncommon in France, Germany, and Swit-
zerland.

This snail has a very strong and pungent smell of gar-
lic, especially when it is irritated ; and I have perceived
it at a distance of several feet from the spot. Having
found living specimens under stones in a bed of wild
garlic, I thought at first that they might have fed upon
this herb and thus acquired the peculiar odour ; but I
afterwards observed that this scent was quite as power-
ful in specimens collected on an open down where there
was no garlic. Mr. Norman informs me that the scent
varies in intensity, and is sometimes scarcely percep-
tible, even after considerable irritation of the animal.

It difiers from Z. cellm^ius, the young of which it re-
sembles, in the darker colour of its body and shorter
tentacles, as well as in the spire of its shell being more
produced, the mouth narrower, and the umbilicus more
open. If the two shells are held sideways, with the
mouth towards the observer, the last whorl of Z. cella-
rius will appear deeper than in the other shell.

There has been much controversy among Continental
writers as to whether this species is distinct from the
HelLv glahi^a of Studer. I incline to the opinion of
Schmidt, that thev are different. One test mentioned
by this author in support of his view is rather curious,
viz. that Z. allim'ius wants the bitter flavour of the other
species ! I much doubt if all conchologists would relish
making such experiments.

ZONITES. 163

3. Z. NiTi DULUs *, Draparnaud.

Helix nitidula, Drap, Hist. Moll. p. 117. Z. nitidulus, F. & H. iv. p. 36,
pi. cxx. f. 8-10.

Body dark-grey or slate-colour, with a brownish tinge,
covered with flat and irregularly-shaped tubercles of a darker
hue, which give a speckled appearance : tentacles rather short
and conical ; bulbs small : foot rather narrow in front, swollen
and keeled behind.

Shell compressed, more convex above than below, thin,
moderately glossy, scarcely semitransparent, brown or yel-
lowish-horncolour above, whitish underneath, especially about
the umbilicus ; sculptured as in Z. cellarius, but having the
spiral striae more regular and distinct : epidermis rather thick :
whorls 4^b, convex and rounded, the last occupying rather
more than one-half of the shell : spire slightly raised, nearly
central : suture rather deep : mouth round, except where it is
interrupted by the periphery of the penultimate whorl : outer
lip not so obliquely set as in the last species, nor reflected :
umbilicus very broad and deep, fully exposing the interior of
the spire. L. 0-15. B. 0-33.

Var. 1. nitens. Shell rather smaller and of a lighter colour,
with a dull and waxy appearance ; last whorl somewhat larger
in proportion to the others and laterally expanded. Helix
nitens, Michaud, Compl. Drap. p. 44, pi. xv. f. 1-5.

Var. 2. Helmii. Shell resembling that of the above-men-
tioned variety, but of a pearl-white colour. Helix Helmii,
GUbertson's MS.

Habitat : Under stones and among dead leaves, moss,
and herbage in woods, hedge-banks, and elsewhere in
this country, from the Moray Firth district to Guernsey.
Var. 1. South Wales, West coast of Scotland, and many
other places. This variety is more widely diffused than
the typical form, which is not uncommon on the banks
of the Thames near London and seems to prefer watery
places, like Z. nitidus. Var. 2. Preston (Gilbertson) ;
Sevenoaks, Kent (Smith). This species is one of our

* Rather glossy.

164 HELICID^.

upper tertiary fossils. On the Continent it ranges from
Russia to the Pyrenees, and the variety nitens extends
also to Sicily.

It is a shy animal and delights in dark places, being
sometimes found underground at a depth of some inches
where the earth is loose. Its flesh is of a rather firm
consistency, and its slime is watery and abundant. It
does not emit any offensive smell.

The shell differs from that of Z. cellar ius in being
smaller, and in having one whorl less, the spire more
raised, and a much larger and deeper umbilicus. Its
surface is also much less glossy.

I cannot recognize anything more than a varietal
distinction between the Helix nitidula of Draparnaud and
the H, nitens of Michaud, which are regarded by Conti-
nental authors as different species. This last is not the
H. nitens of Gmelin or of Maton and Rackett. The
variety Helmii is H. nitens, var. albina, of Moquin-Tan-
don, which I have found near Lausanne.

4. Z. pu'rus *, Alder.

Helix pura, Aid. Cat. Northumb. Moll. p. 12. Z. purns, F. & H. iv.
p. 37, pi. cxxi. f. 5, 6.

Body yellowish-grey or whitish, with fine black specks and
close-set tubercles, slightly transparent : tentacles very long
and nearly cylindrical ; bulbs small : foot very narrow, slightly
pointed in front and rounded behind.

Shell compressed, rather more convex above than below,
very thin, not very glossy but somitransparent, light horn-
colour, with a yellow or reddish tinge on the upper side, ex-
quisitely sculptured transversely by numerous curved striae,
and spirally by still finer and almost microscopic lines, the
intersection of which gives the surface a reticulated appear-
ance : epidermis thin : vjhorls 4, convex, but dilated laterally,

* Clear.

ZONITES. 165

the last occupying scarcely one-half of the shell : spire slightly
raised : suture moderatel}' deep, puckered by the lines of
growth : mouth nearly round and not much interrupted by
the penultimate whorl : outer lip not very oblique : umbilicus
rather narrow, but deep, disclosing all the internal spire.
L. 0-075. B. 0-15.

Var. margaritacea. Shell pearl-white and nearly trans-
parent.

Habitat : Among dead leaves and moss in woods
throughout the greater part, if not the whole, of Great
Britain from the Moray Firth district to Cornwall, as
well as in Ireland, but more local and less common than
the last species. The variety is equally diffused. This
species is one of our upper tertiary fossils. Gerstfeldt,
as well as Middendorff, has recorded its occurrence in
East and West Siberia; and other writers have given
Scandinavian, German, French, and Swiss localities for
it. I found it in tolerable plenty at Alexisbad and else-
where in the Lower Harz and also near Lausanne.

Its habits are almost subterranean, and in other re-
spects resemble those of Z. nitiduJus, with which it is
often found, and from which it differs in its much smaller
size, the delicate form and sculpture of its shell, and the
umbilicus not being so large in proportion. According
to L. PfeifFer, it is the Helix Hammonis of Strom, which
was found at Trondjhem and published in 1765; but
Miiller has referred it to Z. nitidus. Judging from the
description and figure given by Gould (in the ' Inverte-
brata of Massachusetts,^ p. 183, f. Ill) of his Helioc
electrina, I cannot agree with L. Pfeiffer in considering
that species identical with the present, either as regards
form or sculpture; and the habits of each species are
quite different.

166 HELICID^.

5. Z. radia'tulus*, Alder.

Helix radiatula, Aid. Cat. Northumb. Moll. p. 13. Z. radiatulus, F. & H.
iv. p. 38, pi. cxxi, f. 1 .

Body dark horncoloiir : tentacles nearly black, the upper
ones very slender and the lower pair short : foot exceedingly
narrow, pointed behind, its sides marked \^dth minute black
specks.

Shell compressed, equally convex on both sides, very thin,
remarkably glossy, semitransparent, dark horncolour, distinctly
and beautifully marked across the whorls on the upper side by
strong curved and close-set striae which reach the suture, the
under side being also marked, but less distinctly, by similar
striae : epidermis thin : vjhorJs 41, convex, and very little di-
lated laterally, the last occupying rather less than one-half of
the shell : sjnre slightly raised : suture moderately deep : mouth
nearly round, sometimes thickened inside by a broad but slight
white rib : outer lip scarcely oblique : umbilicus narrow, but
rather deep, disclosing all the internal spire. L. 0*075. B. 0*15.

Var. viridescenti-alha. Shell greenish-white.

Habitat : Under stones, logs of wood, dead leaves,
and moss in woods, from the Moray Firth district to
Dorset. The variety is from Shropshire, Co. Cork, and
Co. Tyrone (J.G.J.) ; Belfast (Thompson). This species
is one of our upper tertiary fossils. Malm has recorded
it as a Swedish shell, Scholtz as Silesian, Moquin-Tan-
don and others from different parts of France, Stabile
from Lugano, and myself from the Lower Harz and
Switzerland.

This little moUusk is less shy and inactive than Z.
purus, and usually frequents moister places. It re-
sembles that species in the size and form of the shell ;
but the peculiar sculpture, more glossy appearance, and
narrower umbilicus of the present species will easily
serve to distinguish it from Z. purus.

* Slightly rayed.

ZONITES. 167

It is the Helix nitidula, var. P, of Draparnaud, as well
as the H. nitidosa of Ferussac and H. str'iatula of Gray ;
but both these latter names were nnaccompanied by de-
scriptions. The H. striatula of Linne, Miiller^ and Olivi
are different from that of Dr. Gray and from each other.

6. Z. ni'tidus*^ Miiller.

Helix nitida, Miill. Yerm. Hist. pt. ii. p. 32. Z. nitidus, F. & H. iv. p. 39,
pi. cxx. f. 4, 7.

Body strongly truncate in front, bluish-black or dark-
brown, covered with large round flat tubercles which are in-
terspersed with a few minute milk-white specks : snout small,
short, broad, and tumid ; tentacles rather thick and short ;
bulbs globular: foot obtusely rounded in front, narrow and
somewhat keeled behind.

Shell semiglobular, much more convex above than below,
not very thin, but glossy and semitransparent, chocolate-
brown, marked transversely by numerous curved striae which
are stronger and puckered towards the suture, and very finely
granulated under the microscope : epidermis rather thin :
whorls 5, convex, the last occupying about one-half of the
shell : spire somewhat prominent, with a blunt point : suture
deep : mouth round, except where the penultimate whorl con-
tracts it : outer lip rather obliquely set, thin, and reflected near
the pillar : lonbilicus narrow, but deep, exposing all the interior
of the sphe. L. 0*1. B. 0-275.

Var. alhida. Shell white or colourless.

Habitat : Under loose stones and decayed wood, as
well as at the roots of grass and on mud in bogs and
moist places, from the North of Scotland to Guernsey.
Specimens of the variety were found by Mr. Choules
among the rejectamenta of the Thames at Richmond.
Although dead shells, they have not become bleached
by exposure to the sun. A monstrosity also sometimes
occurs, in which the whorls are slightly disunited, as in

* Glossy.

168 HELICID.E.

Z, alliarius. This species is one of our upper tertiary
fossils. Its foreign range extends from the North of
Russia to Corsica and Algeria, through all the inter-
mediate countries.

Nothing appears to be known as to the habits of this
snail, except that it is, like its congeners, of an inactive
or sluggish nature and that it forms a slight epiphragm
during the heat of summer.

The shell differs from that of Z. radiatulus (which it
somewhat resembles) in its much larger size, more pro-
minent spire, the last whorl not being so large in propor-
tion, and the striae being very much slighter.

Gmelin made one of his usual blunders in changing
the name which Miiller gave this species to nitens ; and
Draparnaud, apparently without any reason, substituted
in his ' Histoire ^ a new name [lucida) for the correct
one which he had pre\iously given in his ' Tableau.^

7. Z. ExcAVATus*, Bean.

Helix excavata, Bean, in Alder's Cat. North. Moll. p. 13. Z. excavatus,
F. & H. iv. p. 40, pi. cxxi. f. 2-4.

Body lead-coloured (Alder).

Shell compressed, more convex on the upper than the
lower side, glossy, semitransparent, light-brown or tawny,
strongly and deeply striate in the line of growth : epidermis
rather thin : ivhorls 5^, convex and nearly cylindrical, the last
occupying not much more than one-thu'd of the shell : sjoire
slightly prominent : suture very deep : 7noutJi round, except
where it is interrupted by the penultimate whorl, somewhat
compressed below : outer lip as in the last species : umbilicus
broad and deep, exposing all the internal spire. L. 0*085.
B. 0-225.

Var. vitrina. Shell greenish-white, transparent. Helix vi-
trina, Fer. Tabl. Syst. p. 45. If. viriduJa, Menke, Syn. Moll.
p. 20.

* Hollowed -out.

ZONITES. 169

Habitat : Under fallen trees and among dead leaves
and moss in sliady woods. The tract of country over
which it is diffused comprises the South and South-west
of Scotland, North of England, West and South of
Ireland, North and South Wales, Isle of Wight, and
Cornwall ; but it is a local species. The variety is from
South Wales, Cork, and Connemara.

This species has been considered peculiar to Great
Britain, and to be the only land-shell which does not
inhabit any other part of the world ; but I have reason to
believe that the greenish- white variety is the Helix vi-
trina of Ferussac, as well as the H. viridula of Menke, H.
petronella of Charpentier, and probably also the H. clara
of Held. In the ^ Malakozoologische Blatter ^ for 1858
will be found a critical dissertation by Von Wallenberg on
the Helix viridula of Menke compared with Z. purus, in
which the author showed that these were quite different
species ; and I can answer for the identity of Z. exca-
vatus var. vitrina (or viridula) with the H. petronella of
Charpentier, having found specimens of the latter on the
Corner glacier in Switzerland at a height of about 7000
feet above the sea-level, and afterwards compared them
with the types in Charpentier^s collect