“esnygrns

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RVARD UNIVERSITY.

MOLLUSKS,

62a y
Vincent Brooks Imr

aay

A PLAIN AND EASY ACCOUNT OF

THE LAND AND FRESH-WATER
MOLLUSKS

OF GREAT BRITAIN;

CONTAINING DESCRIPTIONS, FIGURES, AND A FAMILIAR ACCOUNT
OF THE HABITS OF EACH SPECIES.

BY

RALPH TATE, F.GS,, F.AS.L.,

EX-SECRETARY AND HONORARY CORRESPONDING MEMBER OF THE BELFAST
FIELD CLUB; LATE LECTURER ON NATURAL SCIENCE UNDER THE
COMMITTEE OF LECTURES, DUBLIN.

LONDON:
ROBERT HARDWICKE, 192, PICCADILLY, W.
1866.

cOxX AND WYMAN,
GRIENTAL, CLASSICAL, AND GENERAL PRINTERS,
GREAT QUEEN STREET, W.C.

PREFACE,

LUGS and Snails! What interest can there
be in such slimy, crawling things, from
which we turn away in disgust? Yet these
humble creatures are far from uninteresting to
those who devote a little leisure to their exami-
nation. Many of our leading Naturalists ac-
quired a taste for the pursuits of natural history,
when but youths, in collecting and studying
them.

We are only familiar with the common species
of Snails, and the natural history of the majority
of them is imperfectly known to us. There is
here, then, a field of research open to lovers of
nature.

In order to render this little volume instruc-
tive and interesting, as well to the general
reader as to the young student, a familiar

v1 PREFACE.

account has been given of the habits of each
well-known species of our Land and Fluviatile
Mollusca; and whilst the scientific character of
the work has been uniformly sustained, all
unnecessary complexities have been carefully
avoided.

The classification adopted is that which is
employed by modern Zoologists. The specific
terms are those that have been long familiar to
home Naturalists. A few changes, however,
have been introduced, consisting in the restora-
tion of the older and equally well-known names.

The generic name Helicella is substituted for
that of Zontes, the latter name having been
generally, but erroneously, used in place of the

former.

CONTENTS,

CHAPTER I.

INTRODUCTION ; OBJECT AND NATURE OF ZOOLOGICAL
CLASSIFICATION ; CLASSES OF THE MOLLUSCOUS

PAGE

ANIMALS . : : - : s : : 1
CHAPTER II.

BIVALVES :—
I. STRUCTURE AND PHYSIOLOGY OF THE CONCHIFERA 10
II. DESCRIPTION OF SPECIES . ; ‘ ; « 20
FAMILY MYTILIDZ . : : 5 : Bane,
»» UNIONID# (FRESH-WATER MUSSELS) . 25
- CYCLADIDE . : f F x oe ee

CHAPTER III.

WATER-BREATHING SNAILS . : ; : 7 34
I. STRUCTURE AND PHYSIOLOGY OF THE GASTERO-
PODA Bae) ae fs 2 5 : P é 44

Vill CONTENTS.

II. DESCRIPTION OF THE SPECIES . :
FAMILY PALUDINIDZ (MARSH SNAILS)
>» NERITIDE . ;

5 LITTORINIDZ : :

CHAPTER IV.

AIR-BREATHING SNAILS. 5
FAMILY LIMACID (SLUGS) .

» ONCIDIADA _. ;

» HELICIDA (LAND SNAILS)

» AURICULIDE . :

» LIMNZIDH (WATER SNAILS)
OPERCULATED LAND SNAILS

PAGE

53
53
60
62

65
66
89
92
Lay
18]
220

MOLLUSKS.

CH AVP TA ot
INTRODUCTION.

OBJECT AND NATURE OF ZOOLOGICAL CLASSIFICATION.
—CLASSES OF THE MOLLUSCOUS ANIMALS.

NIMALS differ very much from one another
not only in their form, size, and habits,

but also in their internal structure; and we in-
tuitively group them according to their resem-
blances and differences, and give to each group
a certain distinctive or characteristic name.
From childhood our minds have been engaged,
consciously or unconsciously, in the observation
of natural objects, noting their shapes and
qualities, and rudely comparing and _ classi-
fymg them. The differences of internal struc-
ture have led naturalists to divide the animal
kingdom into five divisions, each division being
distinguished by some striking peculiarity of

B 2

2 LAND AND FRESH-WATER MOLLUSKS.

structure, the animals comprised in each being
constructed upon a plan differmg from that of
any of the other divisions. These primary
groups, which are called sub-kingdoms, are as
follows :—

1. Back-boned animals, termed Vertebrata,
exemplified in beasts, birds, reptiles, and fishes.

2. Jointed animals, termed Annulosa; as in-
sects, crabs, worms, &c.

3. Soft-bodied animals, termed Mollusca; as
the common garden snail, the oyster, and cuttle-
fish.

4, Hollow-intestined animals, termed Cclen-
terata ; as the sea-anemone, the coral polype.

5. Jelly animals, termed Protozoa ; as infusory
animalcules and the sponge.

The creatures living in our land and fresh-
water shells, which form the subject of the
present volume, belong to the group of soft-
bodied animals, to which the term Mollusca
is applied. They have, as the name implies, soft
and fleshy bodies, not divided into segments,
without bones or jointed limbs, enveloped in a
muscular coat called the mantle, and the shell
with which they are commonly protected is
composed of either one or two, rarely more,
pieces: the bodies of some are naked. The
cuttle-fish and slug are examples which will

INTRODUCTION. 3

give a general notion of the naked forms. The
shelled species are familiar to us. The nervous
system of the molluscous animals presents very
marked peculiarities: in the back-boned and
jointed animals, the principal mass of the nervous
system, comprising the brain and spinal column,
forms a continuous trunk throughout the length
of the body, from which the nerves branch off at
determinate points; whereas in the soft-bodied
animals, the nervous system is composed of two
or more pairs of brain-like masses scattered
throughout the body, and united by cords of
nerve-substance, which also send off nerves to
the several parts of the body.

The sub-kingdom Mollusca admits of a very
ready division into minor groups or classes.
Thus we have cuttle-fishes, sea snails, land
snails, bivalves, &c. In the language of the
naturalist, the cuttle-fishes are the Cephalopoda,
or head-footed mollusks; the sea snails are the
Gasteropoda, or belly-footed mollusks; the land
snails somewhat resemble the sea snails, but
breathe air instead of water, and are hence
termed Pulmonifera; the bivalves, as the mussel
and oyster, are the Conchifera. There are four
other classes of the Mollusca, but which, to-
gether with the cuttle-fishes, do not come into
the scope of the present subject, because they
are all marine; so that all our land and fresh-

B 2

4, LAND AND FRESH-WATER MOLLUSKS.

water mollusks belong to the three classes,
Conchifera, Gasteropoda, and Pulmonifera.

The ordinary bivalves (Conchifera)—as . the
oyster, mussel, and cockle—are all aquatic
animals, and by far the greater number of them
live in the sea. They breathe by means of
two pairs of gills in the form of plates or lamine,
and hence are also called Lamellibranchiata ;
they are, moreover, destitute of any distinct’
head, and are inclosed in a shell, composed of
two pieces or valves.

The snail-like animals have a distinct head,
provided with eyes, horns or tentacles, and a
mouth armed with cutting jaws; the under side
of the body forms a single muscular foot, on
which the animal creeps. The body is usually
protected by a shell composed of one piece.
Among these. belly-footed animals some live in
the water, and breathe by means of gills,—these
are the true Gasteropoda; others live on the
land, as the snail and slug, and have the respi-
ratory organ in the form of a lung,—these are
comprised in the class Pulmonifera. Some,
indeed, inhabit our fresh waters ; but, unlike the
true fresh-water Gasteropods, they are compelled
to come to the surface to breathe the air, and are
not capable of suffering a long immersion in the
water.

To pursue the scheme of classification. Hach

INTRODUCTION. y

class contains orders, and the orders are sub-
divided into families; each family is subdivided
into genera, and each genus contains one or
more species. The animal kingdom is composed
of individuals; but among these there are a certain
number which have a close resemblance to each
other, and are recognizable by a character which
is constant and definite. Such groups of indi-
viduals constitute what naturalists call species.
In familiar language, we speak of these in such
general terms as the horse, the oyster, the garden
snail, &c.,—meaning no horse in particular, no
oyster, no garden snail in particular. Let us
examine this matter more closely. Let us collect
a number of snails from a garden; we see that
they form a natural group, for they are all
characterized by a yellowish-coloured shell, beau-
tifully banded with brown. This assemblage of
individuals with like characters we call ‘the
garden snail.” Let us generalize still further
and higher, and extend our sphere of collection
to the neighbouring wood. We now find that
there are other undoubted snails, but which
evidently form a group distinct from “ the
garden snail,’”’ for all their shells are of much
smaller size, and are clothed with hairs ; from
which latter character we may appropriately call
them “the hairy snail.”” Observe that we have
naturally spoken of these two groups under the

6 LAND AND FRESH-WATER MOLLUSKS.

common term “snail”—in Latin, helix. Now
the name employed to designate this assemblage
of species is the generic one. We distinguish
“the garden snail” by a further name, which is
the specific one, because it points out the species
or particular snail among the general assemblage
of snails. Thus the garden snail is known
among naturalists as Helix hortensis; that is,
Helix, a snail, and hortensis, of the garden.
The second species is Helix hispida, the hairy
or hispid snail.

A difficulty that meets us early in our exami-
nation of these animals, is the variation of form,
colour, and size among them. Now in the case
of the oyster, we are all familiar with the nu-
merous variety of shapes that the shell of this
mollusk presents, yet we do not fail to recognize
them as belonging to the mollusk in question.
In the case of less familiar species, the difficulty
increases ; and we must here try to form a series,
with the normal or usual form as a centre, so as
to include the extremes of variation. In most
cases this is practicable. In a few instances
varieties have been produced, which have be-
come fixed or permanent; that is to say, the pe-
culiarities which distinguish the variety have
been perpetuated or handed down from genera-
tion to generation.

The principal causes of variation in shells are

INTRODUCTION. y |

abundance or scarcity of food, differences of
habitat, &c. Thus, the shell of the large pond
snail, Limneea stagnalis, becomes more length-
ened, tapering, and thinner, when the animal
lives in running water, with only vegetable food
as a diet, than the shells of more favoured indi-
viduals inhabiting stagnant ponds, which fare
more sumptuously upon dead dogs and other
animals.

Classification is, then, an arrangement of all
beings according to a certain order, by means
_ of which objects are reunited into groups, recog-
nizable by determinate characters, which, in
their turn, are reunited into other groups of a
still more comprehensive character. We have
thus the ANIMAL KINGDom subdivided into sus-
KinGDoms; these sub-kingdoms are further sub-
divided into cLAssEs; and these classes, again,
Into ORDERS, FAMILIES, GENERA, and SPECIES.

“The practical utility of such a classification is
easily seen by comparing it with the address of
a letter. So it is with the naturalist, who by
his classifications arrives speedily to the groups
to which the animal belongs.’’*

If, for example, he wished to define a garden
snail, without resorting to such means, he would
be forced to compare his description with that of

* M. Milne-Edwards.

8 LAND AND FRESH-WATER MOLLUSKS.

_ 350,000 different animals. But if he says that
the garden snail is a molluscous animal of the
class Pulmonifera, of the family Helicide, of the
genus Helix,—by the first he excludes all the
vertebrated, annulated, coral-like, and jelly-like
animals from his comparison; by the second, he
excludes the bivalves, the water-breathing snails,
and cuttle-fishes; by the third, he distinguishes
the garden snail from the slugs, pond snails, and
the like; and having arrived at the genus to
which it belongs, a few distinguishing characters
in addition will enable him to determine the
species. F'urther,ifthe classification be based upon
natural and not upon artificial characters, then
it expresses the relationship of the species ; for
from the foregoing scheme of classification, it will
be observed that differences in structure in the
animals become less and less as we ascend in
the scale of subdivision. Thus, for example,
animals belonging to the same family, but of
different genera, differ less from each other than
animals belonging to different families.

The subject will be treated according to the
following plan :—

The characters of each class will be studied by
a full examination of the internal structures, as
well as of the external or shelly parts, of a typical
species of each. Technical terms, which we shall
be compelled to use in describing each species,,

INTRODUCTION. 9

will here be fully explained and illustrated.
The characters of the families and genera
will be first defined, giving their resem-
blances and differences, and then the species
contained in each genus will receive the lion’s
share of attention. Here we purpose to give a
short description of the animal and its shell, so
‘that we may be able to distinguish the species
from others, followed by an account of its habits,
where it may be sought for, and how the prize
may be secured ; in fact, all the incidents of its
short but interesting life history will be given.
Analytical tables, however, based on artificial
characters, to facilitate a ready determination of
the species and genera, will doubtless be found
useful.

10 LAND AND FRESH-WATER MOLLUSKS.

CHAPTER II.
BIVALVES (Conchifera).

[.—Srructure oF THE Parnters’ Mussen

(Unio pictorum).

\HE most common of the fresh-water bivalves
is the swan mussel, an ordinary tenant
of our rivers, streams, and ponds, lying half-
buried in the mud. We select, however, the
less widely distributed Painters’ Mussel, as a
type of the bivalves for study; because the
characters of the class are better exhibited by it
than by the swan mussel.

Let us first glance at the characters afforded
by the shelly covering. The shellis at once seen
to be composed of two pieces or valves; one is
applied to the left side of the body of the mussel,
and the other to the right: the valves are equal, and
the shell is therefore said to be equivalve. The
line along which the two valves are joined is the
hinge, and that part in its vicinity, because it
covers the back of the animal, is called the
dorsal region; that opposite to it, the ventral
region. The rounded margin is the anterior

BIVALVES. 11

margin (fig. 1); and the pointed, the posterior.
The prominent part of each valve near the hinge
is the wmbo, u, which, when it isin the middle, the
shell is said to be equilateral ; but in the painters’
mussel, we observe that the portion of the shell
lying in the front of the umbo is shorter than that
behind it, and the shell in this case is said to be
mequilateral. Behind the umbo is a ridge, com-
posed of a horny elastic substance, called the
ligament, 1, which is a mechanical contrivance by
which the valves are opened. The depressed
space in front of the umbo is the lunule. The
length of the shell is measured from the anterior
to the posterior side ; its breadth 1s the perpen-
dicular distance from the umbo to the front; its
thickness is the diameter through the closed
valves. Hxternally the valves are marked by
concentric lines of growth, which diverge from
the umbo, which is the point from which the
growth of the valve commences.

The shell is composed of layers of animal matter
impregnated with carbonate of lime, and con-
sists of three structures :—an outer horny layer,
called the epidermis, which does not contain calca-
reous salts; and which may be removed bysteeping
the shell in an acid solution, when the epidermis
alone remains. Under the microscope, it exhibits
a cellular structure in some parts, and a granular
in others. Beneath the horny layer is a stratum

12 LAND AND FRESH-WATER MOLLUSKS.

consisting of delicate prismatic cells of calcareous
matter, and an internal layer, which is shining and
pearly, and makes up nearly the whole thickness
of the shell. This latter, or nacreous layer, con-
sists of folded plates of carbonate of lime, which,
by refracting the light, give rise to that charac-
teristic pearly lustre of the interior: this por-
tion, when polished, forms ‘‘ mother-of-pearl.”
For the microscopic examination of the shell
structure, sections are necessary ; but in place of
these, thin edges of broken portions of the shell
may be employed. The shell grows partly by
addition to the margin and partly to the interior.
In the interior of the shell, the following
markings and parts are to be distinguished :—
The umbonal cavity corresponding to the umbo.
The hinge-line of the right valve presents a
prominence or tooth (Plate II., fig. 2) towards the
front, which fits into a depression between two
teeth in the left valve. On the posterior part of
the hinge-line of each valve is developed an
elongated tooth: these are said to be lateral;
but when they are situated beneath the umbo, as
in the fresh-water cyclas, they are termed cardi-
nal. On the inner surface of the valves are seen
two impressions or distinct pits, one near the
posterior (a, a’), and one near the anterior sides
in each valve, made by two strong muscles
extending internally from one valve to the other.

BIVALVES. He

These adductor muscular scars, as they are called,
are connected by a faintly impressed line following
the curvature, and near the front of the valve:
this is the impression left by the attachment of
the muscles of the mantle. Near to the ad-
ductor muscular scars, but a little further from
the edge of the shell, are situated the impressions
of the muscles that move the foot.

Figure 1 represents the right valve of the
shell removed soas to disclose the animal. Itis
necessary for all dissections to remove one of the
valves. This may be readily accomplished by
first killing the animal by hot water, when the
valves will gape open. Forcing them now wider
apart, the muscles which close the valves may be
then readily seen, as white cords, which must be
cut with a pair of scissors. The whole body of the
animal is covered bya thin fleshy envelope, termed
the mantle, which consists of two lobes, joined at
the back, but free in front. The disposition of
the lobes has been well compared to the “‘ covers
of a book when it is placed on its edge with the
back uppermost.” Hach lobe of the mantle
corresponds with a valve of the shell, and is at-
tached to it in front by a series of muscles, which
produce the mantle-line of impressions. The
mantle extends as a free portion beyond the
muscles to the edge of the shell, which portion is
much thickened, and secretes the shell. The lobes

14 LAND AND FRESH-WATER MOLLUSKS.

of the mantle are united near the posterior margin
and pierced by two orifices; the upper one is
called the anal opening (fig.1,v), the lower one the
branchial opening, 0.

The digestive organs.—The mouth (0) is a hori-
zontal opening situated anteriorly just above the
foot, between two pairs of soft flattened lips (¢);

Dorsal margin.

Posterior margin.
Anterior margin.

Ventral margin.

Fig. 1.
it is rather difficult to find, but may be discovered
by tracing the lips to their insertions, between
which the mouth is situated. The mouth opens
immediately into a stomach, which contains a
cylindrical jelly-like body, termed the crystalline
style, whose function is not known. The intestinal
canal is a narrow tube wound around a large liver,
and after passing through the heart, 1s continued
along the back to the vent (v), which is situated
near the anal orifice: the excremental matters
are carried away by the water which had passed
over the gills.

BIVALVES. Ss

The cweulatory apparatus consists of a heart
composed of two auricles and a ventricle, and
may be readily discovered, as it is situated in the
middle portion of the back of the animal, under
the hinge; its beatings, which are about six or
eight in a minute, are easily seen under the large
bag, or pericardium, containing the heart. The
heart continues to beat for a long time after the
valves have been opened. The blood of shell-
fish is white, or nearly colourless ; and so essential
is the red character of blood deemed by the
vulgar, that it appears to them little less than
an abuse of language to apply the term to the
nearly colourless fluid of the mussel; but it
possesses all the essential properties of blood,
flows in a similar circle of vessels, and answers
the same purposes in the system. The blood is
propelled by the contraction of the ventricle into
the arteries, and after supplying the waste of
the body, is collected as venous blood by the
veins from the capillary extremities; and after
becoming aérated in the gills, is received by the
gill-veis and conveyed as arterial blood to the
auricles ; from thence it passes into the ventricle,
to be again distributed through the whole system.

The respiratory organs are gills, consisting of
two membranous plates, attached to each lobe of
the mantle ; each plate consists of two folds of
its membrane, and is pierced by innumerable

16 LAND AND FRESH-WATER MOLLUSKS.

holes, which are beset with vibratile cilia ; by the

action of these extremely delicate filaments, a -

current of water is produced, setting im by the
branchial orifice (fig. 1, b), which is surrounded
by a fringe of sensitive tentacular organs, and
sweeping over the gills, it is propelled towards
the mouth (0), and passes out by the anal orifice
(v) : by this agency, the layer of water in con-
tact with the gills is thus renewed, and food is
also brought to the mouth.

These currents may be rendered distinct by

introducing some powdered indigo into a basin ©

of water containing a fresh-water mussel.

The branchial currents are most conveniently
exhibited by the Zebra mussel, possessing, as it
does, two prominent siphons (fig. 2). The in-

halent siphon is densely fringed, and if the pro- —

cesses be touched, the orifice closes, and the
siphon is at once retracted. When unmolested,
a current flows steadily into the one orifice, whilst
another current rises up from the other, as in-
dicated by the arrows.

The wonderful activity of the cilia is a most
striking spectacle ; a magnifying power of about

120 diameters is amply sufficient to obtain a —

general view of the movements. A small portion
of the gill must be carefully spread out on a
glass slide, with a little water, and covered by a
glass disk ; or the animalcule-cage may be con-

BIVALVES. Ly:

veniently used. A much higher magnifying
power is required to observe the movements of
each cilium.

The nervous system consists of three pairs of
white nervous centres, called ganglia, from which
the nerves radiate. Two ganglionic masses (the
cerebral) are situated on the sides of the mouth,
and are united to form a ring around the gullet ;
they are connected with two others (pedal) in the
foot, and with those (the branchial) placed a little
below the posterior adductor muscle near the
anal orifice. This distribution of the nervous
centres is eminently characteristic of the sub-
kinedom Mollusca.

Organs of Sense-—The organs of hearing are
two little sacs, situated on a pair of nerves
arising from the ganglia of the foot, and contain
a fluid in which is suspended a small calcareous
body or otolith. The organs of sight are in the
form of black dots, or ocelli, along the margin of
the mantle.

Muscular Organs.—The ventral portion of
the body is prolonged to form a fleshy tongue-
shaped foot (/), and has some analogy with the
Gasteropods: this locomotive organ is large,
flexible, and muscular, and capable of being
protruded beyond the shell. Change of position
is effected by the insertion of the foot beneath
the shell, and, by being employed as a lever, the

C

18 LAND AND FRESH-WATER MOLLUSKS.

shell is jerked forward; or the extremity of the
protruded foot is made a lever, and the animal
draws itself forward. By means of the same
organ, the animal can bury itself in the sand or
mud, in which it lives. The pedal muscles (p, y’)
retract the foot.

The adductor muscles (a, a’) are two in number,
they extend from one valve to the other, and
by their contraction the shell is closed; they are
hence named adductors. On their relaxation, or
if they be cut, the elasticity of the ligament
comes into play, and the valves are opened. The
term dimyary bivalves is applied to such, as the
Unio, with two adductor muscles; the monomyary

bivalves, as the oyster, have only one. The fresh-

water Conchifera are all dimyarian bivalves.
Reproduction. — Hach individual is male or
female. The impregnated eggs, of which 200,000
are computed to be produced by each indivi-
dual in the year, pass into the external folds of
the gills, which during the breeding season in
early spring are broad and thick: here they are
hatched, and the young remain for some time.
The embryos are very unlike the parent, and
have been described as parasites under the name
of Glochidium. They have a triangular shell
provided with serrated hooks, and have but one
adductor muscle, and a long slender byssal fila-
ment. In this condition they have been found

ee at eee a ee

hinted ae

BIVALVES. 19

attached to the tails of fish, floatmg wood, &c.
We see in this a provision for the dispersion of
these sedentary bivalves. Nothing is known of
the history of the embryo from this stage until
it assumes the form of the adult.

As the Swan Mussel (Anodon cygneus) may be
more within the reach of many of my readers, I
would inform them that it does not possess a dis-
tinct lunule nor inter-locking teeth, nor are the
muscular impressions so distinct; but in all other
respects it resembles Unio.

The Food of bivalves consists of infusoria,
diatoms, and vegetable matter, brought to the
mouth by the portion of the branchial current,
which is projected in that direction.

Collecting, Sc.—The majority of the Conchi-
fera live buried vertically in the mud: they may
be collected by dredging with a kind of perforated
tin saucepan, about six inches across, and fur-
nished with a hollow handle, so as to receive the
end of a stout walking-stick.

After making a scoop with the tin, it should
be shaken, keeping the mouth just above the
surface of the water, for fear of washing out any
of the shelly contents; by this means the mud
and fine sand pass out through the perforations
of the tin, and the shells and gravel are retained.
The large shells may be bagged, the smaller ones
placed in glass bottles or tin boxes. To prepare

c 2

20 LAND AND FRESH-WATER MOLLUSKS.

them for the cabinet, the shells should be first
cleaned with a brush, and after being immersed
in boiling water, the animals may be removed.
The interiors of the shells should be wiped dry,
and the valves closed, and tied with a moist tape
or cotton; they should now be allowed to dry
slowly, for if heated too much they are apt to
crack.

II.—DeEscripTION OF SPECIES.

Tue fresh-water bivalves of Great Britain are
comprised in the three families—Mytilide, Union-
ide, and Cycladide.

Famity Myritipz (MussEzs).

This family is typified by the common marine —
- mussel (Mytilus edulis) of our coasts, and is re-
presented in our fresh waters by

Drizssena PpotymMorPHA (the Zebra Mussel)
(Pl. IV., fig. 25).—This bivalve closely resem-
bles the common mussel ; the shell is equi-valve,
wedge-shaped, rounded behind ; the umbones
are placed at the anterior end; the valves are
sharply keeled in the middle. The principal
differences between this genus and Mytilus are
as follows:—In Mytilus the mantle is open, in
Driessena closed; in Mytilus the gills adhere
through their whole length, in Driessena the
extremities are free. In Driessena the anterior

BIVALVES. 21

adductor muscle is supported on a triangular
shelf below the beak.

The mantle of Driessena is united all round, with
the exception of three apertures (fig. 2)—one the
anal orifice, which is prolonged into a very small
tube; a second, the branchial orifice, furnished
with a prominent siphon or tube, which is fringed
on the inside.

The Zebra Mussel is an attached bivalve, like
its brethren of the sea; the foot (f) is very im-
perfectly developed, giving
place to a gland, which se-
cretes the material of the #
threads with which it attaches (“ZZ
itself to stones, timber, and
shells ; these threads are
termed the byssus (b); and pig, 9. —Driessena
the third opening in the united PART
mantle lobes is for the passage of these mooring
cables. The epidermis of the shell is yellowish-
brown, with undulating streaks, or zebra-like
markings of dark brown.

This mussel was first discovered by Pallas, in
the different rivers of Russia and also in the
Caspian Sea; and from the great variety of
forms presented by this species, he designated
it under the name Mytilus polymorphus. Van
Beneden, in 1835, showed it to differ from Mytilus,
and constituted for it the genus Driessena, de-

22 LAND AND FRESH-WATER MOLLUSKS.

rived from the name of M. Driessenus, an apothe-
cary of Mazeyk, from whom the former received
in the year 1822 a collection of these mussels
alive, from a canal near Maestricht. But as
early as 1824 Mr. J. de C. Sowerby called
attention to its occurrence in the Commercial
Docks on the Thames, where it was already
abundant, and used by anglers as a bait for
perch, whither it had been brought attached to
timber from Eastern Hurope.

The mode by which it has been introduced is

evidently by its being affixed to the logs of tim-

ber before they were stowed in the ship’s hold,
for it has been seen adhering to them before they

were unloaded, and not that it had attached itself —

to the ship’s bottom, and so been conveyed. The
former mode of transport is the more rational, as
the bivalve can survive a removal from the water
for several weeks, especially under such favour-
able conditions as prevail in the moist hold of a
ship.

In 18383 it was found in vast abundance in the
Clyde and Forth Canal, Glasgow; in 1834 it
appeared in the Union Canal, Edinburgh ; and in
1836 it was found in considerable numbers on
the piers of the bridge which crosses the Nen
at Fotheringay, in which locality it had been in-
troduced from Wisbeach, on timber, since 1828.
In 1837, the late Mr. Hugh Strickland found it

a

bo

BIVALVES. 3
completely established on the beds of gravel in
the river Avon, at Evesham, and also in the canal
between Warwick and Birmingham, and in the
canals near Wednesbury, in Staffordshire. He
remarked that, as its propagation was so aston-
ishingly rapid, it would become in a few years
one of our commonest British shells. This has
proved so true, that not only hasit found its way
throughout England, literally paving with its
shells the beds and sides of our navigable rivers
and canals, butit has even taken up its quarters
in the water-pipes of London, Manchester, &c.

The Zebra Mussel made its appearance in the
neighbourhood of Gloucester a few years after
the opening of the Gloucester and Berkeley Canal,
and has increased in numbers to such an extent,
that it may be said to lne the banks from the
edge of the water to a considerable depth,
throughout its entire length of sixteen miles. It
appears in every available inch of space, from
the water-line to the depth of fifteen or sixteen
feet, upon the dock walls at Gloucester.

It is very tenacious of life and exceedingly
prolific, provided the locality is favourable.

This mollusk is evidently sensible to light,
which it would usually avoid, as exemplified in
its occurrence in such prodigious numbers in
water-pipes. If when the animal is at rest, with
the shell partly open, an object is suddenly

24 LAND AND FRESH-WATER MOLLUSKS.

brought before it, the valves are at once closed,
or partially so. On being introduced into the
aquarium, it at once reconciles itself to its new
abode, mooring itself by its threads to the stones,
or the sides of the glass. Young individuals
are harder to please, exhibiting their dissatisfac-
tion by their peregrinations, makmg the circuit
of the aquarium before selecting a resting-place;
but on finding a suitable spot, they follow the
example of their seniors and secrete a byssus,
and there remain fixed for life.

The present species is now found in bait

every part of Hurope, in canals, tanks, running
streams, and rivers, attaching itself by its byssus
of strong threads to stones, the live shells of Ano-
don, and the dead ones of their own species, wood
piles, or brickwork. In docks it luxuriates be-

neath the floating timber; in canals it abounds —

beneath the shadow of bridges. It has not yet
- found its way into Ireland.

Extinct species of Driessena inhabited the
fresh waters of the Isle of Wight during the Upper

Hocene epoch. D. polymorpha is, however, ab-

sent from the newer Tertiaries of this country.

‘

T

/

y: at z.

Vincent Brooks, Imp

BIVALVES. 25

FRESH-WATER MUSSELS.

Famity UNIONID2.

THIs group contains several genera of exclu-
sively fresh-water habits. There are only two
European genera, which are also British,—Unio
and Anodon, characterized by their oblong shells,
the mantle-lobes free all round except at the
posterior side, where the edge is bearded. Ano-
don is distinguished from Unio by the absence of
teeth on the hinge-line; hence called edentulous.

The Unionide have all large shells; the animals
bury themselves vertically in the mud of rivers,
&c., the posterior side upwards. The exposed
portion of the shell is usually encrusted with a
calcareous deposit. The umbones, especially of
Unio, are generally much eroded by the acids dis-
solved in the water. Unios are the most ancient
of the fluviatile Mollusca. A Unio or Anodon
appears in the Old Red Sandstone of Kilkenny.
They characterize the fresh-water deposits of
the Purbeck, Hastings Sands, Weald Clay, and
Middle and Upper Hocene strata. A species,
U. littoralis, now living in the north of France
and Sicily, occurs in the fluviatile deposits at
Clacton, Ilford, and Cropthorn. JU. pictorum,

26 LAND AND FRESH-WATER MOLLUSKS.

U. tumidus, and Anodonta cygnea are found
with it.

Unio tumipus—(the swollen Fresh-water Mus-
sel) (Pl. IL., fig. 2)—(Unio, Lat., a pearl).—The
shell is about three inches long and one and
a half wide, oval, solid with a thick glossy dark
brown epidermis. The umbones are prominent ;
the lunule is lanceolate and narrow; the lga-
ment is short, thick, and prominent ; the anterior
side is rounded and regularly sloping towards
the front ; the posterior side wedge-shaped. The
interior is bluish-white or salmon-colour.

It inhabits canals and slow-running rivers with
a muddy bottom, burying itself in a vertical posi-
tion more than one-half of itslength. It extends
as far north as Yorkshire.

Unio prctorum—(the Painters’ Mussel) (Pl. IL.,
fig. 3).—The specific name originated in the use
of these shells for holding colours by Dutch
painters. The shell is less solid and of a more
oblong form, and necessarily of greater propor-
tionate width than that of U. twmidus. The
epidermis is thin and beautifully coloured, of a
shining greenish-yellow, banded with brown.
The length is about two or three inches. It is
associated with the last species.

Unio MARGARITIFERUS—(the Pearl or Black
Mussel) (Pl. IIL, fig. 15).—This species, also

BIVALVES. Wy

called Alasmodonta margaritifera, is markedly
distinct from the other species; in its superior
size, often five and a half inches long and two
and a half wide, and one thick,—it is thus pro-
portionately much longer and more compressed ;
in its strong and pitch-black epidermis, and in
the adult specimens by the posterior tooth being
obsolete. The umbones are extensively eroded,
and the valves are narrowed in the middle. It
loves to lurk among the gravel and small stones
- in the shallows of quick-flowing rivers or moun-
tain streams. lt is found inthe North of England,
North and South Wales ; near Ross, in the Wye;
Devonshire and Cornwall; in the rivers flowing
from the Scotch Highlands ; and in many of the
North and South Irish rivers.

It burrows its shell somewhat obliquely, a
small portion of which is thus only exposed. A
diligent search is required to find it, as by the
growth of confervee upon the little exposed por-
tion, it cannot easily be distinguished from
amongst the surrounding stones. 7

It is very susceptible to the action of light,
opening the valves on a hot sunny day; but if the
sun be overcast they remain closed. Country
boys wade for them, or take them by thrusting
the end of a long slender rod into the partially
open shell, which closes upon it, and the prize is
thus dragged to shore.

28 LAND AND FRESH-WATER MOLLUSKS. 5

The Pearl Mussel enjoys a reputation as one
of the few British bivalves which contain the
beautiful production whose name this species
bears. The other Unios and the Anodon occa-
sionally yield pearls, as also the marine mussel
(Mytilus edulis) and the oyster.

Pearls are of the same nature as the nacreous
layer of the shell, and are abnormal secretions
of the mantle, composed of alternate layers of
animal membrane and calcareous matter, de-
veloped around some foreign body,—a grain of
sand, a parasite, or an unfertilized ovum.

The great Linnzeus owed in part his elevation
to nobility to a discovery of causing this fresh-
water mussel to produce pearls at pleasure. This
was accomplished, it is conjectured, by boring
small holes through the shell and introducmg a
particle of sand, which would become a nucleus
round which a pearl would be developed; but
the artificial production of pearls had been long
known to the Chinese. The Avicula margariti-
fera of the Indian seas is the most famous for
pearls.

Pearls have been associated with the name of
Britain from the very earliest known times. Sue-
tonius gives as the reason for Ceesar’s expedition
into Britain, the search for pearls, which Pliny
seems to confirm, saying that Ceesar gave a breast-
plate covered with British pearls to Venus Genitrix,

BIVALVES. 29

and hung it in her temple at Rome; he further
adds that they (probably from Mytilus edulis)
were small and ill-coloured, and Tacitus says the
same; but the Venerable Bede, on the other
hand, states that the British pearls were excellent
and of all colours—reddish, pale violet, and
green. In an old translation of Boetius, by
Bellenden (1541), the following allusion is made
to British pearls :—“ In the horse mussillis are
generit perlis. Thir mussillis airlie in the
morning, when the lift is clear and temperate,
openis thair mouthis a little aboue the watter,
and maist gredelie swellis the dew of heaven,
and aftir the measure of the dew they swell,
they conceive and bredis the perle.”? Camden,
still later, in his ‘Britannica,’ speaks of the
shell-fish of the little river Irt, in Cumberland,
“that they, by a kind of irregular motion, take
in the dew and produce pearls.”

The Pearl Mussel was formerly an object of
considerable fisheries in our own country, as it
is now in some parts of Germany. So, also, the
common mussel, a pearl fishery of which con-
tinued to exist up to a very recent period at the
mouth of the river Conway, in North Wales.
A patent was also granted early in the present
century to fish for pearls at the mouth of the
river Irt, in Cumberland. Higher up both
rivers, however, the Unio has been at various

30 LAND AND FRESH-WATER MOLLUSKS.

times also fished to a great extent for the orna-
mental excretions to which it is subject. The
pearls from Mytilus edulis are very much in-
ferior in quality and size to those from the
Unio. Those of the Conway had great fame.
Extensive fisheries existed in the rivers of
Tyrone, Derry, Donegal, near Dundalk, near
Waterford, and in Kerry. In Scotland, the Tay
was the seat of a pearl fishery. “It is said,”
writes Captain Brown, ‘that the pearls sent
from thence to London from the year 1761 to
1764 were worth £10,000, and it is not uncom-
mon at the present day to find pearls in the
Teith and Tay worth from £1 to £2 sterling
each.” The var. Loissyi was formerly much
sought for in the Black River, Kirk Braddam,
Isle of Man, on account of its pearls.

Anopon cyengeus—(the Swan Mussel) (Pl. L.,
fie. 1)—attains a size considerably larger than
the Unios. The maximum size exceeds in length
eight and in breadth four and a half inches.
It is readily distinguished by its rather thin,
oval (truncated behind) shell, compressed in
the young, but becoming ventricose with age.
The epidermis is glossy, dull green, more or less
tinged with dusky, and slightly radiated; the
inside of the shell is bluish-white, pearly in young
and yellowish-white in old shells. The umbones

Plate IT.

: Vincent Brooks, Imp

1 i
x
‘
;
"
’
.
&
1
‘

{

i
tes }

.
pe hae '
(i ’ b
' .
‘
;
zi

; j i ’ ,

i ’ : : :

A CaN or

BIVALVES. ol

are very small and convex ; the lunule is indis-
tinct, and the hinge-line is without teeth.

The Swan Mussels live in lakes, ponds, canals,
and muddy rivers, and are found in suitable
localities throughout the kingdom.

Anodons vary very much, not only according
to locality, but in the same waters; some of the
numerous varieties should, it is thought, be more
justly regarded as species. In ponds where
there is plenty of food, and where the water is
nearly stagnant, they become of large size, with
ventricose thin shells, and are type forms ; whilst
in more rapid rivers, with pure clear water, with
very little decomposing animal or vegetable
matter, they are small and comparatively longer
than A. cygneus, with compressed thick shells,
and are the A. anatinus (Pl. IL., fig. 4) of some
authors; but all intermediate forms and sizes
may be observed.

The manner of locomotion is slow and regular,
leaving their tracks distinctly discernible in the
soft mud. At Bottesford, on the Trent, where
at high tides the water is salt, it is found in
great abundance.

Anodons are thrown up in quantities on the
shores of Lough Schur, co. Leitrim, where they
are eaten by the peasantry. Sliggaun is the
common name applied to the Swan Mussel in the
North of Ireland.

o2 LAND AND FRESH-WATER MOLLUSKS.

Anodons furnish a very favourite repast for
the herons, and crows feed upon them. Pennant
says, “that when the shell is too hard for their
bills, they will fly with it to a great height, drop
the shell on a rock, and pick out the meat when
the shell is fractured by the fall.”

This species is invested with a mite (Atag
ypsilophora), which is so tenacious of life that
they survive an immersion in boiling water.

Famity CyYcCLADID®.

The remaining British fluviatile bivalves be-
long to the family Cycladide, characterized by
the mantle-lobes being united at the posterior
side to form one or two prominent contractile
respiratory siphons. The foot is large and
tongue-like. The shells are small, thin, and sub-
‘orbicular ; the hinge-line with minute cardinal

Fig. 3.—Pisidium umnicum, with its foot and siphon protruded.

and lateral teeth, two cardinals, and a lateral on
each side, in the left valve; in the right, one
cardinal, and two laterals on each side.

BIVALVES. 33

The family contains two British genera, Cyclas
and Pisidium; the respiratory siphons are two
in number in Oyclas (PI. IIIL., fig. 17); there is
only one (fig. 3, s) in Pisidiwm, the branchial
and pedal orifices being confluent (b). The shells
of Pisidiwm are inequilateral, those of Cyclas
rounded, and more or less equilateral.

Genus CyYcLAs.

There are five British species of this genus,
the largest of which is

CycLas rivicota—(the River Cyclas) (Pl. II1.,
fig. 17).—The shell of this species is distin-
guished by its great size, its more oval form,
the strong concentric ridges on the shell, and
the prominent ligament. The oval equilateral
shell is ten lines in length, seven in width,
and five in thickness; the epidermis is thick, of
a glossy reddish or greenish-brown, with two
or three darker bands, strongly striated concen-
trically; the interior of the valves is whitish,
with a bluish or yellowish tinge.

This species burrows in the mud of canals
and slow-running rivers, in the southern and
midland counties of England: it is plentiful m
the docks and canals about London; it occurs in
the Thames, above Chelsea; in the Medway at
Maidstone; Kennet and Avon Canal, Wilts;
Severn, at Wainlode; Tewkesbury; Newent,

D

o+ LAND AND FRESH-WATER MOLLUSKS.

~

Berkeley, and Combe Hill Canals, Gloucester-
shire ; Oxford; Chester; York; Doneaster; &c.
lt is a species of the newer Tertiaries.

Cyctas cornzra—(the Horny Cyclas) (PI. III.,
fig. 18).—The shell of this species is not more
than half the size of the last, and more globular ;
its length about six lines, breadth four, and thick-
ness three and a half; equilateral, finely striated
concentrically, of a yellowish-brown colour, with
paler bands ; ligament indistinct externally.

It varies very considerably: there are three
well-known varieties.—1. var. jlavescens (PI. IIL.,
fig. 16), with a smaller and rounder shell, the
body and shell straw- or lemon-coloured. 2.
Which is probably the fry of C. cornea, with a
small, nearly globular shell. 3. Gibbous at the
beaks, but thin or compressed towards the edges.

Few pools, ditches, or streams throughout the
United Kingdom are without this very interesting
bivalve. In summer it is found among the con-
fervee floating near the surface of the water; in
winter it buries itself in the mud.

No aquarium can be considered at all complete
without this interesting animal, whose habits are
so much at variance with the popular notions re-
garding the way in which mussels, cockles, and
other bivalves pass their days. It crawls readily
by the aid of its long foot, or ascends the sides
of the glass, and, on reaching the surface, moors

a a el nn

BIVALVES. =F 35)

itself with the shell immersed and inverted, by
olutinous threads, which are spun by the foot, or
it may even be observed gliding along the surface
of the water in an inverted position. It is very
active, and climbs the submerged plants with
great facility, among which it is usually found ;
it can suspend itself by its glutinous threads,
which are of the nature of a byssus, as in the
Driessena and Mytilus.

It thrives well and breeds in confinement ;
the fry are hatched in the gills, are but few im
number (each gill containmg not more than
about six), and of different sizes, the largest va-
rying from one-eighth to one-fourth the length
of the parent.

The larve of a fluke (Amplhistoma subclava-
tum) have been found on the surface of the body
of this and other species of Cyclas, as also on
the coil-shells (Planorbis). It is a newer Ter-
tiary species.

Cycias pisipiorpes (Pl. IIT. ie 9) is a recent
addition to science; it was Hesnverid, in 1856,
in the Paddington Canal, near Kensal Green,
London. It has much the appearance of a large
Pisidium ; hence its specific name. ‘The adult
shells are six lines long, five wide, and four thick.
It is distinguished from OC. cornea by its subtri-
angular shell, which is somewhat produced behind

and shghtly wrinkled concentrically.
ee

36 LAND AND FRESH-WATER MOLLUSKS.

The same locality supplied, at the same time,
a species new to Britain,—

Cyctas ovatis—(the Oval Cyclas) (Pl. II1.,
fic. 10)—is a species intermediate in size and
form between C. rivicola and C. cornea. Aver-
age-sized specimens measure half an inch long,
a quarter of an inch thick, and three-eighths
wide. From C. rivicola it is distinguished by
its oblong shape, its pale-drab colour, and
fainter concentric striz, and more markedly by
its straight hinge-line. It has since been found
in the Surrey Canal, at Exmouth, and in Lan-
cashire. It occurs in marshes in the North
of France.

CycLas Lacustris—(the Capped Cyclas) (PI.
II1., fig. 12) —The shell of this species contrasts
strongly with those of the other Cyclads, in its
sub-rhombic form, much compressed, thin, of a
yellowish-white colour; in the prominent um-
bones, which are narrow, and projecting like
little caps, from which latter character it has also
received the specific name calyculata.

The shell is small, delicate, and shining, four
lines long, three wide, and one and a half thick.

From the extreme thinness and semitranspa-
rency of the shell, the young, the lamellated
gills, and the pulsating heart may be easily seen
within.

C. lacustris has much the same habits as C.

BIVALVES. Bie

cornea, but exhibits greater activity than it
does.

We quote a writer in the Zoologist, who gives
in a few words the performances of this bivalve
in confinement.

““When I first put them (C. lacustris) into water
they immediately began to climb the sides of the
glass. One of them also commenced crawling
on the under surface of the water. Its foot was
now spread out very widely, and while preparing
for its exploit, it was apparently kept near the
surface by a minute thread fastened to the sides
of the glass. When it had left the side, its foot
appeared to be depressed in the middle, so as to
act as a kind of boat. I shook the tumbler, so
as to fill the little vessel with water ; but to my
surprise it sunk, not suddenly but gradually, as if
it were lowering itself by a thread attached to
the surface of the water. ‘They also appeared to
give out a quantity of glutinous matter wherever
they went, so much, that in about half an hour
seven or eight were entangled and tied together
by each other’s trailing threads.”

The capped Cycle inhabits ponds, canals,
ditches, and lakes in the South and centre of
England, becoming rare in the North; it is ab-
sent in Scotland, and is rare and local in Ireland,
having been observed only near Dublin, Dundalk,
Youghal, and Cork.

38 LAND AND FRESH-WATER MOLLUSKS. |

Genus Pisipium.

This genus is separated from Cyclas to receive
the smaller species, which have inequilateral
shells, and have only one siphonal tube; the
incurrent aperture being confluent with that for
the passage of the foot (see fig. 3, p. 32). They
have much the same habits as Cyclas, and live
in similar situations. It is very difficult to dis-
tinguish the species from each other, which,
therefore, necessitates detailed descriptions of
each. The largest and one easily recognized is—

Pisipium amMNnicum — (inhabiting rivers) (PI.
III., fig. 11)—The shell is triangular, deeply
grooved concentrically, of a whitish-grey or pale
brown ; umbones very little produced ; four lines
long, one and a half thick, and three wide. It
usually buries itself in the mud, but climbs by
the aid of its long flexible foot among the aquatic
plants. Itis common, and universally distributed
over Great Britain and Europe. It is fossilized
in the newer Tertiaries.

Pisipium CINEREUM (PI. IV., fig. 21) approaches
the last, as regards size, more than any of the
other species. Shell greyish, with one or two
broad bands, more compressed and oval than the
others of the genus, finely striated; umbones
obtuse and prominent, sometimes slightly capped,

BIVALYVES. 39

like Cyclas lacustris. Length three lines, thick-
ness one and a half, and width two and a half.
In ditches and slow streams widely diffused.

Pisipium putcHEeLLum (PI. IV., fig. 24) is the
smallest of the genus, differs from the last im
size, and is of a less triangular form. The
shell is only one and a half lines long and wide,
half a line thick, of a glossy white, sometimes
greyish, finely and irregularly striated.

This handsome and well-marked species well
merits its specific name (pulchellus, small and
beautiful) ; it is universally distributed. It in-
habits stagnant and running water, and at the
same time and place may be found on submerged
plants, and buried in the mud. It occurs in the
newer Tertiaries.

Professor Macgillivray made the following
observations on individuals of this species found
in a ditch near Aberdeen :—‘ When advancing
in the water, the animal opens its valves a little,
places itself erect by means of the foot, which
it gradually protrudes until it extends to a length
and a half of the shell, but often to twice its
length. When thus extended it is of a linear-
oblong form, very little flattened, narrowed but
rounder at the end. It then contracts, and
drags the shell quickly forward; after which it
is again extended, and again contracts. It is
not always stretched out in a direct line, but is

AQ LAND AND FRESH-WATER MOLLUSKS.

moved in an undulating manner, often from side
to side, and appears to act as a tentaculum, as
well as an organ of motion. ‘The siphonal tube,
which is at the same time extended and kept so,
is short, cylindrical, truncate, and changes but
httle ; sometimes, however, it is nearly elliptical ;
it never extends beyond a sixth of the length of
the shell. A current is seen passing out of it,
and minute dark particles frequently escape. In
this manner the animal advances with consider-
able speed by jerks. At other times it ascends
to the surface, where it proceeds in the same
manner, with the shell reversed. The animal
can advance equally with the shell inclined to
either side; it can creep in any direction, on a
level or inclined surface, and ascend or descend a
perpendicular plane. On opening an individual
in which young were seen, I found six lodged
there. They were very large, much compressed,
elliptical, with the umbones nearly central; the
colour white; the surface beautifully glossed,
and almost perfectly smooth. On being re-
moved and placed in the water, some of them
soon began to move in the same manner as
the adults, but with the shell inclined on one
side.”

Pisip1um HeEnstow1anum (Pl. IV., fig. 19),
named after Professor Henslow, is very closely
allied to the last, which may be a variety of this,

BIVALVES. Al

but easily known by the plate-like projection on
seach valve near the umbones. .

_ It occurs in several localities in England and
in South Wales; the only Irish locality recorded
is Finnoe, co. Tipperary. It occurs in the
newer Tertiaries.

PisipiIum nitipum—(the Shining Pisidium)
(Pl. IV., fig. 22).—Shell suborbicular, very
shining, finely and regularly striated, with a few
separate and deeper grooves around the obtuse
and subcentral umbones. Length one-twelfth of
an inch, width one-fifth less. The most obvious
distinctive characters are its rounded outline,
glossy and iridescent appearance, the strong
concentric grooves on the umbonal region, which
are more readily seen in young shells, and
the funnel-shaped siphon with its plaited outer
margin.

It is somewhat generally distributed in lakes,
ponds, and pools. Mr. J. Thompson found it
abundantly in a cold turfy deposit conveyed by
a mountain stream to a pond near Belfast, and
on Utricularia vulgaris, growimg in stagnant
pools. These places are of a very different
nature, the pond at the former being supplied
with clear spring water, and at an elevation of
600 feet above the sea; the latter but a few
feet above it, and supplied only with rain-
water.

42, LAND AND FRESH-WATER MOLLUSKS.

Pisip1um pusittuM—(the Dwarf Pisidium) (PI.
IV., fig. 23).—The yellowish-white shell is oval,
less compressed than the last, very finely but irre-
gularly striated ; the umbones nearly central ; the
posterior a very little more produced than the
rounder anterior side. It is the least inequi-
lateral of the Pisidia. It is the most common of
the genus ; is universally distributed throughout
the country, inhabiting ponds, drains, ditches, &e.
It does not apparently require a constant supply
of water, being often found in marshy spots in
company with and adhering to the same stones
as the land mollusca inhabiting such places.
Mr. Thompson procured it in the North and
South of Ireland, among moss which was kept
moist only by the spray of waterfalls. It is found
in the newer Tertiary deposits.

Pisrp1uM oBTUSALE (PI. IV., fig. 20).—The shell
of this species is closely allied to that of P.pusillum ~
in its blunt, nearly central umbones, but is smaller
and much more ventricose; the umbones are
rather prominent and very blunt. It is one of
the rarest of the genus, but occurs throughout
Great Britain. Mr. J. Jones took it in immense
numbers from a shallow pond on the hill above
Mitcheldean, in the direction of the Wilderness,
of which it appeared to be the only molluscous
inhabitant.

Corbicula consobrina, closely allied to the

BIVALVES. 43

Cyclads, inhabits the river Nile, and ranges from
thence to Cashmere. It tenanted the estuaries
and creeks of Central Europe during the Pleis-
tocene period. It is associated, at Brammerton
and Balcham, with extinct species of Rhinoceros,
Hippopotamus, Mastodon, and Elephants. It is
also found fossilized with living species of Cyclas
and Pisidiwm, in the Pleistocene fresh-water
marls, at Stutton, Grays, Ilford, and Erith.

4A, LAND AND FRESH-WATER MOLLUSKS.

CHAPTER III.

WATER-BREATHING SNAILS.
(Gasteropoda.)

I.—StTRUCTURE AND PHYSIOLOGY OF THE
GASTEROPODA.

HE Gasteropods include sea-snails, as the
whelk, limpet, &c., and a few fresh-water
snails, as the common marsh snail (Paludina
vivipara), which may be studied as a type of the
latter.

Shell. — All the fresh-water snails live in a
single or univalve shell, having the form of a more
or less conical spiral ; it may be regarded as a tube
wound upon itself, eachturn
of which is called a whorl
or volution (a), fig. 4; the
lines of junction of the
whorls are called sutures
(b); by the close coiling of
the whorls, a pillar of shell,
or columella (c), in the

Fig. 4.—Secti f the shell .
oN inde, . .. centre, is left, andeaamem

shells are said to be imperforated ; the axis of the
shell, around which the whorls are coiled, is

UNIVALVES. AD5

sometimes open or umbilicated: this perforation
may be a mere chink (d), or it may be filled by a
shelly deposit in the adult, as in many land
shells. The last turn of the shell or body whorl
is usually large. The base of the shell is the end
opposite to the apex (e); and the aperture is
entire (f), that is, not notched or produced into
a canal. The margin of the aperture is called the
peristome, which in Paludina is continued all
round; in the Rock Snail it becomes so in the
adult; more frequently, among the shells of the
next class, the peristome is incomplete, the left
side of the aperture being formed by the body
whorl; the right side of the aperture is formed
by the outer lip, the left side by the «ner, or
columella lip. The outer lip is thin, not thick-
ened or reflected, as in the majority of the land
shells; but in immature shells of them it is
always thin and sharp. The aperture of the shell
is upon the right-hand side, when the shell is
viewed in a vertical position, with the aperture
directed toward you: this is the general rule,
but in a few of the shells of the air-breathing
snails the shell is twisted in the opposite direc-
tion: in the former case the shell is said to be
deatral, and in the latter, reversed or sinistral.
Lines of colour or sculpture are termed spiral or
longitudinal when they proceed from the apex
around the whorls; radiating,if they extend across

46 LAND AND FRESH-WATER MOLLUSKS.

the whorls; and transverse when they coincide
with the lines of growth. The shell is secreted
by the mantle, and consists of layers of mem-
brane strengthened by calcareous matter, and
does not exhibit such an amount of diversity as
that of the bivalve shells. The colours which
are diffused over the shell are due to the secre-
tion from the mantle, of pigments, which are
impregnated chiefly in the epidermal matter.
The aperture of the shell is accurately closed by
a horny plate attached to the back of the foot, and
is called the operculum (q); it is calcareous in some
other snails. As regards its mode of growth, it
is concentric, that is, increasing equally all round ;
in the genus Valvata it is spiral, growimg only
on one edge, and revolving as it grows.
Animal.—The body of the animal is enclosed
in the mantle, which is open in front, and through
which the head and foot project; the abdomen,
containing the mass of the viscera, is wound
upon itself in the form of the shell. The mantle in
its natural position covers the back and forms a
large fold or cavity, on the left side of which lie
the gills, and into which the terminations of the
digestive, reproductive, and urinary organs open.
When the snail (see fig. 5) is protruded from
its shell, the following parts may be seen :—
The Foot, by which it makes its way in the
world, is avery broad, flat, expanded disk, and is

UNIVALVES. AZ

in close contact with the ventral region of the
body; from which circumstance the class has

Fig. 5.—Paludina vivipara (Woodward).

procured the name “ Gasteropoda,” or “ belly-
footed.” This organ consists of a mass of inter-
woven muscular fibres, and progression is due
to the alternate action of a set of muscles on
each side.

The Head is prolonged into a muzzle, at the»
extremity of which is the mouth; from the
extension of the foot in front, the animal can
only feed when at rest. The head bears two
long and slender tentacles or horns with the
stalks bearing the eyes attached to them on
the outside. The tentacles are extended to the
utmost, and are gently swayed to and fro when
the snail walks: by means of them the animal
feels its way, and is warned of danger. An ap-
pendage may be observed on each side of the
head arising from the tentacles ; that on the nght
side is the largest. The operculum is situated
on the hinder part of the foot.

48 LAND AND FRESH-WATER MOLLUSKS.

Digestive Organs.—The mouth is armed with an
upper horny jaw, and adherent within the cavity
is a horny muscular tongue, which is a mechani-
cal organ for the attrition of the food. This lin-
gual ribbon or tongue (fig. 6, c), as it is termed
(often, but erroneously, pallet), is covered by
more or less regular quadrangular plates, carry-
ing erect amber-coloured and glossy teeth of
extreme tenuity, which are directed backward.
This tongue acts im concert with the horny
jaw (a), the one holding and the other rasping
the vegetable food into the mouth.

As the lingual ribbon is such a pretty and
interesting object for examination with the
microscope, and as it plays so important a part
in the economy of all snails and slugs, land,
fresh-water, and marine; and also because the
teeth vary in number, in arrangement, and in
ornamentation in the different genera and spe-
cies, I will now give a method of preparation,
and will also point out, in its proper place, the
value in a systematic arrangement of the species
of these objects. 3

The tongue forms the floor of the mouth, and
the front part, which
is the only part in use,
is frequently curved or
bent quite over, and its
. teeth are often broken
Me ode cima «and blunted ; the -aaamem

UNIVALVES. AQ

portion descends obliquely behind the mouth,
and its edges are united to form a tube (c), and
enclosed in a membranous sheath, which opens
gradually as the part is brought forward to
replace the worn portion.

The most simple plan to prepare these as
microscopic objects is to boil the head of the
mollusk in a solution of potash in a test-tube,
by which all the parts, with the exception of the
tongue and jaw, are dissolved : care must be taken
to thoroughly wash the tongue before mounting.

The most instructive method is doubtlessly that
of dissection; but certainly, when we have some
of our minute snails to deal with, that of mace-
ration will be a great saving of time and patience.
The head should be pinned down in a gcutta-
percha trough containing water enough to cover
the part; the floor of the mouth may be laid
open by passing the lower point of a pair of
scissors into the mouth, and cutting upwards ;
now pin back the severed portions, and by the
aid of a lancet or needle, work out the lingual
apparatus. The ribbon should be cleaned by
washing with a camel’s hair brush, or by soaking
in potash-water; if the latter, wash the tongue
well before mounting. The preparation may be
mounted in glycerine, or if mtended as an object
for the polariscope, it should be mounted in
Canada balsam.

50 LAND AND FRESH-WATER MOLLUSKS.

The length of the lingual ribbon is short in
Paludina, but is of varying length for different
species; in the marine limpet it is longer than
the whole animal. The teeth are distributed im
straight longitudinal rows, and in transverse
rows, which are variously curved, angular, or
rarely straight. The number of the teeth in the
transverse row is nearly constant for the same
species, and the number of rows is exceedingly
variable in different species ; longitudinally the
teeth are usually arranged im a triple series, and
each transverse row is but a repetition of the
rest. The central area is called the rachis, and
the teeth form usually a single series ; the lateral
' areas are called the plewre, the teeth on which
are termed wncini, and usually are extremely
numerous. The term laterals is employed in a
restricted sense to designate a series of teeth
intermediate between the rachidian and the
Uncint.

The lingual ribbon of Paludina vwipara con-

Fig. 7.—Teeth of Puludina vivipara (Leven).

sists of a few transverse rows, each composed of

UNIVALVES. oe

a central oval tooth (a), slightly hooked and
denticulated ; and three nearly similar wncini
(b, c, d), which are oblong and toothed on the
upper sides: the number of teeth in each trans-
verse row is therefore seven.

The number and arrangement of the teeth are
capable of easy representation by a numerical
formula. Thus, 3.1. 3 represents the system
in Paludina, signifying that each transverse row
consists of one median or rachidian tooth, flanked
on each side by three wneini.

In Vitrina the general formula is «. 1. w;
where oo represents 37; and as there are 100
rows, the lingual teeth of Vitrina are 7,500; the
formula will now stand ***-87 — 7,500. In the
great slug, Limax maximus, there are 28,800
teeth, distributed in 160 rows of 180 teeth in
each. The number of teeth has no relation to
the size of the animal; thus, Helicella cellaria
possesses 1,330, while H. nitidula, less in size,
has nearly three times that number.

The above dental formula will be employed to
indicate the number of teeth im each generic
group or species, as the case may be.

The teeth of the fresh-water Gasteropods are
characterized by their fewness, whilst those of
air-breathing snails are remarkable for their
extraordinary number.

The digestive apparatus further consists of a
E2

5 LAND AND FRESH-WATER MOLLUSKS.

long gullet (fig. 6, b), an intestinal canal, folded
in the substance of the liver, bent to the right,
and terminating close to the margin of the
mantle in about the middle line of the body.
The liver occupies a very large part of the
abdomen.

The Circulatory System is somewhat more
perfect than in the bivalves.

The Respiration is aquatic; the organ is a
plume-like gill, formed of a series of triangular
plates attached to the left side of the branchial
cavity. The water passes into this chamber
through a respiratory siphon formed by the
folding of a small lappet of the neck.

The Nervous System is much the same as in
the bivalves. The eyes are two in number,
placed on short stalks attached to the conical
tentacles. The organs of hearing are situated
near the base of the tentacles, and are sacs
containing an otolith suspended in a fluid. The
sense of smell is possessed by Gasteropods, and
that of touch in a high degree; the tentacles
are endowed with great sensitiveness.

Reproduction. — The sexes are distinct in
Paludina ; the eggs are retained within the
oviduct of the parent until they are hatched,
and the young are not excluded until they
have attained a considerable growth. Palu-
dina is therefore ovoviviparous. The young

UNIVALVES. De

are at first exceedingly unlike the parent; they
are provided with a delicate nautilus-like shell,
and closed by an operculum ; on each side of the
head there extends a fin-like membrane, the
edges of which are fringed with cilia, by means
of which they swim within the contents of the
ego. In most of the oviparous snails, on the
rupture of the egg-cases, the young swim forth
with great activity by the action of the lobes,
and are dispersed far and wide.

Habits, Food, &c.—Paludina is a sluggish
animal; it feeds on vegetable matter, and pre-
fers nearly stagnant waters, or very slow-running
rivers with a bottom of soft mud; it buries
itself for weeks in the mud, and crawls up at
intervals.

II.—DeEscRIPTION OF THE SPECIES.

The fresh-water Gasteropods of Great Britain
are grouped in the families Paludinide, Litto-
rinidee, and Neritinide.

Famity Patupinipm (Marsh Shells).

This family contains a few genera of fresh-water
snails distributed in all parts of the world.
In Great Brita three generic groups occur:
Paludina, the type of the family; Bithinia,

54 LAND AND FRESH-WATER MOLLUSKS.

and Valvata. Paludina is_ ovoviviparous,
Bithinia and Valvata are oviparous; the oper-
-culum of Paludina and Valvata is horny, of
Bithinia shelly. Valvata is distinguished from
the others by the presence of a long plume-like
gill, which is partially protruded when the animal
is crawling, and by the more circular whorls
composing the shell.

The lingual ribbon of Paludimde is very
simple, and presents the same general features
throughout the family, and places it in close
proximity to the periwinkles and others com-
prised in the family Littorinide.

The general formula is 3.1.3; the number of
transverse rows is very limited.

Genus PALUDINA.

PALUDINA VIVIPARA—(the Common Marsh Shell)
(Pl. IV., fig. 26).—The specific name vivipara
was given to this species by Linnzus, from the
animal being ovoviviparous, that is to say, the
egos are retained within the interior of the
parent until they are hatched; it is a peculiarity
possessed by other species of the genus. As
the next species very closely resembles the.
present one, it will be necessary to give a full
description of it.

The shell is conically oval, rather solid, of
rather dull yellowish-green, with three broad

Plate LV.

p

tm

Vincent Brooks,

UNIVALVES. 55

brown spiral bands on the last whorl, and two
upon each of the two preceding whorls ; the
shell is also finely striated longitudinally ;
whorls six, rather convex, with a well-defined
suture; aperture oval, peristome continuous,
umbilicus represented by a narrow slit behind
the inner lip ; the operculum horny, rather thick.
Length an inch and a half, and one inch broad.
The body is a dark grey, or brown speckled
with yellow. The young shells are sometimes,
at least, clothed with a downy epidermis, rising
into short spies round the middle of each
whorl,—disappearing much on dying.

In the timber docks on the Thames, and in the
various canals about London, this species is very
abundant, and in fine condition. Following the
ramifications of our system of water-roads, the
species inhabits the Kent and Avon canals, the
canals of Gloucestershire, Staffordshire, &c. ; but
is by no means restricted to such habitats, for
it is found in many of the slow rivers in the
midland and southern counties of England. It
occurs in the river Ouse and Barnsley Canal, at
Wakefield, in Yorkshire, which are probably its
northern limits. Dead shells of this species and
of some southern forms are frequently introduced
with the ballast into localities where it is not
indigenous.

M. Joly, after keeping several individuals of

a6 LAND AND FRESH-WATER MOLLUSKS.

Paludina vivipara without food for three months,
submitted them in their enfeebled state to a
temperature of 25° F., and on dissolving their
icy prisons he found them all living. Hema
hke manner experimented with Anodon cygneus
with similar results.

Patupina Listeri (Pl. IV., fig. 27) differs from
P. vivipara in its shell beg thinner and shorter,
the whorls more inflated or swollen, and the
sutures consequently deeper, the mouth more
circular, and the umbilicus more distinct. It
is usually somewhat larger.

This species is generally associated with the
last, but is not of such frequent occurrence.

The shells of this species collected from a
pond on Hampstead Heath, London, have their
apices eroded, which is due to the action of sul-
phuretted hydrogen given off from the decom-
posing animal and vegetable matters.

The animal is very sluggish, and on being
touched generally falls off the body upon which ~
it may be crawling. The female in the autumn
contains from twenty to thirty eggs, and the
young are excluded at the end of two months.

Genus BIvrHINIA.

BITHINIA TENTACULATA—(the T'entacled Bithinia)
(Pl. III., fig. 14)—is a very common species on
aquatic plants in streams, ditches, and canals

UNIVALVES. ye

throughout Great Britain. The. shell is ovately
conical, of a yellowish horn-colour, smooth and
semi-transparent, very frequently incrusted witha
green confervoid growth. There are five or six
whorls, the last one large ; aperture oval, angular
behind, the shelly operculum closely fitting the
aperture, no umbilicus. Shell half-inch long,
three-tenths wide. The animal is_ blackish,
speckled with golden-yellow dots; the foot is lobed
in front, narrow and rounded behind; the ten-
tacles long and slender ; eyes black, large, and ses-
sile. Bouchard says that Bithinias deposit their
-- eggs on stones and aquatic plants; the female
lays from thirty to seventy eggs ina band of three
rows, cleaning the surface as she proceeds; the
young are hatched in three or four weeks, and
attain their full growth in the second year.

Brrumnta Leacui (Pl. III., fig. 18), named
after Dr. Leach, one of the earliest systematic
writers on English zoology. The shell of this
Species is much smaller than that of the last,
being about a quarter of an inch long and two
Imes broad; the whorls are more swollen and
rounded, distinctly separated by a deep suture ;
the aperture is nearly circular, and there is a
small umbilicus. It is found in the same habitats
as the last, but is local and less abundant, and
is confined more to the southern and middle
counties of England.

58 LAND AND FRESH-WATER MOLLUSKS.

It can live in slightly brackish waters under
tidal influence, as along the banks of the Thames
below London. Dr. Gray says that the eggs are
disposed on a tough strap-shaped green mem-
brane, in a double row, consisting of six or seven
pairs; the whole is, fixed to the under side of
aquatic plants.

GENUS VALVATA.

VALVATA PIscINALIs—(the Stream Valve-shell)
(P1.II., fig.5),so named from inhabiting fishponds.
The shell of this species is readily distinguished ;
it is globular, of four rounded well-defined whorls;
colour brownish-yellow, very finely ridged, in a
spiral direction; aperture circular, united all
round, with a thin greyish-white operculum ;
there is a deep central umbilicus. Length one-
fourth of an inch, and as much broad. ‘The
shell is very variable in the degree of elevation
of the spire, and consequently in its diameter
relatively to its height. The lngual ribbon of

; V. piscinalis is long ;

the central tooth (a,

ten ec fig. 8) is subquadrate,

with a produced base;

g hooked and denticu-
lated ; the three un-
cunt (b, c, b) are lan-
ceolate, and toothed on each side. A common

Fig. 8.—Teeth of V. piscinalis (Loven).

UNIVALVES. 59

and widely-distributed species, very abundant
on the bottoms of shallow muddy streams, on
marsh lands, or on aquatic plants in ditches and
canals.

Mr. Benson some years since favoured me
with what appeared to be a shell of this species ;
but, strange to say, it was the house of a South
American species of caddis-worm. The domicile
was a perfect imitation of the shell of our little
V. piscinalis, and of the same size. The mate-
rials of which it is constructed are not the less
singular. The spiral valvata-like tube was of
the ordinary secreted matter, to which were
affixed remarkably fine grains of sand; and for
an operculum the scale of a fish was ingeniously
appropriated.

Vatvata cristata—(the Crested Valve-shell)
(Pl. II., fig. 6)—is a minute species, living on
the aquatic vegetation of lakes, ponds, canals,
and ditches; and though it is widely diffused
throughout our islands, is by no means a
common species. The shell is flat, lke that
of a Planorbis, but easily distinguished from
it by the continuous margin of the aper-
ture, being circular, like that of V. piscinals,
for which it could never be mistaken ; for in all
stages of growth the shell of this species is flat
above, whereas that of V. piscinalis is more or
less globular. The shell is only one-tenth of an

60 LAND AND FRESH-WATER MOLLUSKS.

inch in diameter, and is of a pale horn-colour,
finely striated transversely, with three whorls.

The animal of this handsomely-formed species
(Pl. XI., fig. 143), like that of V. piscinalis, has
a plume-like gill, furnished with about fifteen
branches on each side, which is usually partially
protruded on the right side when the animal is
crawling; on the same side of the animal there
is an accessory respiratory organ, in the form of
a filament, arising from the mantle: in the pre-
sent species this appendage is rather shorter
than the tentacles, which it so much resembles ;
its position, however, will not allow us to re-
gard it as one.

Famity NERITIDS.
Gunus Neritina, diminutive of Nerita, a sea-snail.

NeRITINA FLUVIATILIS— (the River Neritine)
(Pl. IV., fig. 28)—is the only British repre-
sentative of the large family Neritide of tro-
pical seas and rivers, characterized by a thick
semiglobular shell. The species of Neritina
are more especially confined to rivers, and
have small globular shells, coloured by bands
or spots, and furnished with shelly opercula.
The pretty speckled species found abundantly
in many of the English rivers adhering to
stones and to other shells, is about three-

UNIVALVES. 61

eighths of an inch long, by a quarter broad,
composed of three whorls, the last one exces-
sively disproportionate; the spire very short,
and as if lateral. A polished brownish-green
horny epidermis covers the shell; in dead shells
the beautiful spots or bands of white purplish-
brown or pale brown are seen to perfection, for
in fresh shells this colourmg is much hidden by
the epidermis, but may be seen by the aid of a
macnifying-glass.

The species is common in all the larger rivers
where the bottom is stony, and in canals upon
stones. It does not occur in the north of Ire-
land, and is rare in Scotland, but is recorded
from Loch Stennis, in the Orkneys.

The animal is rarely to be seen in motion: it
crawls slowly, with the shell slightly raised; the
long, slender divergent tentacles, the large black
eyes, placed on short stalks at the base of the
tentacles, are then shown; the skin is covered
with stiff silky hairs. —

The lingual teeth (see fig. 9):—the central
tooth (a) is minute; the first lateral tooth is

Fig. 9.—Teeth of Neritina fluviatil:s (Loven).

62 LAND AND FRESH-WATER MOLLUSKS.

large, subtriangular, succeeded by two very
minute ones; the uncini are about sixty im
number ; the first one is very large, and of a
remarkable shape; the rest are very slender,
hooked, and denticulated.

Hach female deposits her egg-capsules in
clusters of fifty or sixty, on the surface of the
shell of her neighbour and not to her own;
sometimes, but rarely, to stones, or to the shells
of other mollusks. Hach capsule contains from
forty to sixty eggs, but only one embryo is de-
veloped ; for the other eggs constitute the food
of the young Neritina until it quits the capsule.
The capsules, which are usually mistaken for
the eggs, are globular, and consist of two sepa-
rable portions; the upper and larger falls off
when the young is about to escape; the lower
portion remains attached to the surface of the
foster-parent’s shell, the raised margins of which
produce small indentations.—Clapereéde.

The young appear in August and September,
and creep about on the shells or stones which
bore their egg-capsules, feeding on the micro-
scopic organisms, diatoms, alge, &c., which now
serve for its nourishment.

Famity LirroRinipzZ.

The three following species have little claim
to be regarded as fresh-water shells; the above

\

UNIVALVES. 63

family, to which they belong, contains the peri-
winkles and numerous other marine snails. The
family may be distinguished from the preceding
ones by the shell being spiral and conical, the
operculum spiral, and the eyes sessile at the
outer bases of the tentacles.

The genus Assrurnta (from the Latin assimilis,
very like) is represented by one British species,
Assiminia Grayana (PL. II., fig. 8), imhabiting
the banks of the river Thames between Green-
wich and Gravesend, living on the mud beneath
the shade afforded by Scirpus maritimus, Festuca
arundinacea, &c. It is very abundant.

The animal of <Assiminia differs from the
marine Fissoa, in the tentacles bemg united to
the eye-stalks, which equal them in length. The
shell of A. Grayana is ovate, acute, solid,
shining, of a liver-brown colour, and is about

Fig. 10.—Teeth of A. Grayana (Lovén).

a quarter of an inch in length; the whorls are
five in number; the suture is slightly im-
pressed ; there is no umbilicus; the aperture is
ovate ; the operculum is horny, ovate, and of a

64 LAND AND FRESH-WATER MOLLUSKS.

black-brown colour. The teeth are seven in
number; the central with a base produced
into’ a horn, with five to seven pointed lobes;
the first lateral tooth with seven lobes; the
second is slender, claw-like, and serrated; the
third is rounded at the tip, with minute denticu-
lations.—Loven.

In company with the last species are two other
brackish-water shells, belonging to the allied
genus Hyprosia, species of which are more par-
ticularly marine. Hydrobia differs from Assiminia
in having the eyes placed on tubercles, and from
Rissoa in its smooth shell.

The form of the shell of one species, HypRoBIA
stmiLis (Pl. I1., fig. 7), resembles that of Bithinia
Leachii, but is distinguished by its smaller size
and grooved suture; the operculum is horny,
concentric, with the nucleus lateral; whereas in
Bithinia it is somewhat shelly, and marked by
concentric ridges having the nucleus central.

A second species, HyDROBIA VENTROSA, iS
closely allied to H. ulve, whose habits are more
marine, from which it differs in being half the
size, with a deeper suture ; from H. similis in its
longer spire, and the absence of the channelled
suture, and by its much smaller umbilicus. This
latter species is very abundant on many parts of
our coasts, in estuaries and in brackish water, or
upon the mud banks of tidal rivers.

Co AP Bb ie We
AIR-BREATHING SNAILS.
Ciass PULMONIFERA.

HIS class embraces all the land snails, land.
slugs, and such of the water snails which
breathe air: they are closely related to Paludina,
and to the plant-eating sea snails. Their breathing
organ is the simplest form of lung, formed by
the folding of the mantle, over which the blood-
vessels are distributed, and occupies the same
position as the branchial chamber of Paludini,
&c. This chamber opens externally by a round
contractile aperture on the margin of the mantle
over the neck, on the right side. There is no
special mechanism of respiration. The functions
of both sexes are united in each individual. The
Pulmonifera vary much in appearance and habits.
The form and number of teeth on the lingual
ribbon afford good characters for the distinction
of genera and families, as also for the separation
of allied species. ‘The class is divided into two
orders,—Inoperculata, without an operculum, and
Operculata, possessing an operculum. |
E

66 LAND AND FRESH-WATER MOLLUSKS.

The Iyoprrcutata, or typical Pulmonifera, are
naturally divided into the slugs, land snails, and
water snails; and are embraced in the following
famihes :—

1 { Animal slug-like cea wines. Seas er
Ate » contained in a more or less spiral shell... 3
> § Mantle small, shield-like ... ... ... Limacide
“sity » enveloping the body... ... ... Oncidiade
. § Two pairs of retractile tentacles ... ... Felicide
” ) Tentacles two, eyes sessile ee
4 { Animal aquatic, aperture of shell edentulous, Limneide
‘ / Aperture of shell toothed ... ... ... Auriculide

Stues (Famity Limacipz).

Slugs are very conspicuous among the mollusca,
and readily recognized by their elongated, more
or less naked bodies. The body is united in its
whole length with the foot beneath; the head
is furnished with four cylindrical tentacles, and
eyes are situated on the upper pair. The slugs
resemble in many respects the snails, and are
regarded by the vulgar as such, which have the
peculiar power of leaving their shells during the
summer and retiring to them again for protection
on the approach of winter; so that, if this were
true, we ought only to find snails during one
season and slugs during another. But the snail
cannot leave its shell, being attached to it by
muscles. There are many points of difference

SLUGS. 67

between these two familiar animals. Firstly, one
afforded by the nature and position of the shell.
Observe the oval prominence on the back of that
large spotted slug (Limax maximus) ; this is the
mantle which in the snail forms a sack through
which the head and foot protrude, but in the
slug covers but a small part of the body. Be-
neath the shield-ike mantle hes a thin shelly
plate which protects the viscera. A snail may
be viewed in the light of a slug whose visceral
matter and mantle are elongated upwards,
and then spirally coiled, the mantle secreting
an external shell, instead of depositing shelly
matter from its mner surface. The shelly
plate of the slugs has been called the snail’s
stone, and was formerly esteemed a valuable
medicine in cases of gravel and strangury. This
internal shell varies in size, structure, and
position in the different species and genera, a
fact overlooked by Swammerdam ; for to account
for large slugs having “ very small membranous
plates, while the smaller ones had them often
much larger, and formed of solid stone,” he was
inclined to think “that the snails change this
their little stone yearly, in the same manner
as crawfish change those two semiconvex and
plain stones which are likewise placed in their
thorax, and are improperly called crab’s eyes.”’
Beneath the mantle on the right side of the
F2

68 LAND AND FRESH-WATER MOLLUSKS.

body is an aperture leading into the bie cai a
orifice.

The lingual ribbon of the slugs is characterized
by its numerous transverse rows, containing a
large number of very similar teeth; in general,
the central tooth has a long central point with
a small denticulation on each side of it; the
lateral teeth, as they approach the margin, be-
come spine-like, having but a long projecting
point.

All molluscous animals excrete a mucous fluid
to lubricate the skin, furnished by glands situated
in it; the slugs copiously exude this slime, more
especially when iritated. The “ silvery slimy
trails’? of slugs and snails are depositions of
mucus left in their tracks. Theslugs are divided
into four genera, characterized principally by the
relative positions of the mantle, shell, and respi-
ratory orifice. Thus in Arion the shell is repre-
sented by mere calcareous granules in the mantle ;
the respiratory orifice is near the fore part of
the shield; the body is truncated behind, and
terminated by a mucous gland. In Limaz the
shell is of the nature of a thin oblong, or slightly
concave plate, the mantle-shield marked with
concentric lines, and the respiratory orifice near
the hind part of the shield. Geomalacus has a
gland at the extremity of the tail ike Arion, the
- respiratory orifice nearer the front than in Limaa,

SLUGS. 69

and the internal shell claw-shaped. In Testacella

we have a near approach to the snails, and |

through Vitrina is connected with them; the
shell is small, ear-shaped, placed externally at
the hinder extremity of the body, and covers the
mantle, beneath which, on the right side, is the
respiratory orifice.

Genus ARION.

Arion was a horse remarkable for its speed,
but our Arion is remarkably slow.

Arion ATER—(the Black Slug) (P1.V., fig. 31)—
is familiar to all as a common object of our gar-
dens and waysides, and is also too well known to
the gardener, as being more or less injurious to
the early cabbages and other garden produce;
and in the autumn as one among other mollusks
_ that mutilate and render repulsive the fruits of
that season. Dead animal matter—even that
of their own species—does not come amiss to
them; they also feed on the common earth-

worm.

- The adult animal is usually brownish or
ereyish-black; at other times brown or red-
dish; the young individuals are grey, whitish,
bluish-white, or yellow-coloured. It attains a
leneth of from three to five inches. The shell
is composed of loosely aggregated calcareous
particles,

70 LAND AND FRESH-WATER MOLLUSKS.

Cuvier writes, that “the finest injections do
not produce anything more agreeable to the eye
of the anatomist than the white ramifications of
the arteries in the black slug.” The arteries
are opaque and milk-white, and strongly con-
trast with the dark grounds upon which they
trace their course; as, for example, the dark
green of the intestines, or the blackish-brown
of the liver. The heart is mcluded in a very
thin bag’, or pericardium, in the cavity of which
there is abundance of a watery fluid, as clear as
crystal.

Arion ater frequents damp and shady woods
and thickets, gardens, and hedge-banks; during
the day it is never seen abroad, except after rain,
retirmg under stones and logs of timber, or
burying itself in the earth; for the dry atmo-
sphere would deprive the body of its moisture,
so essential to the existence of the animal.

It deposits its globular, semi-transparent eggs
in May, among the roots of plants. This slug,
as also some other of the larger species, is
infested by a small yellowish-white mite,
Philodromus limacum of Jenyns, who has given
a very interesting account of the habits of the
little animal. The parasites may be seen running
in some numbers over the body of the slug. It
is curious that the slimy surface of the slug’s
back does not impede the progress of these .

SLUGS. ri’

mites ; but they seem never to be at rest, moving
with the greatest rapidity. <A striking feature
in the history of the little animal is that it
appears to take up its abode within the inte-
rior of the slug; effecting an entry by means
of the respiratory aperture, and coming forth
occasionally to ramble over the surface of the
body. The slug does not appear to suffer any
inconvenience from these parasites, and even
allows them to run in and out of the lateral
orifice without betraying the slightest symptoms
of irritation. Arion ater has a wide geographical
range.

ARION HORTENSIS—(the Garden Arion Sluq)
(Pl. V., fig. 29)—differs from the last species ;
it is much smaller and more slender, and is
provided with grey longitudinal stripes. The
foot is bordered with orange. The imperfect
shell is more compact than that of A. ater.

The horny jaw (fig. 11) is arched,
strongly ribbed, and its margin (SAMUS
crenulated ; it contrasts strongly 5. 41 ~ saw ot
with the smooth rostrated jaw of 4: hertensis.
Inmaz (see fig. 12).

Like the last species, it 1s common in woods,
damp ‘hedges, and gardens. The eggs of this
species are said to be phosphorescent for the
first fifteen days after they have been laid.

72 LAND AND FRESH-WATER MOLLUSKS.

Genus Limax (Limaz, a slug).

The Limaces differ little from the Arions, but
are destitute of a mucous pore at the end of the
tail; the mantle is concentrically marked and not
granulated, and the respiratory aperture near the
hind part of its border; the tail is carinated, or
ridged.

The horny jaw of Limaxz (fig. 12) is strongly

arched, smooth and rostrated in

Za 5 front; it differs markedly from that

palaakiynsy OF Arion, and resembles that of

L.gagates. HHelrcella (fig. 18) and Vitrina.

The species feed chiefly on tender herbage,
fruits, and vegetable substances in general; they
are very voracious, feeding after rain, or in the
evening to early morn; during the heat of the
day they remain concealed, and during droughts
and frosts they are torpid, buried underground.
They are the great pests of our gardens and
cultivated lands,—to young oats, peas, tares,
clover, and turnips, they give preference ; and
many fields have been made barren by them,
and have had to be ploughed down and resown.
Although vegetables are the legitimate food of
the slug, most of them are occasionally carni-
vorous, not from necessity, but from pure and
decisive choice; some of them may be even
convicted of cannibalism. They have, however,

Vincent Brooks ,Imp

SLUGS. fie

numerous enemies, especially among birds: the
principal of these are the blackbird and thrush,

whose notes
Nice finger’d Art must emulate in vain.

Ducks and geese are very partial to slugs.

The Limaces when irritated withdraw their
heads beneath the mantle; this attitude is also
assumed during repose.

Liwax maxtmus (PI. V., fig. 32), so called from
its being the largest of the slugs, attains the
length of five or six inches. ‘This large grey
slug is spotted and striped with black. The shell
is thin, flat, oblong, about six lines long and
four broad. The dental formula is *").

This species is widely distributed, is a frequent
visitor to our pantries and cellars, lurking in
damp corners, or remaining concealed in the
dust-bins, or other sheltered situations, during
the day ; foraging during the night, its peram-
bulations are rendered distinctly visible by its
trail, for the thick glutinous slime which is
copiously exuded becomes very iridescent when
dry. It is very omnivorous, preferring certainly,
as indicated by its attachment. to the dwellings
of man, the refuse from our kitchens and the
delicacies of our tables when within its reach.
lt is, however, frequent in moist woods, hyber-
nating in the mossy crevices of trees, or in

74. LAND AND FRESH-WATER MOLLUSKS.

decaying wood, or enveloping itself in dead
leaves in damp situations.

The eggs are white, and are deposited in a
cluster under stones in spring. Like Arion ater,
this Limae is infested with the slug-mite.

Limax riavus — (the Yellow Slug) (Pl. VI.
fig. 89).—This slug has a yellowish body, spotted
with blackish-brown, and with numerous undu-
lated or granulated ridges. ‘The dental formula
is £41.61, The shield is short, broadly rounded
behind, and marked with concentric granulated
wrinkles. The shell is thin, very like that of L.
maximus, but is smaller, about four lines long,
and two and a half broad. It differs from L.
maximus in having the end of the tail keeled,
and in its inferior size and different markings.
This large fleshy slug attains the length of four
or five inches.

Its slime is limpid and yellow, but when the
animal is irritated it secretes a thick bluish-white
mucus.

The species is gregarious and active, and is
commonly found in cellars and damp places in
our large towns. At nightfall it sallies forth
from its place of retreat to feast upon the
refuse lymg about; it cleans bones well, and is
fond of boiled potatoes and table delicacies :
they invariably retire to their quarters at the
approach of morning. When a candle-light is

SLUGS. Pigs

brought near them they shrink back, but for a
moment, and leisurely pursue their way; by the
aid of this light they are pretty objects in their
almost transparent flesh variegated with mark-
ings. It also occurs in damp places, beneath
stones, and among plants in woods.

I. flavus is one of the few European Pulmo-
nifera introduced to America; it occurs rarely in
Portland, Maine.

Limax acrustis—(the Field Slug) (PI. V., fig.
30).—The form is oblong, very convex above, the
shield large, broader behind, marked with concen-
tric lines ; the body on the upper side of a yellow-
ish-grey or pale brownish-yellow, often mottled
with dusky and whitish, with numerous longitu-
dinal interrupted ridges ; it varies considerably
in colour, being sometimes whitish or cream-
coloured, or grey or dusky; back with a short
keel, bent obliquely towards the end; the under
side pale grey, margined with yellow. Length
about an inch and a half; shell one line and a half
long and one broad, concave above, concen-
trically wrinkled, with a membranaceous margin.
The horny jaw is crescent-shaped, with blunt
ends; the exterior surface is marked with nume-
rous slight longitudinal ribs, which project over
_ the cutting edge; the dental formula is 22-22,
the central plate is longer than wide, carrying
a tooth as long as itself, shouldered at the base ;

76 LAND AND FRESH-WATER MOLLUSKS.

the laterals similar, but the apex not so central ;
the uncini are bidentated.

It is abundant, and generally distributed in
fields, gardens, and woods. In gardens it is a
serious pest; its ravages among crops, as oats,
peas, clover, and tares, are such as often to
necessitate the resowing of the land. We give
a recipe for a decoy for snails and slugs :—Warm
cabbage leaves until they are quite soft; suffuse
the hands slightly with unsalted greasy matter,
pass the leaves one by one between the hands,
so that some taint of grease may be transferred
to the leaf. Lay the leaves in the haunts of the
slugs, which will attract them to their destruc-
tion. A few ducks, however, will be found to
relieve one’s garden of these pests more effec-
tually than such agencies.

Timaz agrestis is unfortunately very prolific,
producing several families in the course of a
year; according to M. Bouchard, two indivi-
duals have been observed to lay no fewer than
380 eggs. A very subtle enemy is at work at
a very early period of the slug’s life; for M.
Laurent has found a fungus in the eggs, even
before they are excluded from the parent.

The field slug is somewhat carnivorous, and
cannibal-like inclined. When irritated, it emits
a thick milky slime, which, when dry, leaves a»
white film: the nature of this slime and the

SLUGS. TT

small size of the animal serve to distinguish this
species.

I. agrestis 1s common in fields, and abundant
in cellars and gardens in Portland, Maine; it is
indigenous to Greenland.

Limax Brunneus—(the Brown Slug) (Pl. VI.,
fig. 42)—This slug was added to the British
fauna by the late Dr. Johnston, of Berwick, who
observed that it differed from every variety of
Limae agrestis in its darker colour, its colourless
mucus, in the abrupt termination of the tail, in
the position of the shield, which is nearly central
when the animal is fully extended, and in the
size of the shield, which is as long as the pos-
terior half of the body; nor is there any keel
on this part.

It inhabits shady woods, in damp places, under
stones, and amongst decaying leaves; and is
comparatively rare in Berwickshire and in the
north-east of Hngland; at Thirsk, Yorkshire ;
woods between Cooper’s Hill and Birdlip, Glou-
cester (Jones).

Limax TENELLUS—(the Tender Slug) (PL V.,
fic. 34).—This species finds a place in the list
of British slugs in that a single specimen was
found in a wood at Allansford, in Northumber-
land. The animal is yellow, with the back
rounded, compressed near the tail; shield
wrinkled; mucus yellow.

18 LAND AND FRESH-WATER MOLLUSKS.

Limax arsorum—(the Tree Sluq) (Pl. V., fig.
33).—This arboreal species bears a consider-
able resemblance to the young of L. maximus,
from which it may be distinguished by the
upper tentacles being much shorter, in pro-
portion, than those of that species, and in
the less pointed hinder margin of the shield.
In colour it is greyish, spotted with yellow-
ish-white, with a central dusky stripe and a
darker band on each side. The back rounded,
carinated at the tail; the shield wrinkled, and
pointed behind; upper tentacles short. The
length of the body nearly three inches. The
shell is oval, thin, nearly flat.

This species is not well known, and its apparent.
rarity is due to its bemg mistaken for the young
of L. maximus. Its habitats are, however, not
those of that species. Jt lives on trees, especially
the beech, and those that are decaying, feeding
on the wood. It also may be found under stones,
and under fallen trunks in woods, or even upon
bare rocks. Like some other slugs, the young
descend from the branches of the trees by threads
of slime. This species has been met with through-
out Great Britain by several critical observers,
though generally absent from local lists of
species.

The capability of this species of letting itself
down from a height to the ground by the tenacity

SLUGS. 79

of the slime exuded from the body, is a feat that
most slugs can perform. Certainly the other
species, as L. agrestis, L. Sowerbii, &e., do not
appear to possess the same facility, and are more
reluctant in resorting to this expedient for
escaping from places they have no liking for ;
they, however, may be forced to use this means
for conveying themselves in safety to the ground
by leaving them on an evergreen or other tree
which may not be congenial to their tastes, when
they will speedily effect their escape im this
manner.

The thread spun by L. arborwm is not stouter
than a cobweb, and is of a uniform thickness,
except close to the body, where it is sensibly
thicker. The slug can climb up its suspended
thread; in doing which, the head is curved up-
wards and inwards until it touches the hinder
portion of the body; the animal then takes the
thread and advances with great facility.

It has been observed at Sandown, Isle of
Wight; Connor cliffs, Dingle; Nottingham, pre-
ferring walnut trees; Thirsk, at an elevation of
900 feet; Gloucestershire.

Limax Sowzrpiu—(the Keeled Slug) (Pl. V.,
fig. 35).—This and the following species are
readily distinguished among the Limaces, by
the back being keeled throughout its whole
length, and by the finely granulated shield.

50 LAND AND FRESH-WATER MOLLUSKS.

The colour of LZ. Sowerbii is yellowish, speckled
with brown; head and horns black ; shield as if
minutely warted with a furrow near its margin.
Shell oval, thickened, two or three lines long,
and one and a half to two broad.

Fig. 13.—Limux Sowerbii.

The keeled slug, when at its greatest exten-
sion, is about three inches in length; its graceful
and lanceolate figure, neat yellowish-brown hue,
and the amber-coloured keel, make it really not
such a disagreeable object for a slug. The
hinder portion of the body is much compressed ;
the shield measures three-quarters of an inch.
When touched, it withdraws the head under the
mantle, and contracts to about an inch anda
half in length, as in fig. 13. In drought they
exhibit greater contractedness, and the smaller
specimens when covered with particles of soil
and dust, resemble so many pellets of mould.
The keel is folded into transverse wrinkles on
the contraction of the animal. The dental for-

mula is #22,

SLUGS. 81

DL. Sowerbti is common in gardens and shady
places in the vicinity of most of the cities and
towns of the South; Sandown, Isle of Wight ;
Norwich ; Chester; becoming rare northwards.
In Ireland, Cork, Dublin, Youghal, and Gal-
way. It occurs in the South of France and in
Spain.

They feed on cabbages and other vegetables,
when in a more or less decayed condition, are
very destructive to the celery and bulbs under
ground. ‘They are foul feeders, and, like other
slugs, have a decided liking to animal matter,
devouring the dead remains of each other, and
not refusing carrion: they have been observed
feedmg on living smaller ones of their own
species.

They lay their eggs in clusters of about a
dozen, in the soil, towards. the end of the year.
The eggs are oval, soft, elastic, two-tenths of an
inch and more in breadth, transparent.

They are infested with Philodromus limacum.

Limax cacates—(the , Jet-black Slug) (Pl. VI.,
fie. 36)—1is a local species ; it is fountl in several
localities in Ireland ; plentiful near S. Shields ;
rare in the South of England; Sandown, Ishe of
Wight; Tenby; and the Isle of Cumbra, Clyde.
It resembles L. Sowerbii in the back being keeled
or carimated throughout, and in its granulated
shield; it differs from it in colour, and in the

G

82 LAND AND FRESH-WATER MOLLUSKS.

relative proportion of the shield and body. Its
general colour is lead-grey, tawny, dark red, or
even black, becoming paler towards the sides, and
near the margin of the foot almost white. The
shield, usually of a darker colour than the body,
is oblong, rounded behind, and somewhat trun-
cate in front, much larger than in L. Sowerbw.
The respiratory orifice is placed nearer the centre
than in that species. When at rest, the strongly
carinated back is beautifully arched ; it then as-
sumes a morerounded form than any other slug, its
height scarcely exceeding its length. It ismore
than two inches in length when in motion. The
slime is colourless, thick, and glutmous. The
egos are transparent and globular, and appear
to be deposited during the winter, or at the close
of the autumn. It is ashy and retiring species,
seldom venturing from its retreat in dusk or
during dull weather. Like the others of its race,
it 1s very pernicious and destructive to tender
plants.

LTimax gagates is a littoral animal; in Great
Britain it is attached to the neighbourhood of
the sea. On the continent, from the department
of Finisterre, in France, it follows the sea borders
of Morbihan, Charente-Inférieure, Gironde, &c.,
passes into Spain and Portugal, and appears on
the shores of the Mediterranean in many places
in Italy, Sicily, Algeria, Morocco, &e.

SLUGS. 83

Genus GEOMALACUS.

GHOMALACUS MACULOSUS—(the Spotted Irish Slug)
(Pl. VI., fig. 40)—-was discovered by Mr. W. An-
drews, in 1842, in co. Kerry. This interest-
ing slug-like mollusk is generically allied to
Arion, and is a remarkable link between it and
Inimax. It differs from both in the position of
the generative aperture ; its shell approaches to
that of Limaz, is solid, flat, unguiform ; the res-
piratory orifice is placed more anteriorly than in
Inimaz ; and it possesses a mucous gland at the
extremity of the tail. G.maculosus is an exceed-
ingly beautiful animal ; its length when creeping
is about two inches; the colour of the whole
upper surface is black, elegantly spotted with
yellow or white; the under surface of the foot
light-yellow, and divided into three nearly equal
bands; the margin of the foot is brown, trans-
versely furrowed. Dr. Allman describes it as
possessing a singular power of elongating itself
so as at times to assume the appearance of a
worm; by this means it can insinuate itself into
apertures which we could scarcely conceive it
possible for it to enter.

The haunts of Geomalacus are thus depicted
by its discoverer :—

“ Take Carogh lies to the south of Castlemain

G 2

— -B4 LAND AND FRESH-WATER MOLLUSKS.

Bay, in the county of Kerry, and stretches nearly
north and south five miles. The lake narrows at
its centre, where huge cliffs, principally of the
Old Red sandstone formation, rise precipitously
from the margin on either side. On the east side
are those of Oulough. The broad surfaces of the
rocks are beautifully pictured with a map-like
coating of Decide and Lecanore, and on those
rocks, within a limited circuit, and at a distance
of about 50 yards from the water, the Geomalaci,
on a misty or showery day, may be noticed quies-
cently stretched, their richly maculated character
being strikingly conspicuous. On the opposite
side is the romantic little glen of Limnavar, and
on similar rocks, at the same range from the
water, Geomalacus is again met with, particularly
the white variety, but more sparingly than at
Oulough. On no other rocks around the lake or
the country are they to be observed.”

It is peculiar to the locality given. An allied
species occurs in Portugal.

Genus TESTACELLA.

The above generic appellation is derived from
the diminutive of Testa, a shell or covering. The
distinctive characters of the genus have already
been given at p. 69.

TESTACELLA HALIOTIDEA—(the Har-shaped Testa-

SLUGS. 85

cella) (Pl. VI., fig. 38).—This slug is of a dirty
yellow colour, sometimes uniformly black, rarely
pale yellow; spotted with brownish specks, mixed’
with pale orange along the margin of the foot ;
and is furnished with a small roundish oval shell,
with a minute spire at the end of the tail (see
fig. 14), which covers the mantle. A lateral
furrow commences from near the tip of the shell
by a double wavy line on both sides of the body,
dividing the lateral portions of the animal in two
unequal parts, until it terminates near the head.
The surface of the body is granulated. This
slug exhibits, as it were, a third pair of ten-
tacles, by the protrusion of the corners of the
lip ; they resemble, but are scarcely so long as, the
pair of tentacles abovethem. See fig. 14, show-

Fig. 14.—Testucellu haiiotidea.

ing a front view of the head; the centre figure
represents the back view of a half-grown indi-
vidual; the other, a side view of the shell on the
tail; the respiratory orifice is also seen.

When crawling, the Testacella is about three
inches in length.

The shell is oval, ear-shaped, depressed,
rugous; striated in the lines of growth. Epi-

86 LAND AND FRESH-WATER MOLLUSKS.

dermis thin, readily peeling off; spire very short,
of one whorl and a half; suture rather deep ;
summit shining, nearly in the middle, not de-
tached from the columella. Aperture very large,
rounded and dilated in front; interior nacreous,
whitish, sometimes bluish. Shell one-quarter to
two-fifths of an inch in length.

This species is very variable in its form, as
regards the shell; sometimes nearly round,
quadrangular, oval, &c. The variety scutulum
differs essentially, in the shell being very acumi-
nated posteriorly. This form was established in
1823, on specimens obtained at Lambeth, Surrey.

This species is found in kitchen and market
gardens around London, Norwich, Gloucester,
Taunton, Bristol, and in several localities in
Devonshire, Tenby, and in the Channel Islands.
In Ireland it has been taken at Youghal and
Bandon. It alsoinhabits West Hurope, Madeira,
and the Canaries.

It is a highly curious animal, exclusively car-
nivorous, and is the dread of the earth-worm,
which it follows in its burrow. Its organization
is admirably adapted for its worm-hunting habits,
its slender attenuated body enabling it to pro-
gress through the loose and broken soil. The
worms are caught alive, and are swallowed whole,
being drawn into the mouth by the introversive
action of the tongue.

SLUGS. 87

Dr. Ball observes, “I first became aware of
this Testacella preymg on worms by putting
some of them in spirits, when they disgorged
more of these animals than I thought they could
possibly have contained: each worm was cut,
but not divided, at regular intervals. I after-
wards caught them in the act of swallowing
worms four and five times their own length.”

Testacella, and the other predaceous pulmo-
niferee (Daudebardia, Glandina, and Cylindrella),
do not possess horny jaws. The lingual ribbon
is very large and wide, composed of about fifty
transverse rows, which are oblique, and descend
towards the middle ; the teeth are conical, regu-

SSX SQA ; Mie: is LZ
SOW
SS DOOLLF

Fig. 15.—Part of the lingual ribbon of T. haliotidea.

V el

a

larly curved, barbed at the point, and having a
projection on the middle of the posterior side,
from which the remainder thickens; the teeth
diminish in size towards the centre; there are
51 in each row.

The animal, while engaged in laying its eggs,
about ten in number, draws the head and tenta-
cles in; the reproductive orifice is situated on

88 LAND AND FRESH-WATER MOLLUSKS.

the right side behind and near the upper ten-
tacle. The eggs are oval, inflated at the middle,
hard, and opaque, with a calcareous shell, and
resemble the eggs of some reptiles ; when placed
before a fire, or even exposed in a dry atmo-
sphere, they in a few minutes explode with a
loud crack. The mollusk lays its eggs, ten to
fifteen in number, in a subterranean gallery
during the months of May, June, and July; the
egos are isolated tone from the other, and are
not united in a mass, as in the true slugs; the
young Testucelles are excluded in from twenty-
five to thirty days. The food of the young slugs
consists of small worms, and the white, slender,
vermiform animals which live upon putrefying
vegetables. They do not grow so rapidly as the
Tnmaces. |
The Testacelle, though subterranean in
their habits, may be met with at the surface
during the autumnal months, and before day-
break in April; in winter, they bury from one
to two feet deep in the soil, and “ form a kind
of cocoon in the ground by the exudation of
= mucus. If, this celia
broken, the animal may be
seen completely shrouded in
its thin, opaque, white mantle
bine let (fig. 16, m), which rapidly
disturbed from its sleep. contracts until it extends but

Late V1.

Vincent Brooks, Imp.

SLUGS. 89

a little way beyond the margin of the shell (s).”
— Woodward.

Testacella appears to live five or six years.

Trstacetta Mavezt (PI. VL., fig. 37), a kindred
species, is a native of the South-west of Kurope,
and is confined to the coast; it was imported to
Bristol about the year 1830, where it is now
very plentiful, and has since been found at
Devizes. The slug is of a dark brown colour ;
its shell, which is represented in Pl. VL., fig. 37,
is larger and more cylindrical than that of T.
haliotidea.

FamInty ONCIDIADS.

The above group is allied to the true slugs,
and was founded to receive certain slug-like
animals destitute of any shell, and completely
covered by a leathery mantle. The species are
almost all inhabitants of tropical.countries, many
of them living on the sea-shores, others m
marshes and woods. The family is represented
by one British species—

Oncipium crLticum (Pl. VI.; fig. 41)—The
body is oblong, covered with short, thick, convex
tubercles; it possesses only one pair of retractile
horns, which bear the eyes. The dental formula

1s pele Sy
70

This species frequents the sea-shore, and

90 LAND AND FRESH-WATER MOLLUSKS.

though living in immediate contact with marine
conditions, is truly pulmoniferous ; it occurs on
the rocks at West Comb, in Lantivet Bay, be-
tween Polperro and Fowey, Cornwall, where it
was discovered by Mr. Couch. They congregate in
little groups about a foot or so from the margin
of the sea where the waves break over them,
ascending and descending so as to maintain
their distance as the tides fluctuate.

A few words more as to the methods by which
slugs may be preserved :—As regards the inter-
nal shell, it may be obtained by making a crucial
incision in the shield, taking care not to cut down
upon the calcareous plate, which can then be re-
moved without difficulty. The animals can only
be conserved by keeping them in some preserva-
tive fluid; but the great object to keep in view,
is to have the slug naturally extended. Most
fluids contract the slugs when they are immersed
in them. The slugs should be killed whilst
crawling, by plunging them into a solution of
corrosive sublimate, or into benzine. Models in
wax or dough are sometimes substituted for the
animals. A writer in the Naturalist gives a pro-
cess for the preservation of slugs, which he states
to answer admirably, and to be very superior to
spirit, glycerine, creosote, and other solutions :—
“ Make a cold saturated solution of corrosive sub-
limate ; put it into a deep wide-mouthed bottle ;

SLUGS. 91

then take the slug you wish to preserve, and let it
crawl on a long slip of card. When the tentacles
are fullyextended, plungeit suddenly into thesolu-
tion; in a few minutes it will die, with the ten-
tacles fully extended in the most life-like manner;
* so much so, indeed, that if taken out of the fluid
it would be difficult to say whether it be alive or
dead. The slugs thus prepared should not be
mounted in spirit, as it 1s apt to contract and dis-
colour them. A mixture of one and a half parts of
water and one part of glycerine I find to be the
best mounting fluid. It preserves the colour
beautifully, and its antiseptic qualities are unex-
ceptional. A good-sized test-tube answers better
than a bottle for putting them up, as it admits
of closer examination of the animal. The only
drawback to this process is, that unless the solu-
tion is of sufficient strength, and unless the ten-
tacles are extruded when the animal is immersed,
it generally, but not invariably, fails. Some slugs
appear to be more susceptible to the action of
the Huid than others; and it generally answers
better with full-grown than with young specimens.
But if successful, the specimens are as satisfac-
tory as could be desired; and, even if unsuccessful,
they are a great deal better than those preserved
in spirit ; for, although the tentacles may not be
completely extruded, they are more or less so.”

92 LAND AND FRESH-WATER MOLLUSKS.

Famity Huticipm (Land Snails).

The appellation of this wide-spread family of
the Land Snails is derived from Helix, a snail,
the typical genus of the group. The Helicide «
are provided with an external spirally-coiled
shell, capable of containing the entire animal.
The body is conformable with the shell, and is
distinct from the foot. The head of the snail is
short and retractile, furnished with two pairs of
cylindrical tentacles; the tentacles of the upper
pair are the longest, and bear the eyes at their
summits. |

The snail and slug have both the power of
drawing in their horns on bemg touched. We
shall now proceed to explain ‘‘ how this is done ;”
for the snail can be examined more conveniently.
On lifting our snail, the head and tentacles are
retracted ; but not doubting the efficacy of the
words of the old doggerel, we admonish the
snail “to come out of his hole.”? And we ob-
serve that the tentacle is lengthened by gradu-
ally unfolding itself, and not by being pushed
out from the base. Hach tentacle is a hollow
cylinder (see fig. 17), to the apex of which is
attached a muscle (g), arising from the retractor
muscle (m) of the foot, and by its contraction
the tentacle is simply inverted and retracted,

LAND SNAILS. 93

like the finger of a tight glove; its protrusion,
on the other hand, is effected by the alternate

LIL | i NG AN

Fig. ‘7.—Structure of the tentacles in Heliz,
a, b, c, d, Tentacles in different states of protrusion ; 7, brain mass;
f, h, nerves of tentacles ; g, muscle of tentacle; m, eye. (Owen.)

contraction of the circular bands of muscle
which compose the walls of the tentacle.

The mouth of the snail is armed with a horny
semicircular jaw, which, by pressing against the
floor of the mouth, cuts off the fragments of its
vegetable food. The jaw presents various forms
in the several species. The lingual ribbon com-
prises a central inconspicuous row, and two
lateral rows with numerous teeth. The teeth
differ from those of the slugs (Limacide), in
that the apices of the lateral teeth, as they ap-
proach the margin, bifurcate and become ser-
rated. However, those of Vitrina and Helicella
resemble those of Arion and Limaz.

Snails are vegetable-feeders, but some exhibit
carnivorous propensities, the objects preyed upon

94, LAND AND FRESH-WATER MOLLUSKS.

being worms and small beetles; yet, on the
other hand, the larvee and imago of many beetles
are the aggressors and not the victims. Snails
also furnish food to the thrush, blackbird, star-
ling, &c., the smaller species being swallowed
entire; of the larger kinds the shell is broken
on a stone, and the snail extracted. The do-
mestic fowl will also feed upon them.

The respiratory orifice 18 seen on the right
side, beneath the margin of the shell, when the
snail is in motion. The reproductive orifice, as
in the slugs, is situated near the base of the
right upper tentacle. The eggs of most of the
Helicide are globular in shape, and transparent
or opaque; some are enveloped in a hard cal-
careous shell. They are usually laid in the ©
summer, and vary in number from ten to one
hundred, according to the species, either isolated
or united together into a mass. The young
appear at the end of about fifteen to twenty
days, and attain about a third of their full size
before hybernating, and usually complete their
shell on their attaining their first year. The
Helices do not live to a venerable age, for the
majority of the species apparently do not sur-
vive the second winter.

Mr. E. J. Lowe communicated to the Royal
Society, in 1854, observations he made on the
growth of shells of land snails. The facts arrived

LAND SNAILS. 95

at were, that the shells of the Helicide increase
but little for a considerable period, never arriving
at maturity before the animal has once become
dormant. The shells do not grow whilst the
animal itself remains dormant, and the growth
is very rapid when it does take place. Most
species bury themselves in the ground to in-
crease the dimensions of the shells. In illus-
tration follows here one of his experiments :—
“A pair of Helix aspersa had deposited their eggs,
which began to hatch on the 20th of June;
these young ones grew but little during the
summer. ‘They buried themselves in the soil
on the 10th of October, coming again to the
surface on the 5th of April, not having grown
during the winter. In May they buried them-
selves with their heads downwards (in winter
they and other species buried themselves with
the head upwards), appearing again in a week
double the size. This process was carried on at
about fortnightly intervals until the 18th of July,
when they were almost fully grown.

“The process of growth within the ground
takes place with Helix nemoralis, H. virgata, and
H. hispida. But H.rotundataburrows into decayed
wood to increase the size of its shell; whilst
Helicella radiatula appears to remain on decaying
blades of grass; and Pupa wmbilicata, Clausilia
rugosa, and Bulimus obscurus bury their heads

96 LAND AND FRESH-WATER MOLLUSKS.

only to increase their shells. With respect to
Helicella cellaria, H. lucida, and H. nitidula, it
was not satisfactorily ascertained whether their
heads were buried during the process of growth.”
The habits of the British Helices vary with the
species; they are all terrestrial ; the majority of
them are denizens of woods and shady places,
climbing trees or rocks, or concealed among moss
and under stones ; others affect open heaths and
pastures ; a few are, as it were, domesticated ; and
Helix aspersa has the greatest claim for the title
of the “ Domesticated Snail ;”? some others live
on plants growing on the margins of pools, &e.
Independently of changes of temperature,
the land snails have the power of becoming
dormant at will. If asnail be deprived of food
by placing it in a box, it will attach itself by a
thin parchment-like secretion, or epiphragm, and
will remain, if undisturbed, in a torpid state for
a lengthened period. ‘There is an account of a
snail that thus lived without food for fifteen years.
The snail in such cases may be resuscitated by
plunging it into lukewarm water. In their
native haunts, they are found in this state of
inactivity during the summer season, when there
is continued drought, but on the first shower they
recover and move about in search of food. Such
as live in exposed situations necessarily become
inactive during the heat of the day, but are up

LAND SNAILS. 97

and doing soon after the dew begins to fall.
For these reasons a collector should remember,
**it is the early bird that catches the worm,” and
be on the alert after rain.

Cold acts much in the same respect as heat,
for in all temperate latitudes the majority of the
Helicidee hybernate ; they then form a more dense
epiphragm, and retreat farther into the interior of
the shell than during their daily repose; ina
few species the epiphragm is strengthened with
carbonate of lime. During this winter sleep the
animal functions are nearly suspended ; respira-
tion is still carried on, and airis admitted to the
animal by a minute perforation in the epiphragm
opposite the respiratory orifice.

Land shells are most abundant on limestone -
soils, which are most congenial to their existence
and perpetuation; and in explanation I would
observe: firstly, that the shell is composed almost
entirely of carbonate of lime; secondly, the
plants upon which the snail feeds are the sources
from whence the mineral matters are derived
thirdly, that plants affecting calcareous soils con-
tain proportionately a larger amount of salts than
_ those inhabiting clayey or sandy soils, and such
are therefore in greater request among mol-
luscan life; so also many species of horse-tails,
and grasses which contain a large percentage of
earthy salts, are much frequented by land snails.

H

98 LAND AND FRESH-WATER MOLLUSKS.

Many mollusks are found in every situation
and on every variety of soil, while others are to
be found only in particular habitats.

The geological pecuharity of a district influ-
ences the distribution of land shells much more
than geographical distribution. Thus, the
majority of the snails occur throughout the
length and breadth of Great Britain; of the
remainder, those that are peculiar to the South
of England flourish on soils derived from chalk
and oolitic limestones. And the fact that
a large portion of the life of the mollusk is
passed in a state of hybernation, when the influ-
ence of climatical peculiarity is scarcely felt,
accounts for the absence of any striking differ-
ence in the land molluscan fauna of the two
opposite extremities of our island.

The British species are collected with advan-
tage in the autumn, when they are full grown;
the winter rains destroy much of the original
beauty of the shells.

Land and fresh-water snails may be killed with
boiling water, and the animals may be removed ~
from their shells by the aid of a bent pin; Olau-—
silice, Helicelloe, &c., which retire too far to be
reached by this ordinary expedient, may be killed
by placing them in tepid water, and adding —
gradually hot water; the animals may then be ~
partially removed. The shells should be well

LAND SNAILS. 99

dried, to remove the moisture and harden the
soft parts remaining; but the heat must not be
too great, or else the shells will be discoloured,
and are liable to be broken. And, further, the
specimens should be wel! dried before placing
them in the cabinet, which should be in a well-
ventilated place, free from damp ; for their fresh-
ness and beauty are apt to be lost by the growth
of fungi upon their surfaces. |

The following synoptical table represents
the genera into which the family Helicide is
divided :—

Shell oval... .. . ... Succinea
1 hs globular or depressed, mouth transverse... 2
», more or less cylindrical, mouth longitudinal 4
2. Shell glassy, outer lip thin...

» notglassy, outer lip usually reflected ... Helix
3. phellimperforated “10.5, essen een oes ee
Prema eaGed 1.8 aa} tage eae sae ” Helicella
Setieraanormd. sistral 5 fe.) jane aces |. ee geeae EO
4. a turreted ee Btian, rt aeiey micah! Seek eat ert ea Og
PPPOE VURAL TIG AN 3.5 sik) ae! nisl af Boe ahahdiseadel coin &
Mate bionic)... no. BE ces by dae Nee iy eR
5, Aperture with a Saeco, Sus) pee ihm wae gael COL SLU
No clausium, aperture toothless ... ... ... Balea
6. Columella truncated in front... ... ... Achatina
Frontrentire 2.) 22. .-0. ee ee». Dulumus acutus
Shell dextral, animal ai four tentacles . Pupa

” sinistral or dextral, lower tentacles
SOE ede a ellis behead nce), RAkgO
8. rer scsi ase yd aa tee) aise! 'n'uad “pope ag oe
AVULE, ReM eCard eae Nacio. vave< tes)” ce ENUODEWS
9. Aperture fouthtewmm mes wwe: 6.0 Wy Gua Lua
mn denticulated ... 1. 1. we ee — -Arzcoen

H 2

100 LAND AND FRESH-WATER MOLLUSKS.

GrENus VITRINA.

The distinctive generic title is derived from
the Latin word vitrwm, glass. This generic
group isa connecting link between the Slugs and
the true Snails or Helices ; for it has the lingual
dentition and the shield-like mantle of Limaw and
the globular external shell of Helix. They appear

to be occasionally animal-feeders, like the slugs, —

a propensity equally possessed by some of the
Helices. Vitrina may be readily distinguished
from Helicella, by the absence of an umbilicus ;
for all the shells of species of the latter are per-
forated. The genus is represented in Britain by
only one species :—

VITRINA PELLUCIDA—(the Green Glassy Snail)
(Pl. VI., fig. 43).—The body of this snail is elon-
gated, too large to allow of the animal retracting
completely into the shell. The mantle is pro-
duced into a shield and reflected over the front
of the shell when the animal crawls, and furnished
with a tongue-like lobe on the right side; the
lingual teeth are like those of Limaza, of 100 rows
of 75 each, and the jaw resembles that of the
true slugs and cellar snails, in being strongly

arched from before backwards, produced into a

beak, smooth or nearly so.

The beautiful greenish-glassy shell of this

?

LAND SNAILS. 101

species is very thin, depressed and compressed,
composed of three whorls: the last one is large.
The aperture is oval, with a thinedge. There is
no umbilicus. The breadth is about one-fourth
of an inch, and the height one-twelfth and a half.
It varies in colour and shape. The green trans-
parency gives place to a white opacity in dead
shells that have been long exposed.

The little Vitrine are thorough gourmands ;
their appetite never fails them. ‘These litle
snails feed on mosses and fallen leaves; vege-
table substances in a state of decomposition
are preferred by them. But it must not be sup-
posed that they are exclusively vegetarians; on
the contrary, they are often carnivorous, and not
only satisfy their hunger with dead prey, but
even with living prey. The observations made
upon this little species by M. le Dr. Baudon are
very curious and interesting. He writes, in his
* Catalogue des Moll. de l’Oise,” 1862 : “I placed
@ great number of individuals under a bell-glass
with other mollusks, taking care to provide them
with rocks, leaves, and mosses, upon which they
lived. One of the Vitrines attacked and devoured
a Helicella cellaria ; two Zonites candidissimus,
killed by their bites, were devoured in two days.
a I then placed under the glass a piece of
raw mutton, of the size of a hazel-nut; five
minutes had not elapsed, when the Vitrines in the

102 LAND AND FRESH-WATER MOLLUSKS.

immediate vicinity quitted the leaves, which they
were then eating; . . . . from all quarters were
the Vitrines seen marching on, leaving the holes
where they had been reposing ..... it was a
general rendezvous. One that was feeding upon
the remains of Helicella cellaria abandoned its
victim to satisfy the craving of a newly acquired
taste. I remarked, at this moment, a veritable
expression in their tentacles; when the nervous
ganglion had received the odoriferous impression,
the horns were no longer swayed to and fro, but
steadily fixed on the object which attracted
them. It is believed that life is concentrated
in these delicate stalks. Animation has been
pointed out in the ear of certain beings of a
superior organization ; why may it not be found
to exist, though in a less degree, in the tentacle
of a snail,—principal seat of its physiognomy !
After its heavy meal, the Vitrine takes no
food for many days, and its activity is not so
great as when its aliment is vegetable.”

Vitrina pellucida is abundant in suitable local-
ities,—humidity is essential to it,—among moss
and decaying leaves in woods and glens; under
stones and herbage in meadows on the coast-line,
and to a great altitude in the mountain glens.
Shelter, it apparently needs none, further than
what is imperfectly provided for it by its own
comparatively small shell; for it may be seen

LAND SNAILS. 103

actively in motion at all times of the year, and
not more frequently at other seasons than during
the winter months. I, as well as many others,
have seen this hardy creature creeping upon the
snow.

Bouchard-Chautereaux, a French conchologist,
who made the habits of the land and fresh-water
snails of his country objects of especial study,
says that the eggs are not laid until towards the
close of the year, and that the young attain their
adult condition at the end of the eighth or tenth
month ; and he is of opinion that they do not live
longer than from twelve to fifteen months.

Genus Huriceria (diminutive of Helix, a Snail).

The shells of this genus are thin, shining, and
depressed (except in H. fulva) ; the peristome is
sharp and not reflected, and the aperture obliquely
crescent-shaped.

The animal of Helicella has an elongated ex-
tremely compressed foot, which extends far
behind ; the upper tentacles are long, the lower
ones short, all terminating in a knob. The
lingual dentition is somewhat intermediate be-
tween Vitrina and Heliz, and resembles Jimaz in
the long projecting single apex to the edge teeth ;
the teeth, however, are not so numerous (see

fig. 19). The jaw is, like that of Limaz, Vitrina,

104. LAND AND FRESH-WATER MOLLUSKS.

and Suecinea, smooth, with a more or less pro-

minent beak in the middle
of its lower edge (see fig.
18, which represents the
Up

horny jaw or buccal plate
of the cellar snail).

When the animal crawls, the shell is balanced
nearly horizontally on its back. The tentacles
are protruded and withdrawn with surprising
quickness. The species feed on vegetable sub-
stances, and inhabit damp or shady places, as
under stones, or among grass or moss.

The species are very difficult to distinguish ;
I have given therefore full descriptions of each.
The following analytical table may be found
useful :—

Fig.18.

l Shell depressed, umbilicus apparent... ... ... 2
; » trochiform, umbilicus minute ... ... H. fulva
2. § Opacity around the umbilicus... ... ... ... .«. 3
(No opacity jive sed oleae
peer large ; very cloned Coleen Hl. cellaria
3. « Upper surface more convex, dull... ... H. nitidula
Shell smaller, surface shining... ... ... H. alliaria

4. Shelli white ;. 4... 0 0.00 sec, ase es aes
ie horn-coloured :.,.... .... s+ «+s ee
5, Whorls not rapidly aeibe wae. A. crystallina
Last whorl capacious «4... ... 0.) ths | ee eee
6. Umbilicus very large... ... ... ... HL. excawata

Umbilicus moderate eres

. {Surface radiately striated ... ... ... H. radiatula
a ) », transversely wrinkled... ... ... HH. niteda

Ne ee

LAND SNAILS. | 105

HELICELLA CELLARIA—(the Cellar Snail) (PI.
VIL., fig. 63)—is one of our common shells, uni-
versally distributed throughout Great Britain ;
beneath stones, about walls, in gardens, and
woods. It has a predilection for wet situations,
and is not unfrequently found in damp cellars.
It has been introduced into Portland, Maine, U.S.,
where it is rare, in cellars and gardens.

The shell is flattened, with the spire very little
raised ; the colour is a dirty yellow or pale horn,
upper surface rather opaque, under surface
clouded with opaque white, especially about the
umbilicus, which is very large, and exposes the
second whorl; the whorls are five or five and a
half im number; the aperture is obliquely cres-
cent-shaped, rather broaderthan high. It is the
largest of the British species, having an average
diameter of two-fifths to half an inch, but attain-
ing even to three-fourths of an inch.

The dental formula is +7737. ‘ The central
plate is very long and narrow, with three teeth,
occupying nearly the centre of the plate; the

Kacegey ay |

Fig. 19.

first four laterals are irregular in shape, ap-
parently bidentated ; the wncini are long, single,

106 LAND AND FRESH-WATER MOLLUSKS.

and aculeate”’ (see fig. 19)—Morse. 'The horny
jaw of the cellar snail is represented in fig. 18,
p. 104.

Species of the genus Helicella are preyed upon
by thrushes, blackbirds, and starlings, which may
be found perfect in the stomachs of these birds.

HELICELLA ALLIARIA—(the Garlic Snail) (PI.
VIL., fig. 59)—is a widely-diffused species, but
not so abundant as the last, and readily distin-
guished from it and the other species of the
genus by the diffusion of a garlic odour, which
may frequently guide the collector to its retreat.
The emission of the peculiar odour is not always
obvious, but may generally be excited by press-
ing the animal with a stalk of grass; or on
immersion in hot water, those that may have
retained it, do not generally fail to emit in death
the yellowish fluid, which appears to be the
source of this alliaceous smell.

It frequents the same habitats as the last, and
attains a great elevation on mountains.

Shell flattened, with the spire very. little
raised ; colour pale amber or horn, transparent,
very shining; around the umbilicus there is a
little opacity; upper surface smooth, or but
slightly wrinkled ; whorls three and a half to
four; umbilicus moderately large, scarcely ex-
posing the second whorl; aperture crescent-
shaped, not very oblique, rather broader than

LAND SNAILS. 107

high; diameter one-fifth to a quarter of an inch.
The dental formula is #2.

HELICELLA NITIDULA— (the Dull Snail) (PI.
VIL., fig. 60)—is generally distributed, but not
avery common shell. Under stones, about old
walls, among mosses in glens and sheltered
places.

The shell is flattened, with the spire somewhat
raised (more so than either of the preceding) ;
colour that of horn, not shining, and darker than
that of H. cellaria or H. alliaria, dull, semi-
transparent above, more transparent below, ex-
cept about the umbilicus, where there is a slight
white opacity ; upper surface irregularly wrinkled
or striated; the strie interrupted by the sutures,
and not continued from whorl to whorl, as in
H. radiatula ; whorls four and a half, with a
well-defined suture ; umbilicus large, exposing
the previous whorl; aperture crescent-shaped, a
little oblique, rather broader than high; dia-
meter three-eighths to three-tenths of an inch.
The dental formula is 22-22.

HeiceLta pura—(the Delicate Snail) (Pl. VIL,
fig. 55)—is not uncommon among moss, decay-
ing leaves, stumps of trees, and under stones in
woods and pastures.

The shell is flattened, with the spire very slightly
raised; colour white, rarely very pale amber ;
transparent, not very shining; under surface

108 LAND AND FRESH-WATER MOLLUSKS.

without opacity ; upper surface smooth or slightly
wrinkled ; whorls three and a half to four, rather -
flattened above; body whorl much larger than
that preceding it; sutures well defined, deep |
and narrow ; umbilicus moderately large ; aper-
ture oblique, crescent-shaped, broader than high ;
diameter one-tenth to one-sixth of an inch.
HB&LICELLA CRYSTALLINA—(the Crystalline Snail)
(Pl. VII., fig. 58)—is common among moss,

herbage, decaying leaves, and under stones in

woods, pastures, and hedgerows.

The shell is flattened, with the spire very
slightly raised; colour white, or with a slight
greenish tinge, very shining and transparent ;
under surface without opacity; upper surface
smooth or slightly wrinkled ; whorls four and a
half to five, of gradual increase, the body whorl
being but little larger than that preceding it;
whorls flattened above; sutures well defined ;
umbilicus very small; aperture not very oblique,
crescent-shaped, about as broad as high; dia-
meter from one-twelfth to one-eighth of an
ich. |

HELICELLA ExcavATA—(the Hacavated Snail)
(Pl. VII., fig. 52).—The shell is depressed, ‘sub-

globular ; colour that of darkish horn, shining _
and transparent ; under surface not obscured by -

any white opacity ; upper surface strongly and:
regularly striated, the striz being continued

LAND SNAILS. 109

over the base, but not so well defined on this
aspect; whorls five to five and a half, well
rounded, especially on the inferior surface ; um-
bilicus very large and capacious, disclosing all
the whorls; aperture rather small, lunate, as
broad as high; diameter three-fourths of an
inch. |

This species inhabits woods, about the decay-
ing stumps of trees, and among dead leaves and
moss. It is peculiar to Great Britain, and is re-
corded from Yorkshire, Northumberland (Aln-
wick), Durham, and other counties in the north
of England; South of Scotland; Tunbridge ;
Wootton, near Gloucester; Sandown, Isle of
Wight; and Clifden, co. Galway.

HELICELLA RADIATULA—(the Rayed Snail) (Pl.
VIL., fig. 61).—This is a minute and well-marked
species.

Its favourite habitat is among grass and moss
in damp pastures, under stones, and among
moss, grass, and decaying trunks of trees in
woods.

The shell is flattened, spire scarcely raised ;
colour deep horn or amber, shining, transpa-
rent ; under surface without any white opacity ;
upper surface regularly and distinctly striated,
the striz continued from whorl to whorl, and
not interrupted by the suture; whorls three and
a half to four; body whorl much larger than

110 LAND AND FRESH-WATER MOLLUSKS.

that preceding it; umbilicus moderately large;
aperture oblique, crescent-shaped, broader than
high ; diameter from one-twelfth to one-sixth of
an inch. ;

HELICELLA NITIDA—(the Glossy Snail) (Pl. VIL.,
fig. 54).—The shell is flattened, with the spire
somewhat raised, more so than in H. nitidula, of
a greyish-brown colour, glossy and semi-trans-
parent, rather strongly transversely wrinkled;
there is no whiteness or opacity beneath ; whorls
five; the umbilicus large and deep; aperture
oblique, roundish, longer than-broad ; diameter
three-twelfths of an inch; height nearly half
the breadth.

The animal is bluish-black, and the shell when
it contains the body appears of a dark chocolate-
brown. ‘This species differs from H. nitidula in
its greater convexity, stronger striations, wider
umbilicus, and in being destitute of an opacity
underneath.

It is not a common species, inhabiting moist
places among herbage, on the margins of muddy
streams, ditches, and marshy places.

HeLicenta FuLVA—(the Fulvous Snail) (PL.
VIL., fig. 56).—This species is easily recognized
by its conical shell with a shallow ill-defined
umbilicus. The shell is thin, glossy, semi- ~
transparent, and horn-coloured, as in the other
Helicelle.

LAND SNAILS. 111

The diameter of the pyramidal shell is a tenth
of an inch, and the height nearly the same. The
dental formula is 722-22.

It is widely distributed, though seldom met
with in abundance in any one locality. It in-
habits beneath stones in quarries and old walls,
and among moss and herbage in woods and moist
pastures.

There is a very striking resemblance between
H. fulva and H. chersina of America, yet these
species have never been united.

All the above-mentioned species of Helicella
are fossilized in the Pleistocene fresh-water marls
at Copford, Clacton, &c.

Genus HELtx.

The British Helices are comprised in 25 species,
which I have arranged into artificial groups,
founded upon characters afforded by the adult
shells. These are exhibited in the following
table, which is merely intended to assist the
student in discovering the species :—

hortensis
» umbilicated

9 Shell more or less globular
: », depressed aes

Shell imperforated,—H. aspersa, H. nemoralis and H.
¥.

op NW bO

3 3, Mouth with an internal band ..
No internal band ; minutely umbilicated

iH? LAND AND FRESH-WATER MOLLUSKS.

: Shell with coloured bands,—H. Pisana, H. virgata, and
HI. caperata
», uniformly coloured, more or less hairy, at least in

- the young, re Cartusiana, H. Cantiana, H.
rufescens, ie concinna, H. hispida, and H.
sericea

Shell subglobose, thin, and very transparent,—H. revelata

5. ‘and H. fusca

99) Slobosely conteal:® 5.54 2.5) vege wat ie a
Shell with raised epidermis,—H. aculeata and H. lamel-

6. lata
», very large, banded,—HH. arbustorum and H. pomatia
7. Peristome united all round,— AH. upc pens:
5 incomplete. .../ 2. 8
g {Aperture toothed... ... H. obvoluta
» withno denticulations, outer lip not reflected, 9
Shell banded, large... ... LH. ericetorum
» not banded, —H. rotundata, Hi. rupestris, and H,

pygmea

Hetrx aspersa—(Common Snail) (Pl. VIL,
fig. 57).—The shell of this species is globular,
with a wrinkled surface; the colour is yellowish-
brown, with five spiral dark bands, traversed
by white zigzag streaks; the whorls are four in
number, and the aperture is obliquely oval, with
a white reflected lip. It exhibits great variation
in colour and marking, but its wrinkled epidermis
is a sufficiently distinctive feature.

Reversed monstrosities occur, as also others
with an elongated spire, with the whorls pro-
duced and separated from one another, so that
the shell resembles a ram’s horn.

LAND SNAILS. 113

Dr. S. P. Woodward has in his possession “ an
adult shell with a second half-grown individual
fixed to its spire, and partly imbedded in the
suture of the body whorl. The epiphragm re-
mains in the exposed part of the small shell’s
aperture, showing that it had died during the
first hybernation, whilst its neighbour had sur-
vived, and not getting free from the incubus of
the empty house of the deceased, had partially
enveloped it in the course of its growth to
maturity.” M. d’Orbigny bred for many years
im succession from a reversed monstrosity of H.
aspersa—one of our commonest and most gene-
rally-known snails.

Theoretically considered, there are no useless
animals. All the beings disseminated over the
surface of the earth must be regarded as playing
each their part in the economy of nature, from
the single fact of their existence. They, by their
incessant co-operation, maintain that admirable,
unalterable equilibrium of the natural world.
But practically considered it is another thing;
and in inhabited districts a distinction arises as
to what are the useful and what the injurious ani-
mals Man finds around him. Against the latter,
wrongfully or justifiably, a war of extermination
is declared, whilst the others are surrounded by
_ all the protection they appear to require.

_ The agriculturist, and especially the horticul-
I

114 LAND AND FRESH-WATER MOLLUSKS.

turist, count among the former group the slugs
and snails: even our present acquaintance, HH.
aspersa, is regarded by them as a great pest in the
gardens, devouring vegetables with the greatest
avidity, and is treated accordingly. Many of these
enemies have been mentioned ; some still remain
to have their misdeeds published to the world.
Those snails which derive their nourishment
from culinary and cultivated plants belong to the
second category. ‘The means to be employed for
their destruction are :—

Ist.—By the aid of their natural enemies.
Thus many insects, especially of the genera
Drylus, Lampyris, Staphylinus, Sylpha, attack
the terrestrial species, and deposit their eggs in
the substance of the snail’s body. Ducks, geese,
fowls, thrushes, blackbirds, prey upon them;
the hedgehog devours with avidity Helices and
Bulimi.

2nd.—By protecting the trees and plants from
their attacks,—encircling them with absorbent
powders,—washing the walls with a weak solu-
tion of corrosive sublimate.

3rd.—By the destruction of the eggs and
individuals: and to do this, dig deep the soil,
leaving it exposed to the sun, for some days,
before consigning to it the grain and plants. The
individuals may be decoyed, gathered, and de-
stroyed by throwing into lime-water, &c.

LAND SNAILS. 115

Yet a few of these humble and persecuted objects
may be ranked among the useful class of animals :
some, as H. pomatia, aspersa, nemoralis, hortensis,
Pisana, serving for food ; and recently they have
silently rendered a great service to man, in giving
to Dr. de Lemare his precious Helicine. This
material is the concentrated mucilage of snails ;
and by means of this preparation, known under
the names of the syrup of snails, pommade of
snails, and helicine, this learned physician is
stated to have radically cured, in the last few
years, numerous cases of phthisis. From French
newspaper reports it would appear that the
effects of the employment of Helicine are truly
marvellous. One provincial paper writes, that the
Helicine of Dr. de Lemare is for phthisis what
quinine 1s for intermittent fevers.

In this country this species, boiled in milk, is
still used by some in theirdomestic pharmacopeeia,
and great faith is placed in it as a cure for pul-
monary complaints ; but, so far as the experience
of medical men goes, it does not appear to be a
remedy of any efficacy. Like many other articles
of a peculiar and out-of-the-way character, a
dose of snail-broth may be productive of good,
provided the patient indulging in its use is
firmly convinced of its salutary powers. Reme-
dies of the above nature in use among the lower
classes owe their popularity to a vulgar creed,

ype

GEG LAND AND FRESH-WATER MOLLUSKS. ~

that whatever is disgusting and nauseous, must
necessarily be fraught with healmg virtues.
Dr. Gray writes, that “the glassmen of New-
castle once a year have a snail-feast, and that they
generally collect the snails themselves in the
fields and hedges the Sunday before the feast.”
The working population of Lancashire have a
reputation for the hike custom.

In the South of France an annual snail-feast
is held on Ash-Wednesday, on which day there
is a very large consumption of the very unsub-
stantial and indigestible flesh of snails. Vendors
are seen standing in the streets with great ham-
pers full of Helix aspersa and H. nemoralis ; the
former of the two is preferred. They are sold at
the rate of 25 centimes, or 24d., per 100. From
seven to eight thousand of H. aspersa form
part of the provisions of a ship leaving the port
of Bordeaux for a long voyage. Nearly all the
snails that constitute so important a part in the
live stock of ships come from one commune,
that of Cauderan, which is infested by them.

Mr. J. G. Jeffreys, quoting Lister, writes that
“the fluid which exudes so copiously from the
body of H. aspersa when pricked, was used in
his time in bleaching wax for artistic purposes,
as well as in making a firm cement, mixed with
the white of an egg.’? In the London streets I
have frequently seen a man vending an article,

LAND SNAILS. 117

stated to be a compound of the juices of this
snail and the green matter of ivy-leaves, as a
plaster for corns.

Perforations of two or three inches in depth
on the under surface of projecting masses of
limestone, in which fH. aspersa, H. nemoralis,
and a few other species, are found tenanting as
winter-quarters, are regarded as the result of
the constant resort to the one spot for shelter
by the snails, winter after winter in the course
of ages. It is usually accepted that the erosion
is due to the action of the foot, aided by an acid
secretion. Another theory is, that the snail works
with its shell, after the manner of an auger. A
more probable solution is, that the snails abrade
the walls of these lmestone cells with their
tongues, for the purpose of obtaining the car-
bonate of lime. HH. aspersa possesses 105 teeth
on each transverse row, of which there are 135.

We must not forget the poetic allusion by
Gay to the pretty conceits of the English rustic
beauty, of the power of the snail to reveal to
her the name of her destined lover. May-day
morning is the auspicious occasion on which the
tender-hearted maidens can read their fortunes
in the meandering of the snail :— |

Last May-day fair I search’d to find a snail,
That might my secret lover’s name reveal.

118 LAND AND FRESH-WATER MOLLUSKS.

Upon a gooseberry-bush a snail I found

(For always snails near sweetest fruit abound) :

I seized the vermin, home I quickly sped,

And on the hearth the milk-white embers spread.
Slow crawl’d the snail; and, if I right can spell,
In the soft ashes mark’d a curious L.

Oh! may this wondrous omen lucky prove !

For L is found in Lubberkin and Love.

This species appears to be very susceptible of |
cold, retiring early to their winter-quarters in
the cracks and holes of old walls and trees, and
in other equally sheltered situations, where they
are to be seen clustered together by their epi-
phragms, as if the gregarious propensity were ~
induced for the purpose of communicating
warmth to one another.

Within that house secure he hides,
When danger imminent betides,
Of storm, or other harm besides

Of weather.—Cowper.

Helix aspersa is very universally distributed ;
yet I find it to be a comparatively rare snail in
the North of Ireland, and it is there only met with
in the valleys, and in sheltered spots in the im-
mediate vicinity of the sea, and always at low
elevations. Fleming states that it occurs in Aber-
deenshire, “ here and there in the maritime and
lower inland tracts, especially in gardens, about

LAND SNAILS. 119

old walls, and on hedge-banks, but chiefly along
the coast.”

in the northern parts of Great Britain it seems
thus to be partial to the vicinity of the sea. At
Whitehaven it is found in innumerable quantities
attached to a wall fronting the beach, and ex-
posed to the sea-breeze. So, also, the late Mr.
J. Thompson observed numbers of them on
rocks subjected to the spray of the waves, which
had bleached the portion of the shell thus ex-
posed as white as it usually becomes in the pro-
_gress of decay, although the animal inhabitants
were all in the highest vigour.

The amours of this snail, as in fact of the
other Helices, are conducted after a curious
fashion. During the spring and summer the
snails are furnished with spicula—crystalline
darts, which they eject at each other; the tender
passion is further excited by long-continued
caresses with their horns, and they have been ob-
served engaged in this love-making for the space
of ten hours. The love-missiles are contained in
a special pouch, and are peculiar to the genus
Heliz; their shape, dimensions, and number,
vary in the several species. In H. aspersa they
are half an inch long, hollow, and square at the
base. If there be but the one use for these
weapons, it would seem that the snail occa-
sionally misses his mark ; for Mr. Hyndman, of

120 LAND AND FRESH-WATER MOLLUSKS.

Belfast, once found a spiculum of H. nemoralis
stuck through a dandelion leaf.

The garden snail is the most prolific of the
Helices, depositing from 100 to 110-eges. The
spot selected for the purpose of depositing these
is under a stone, or piece of decaymg wood,
lying in some damp and unfrequented part of
the garden, or it may be buried in the moist
soil. The young snails appear at the end of
from fifteen to thirty days, and at the end of the
autumn are about the size of a hazel-nut, and
attain their adult condition in the latter part of
the following year.

Heiix nemoratis — (the Wood Snail) (Pl.
VIL., fig. 45).—The shell of this snail is familiar
to all, and is one of our prettiest. It is either of
a yellow or chocolate-brown, encircled with from
one to five brownish spiral bands; of a globular
form with a roundish aperture; the reflected
margin is brown; the diameter is not quite an
inch, and the height is about three-quarters.

The jaw of this snail is strongly arched, and
marked with five longitu-
dinal ribs, which indent the
edges of the plate. The
lingual ribbon contains 135
rows of 100 teeth each.

Its specific name implies
that it is a woodland species ; it is frequent though

Fig. 20.—Jaw of H. nemoralis.

LAND SNAILS. 121

in our hedges and about rocks or hills ; it is cer-
tainly more maritime, and lives at greater alti-
tudes, than the next species, to which it is closely
allied.

The shell exhibits great variation in size, in
the intensity of the colour, and in the size, dis-
position, and number of the bands. A French
conchologist, M. Moquin-Tandon, characterized
77 varieties of this species; another author, M.
A. Gras, has enumerated no less than 198. In
general the varieties with five and three bands are
the most common ; next with two, with one, and
four: the same with regard to H. hortensis.

Hetrx Hortensis—(the Garden Snail) (PI.
VIL., fig. 47)—is regarded by many authors as
a permanent variety of the last species, but it
differs in a few particulars from it. The shell
is always smaller, usually of a hghter colour and
thinner, with a white reflected margin around the
aperture. It is a common species everywhere in
our gardens and hedgerows. The two species
are not usually found living together. In the
neighbourhood of Hastings, and other similarly
situated localities, I have found H. nemoralis
along the coast-line, feeding on Ononis arvensis,
&c., and becoming uncommon inland, where it
is replaced by the present species.

Hi. hortensis is subject also to many variations
incolour. M.Moquin-Tandon distinguished forty-

122 LAND AND FRESH-WATER MOLLUSKS.

six, and M. Bouillet ninety. One pretty variety
I have met with is of a white colour, with colour-
less bands. A more permanent variety, and by
some raised to the rank of a species under the
technical appellation of H. hybrida, is of a more
uniformly yellowish-brown colour, with a beauti-
ful rosy lip, whitish towards ae edge: it is local,
but not rare.

H. hortensis is a favourite food withthrushes and
blackbirds. Hvery country schoolboy is familiar
with the snail-hunting propensities of these birds.
In a country walk one may frequently see a large
stone surrounded by fractured snail shells ; these
are the slaughtering-blocks whereon the poor
snail is sacrificed for the welfare of our songsters
and their young progenies. The shells are very
systematically broken. The bird strikes the shell
upon the stone in such a position as to expose the
principal mass of the snail at about the commence-
ment of the last whorl, and the part immediately
above of the preceding whorl. The shells of
other snails, as H. arbustorum, H. nemoralis, and
H. aspersa, occur among the debris in the
thrushes’ haunts; the former not so often, on
account of its less frequency ; and the latter also,
because of the greater thickness of their shells.

The garden snail 1s found apparently indi-
genous on islands off the coast of Maine, North
America; it inhabits Greenland.

LAND SNAILS. I ts

Hettx prsAanAa—(the Banded Snail) (Pl. VIIL.,
fie. 66)—The specific name, “ Pisana,’” was
given to this species from its having been first
found at Pisa.

This species is the most beautiful of our snails.
The shell is solid, moderately glossy, about afourth
of aninch in diameter, and half an inch high,
with five whorls of yellowish-white ornamented
with numerous brown spiral bands, interrupted by
short oblique streaks of the same colour, giving
the upper surface a speckled appearance.

The aperture is rounded, rose-coloured in the
interior, with an internal rib: the umbilicus is
narrow, nearly closed by the reflected margin of
the lip. The dental formula is #535,

In Great Britain it is only found on the coast-
line. On the sand-banksbetween Tenby and Kilter
Point it is very numerous. Another locality is
St. Ives, where in the hot weather the snails
have been observed buried in the sand at the
roots of Carex arenaria to the depth of some
inches. It also occurs abundantly near Dublin,
and in Jersey. On the Continent it is confined
to the southern countries, but itis found at Con-
stantinople, with such western species as H. Oar-
tusiana, H. virgata, and H. ericetorum.

Heurx virgata—(the Zoned Snail) (Pl. VIIL,
fic. 80).—This snail, with H. caperata, H. ericeto-
rum, and Bulimus acutus, affects the dry stunted -

124 LAND AND FRESH-WATER MOLLUSKS.

vegetation on downs and heaths. Itis generally
found in greater abundance on the sea-coast, but
occurs in many inland districts. It is a very
abundant and gregarious species, adhering in
clusters to the stems of various plants. During
the hot weather they bury themselves about the
roots of plants; but after a shower of rain they
appear in such abundance that they are supposed
by country folks to come down from the clouds
with the rain.

Helix virgata has the propensity of feeding upon
Coccinella and other small insects, and is itself,
with its congeners, accidentally eaten by sheep
pasturing on the downs and commons, where it
occurs in such profusion. ‘Tor it is indeed im-
possible that the sheep can browse on the short
grass without devouring a prodigious quantity of
them, especially in the night, or after rain, when
they ascend the stunted blades;” and in the South
of England it is a prevalent, and probably a
correct opinion, that these snails contribute much
to the fattening of sheep. The superiority of the
Dartmoor and Southdown mutton is presumed
to be attributable to the flavour imparted to it by
these mollusks. The distoma, or fluke of sheep,
possibly may be derived from the embryonic
form which lives parasitically in the snail.

Some authors have remarked, from their own
observations, in particular localities, that it is

LAND SNAILS. 125

never found in company with H. ericetorum. This
observation is not of general application.

The shell of the ‘“‘zoned snail” is conical; white,
or cream-colour ; with a single dark-brown band
in the middle of the iast whorl, and with many
smaller ones beneath. It varies much in colour
and external markings. A pretty variety has
two narrow brown bands on the under surface,
between which is a row of brown spots, eaeh
connected by a narrow brown band. Within the
aperture of the shell, and at a distance of two
lines from its reflected margin, is a narrow but
well-marked ridge, usually corresponding to that
of the mouth, which is a purplish-brown.

The whorls are six in number, and the shell
has an average diameter of a fourth of an inch.
A few specimens collected by me in corn-fields
on the chalk downs, near Eastbourne, have a
breadth of seven-tenths of aninch. Mr. J. G.
Jeffreys has seen specimens from Weymouth a
tenth of an inch broader.

Hewix caperata—(the Wrinkled Snail) (PI.
VIIL., fig. 78).—So called from the numerous con-
centric rib-like striz upon the whorls; it is
further to be distinguished from H. virgata by
its depressed spire and larger umbilicus, and is
usually of a much smaller size. The colour of
the shell is usually of a dull yellowish-white,
with narrow brown bands. The spire is tipped

126 LAND AND FRESH-WATER MOLLUSKS.

with black or brown, from which latter character
it is known by another name, that of H. fasciolata.
The dental formula is 25125, It is extremely
variable in colour, from white to reddish-brown,
and in the number and colour of the bands.

It is generally associated with the last species,
but is not so abundant; it is, however, more
widely distributed.

Heurx Cantrana—(the Kentish Snail) (PI.
VIII., fig. 64)—The shell of this snail is sub-
globose, thin, semi-transparent, and yellowish-
white, with atinge of pale rose-colour, especi-
ally towards the aperture. The margin of the
aperture is thin and but slightly reflected, and
at a little distance from its edge is an internal
thick and white rib; there is a small narrow
and deep umbilicus ; the whorls are six or seven
in number; the diameter of the shell is three-
fourths of an inch. Young shells want the
internal rib, and are clothed with short hairs,
which disappear in the adult. The dental for-
mula is 91-42,

H. Cantiana is a southern species in Europe,
and attains its northern limit in England; it is
indigenous in the south-eastern counties. Itis
abundant on nettles, and plants in wet places,
and by ditches in Kent and Sussex, and in the
counties bordering the river Thames.

It is plentiful on the downs at Bedminster, &c.,

LAND SNAILS. 127

in the vicinity of Bristol; Swansea; and on the
banks of the river Tyne, about Newcasile: in
these localities it is said to have been introduced
with ballast.

In the Bristol district it was first observed
between Brishngton and Keynsham, in 1825.
Gardner, in his “ Natural History of Stafford-
shire,” says, “it is not rare in the Dovesdale
and Wetton valleys.” And as it occurs also in
North Gloucestershire, at Evesham, there is no
reason to doubt that the Kentish snail is truly
indigenous to the western counties of England.

Hetix Cartustana— (Pl. VIIL., fig. 70).—So
called from its having been first discovered near a
Carthusian Monastery ; it is closely related to the
Kentish snail, and possesses a white internal rib
and an umbilicus, as in that species, but differs
from it in its much smaller size, being about half
an inch in diameter, more solid and not so glossy,
nearly opaque; it is more depressed, and the
umbilicus is minute.

It is found on the short herbage clothing the
chalk downs of the Kentish and Sussex coasts.
It appears to be confined to the neighbourhood
of the sea, and to the chalk soil; though there
are many favourable localities for it along the
coast intervening between Folkestone and Hast-
bourne, yet I have failed to find, though often
sought for it. The sameis true of H. ericetorwm

128 LAND AND FRESH-WATER MOLLUSKS.

and Oyclostoma elegans. Now the strata embraced
within that line of coast are composed of sand-
stones, sands, and clays belonging to the Green-
sand and Wealden formations, and the recent
alluvial deposits. |
Though much has been written for and against
the restriction of snails to certain ‘soils, never-
theless I adduce the above case as a very
striking example in favour of the association of
certain land shells to particular kinds of rocks,
though not necessarily to any given formation.
The specific name is usually written Carthu-
siana, but Mr. J. G. Jeffreys thinks “ the original
spelling of Cartusiana ought to be retained.”
HeELix rurescens—(the Rufous Snail) (Pl. VIIL.,
fig. 76).—So called from the rufous-brown of the
shell. Though usually of this colour, yet it pre-
sents intermediate shades, even to a pure white.
The shell is depressed, slightly angular below,
composed of six or seven whorls ; the aperture is
oblique, semielliptical, thin, and shghtly reflected,
with a broad internal band, distinctly visible
from the outside; the umbilicus is narrow, but
distinct. In very young shells the exterior is
clothed with hairs, and in this state may be con-
founded with H. hispida, but is easily distin-
guished by the keel on the margin of the outer
whorl, whilst in H. hispida the last whorl
is rounded. }

LAND SNAILS. 129

This snail inhabits gardens, hedge-banks, and
under stones in the vicinity of dwellings; it
is more abundant in limestone districts. It is
common as far north as Yorkshire, and is un-
known in Scotland and in the North of Ireland.

Heuix wisprpa—(the Bristly Snail) (Pl. VIIL.,
fig. 75)—is an extremely common snail in woods,
among moss and herbage, and under stones, in
shady places. ‘The shell is about a quarter of an
inch in breadth and about the same in height, of
a dark yellowish-brown, transversely striated ;
the epidermis is clothed with crowded, fine,
white, and recurved hairs. The umbilicus is
small, narrow, but deep.

It varies in colour and in the elevation of the
spire, but the thick yellowish-white foot of the
animal affords a good distinction between it and
the following species :—

Hettx concinna—(the Neat Snail) (Pl. VIIL.,
fig. 77)—is closely related to the last, and by
some regarded as a variety of that species. The
shell however is rather larger and less globose ;
the umbilicus is wider; the hairs are more scat-
tered and readily fall off, and the shell thus often
presents a smooth surface. The darker colour
of the animal, the narrower and less fleshy foot,
are good characters by which this species may be
separated from H. hispida. Both species, more
frequently than otherwise, have a white spiral

K

1380 LAND AND FRESH-WATER MOLLUSKS.

band in the last whorl, as in H. rufescens. The
present species differs from the Rufous Snail in
its smaller shell and in its more rounded and
compact whorls, though equally numerous.

These three species are found together.

A. concinna has as wide a range as H. hispida,
but.is less frequent; in Ireland I have found the
former in more exposed situations, about rocks
upon the hill-slopes, than in which H. hispida is
usually met with.

The number of teeth on the lingual ribbon
approaches to that of H. caperata; there are a
hundred transverse rows of fifty-one teeth.

Heuix sericea—(the Silky Snail) (Pl. VIIL.,
fig. 65)—so called from the long and very fine
white downy hairs which thickly cover the shell ;
when these are worn off, the surface presents a
minutely granulated appearance; from which
latter character Mr. Alder il it the name of
Hf. granulata.

The shell is conical, more globose than that
of any of its allies, and is less than a quarter of
an inch in diameter and as much high; thin, of
a greyish-white; whorls very convex, six in
number; the umbilical aperture is extremely
small, which alone is sufficient to distinguish it
from its congeners or any of their varieties.

This species is rare and local; in England itis
chiefly confined to the South and West ; it occurs

LAND SNAILS. Lok

in Scotland, and has not yet been found in Ire-
land. It is distributed throughout the temperate
parts of Kurope.

It lives in moist woods, damp places on the
banks of streams, among the grass and rushes or
under the leaves of Petasites vulgaris.

Heuix- rusca— (the Brown Snail) (Pl. VIL,
fig. 50).—The shell of this species is: of a glossy
amber-colour, and is especially characterized by
its strong, irregular, transverse wrinkles, and
its extreme thinness and fragility. It has a
minute umbilicus, like H. sericea, but the spire
is more depressed, and the last whorl propor-
tionately large. The height is a quarter of an
inch, the breadth three-eighths.

In the northern parts of Great Britain this
snail is common, in damp shady places and
wooded mountain glens ; on the fallen leaves of
trees in the autumn, and in the summer upon the
young trees of the sycamore and alder. Itisa
hardy species; for in the damp woods in the neigh-
bourhood of Belfast I have frequently collected
it in great numbers, during the winter months,
gliding rapidly over the leaves of the wood-rush
(Luzula sylvatica), to which it is very partial ;
it has occurred to me under similar circumstances
in the glens of the lake districts of Scotland.
It is very rare in the South of England; and on
the Continent has hitherto only been found near

K 2

toe LAND AND FRESH-WATER MOLLUSKS.

the sea at Boulogne and on the west coast of
France.

Henix reverata—(Pl. VIII., fig. 72).—The
specific term signifies ‘‘ discovered ;” the vulgar
name by which it is known is the “ Green Snail,”
on account of its peculiar colour. The shell is
subglobose, about a quarter of an inch in dia-
meter, very thin, nearly transparent, green, :
wrinkled in the lines of growth; the umbilicus
is small and narrow; in the living state the
epidermis of the shell is provided with short
rigid hairs, sparsely distributed.

H. revelata is one of the rarest of British
snails, and was added to our fauna in 1841, by
Mr. Bellamy, who found it near Mevagissey,
between Falmouth and Plymouth. It occurs at
Pendennis, near Falmouth; Whitesand Cliffs,
near the roots or under the foliage of plants of
recumbent growth; at Stanton-on-the- Wolds,
Notts, i woods. It is procured under stones
on the open downs in Devon and Cornwall, but
in Guernsey in shady places among nettles. It is
found in the South-west of France and in Portugal.

Mr. J. G. Jeffreys writes — ‘In winter and
dry weather it buries itself rather deep in the
earth, and must be looked for by pulling up
tufts of grass and large stones which are sunk
in the ground, as well as by searching among
the roots of shrubs and furze-bushes.”’

LAND SNAILS. 133

HELIX LAMELLATA—(the Plated Snail) (Pl. VIL,
fig. 51)—is a characteristic northern shell. It
inhabits woods, on decaying leaves of Luzula
and fronds of Lastrea, &c., and about rocks near
running water. It was first discovered near
Scarborough, and is now known throughout the
_ North of England, the North and West of Scot-
land, and the North of Ireland. Until recently,
this species was peculiar to North Britain, but
it has been found in North Germany and in
Sweden.

This beautiful conical globose shell is only
one-tenth of an inch high and broad, of greyish
‘colour; and in certain lights it exhibits a satiny
appearance, which is due to the action of the
rays of light upon the fine, sharply-cut striz

_ which cover its surface.

Herix acuteata—(the Prickly Snail) (Pl. VIL.,
fic. 48).—This, also, is a minute species, and
differs especially from the last in the epidermis
of the shell bemg raised into from twenty to
thirty plaits, which rise in the middle of each
whorl to a sharp pomt. Fresh specimens are
exquisitely beautiful objects, exhibiting the ap-
pearance of a coronet of bristles encircling each
whorl.

This species is so minute, and its colour so
closely resembles that of the dead leaves upon
which it is usually found, that it is detected with

134 LAND AND FRESH-WATER MOLLUSKS.

difficulty, and it is advisable to lift the leaves
and turn them over in the hand to find it. In
Gloucestershire it is found on the under sides of
the leaves of the hazel; it is occasionally seen
on lver-worts (Jungermannie). H. aculeata is
distributed throughout Britain and Europe.

Heiix pomatia—(the Apple Snail) (Pl. VIIL,
fig. 73).—This snail is commonly regarded as
the one which was held in so great repute by
the epicures of ancient Greece and Rome; but
this is not the fact, for a larger species replaces
Hf. pomatia in Southern Europe. In the North
of France and in Switzerland the Apple Snail,
however, 1s a much-prized mollusk as an article
of diet.

The shell of this species, the largest of our
British snails, is globular, thick, and strong, of
a yellowish-white, with spiral bands of brown ;
it is aS much as two inches in breadth and
height ; the whorls are five in number, the last
one extremely large and inflated.

This, the largest snail, possesses the greatest
number of teeth among the
Helicidee, and .they are only
exceeded in number by those of
the Limaces ; the number is

rig ai_tawor'e ls t40, contamed im 140 rows
ia as of 151 each. The jaw (fig. 21)
is strongly arched, with a moderate number of

Vincent Brooks, Imp

LAND SNAILS. fap

prominent ribs, which form strong teeth on the
free margin.

H. pomatia is to be met with on the borders
of copses and woods on a calcareous soil. It is
found at Sevenoaks, in Kent; Croydon, Reigate,
and Dorking, in Surrey ; in Hertfordshire, Ox-
fordshire, and Wilts; it is common on the Cots-
wold range. In early spring these snails unite
for propagation. The eggs are globular, and
covered with a white opaque skin, and are
about the size of small peas; these are laid in
a kind of nest, made in the loose earth, in the
months of June and July. The eggs are hatched
in twenty to thirty days, according to the season
and temperature ; when first excluded, the young
live solely on the egg-cases; at the end of the
year they are about the size of Helix hispida,
and arrive at maturity in a little more thana
year.

The Apple Snail, on the arrival of the period
of hybernation, constructs, by the aid of its
large muscular foot, and a very glutinous secre-
tion, a hole in the ground, just large enough to
receive the shell; this it lines with dead leaves,
retires to its hybernaculum, and closes the aper-

ture of the shell with a solid calcareous plate, ~~

secreted .and formed by the mantle; it then
withdraws considerably within the shell, and the
more effectually to exclude the cold air, forms

136 LAND AND FRESH-WATER MOLLUSKS.

several but much thinner epiphragms, behind
which it rests ina torpid state during the winter ;
thus it remains unconscious of what is going on
around it—sleeping through the winter months,
until the genial showers of April call it forth.
Its specific name pomatia is derived from the
Greek poma, an operculum, from the thick cal-
careous epiphragm it forms.

This snail has been the object of numerous
experiments, with the view of ascertaining the
extent of the remedial power among land mol-
lusks. The Abbé Spallanzani cut off the tenta-
cles, which were reproduced even to the eyes at
the end of two months; not content with sub-
jecting the creature to such torture, he tested
the reparative power in a greater degree, by
removing the entire head, which was reproduced
to perfection. The snails thus experimented
upon, retired immediately into their shells, and
there remained weeks or months, outwardly in
a state of quiescence, but internally the won-
derful power of reproduction was silently at
work until the end was attained.

The Helices diminish in size with their range
in elevation; but H. pomatia, on the other hand,

» Increases in size according to the altitude at-

tained. Itis found on the Vaudois Alps, up to
the very verge of the forests, 5,850 feet above
the level of the sea.

LAND SNAILS. E57

Some writers have asserted that this species
has no claim to rank as indigenous to this coun-
try, but that it was introduced either as an
article of food, or for medicinal purposes.

HeLix arsustorum (Pl. VIL., fig. 62), as the
specific name implies, the “ Shrub Snail,” is a
tenant of our woods and groves, preferring
moist situations, but more frequently its habitat
is among the willows and reeds of our ditch
sides and river banks.

The shell of H. arbustorum is each hand-
some; it is globular, about three-fourths of an
inch i diameter, generally brown, marbled with
yellowish spots, and having a single blackish
band winding round the middle of each whorl.
The animal is covered with tubercles, and is of
a greenish-black colour, of a light grey beneath
the foot ; the tentacles are short and black, with
very globular extremities.

The shell presents numerous variations, both
in form, and more especially in colour. Some
are very thin and almost transparent, of a dark
colour, with or without the band; in others the
shells are variegated, with a brown band, or
more strongly marked with a black one; whilst
in others the spire is much more prominent.

The Shrub Snail is distributed over the greater
part of Europe; in Great Britain it is somewhat
localized, though it has a place in most local .

138 LAND AND FRESH-WATER MOLLUSKS.
?

lists. This species reaches a higher elevation
than any other, being found high up on moun-
tain-sides ; in the Alps it attains to the region
of perpetual snow. At this great altitude the
shell is smaller, and the spire more elevated, and
is the variety alpina (Pl. VIL., fig. 62a).

HELIX PULCHELLA—(the Pretty or White Snail)
(Pl. VIII., fig. 67)—is another of the little-isms
of molluscan life. The animal is milk-white, and
its black eyes contrast strongly with the trans-
parency of the upper tentacles. The shell par-
takes of the colour of the animal, is rather opaque
and depressed in form; there are three and a
half rounded whorls, the last one exceeding the
rest of the shell in size: the circular aperture
has a very thick and strongly reflected margin,
forming a complete peristome; the umbilicus is
large and deep; the diameter is a tenth of an
inch.

The accompanying figure repre-
sents the striated horny jaw of this

Mg chan. ttle beauty. The number of

teeth far exceeds in number those
of Helicella cellaria, which possesses a shell many
times the size of this minute species; the dental
formulatiss.., — 1860.

It is widely distributed throughout Britain and
Europe, and ranges to Siberia, and is found in
Madeira and the Azores.

LAND SNAILS. 139

This species is usuallyregarded as an inhabitant
of North America, but the species there is clearly
distinct from the Huropean H. pulchella; the
American H. minuta of Say is clearly indigenous,
for it is widely and abundantly distributed, and
in regions remote from the sea, throughout North
America.

It frequents walls, under stones, and among the
short herbage of downs.

A variety—H. pulchella 3. costata (Pl. VIIL.,
fic. 69)—has the shell furnished with elevated,
transverse, and curved ridges, and is stated to be
peculiar to marshy and damp situations. In this
I do not acquiesce, for I have found both living
together in dry places, as on the walls of Hast-
ings Castle, under stones on the Chalk Downs
of Sussex, and at Bristol; and in damp and
low situations, as among the osier beds bor-
dering the banks of the river Thames, both the
smooth form and costated variety occur. In
a parcel of shells of this species from any of
these localities, specimens showing the transition
from the ridged variety to the smooth form are
not rare.

The variety costata should be regarded as the
normal form, as the ribless condition results from
the disappearance of the coste upon the shell,
which is due to the occasional wearing away by
age, Just as in the case of H. aculeata, which is

140 LAND AND FRESH-WATER MOLLUSKS.

sometimes found without the longitudinal plates
which generally cover the shell.

Hex tapicipa—(the Variegated Rock Snail)
(Pl. VIII., fig. 79)—the technical name, signi-
fying ‘a stone-cutter,”’ is very inappropriate, and
was given to this species by the great Linnezeus,
from an erroneous idea that it ate or excavated
limestones.

The shell is depressed, lens-shaped, convex
above and below, with a sharp keel on its outer
circumference ; the aperture is longitudinally oval
and angular; the white and reflected peristome is
united all round; the edge is acute but not
thickened. The colour of the shell resembles
that of H. rotundata, is yellowish-red, irregularly
streaked across the whorls with reddish-brown ;
the surface is also striated with closely-set lines
of growth; the umbilicus is large. ‘The dental
formula is *°.>.

This snail is truly a woodland species, and
is confined to the central and southern counties
of England; it is found as far north as Brocker-
dale near Pontefract. It has a wide range in
Hurope.

It has been supposed to be restricted to lime-
stone tracts, but I have found it very general in
the woods of the Wealden district, where the
rocks are especially characterized by the absence
of the calcareous element. In Gloucestershire,

LAND SNAILS. 14]

this snail occurs in great plenty on the trunks of
beech trees having a southern aspect.

Hutrx opvotutra—(the Cheese Snail) (Pl. VIL,
fig. 49)—the aperture of the shell of this species
is rather curious, and alone is sufficient to distin-
suish it; it is obliquely triangular, with a tooth-
like protuberance. The shell is nearly circular,
flatabove, with the spire slightly sunk, compressed
below, and with a large umbilicus; the whorls,
six in number, are closely wrapped together, cylin-
drical, compressed from side to side, and gradually
increasing in size ; the last one is dilated towards
the mouth. Young shells want the triangular
mouth and reflected lip.

The colour of the shell is reddish, with the
epidermis raised into curved ridges, and clothed
with short stiff brown hairs. The dental for-
7 1G)

The principal locality for this shell.is Ditcham
Wood, near Buriton, Hampshire; it is also found
at Uppark and Stoner Hill, in the same county.
In Ditcham Wood it occurs abundantly, and
hybernates at the base of hazel trees; the
epiphragm is thick and of a chalky-white colour.

Huiix ERiceroruM—(the Heath Snail) (Pl.
VIIL., fig. 68).—The shell of this species 1s very
elegant, of a circular flattened form, with an ex-
ceedingly large umbilicus and a nearly circular
mouth. These characters will enable one readily

142 LAND AND FRESH-WATER MOLLUSKS.

to separate it from H. virgata, and the other
banded snails. The shell is composed of six
whorls, usually of a white colour, with a broad
band around the middle of the whorl, with from
two to six narrower ones below.

The diameter of the shell is one inch. The
dental formula is “473°

The animal is very sluggish in its movements,
timid, and retreating within its shell on the
slightest touch. Excessive rains destroy great
numbers of them, as I have observed on the
Cotswold Hills.

It is an abundant species on the chalk and
oolitic hills of England, and is pretty generally
diffused throughout Ireland and Scotland.

It has a predilection for limestone soils, though
not confined to them, for many of the sand dunes
around our coasts claim it.

Hetrx rotunpata—(the Radiated Snail) (PI.
VIII., fig. 74)—is one of our common Helices,
and is provided with not an unhandsome shell,
which is flattish and circular; the whorls are six
in number, slightly convex above, more com-
pressed below; the last one is slightly angular ;
the umbilicus is very large, exposing the interior
of all the whorls; the colour is reddish-brown,
marked in a radiating manner with spots of brown
and yellowish-grey ; it is sometimes found trans-
parent and colourless. Anothervariety, H.Turtoni,

LAND SNAILS. 143

has the spire quite flattened. The diameter of
the shell is one-third of an inch.

This snail inhabits a great variety of situations,
—beneath stones in damp woods, on rocks, among
fallen leaves, and shows a predilection for decay-
ing wood.

Heix rupestris—(the Wall Snail) (Pl. VIL,
fic. 46)—is one of our minute species, passing
its days between the bricks and stones at the
tops of old walls and ruins of castles, on the
rocks, and under débris on hill-sides, usually
in dry, lofty, and exposed situations, and at-
taches itself more markedly to lmestone rock,
though I have found it on sandstones in the
North of Ireland ; on the quartzose conglomerate
of Bristol; but certainly very abundantly on the
limestone of the oolitic rocks of the West of
England, among the débris of the quarries and
on the bare rock surfaces. It is rare in Ireland.

The shell is somewhat conical, of a blackish-
brown colour, slightly glossy, marked trans-
versely with strong, oblique curved striz; the
whorls are five in number, rounded, separated
from one another by a deep suture; the aperture
is nearly circular ; umbilicus very large; the
diameter of the shell is one-tenth of an inch.
A well-known synonym for this species is H.
umbilicatus, suggested by the open umbilicus,
which so markedly characterizes it.

- 144 LAND AND FRESH-WATER MOLLUSKS.

The spire in old specimens is whitish, by
exposure. ‘The snail in crawling carries its shell
upright, and not inclined to one side, like the
majority of the Helices. A peculiarity possessed
by this snail is that of retaining the eggs in the
interior of the shell (ovoviviparous) until they
are hatched. Mr. J. G. Jeffreys has found the
young under such circumstances, with a whorl
and a half formed.

Hewix pyamma—(the Piqmy Snail) (Pl. VIIL.,
fie. 71).—This beautiful tiny gem, so interesting
from its minuteness, is no bigger than the head
of a good-sized pin; and on account of its
minute size, it is difficult to find; but the much-
prized treasure is within the reach of all, and will
be found by him who searches properly for it; for
it is widely diffused throughout Britain. Firstly,
then, to describe the object of our search, and
then to direct attention to where it is likely to
occur.

The shell is nearly circular, with four convex
whorls, of a pale brown colour, semi-transparent,
and having a-silky lustre, slightly striated ;
aperture crescent-shaped; umbilicus large.

It differs from H. rupestris, its closest ally,
in its much smaller size, finer texture and orna-
mentation, lighter colour, fewer whorls, more
depressed spire, and more open umbilicus.

It is partial to shade and moisture, under

LAND SNAILS, 145

stones, and at the roots of grass; but more fre-
quently on dead leaves in woods and plantations.
Moquin-Tandon, in his “ Natural History of
the Land and Fresh-water Mollusks of France,’
writes of this pigmy, that it is timid and irri-
table, avoids the bright sunlight, retires within
its shell at the shghtest touch; and that the
first part of the body protruded from the shell
is the hinder portion of the foot.

GxroLtocicaL Distrisution or HeEtix.—One
of the most ancient of the Helices that has sur-
vived through a long space of time—from the
deposition of the Upper Hocene, at the close of
which period in the Isle of Wight it became
extinct—to the present day, is H. labyrinthica ;
for it has been driven from the hemisphere in
which it first appeared to North America, where
it is now a widely-spread species.

Of the living British species, the following
are found fossilized in the Upper Tertiaries at
Copford, Grays, &c., Essex :—H. hortensis, H.
nemoralis, H. arbustorum, H. hispida, H. con-
cinna, H. pulchella, H. fusca, H. rufescens,
H. aculeata, H. lamellata, H. sericea, H. lapi-
cida, H. virgata, and H. rotundata, associated
with H. fruticum, H. incarnata, and H. ruderata,
which, though distributed throughout Northern
and Southern Europe, ceased to exist in Great
Britain at the close of the period of the deposi-

L

146 LAND AND FRESH-WATER MOLLUSKS.

tion of the Pleistocene fresh-water marls of
Hssex, &c. With them is also Hydrobia mar-
ginata, which, though not now found living in
Britain, is repelled to Switzerland and Southern
France. fH. hispida and H. arbustorum lived
during the Mammiliferous Crag epoch; and
H. pulchella and the extinct H. rysa as early as
that of the Red Crag. H. pomatia is fossilized
in the bone-caves of Belgium, and H. aspersa in
those of Gibraltar ; and in the Uppermost Ter-
tiaries at Newbury. The majority of the species
occur in the sub-aérial deposits of the districts
which they now inhabit. |

Genus ButLimus.

The animal of Bulimus presents no real dif-
ferences from that of Helix; the body is elong-
ated, the tentacles are rather shorter, and the
dentition is Helicine: the transverse rows ex-
tend in a straight line to about half their breadth,
and then in a slight curve to the margin; the
teeth are minute, and have a central, bluntly
conical point, flanked on each side by a very
much smaller but similar one. The shell is oblong,
or turreted; the peristome is thin, or reflected.
There are only three British species, belonging
to two sections—JB. acutus, with a turreted shell
and a simple peristome; B. montanus and DB.

LAND SNAILS. 147

obscurus, with an oblong shell and a reflected
peristome.

Bulimus has persisted since the period of the
Bembridge Limestone of the Upper Hocene. B.
montanus and B. obscurus are both fossils of the
Pleistocene marls; the former at Clacton and
Orton, the latter at Copford.

Many of the pulmoniferous snails now rare in
this country were formerly abundant, and had a
wider geographical range than at present; ¢. 9.,
Bulimus montanus, Clausilia biplicata, C. Rolphii,
Pupa substriata, Vertigo minutissima, V.angustior,
Helix lamellata, and Suecinea oblonga.

Buummus acutus— (tke Banded Twist Shell)
(Pl. [X., fig. 83)—is a very conspicuous shell,
from the contrast of colours presented by it,
thus differing from its congeners, which have a
uniformly coleured shell. The shell is cylindrical,
acute, with eight or nine rounded whorls, gra-
dually increasing in size; the aperture is small,
and the outer lip is thin and plain, not reflected,
as in the majority of the Helicidw; it rarely
exceeds half an inch in length. The colour is
generally yellowish-white, with bands of reddish-
brown to black. The dental formula is +825,

It is a somewhat local species, and inhabits
the calcareous downs and the sandy pastures and
dunes on the sea-coast, especially in the South
and West of England, North and Kast of Ireland,

L2

148 LAND AND FRESH-WATER MOLLUSKS.

and the west of Scotland. It lives in company
with Helix virgata and H. caperata, which it ex-
ceeds in abundance. In the marshy grass lands
of the alluvial plains of Pett and Pevensey
Levels, in Sussex, B. acutus does not occur ; but
its usual associates literally carpet the swards
in many parts; on the other hand, the two
Helices may be absent, and B. acutus is the sole
molluscan tenant of the almost barren sandy
wastes skirting, here and there, our coasts.

Butimus mMontanus— (the Mountain Turst Shell)
(Pl. IX., fig. 51).—The shell of this species is
nearly three-fourths of an inch in length, coni-
cal, oblong, semi-transparent, glossy, of a light
reddish-brown colour, marked with spiral, close-
set, fine, undulating striz. The spire consists of
seven whorls; the aperture is about one-fourth
of an inch wide; the peristome is reflected.

It occurs in great abundance from April to
September, associated with B. obscwrus, Balea
fragilis, Clausalia laminata, and Helix lapicida,
upon the large beech-trees in the woods on the
oolitic hills of Gloucestershire. It prefers a
southern aspect, and ascends the trunks of trees
to heights which render it undistinguishable.
The beech is an especial favourite with snails,
more so than any other tree: its smooth bark is
what they delight in; and after showers the
trunks may be seen studded with them; the

LAND SNAILS. 149

probable explanation_is, that this tree is resorted
to by the snails for the purpose of feeding upon
the minute parasitic vegetation which clothes it.
The supposed scarcity of this snail, and some
others, in localities where they are in reality most
abundant, is due to this peculiar habit of ascend-
ing trees during the summer months; for at
this season only dead shells will reward a search
among the herbage at the bases of the trees.

B. montanus is readily to be distinguished
from B. obscurus, which accompanies it, by its
superior size and somewhat polished appearance ;
B. obscurus, in all stages, 1s covered with a dirty
incrustation.

This species is recorded from Wiltshire and
Hampshire, and in Suffolk near Bury St. Ed-
mund’s; it is thus local, but plentiful where it
occurs.

The specific name, montanus, implies that its
usual habitat is in elevated situations, and in
such it is only known in Central Hurope.

Butimus opscurus — (the Dull Twist Shell)
(Pl. IX., fig. 82).—This species differs from PB.
montanus chiefly in its smaller size, for the shell
is about half an inch in length; and in the white
reflected margin of the aperture. Albinos. have
occurred.

The animal is of a greyish-brown, cr dark
brown above; the foot is of a lighter colour;

150 LAND AND FRESH-WATER MOLLUSKS.

when viewed under a lens, darker spots and
markings are seen arranged in a_ beautiful
pattern. The tentacles are cylindrical, granu-
lated, and distinctly club-shaped. The dental
formula is 242-27,

B. obscurus is distributed throughout Britain,
but not generally frequent; it is very local in
Ireland ; its habitats are under stones in woods,
on rocks, and more frequently, when of course
it is not hybernating, upon the trunks of trees.
This little snail, in all stages of growth, covers
itself with a coating adapted to the different
situations in which it is found, rendering its
detection difficult. ‘If its abode,” according
to Mr. Sheppard, ‘‘ be upon the trunk of a tree
covered with lichens, then is the epidermis so
constructed as to cause the shell to resemble a
little knot on the bark, covered with such sub-
stances. If on a smooth tree, from whose bark
issue small ‘sessile buds, as is frequently the
case, it will pass off very well for one of them ;
and on a dry bank, or the lower part of the body
of a tree splashed with mud, its appearance will
be that of a little misshapen pointed piece of
dirt.”

Genus Zva.

This genus is distinguished from Bulimus by
the glossy transparent shell, and the thickened

LAND SNAILS. bau

but not reflected lip. The animal resembles
that of Bulimus. The genus contains only one
British species—

Zua Luprica—(the Common Varnished Shell)
(Pl. IX., fig. 84).—The shell is glossy, of a brown
or yellowish colour, sometimes greenish-white ;
about one-fourth of an inch long, usually of an
oblong, cylindrical shape, but subject to some
variation in shape and colour.

It is common and generally distributed; in-
habits woods, among decaying leaves and wood,
at the roots of plants, and on mossy banks and
swards. It is a favourite food of the starling.
It is a fossil of the Newer Tertiaries of Grays,
Clacton, Copford, &c.

A North American species, Zua lubricoidea
(Stimpson), has been unhesitatingly referred to
the common Huropean species by all concho-
logical writers, with the exception of two—
Stimpson, who named the species as above,
deeming it impossible that an introduced species
could have spread so generally over the American
Continent; and Morse, who has shown, during
the past year, that certain marked aiid constant
characters plainly indicate the distinctness of
the species. Slight differences in colour, size,
and number of whorls may be pointed out, as
also differences in the lingual dentition; that of

Z. lubrica being 2°+2° ; of the American species,

152 LAND AND FRESH-WATER MOLLUSKS.

21231, . The central tooth in each is small: that
of Z. lubrica is simple, whereas that of Z. lubri-
coidea has a minute denticle on each side.

‘ Gunus AZECA.

Azeca and Zua are separated from Bulimus by
artificial characters; for there are no structural
differences between the animals of these three
genera. The shell of Azeca in form and colour
is ike that of Zua, and is equally polished; but
the aperture is furnished with folds or teeth, of
which there are usually three. There is only
one British species—

Azmca TRIDENS— (the Glossy Trident Shell)
(Pl. IX., fi2.85) —This snailis rare and sparingly
distributed throughout Hngland, and is more
frequently met with on the chalky and oolitic
soils of Suffolk, Hssex, Kent, Surrey, Glouces-
tershire, &c.; inhabitmg the moss and dead
leaves in moist woods, congregated in little
parties of six to nine. It occurs in the Newer
Tertiary deposits of Copford and Clacton.

Genus Pura (Chrysalis Snails).

The animal is furnished with a short foot,
acute behind; the tentacles are short, especially
the lower ones; in the Sup-Gmenus VERTIGO the
inferior tentacles are obsolete.

LAND SNAILS. 153

The Chrysalis Snails, or Pupe, are so named
from the fancied resemblance of their shells to
an insect in the second stage of its metamor-
phism—that is, to a chrysalid ; also to dolls or
puppets.

The shell is cylindrical or oblong, with many
narrow whorls, minutely umbilicated; the aper-
ture is oval or lunate, generally toothed within ;
the peristome is incomplete, thickened, and re-
flected.

The Pupe are widely distributed on the globe ;
the majority of them inhabit South-eastern
Hurope. Four species are indigenous to this
country and, excepting LP. secale, are found fos-
silized in the Newer Tertiaries of the East of
Eneland. Pupa is the most ancient genus of
the land mollusca, the earliest known species of
which is P. vetusta, of the Coal-measures of
Nova Scotia. Two species are extinct in the
Upper Eocene of the Isle of Wight. The species
now inhabiting Britain may be characterized as
follows :—

1. re tooth, or edentulous tte tee nee ee
Aperture with Many teeth picshi he. tred. . aaeyere ove

Tooth in the upper angle of the outer oan umbilicata
Peristome with external rib, tooth central,—P. muscorum

3 Shell ventricose, shining, 5-toothed ... P. anglica
Shell cylindrical, dull, 8-toothed ... ... ... P. secale

Pura umBiLicaAta—(the Umbilicated Chrysalis

154 LAND AND FRESH-WATER MOLLUSKS.

Shell) (Pl. IX., fig. 97)—is one of the most
common of the land mollusca throughout the
British isles. It frequents old ivied walls, about
rocks, under stones, among moss and herbage
and dead leaves; from the sea-shore to great
elevations.

The shell is oblong, cylindrical, glossy, yel-
lowish-brown or dark horn-colour, composed of
six rounded whorls, which are faintly and irre-
gularly striated in the line of growth; the
aperture is subangular ; the lip is thickened and
much reflected, and white or pale yellowish-grey
on the inside; a single tooth occupies the angle
formed by the junction of the outer lip; there
is a small and narrow umbilicus; the length of
the shell is two-twelfths of an inch, and the
breadth about half. It is subject to variation in
form and colour: some want the tooth; speci-
mens with two teeth have occurred to collectors ;
others have the shell whitish or colourless.

This species is Ovoviviparous.

Pura muscorum—(the Margined Chrysalis Shell)
(Pl. IX., fig. 98)—is very closely allied to P.
umbilicata, but differs from it m being more
cylindrical, with the last whorl smaller; the
mouth. is more oval, less triangular, and the
tooth is placed centrally and considerably within
the aperture, but is, however, often absent. It
is more especially to be distinguished by the

LAND SNAILS. bop

margin of the aperture being expanded, reflected,
and strengthened by a thick white external rib ;
from which latter character it has received the
name of P. marginata. Individuals living in
moist and grassy places are light brown, and
more or less glossy and transparent; those much
exposed to the weather are often grey or whitish
and opaque. This is equally the case with many
other glossy shells.

P. badia of Adams, a North American snail,
is considered by some European authors to be
identical with this species, and it, like its ally,
is OVoviviparous.

The species is common throughout Britain ; it
is partial to dunes and sandy pastures, among
grass and roots of Psamma arenaria, bordering
the sea-coast, and among the rejectamenta of
our tidal rivers ; inland it occurs on rocks, under
stones, on walls, and among moss.

Pura anatica—(the English Chrysalis Shell) .
(Pl. IX., fig. 99)—This species was added to
our molluscan fauna in 1822, by Mr. Bean, and
was considered peculiar to England when de-
scribed by Ferussac; hence its trivial name. It
is found throughout the northern counties of
England, the West of Scotland, and all Ireland ;
it is by no means general, or, except in parti-
cular spots, plentiful.

Though a British species of a northern type,

156 LAND AND FRESH-WATER MOLLUSKS.

it is, however, found in Algeria, and in the neigh-
bourhood of Oporto, in Portugal.

The shell is sub-cylindrical, shining, and vary-
ing in colour from pale greyish- to a deep reddish-
brown, or rarely white ;:the whorls are six; the
aperture is triangular, and rounded below, with
five folds; the margin of the aperture and the
folds are generally of the colour of the shell,
but sometimes white.

It frequents dead leaves and moss in moist
woods, and generally in company with Jlelix
lamellata, with which it is also associated in a
fossil state, in the newer Pleiocene deposits of
Copford, in Essex. The Rev. J. Dalton ob-
serves, that ‘I have been told that this species
never ascends trees, but I took no less than
fifty-three specimens in one day from the trunk
of a young ash-tree, covered with woodbine, in
Hackfall, Ripon. This was after long-continued
rain. In dry weather it is very seldom found ;
and until the above-mentioned day I believed it
to be a very rare species.”

Mr. J. G. Jeffreys writes of the habits of this
snail, that ‘this is a shy little creature, although
tolerably active when inclined to make its ap-
pearance. It has a singular habit of withdrawing
slowly one of its eyes, which rolls backwards
like a little ball until it reaches the neck, while
the tentacle which supports it remains extended

LAND SNAILS. £37

to its full length. This I have observed being
done when there was no obstacle in the way.
It also retracts occasionally, and apparently
without any reason, one of its horns and not the
other. It does not appear to be oyoviviparous,
like P. wmbilicata.”

Pupa sEcaLE—(the Juniper Chrysalis Shell)
(Pl. IX., fig. 96).—The shell is larger and more
tapering than that of any other British Pupa ;
is a quarter of an inch or more in length, cylin-
drical in form, and composed of eight or nine
rounded and gradually increasing whorls, ob-
liquely striated in the line of growth; the colour
is a light brown; the aperture is much con-
tracted by the seven laminar folds—two, and
sometimes three, are on the pillar, two occupy
the pillar lip, and four the outer lip; the teeth
on the outer lip are distinctly visible on the ex- .
terior of the shell as white bands. The number
ef rows, and number of teeth in a row, com-
posing the palatal membrane of P. secale, are
thus—100 rows, 41 in a row; total, 4,100.

This species is local, and chiefly confined to
the limestone tracts of the South and West of
England. On the oolitic hills it is very abun-
dant, attached to stones or to the bare rock
surface by a thin pellicle during the daytime:
from the accidental adhesion of earthy matter
to the shell, especially of the young, it may

158 LAND AND FRESH-WATER MOLLUSKS.

escape notice. The animal is sluggish, and is
not frequently to be seen stirring about.

Genus Vertico (Whorl Snails).

The animal differs from that of Pupa in being
destitute of the lower pair of tentacles. The
shell is minute, sometimes sinistral; the peri-
stome is thinner than in Pupa. Of the nine
species inhabiting this country, V. Moulinsiana
is the only one not known in a fossilized state.

The species may be distinguished as follows :—

Nad

Shell dextral . 2
Shell sinistral ... 8
2 Aperture edentulous 3
* ( Aperture toothed sheue Conemete 4
Shell small, slightly striated ... 1... ... OV. 7. ee
Shell minute, strongly striated ... V. minutissima
4 “SIEM 03:7 | Soe ale a 5
* {Shell cylindrical... 7
Aperture toothed... ... 6

5, ¢ Aperture with many ‘teeth, aperture contracted, —
V. antivertigo
6 SIE eTT ccys ess’ sea, eee one-one
* ( Shell large Sh oe wee ee) )6 Ve Moulinsiana
Shell subcylindrical, ea 1 ae Vi apeetras

7. « Shell inclned to fusiform, strongly striated,—
V. substriata
Aperture subquadrate, six to seven teeth,—V. pusilla

8. < Aperture triangular, contracted, four to six ‘teeth, —
ha angustior

LAND SNAILS. 159

VERTIGO EDENTULA—(the Toothless Whorl Shell)
(Pl. X., fig. 101).—The shell is dextral, cylin-
drical, with five or six rounded whorls, which are
shghtly transversely striated; the third whorl
is the largest ; the aperture is semicircular and
toothless, with the peristome very slightly re-
flected ; the colour is brown or horn, with the
peristome paler; the length is one-tenth of an
inch.

An elongated variety has seven or occasionally
eight whorls, and attains the maximum length
of one and a half lines.

The typical form is generally found under
stones and on rocks ; the variety inhabits moister
places; both, however, occur in woods, on the
fallen leaves of trees in the winter and autumn;
in the summer frequenting the under fronds of
Aspidium filiz-mas and other ferns.

This elegant little mollusk presents a grotesque
appearance when crawling, for the shell is car-
ried in a singularly erect position.

VERTIGO MINUTISSIMA—(PI. X., fig. 100).—As
the specific name implies, this is a tiny shell, and
is not a line in length; it is nearly cylindrical,
with five rounded whorls, which increase sud-
denly to the third, and then continue nearly of
the same size, ornamented with acute oblique
transverse striations. It resembles V. edentula
in the aperture and in the absence of teeth, but

160 LAND AND FRESH-WATER MOLLUSKS.

is distinguished from that species by its very
minute size, and in the strongly striated surface
of the shell. It occurs here and there in Eng-
land and Scotland; it harbours under stones on
hills, chiefly those that are limestone. In Scot-
land it occurs in Skye; Balmerimo, Fifeshire ;
Arthur’s Seat. In England, on magnesian lme-
stone, Falcon Clints, near Sunderland ; and near
Pontefract, in Durham; Wakefield, and Went
Vale, Yorkshire; Durdham Downs, Bristol ;
Sulworth, in Dorset; and on the Undercliff, in
the Isle of Wight. Its minute size may account
for its apparent rarity. It is a continental
species, and widely diffused.

Vertigo premma—(the Pigmy Whorl Shell)
(Pl. [X., fig. 90).—The shell is oval, about one-
tenth of an inch long, of a brown shining colour ;
the four or five whorls gradually increase in size ;
the aperture is dextral, with a slightly reflected
margin, and provided usually with four teeth,
one of which is central on the upper side or
pillar.

This is one of the most widely distributed of
the Vertigos ; it may be easily procured under
stones upon dry and elevated situations.

A thinner shell, and of a lighter colour than
the typical form, is known to collectors; I have
found it under stones on the shores of the Irish
upland lakes, and in damp fields in England.

ae Meo

!

LAND SNAILS. 161

VertTico ALPEstRIs—(the Alpine Whorl Shell)
(Pl. IX., fig. 88)—differs from the last species,
and is regarded by many asa variety of it, in
being more cylindrical, of a paler colour, slightly
striated, and in the absence of any rib, either
inside or outside, to the mouth.

Messrs. Forbes and Hanley say, ‘‘ It may be
taken in great numbers by laying a piece of old
wood upon the grass at nightfall, and examining
it in the morning.”

It occurs in a few places in Cumberland, Lan-
cashire, and Northumberland; at Over, Glou-
cester, and among moss on the canal banks at
Sharpness (Mr. J. Jones) ; and is sparingly dis-
tributed in North and Central Europe.

VERTIGO ANTIVERTIGO—(the Marsh Whorl Shell)
(Pl. X., fig. 103).—The shell of this species is
dextral, and is not reversed, as in some others
of the genus; it is of an oval form, thin, shghtly
polished, and of a brown colour; whorls five ;
the aperture is small, subtriangular, with a
whitish margin, and provided with three unequal
folds above on the pillar, and three on each side.

A very appropriate specific name given to this
snail was palustris, as denoting that it was an
inhabitant of marshy places, about the roots of
plants; it is also to be met with under stones
on the banks of streams and lakes, even in
elevated situations. Though an inhabitant of

M

162 LAND AND FRESH-WATER MOLLUSKS.

such places, the shell is always free from dirt
and has a bright glossy lustre.

Vertico Movtinsiana (PI. X., fig. 105), named
after M. des Moulins, a French conchologist, by
the Abbé D. Dupuy. It is one of the most
recent additions to our land shells. T’his acquisi-
tion to the British mollusca was made by Mr. J.
G. Jeffreys in 1845, but not until the last few
years was this discovery published. The only
British locality is Ballinahinch, near Round-
stone, co. Galway, where it inhabits under stones
by the side of a small lake at the fore-mentioned
place. It is local and rare in Central Europe.
The affinities and differences here given of the
shell of this species are quoted from the above-
named author :—‘ The species differs from V.
antivertigo in being larger, more ventricose, in
the mouth and lip not bemg contracted, and
especially in the number and position of the
teeth, which never exceed four. From V. pygmcea
by being twice the size and very much more
ventricose. V. Moulinsiana resembles V. anti-
vertigo in form, and V. pygmeea in the number of
teeth. It is among the largest of our native
species of Vertigo.”

VERTIGO SUBSTRIATA — (the Sia-toothed Whorl
Shell) (Pl. X., fig. 104).—The shell of this species
is somewhat fusiform, strongly striated trans-
versely, and of a yellowish-horn colour; the

LAND SNAILS. 163

aperture is furnished with from four to six folds
—two or three on the pillar, and two or three on
the outer lip. It is easily distinguished from
the other Vertigos with dextral shells, by its form,
the strong strize, and in the number and position
of the teeth.

It is a rare species, occurring chiefly in the
North ; it has a wide distribution, though rare,
in Ireland; and has a limited range in Hurope.
It occurs among decaying leaves in glens, but
more usually under stones on the banks of lakes,
and at the roots of rushes. It is abundant in a
fossil state in the Copford deposits.

VERTIGO PUSILLA— (the Wry-necked Whorl
Shell) (Pl. X., fig. 102).—The shells of this and
_the following species are sinistral and spindle-
shaped; that of V. pusilla possesses six or seven
folds within the aperture, which is subquadrate.

It lives on old walls and dry banks, under
stones, among leaves in woods, and is diffused
throughout England, but is local and rare ; it is
very rare in Ireland, and has been found in only
a few localities in the North-east and West. It
is a North and Central European species.

VERTIGO ANGUSTIOR—(the Narrow Whorl Shell)
(Pl. X., fig. 111).—The shell of this species
differs from the last in its much smaller size,
in being proportionately narrower, and in pos-
sessing only four to six teeth. The aperture is

mM 2

164 LAND AND FRESH-WATER MOLLUSKS.

narrow and triangular, in consequence of the
great contraction of its outer edge in the middle.
It is found about the roots of grass m marshy
places in a few localities :—Singleton, near Swan-
sea; Tenby; rejectamenta of the river Avon, at
Bristol ; Battersea ; in Ireland, at Miltown Malby,
co. Clare; Connemara, Galway; and at Cork.
It occurs in Central Europe.

GrEnus BALEA.

The animal is bulimus-like ; the lingual ribbon
is furnished with 130 rows of teeth, each row
containing 50. ‘The shell is thin, slender, elon-
gated, of many reversed whorls; the aperture is
ovate, with the peristome thin, and sometimes
furnished with an imperfect fold on the columella.
The genus is intermediate between Pupa and
Olausilia, but differs from the former in the
shape of the aperture and the elongated spire,
and from the latter in having no clausium.

This generic group contains only a few species,
one of which is indigenous to this country :— |

BALEA PERVERSA—(the Fragile Moss Shell) (PI.
IX., fig. 86).—The shell is oblong, slender,
yellowish, transversely striated with seven or
eight distinct whorls; the aperture is roundish,
oval, and reversed ; the peristome is thin, and a
little reflected on the columella, where there may

LAND SNAILS. 165

be observed, in full-grown shells, a tubercle-like
tooth ; the length is’ usually about a quarter of
an inch. The shell varies in size, shape, and
colour ; greenish-white and transparent examples
have been found. The dental formula is 292°,

This species is generally distributed through-
out Britain. In moist weather, these snails may
be seen in some numbers on the trunks of trees;
in dry weather, sheltering beneath the loose
bark, or in the hollows and crevices of the trunks.
Other favourite haunts are among decaying wood
and dead leaves, or lurking in moss, or even on
the tops of old ivied walls. .

It occurs in a fossil state at Grays, in Essex.

Genus Cravsiti1a (Close Snails).

The animal, closely resembling that of Bulimus,
has a short, broad, and obtuse foot; the upper
tentacles are short and the lower ones very small
(PLIX., fig. 94). The shell is fusiform, of many
reversed whorls; the last one is smaller than the
one before it; the aperture is elliptical or pear-
shaped, united all round,and toothed. In addition
to the contraction and folds of the shell for the
protection of the snail within, there is added
an elastic appendage termed the clausiwm, which
is capable of closing the aperture. The clausium
is situated at the distance of about half a whorl

166 LAND AND FRESH-WATER MOLLUSKS.

from the mouth, and may be seen in position by
breaking off the outer part of the last whorl ; it
consists of a thin, spoon-shaped shelly plate
attached to the folds of the columella by an elastic
filament. When the animal comes out of the
shell, the clausiwm is pushed against the colu-
mella; and the elasticity of its filament also
admits of it closing the aperture on the snail
withdrawing within the shell. The clausiwm is
not secreted until the snail is about to complete
its shell; and is not attached to the animal, but
is merely an appendage to the mouth of the
shell.

About 300 species of Clausile are known, the
majority of which inhabit South-eastern Kurope.
Clausila is represented in the Upper Hocene of
the Isle of Wight; and the four species at present
living in England, also found fossilized in the
newer Tertiary deposit of Essex, are as follows :—

Shell smooth, glossy... ... ... ... .. «.- CO. laminata
,, streaked, with raised te.
fs " with two columella folds... C. biplicata
i *: + anree | x a C. rugosa

i. 4 », ‘four or five ; very Fasifoben C. Rolph

CLaUsILIA BIPLICATA—(the Folded Close Shell)
(Pl. IX., fig. 95)—is larger than any of its con-
geners. ‘The shell is two-thirds and occasionally
three-fourths of an inch in length, with about

LAND SNAILS. 167

twelve whorls; it is slender and thin, of a reddish
or greyish-brown colour, with raised white lines ;
there are two folds on the columella.

C. biplicata is very rare, and was first described
as British by Montagu. It may be found in
some abundance under the larger osiers border-
ing the banks of the river Thames about Ham-
mersmith. In the winter it buries the front of
the shell in the loose soil among the tufts of
grass or at the base of the trees. It is also re-
corded from two localities in Wiltshire.

Crausinia LaMINata—(the Laminated Close
Shell) (Pl. IX., fig. 87).—The shell is large,
handsome, and at once distinguished by its
polished appearance; it is usually semi-trans-
parent, glossy, yellowish- or reddish-brown, and
sometimes greenish-white and transparent. There
are twelve whorls ; the aperture is oval, with two
folds, from which latter character it is known
as CU. bidens, one of them curved and situated
on the middle of the columella-lip, and the other
is straight and near the top of the aperture; in
addition there are three or four folds deep within
the aperture, which are visible from the outside,
owing to the transparency of the shell. The
shell attains a length of three-fourths of an inch,
but it varies in size and colour. The dentition
is thus :—Number of rows, 120 ; number of teeth
in a row, 51; total, 6,120.

168 LAND AND FRESH-WATER MOLLUSKS.

This elegant species is local, and chiefly con-
fined to the southern counties in England, reach-
ing the limit of its northern distribution in
Hulne Woods, Alnwick; it is rare in Ireland.
C. laminata is especially met with in woods on a
limestone soil; it is gregarious on the trunks of
beech and other trees, durmg the mght and
after rain.

The eggs of this snail are very large in pro-
portion to the animal, and are deposited among
decaying wood in the autumn, to the number of
ten or twelve; the young appear at the end of
twenty days, and do not attain the adult state
until the end of the second year.

CLAUSILIA RUGOSA— (the Rugose Close Shell)
(Pl. IX., fig. 91).—This species is also known
under the names of C. nigricans and C. perversa ;
it is the commonest of the Clausilic, and lives on
walls, about rocks, and under stones, and on the
trunks of beech and ash in woods.

The shell is more or less fusiform or spindle-
shaped, of about half an inch in length, and com-
posed of nine or ten, and not unfrequently twelve
or thirteen whorls ; the colour varies from a very
pale greyish-white to a deep reddish-brown ;
greenish-white specimens are of rare occurrence ;
the shell is streaked with lines of grey, and stri-
ated obscurely or prominently in different indi-
viduals. The peristome is thickened, detached

Vincent. Broo!rs. Imp

LAND SNAILS. 169

all round, more or less reflected, and whitish ; it
varies in form, being ovate, oblong, or subquad-
rate; the internal plaits are usually three in
number, and all situated on the pillar. The
clausium is curved, thin, with a thick revolute
smooth margin. ‘The dental formula is #°-2°,

The animal is very slender and elongated, and
drags its shell in the same line as the foot and
neck (see Pl. IX., fig. 14) ; for it is mcapable
of raising it, unless when about to repose, when
the shell is inclined at an angle of about 70°.

A marked and persistent variety, C. dubia
(Pl. IX., fig. 92), is characterized by its larger
size and more spindle-shaped form; it is only
recorded from the counties of York, Durham, and
Northumberland.

Crausitia Rotpan (Pl. IX., fig. 93).— This
species was named by Dr. Gray after Mr. Rolph,
an English conchologist. It is easily distinguished
from the other species of the genus by its more
spindle-shaped shell, and in the presence of four
or five folds, two of which are longer than the
rest, within the aperture. The shell is half an
inch to three-fifths in length, and one-seventh
to one-eighth in breadth, of a slightly glossy red-
dish-brown, with regular transverse striations ;
there are ten and a half whorls; the aperture
is subquadrate sinuous on the outer side; the
margin is thick, white, and detached all round.

170 LAND AND FRESH-WATER MOLLUSKS.

This rare species is found among dead leaves
and at the base of trees in woods in a few locali-
ties: in Kent— Ashford, Sevenoaks, Charlton
near London, Southborough, and Tunbridge
Wells; in Sussex—Hastings ; in Hampshire—
Buriton, and Petersfield ; and in Gloucestershire
—Birdlip, Cooper’s Hill, and Charlton, near
Cheltenham. Excepting in the Sussex localities,
where the soil is arenaceous, the rock formations
are chalk and oolite. It is not uncommon in
Central Europe.

A variety of the above species, but regarded
as having specific claims by Continental authors,
is C. Mortilleti; it has only been added to the
British list smce 1856. It was discovered, by
Dr. 8. P. Woodward, at the roots of ivy in
woods, on the chalk hills at Charing, Kent;
by Mr. Prentice, at Charlton-Kings, near Chel-

tenham; and by myself in damp shady places.

among decaying leaves, in Coghurst Wood,
Hastings.

C. Rolphit occurs in each of the above districts,
which makes it the more probable that C. Mor-
tilleti is but a variety of it. In C. Rolphiw the
shell is usually more elongated, and the spire
more gradually decreasing in breadth towards
the apex ; not ventricose, and suddenly narrow-
ing to the attenuated upper portion of the spire,
asin C. Mortilleti. It is lighter in colour, with

SS ee

LAND SNAILS. 17k

a fulvous tint rather than the purplish hue which
pervades the latter; C. Mortilleti has fewer
teeth.

Genus Acuatina (Agate Shells).

The shells of this genus are elongated, cylin-
drical, thin, glossy, and smooth ; the aperture is
oval, and the outer lip thin and not reflected ; the
columella is twisted and truncated in front, that
is, appearing as if cut off below. The species
are very numerous, being about 150 in number,
and especially inhabit tropical and subtropical
forests and wastes. The majority of the agate
shells are beautifully coloured.

The genus is represented by A. costellata in
the Upper Eocene deposits of Bembridge, Isle of
Wight.

The great African species are among the
largest of the land mollusca, and attain a
length of eight inches. The only British
species 1s—

AcwaTina AcicuLa—(the Needle Agate Shell)
(Pl. IX., fig. 89)—and is a perfect Lilhputian
among the snails with which it is generically
allied; a pill-box, that may be carried in one’s
waistcoat pocket, is amply capacious for many of
these pigmies, which rarely exceed one-sixth of
an inch in length; whereas a collector among

172 LAND AND FRESH-WATER MOLLUSKS.

the giants of the race in tropical Africa and
America requires a good-sized basket to bring
home only a few specimens.

The animal of Achatina acicula is white and
pellucid; the upper tentacles are long, but with-
out eyes; the central tooth of the lingual ribbon
is very small and pointed. The shell is very thin,
slender, polished, and white, and, from its trans-
parency, the dilatation and contraction of the
respiratory cavity may be distinctly observed by
the aid of a microscope, as irregular pulsations,
reminding one of the action of the heart, for
which it has been mistaken.

This handsome species is recorded, in the ma-
jority of local lists of land shells, as being found
upon old walls or among the rejectamenta of
rivers, but as dead shells; this appears to be
accounted for by its subterranean habits, for its
occurrence in a living state has been noticed
when the soil or gravel has been overturned to a
depth of some six or eight inches.

That such is not its sole habitat, I have had
opportunities of satisfactorily determining ; —
thus, in many parts of the Cotswolds, this species
has occurred to me in a living state, in bleak and
dry situations, at an elevation of 500 to 1,000
feet, under stones, among the turf of these cal-
careous hills, or concealed deep in the fissures of
the limestone rocks. I have even taken it among

LAND SNAILS. 173

the acicular leaves of the larch and pine, in
company with Helicella pura, H. crystallina, and
Vitrina ; this latter habitat is exceptional, be-
cause, ‘‘it is unusual to find molluscan life in
such situations,” for the presence of coniferous
trees exerts a retarding influence on the growth
and increase of land snails.

Its occurrence has been noticed by Mr.
Bridgman, at Norwich, on a sunny bank near the
Thorpe toll-bar, adhering to the roots of grass in
the loose earth between the stones. “It was
not, however,” this gentleman writes, “at the
roots of the grass, beneath the surface of the
soil, but quite on the top, and also in the fine
loose earth among the large flints, with which
the bank is faced, and, in the first instance, ad-
hering to the flint itself.”

It is found sometimes abundantly amongst
rotten wood.

It is inferred, because A. acicula usually lives
underground, and has rarely been observed on
the surface in a living state, that it feeds upon
animal matter.

At the present time, this species has only been
found here and there to the South of Yorkshire,
and in the South and West of Ireland. It is dis-
tributed throughout Europe, and ranges into
Asia Minor and Syria, and inhabits Algeria and
Madeira.

174 LAND AND FRESH-WATER MOLLUSKS.

Genus Succinza (Amber Snails).

The amber snails are so named because of the
colour of the shells, which has some resemblance
to that of swccinwm or amber ; they have a large
body with a broad foot, with the tentacles short

BORSA DUE CCEA -

Fig. 23.—A transverse row of the lingual ribbon of 8. putris (Lovén).

and thick, as shown in Pl. VI, fig. 44. The
lingual teeth are like those of Helix ; in S. putris,
the formula is 22+-5?, the central tooth differs
only from the laterals in size: the teeth are
three-lobed, the central is large (see fig. 23). .
The shell is thin, oval or oblong, with a small
spire and rapidly enlarging whorls, the aperture
is large and obliquely oval. The oblong shape of
the shell distinguishes it from those of the other
members of the Family Helicide, but allies it to
those of Limneide, but separable from them by
the absence of any oblique fold on the columella.
They all inhabit damp places, and though
thriving on the stems of plants growing in the
water, yet they rarely enter that element.
The most common and largest of the species is
Succinga PuTris—(the Common Amber Snail)

LAND SNAILS. EZ5

(Pl. VI., fig 44; Pl. X., fig. 106).—The shell is
oblong-oval,very thin, glossy,irregularly striated,
and of an amber colour; the whorls are three in
number; the spire is short; and the aperture
ovate, two-thirds of the length of the shell, which
is from a half to three-fourths of an inch.

This is an abundant species among herbage in
marshy places, on the banks of ditches and pools ;
among sedges, grasses, and flags; in very hot
weather, when the plants are desiccated, con-
sequent upon the drying up of the water in the
ditches, the amber snail descends to the lower
parts of the stems of the plants upon which it
feeds, whence it appears to follow the receding
water at a certain distance.

S. putris is a fossil of the Mammaliferous Crag
of Bramerton, and of the Pleistocene marls of
Copford, &c.

Succtnea ELEGANS—(the Elegant Amber Snail)
(Pl. X., fig. 107) — also known by the specific
appellations of Pfeifferi and gracilis, is a closely
allied species, or it may be but a variety of the
last. The shell is more slender in shape, and
with a longer and more pointed spire, and some-
what smaller in size; the shell, when containing
the animal, appears of a greyish-blue, or bluish
or greenish-black, for the body of the snail is
black.

This species, though frequently associated with

176 LAND AND FRESH-WATER MOLLUSKS.

S. putris, I find more generally on plants in bogs
and maritime marshes; on plants and stones by
mountain rills and lakes. It occurs with the last
species in the Copford beds.

Succingea oBtonca—(the Oblong Amber Snail)
(Pl. X., fig. 109) —is one of our rarities, and is
markedly distinct from the two other species ;
it is always much smaller in size, with three or
four distinctly separated whorls; the aperture is
oval, and small in proportion to the size of the
shell, being as long as the spire. The form of
the shell of this species closely resembles that of
Limnea truncatula, but the absence of a reflected
lip on the columella at once distinguishes it.

S. oblonga inhabits ditches near the coast, on
sand-dunes near the sea, covering its shell with
a viscous secretion, and in winter burying itself
in the sand. There are two inland stations for
it, both in Ireland: turf bogs, Finnoe, co. Tip-
perary ; and damp woods, near Armagh: it is
also found in woods in Central France, where it
is nearly always met with slightly beneath the
humus, which probably furnishes it with moisture,
which it requires. It occurs near Swansea,
Bideford, Berwick, Glasgow, and Cork. It is
diffused throughout Europe, and is fossilized in
the Pleistocene freshwater marls of Clacton,
and in the Mammaliferous Crag at Bulcham and
Maidstone.

LAND SNAILS. We7

Faminy AURICULIDA.

This section of the Inoperculata contains only
two British genera: Carychium and Conovulus.
The former is truly terrestrial, whilst the Cono-
vuli live on the mud at the mouths of rivers, or
in the sea, and were long regarded as marine
animals, but they are truly pulmoniferous.

The shell of Carychium is minute and ovate,
with an oblong, three-toothed aperture; the
shell of Conovulus is also ovate, but the pillar
presents two or three plaits.

Genus CARYCHIUM.

,CarycHIUM MINIMUM — (the Minute Sedge
Shell) (Pl. XI., fig. 135).—This is an excedingly
beautiful creature, and the smallest of British
snails ; it is yellowish-white, provided with two
conspicuous black eyes, near together at the
. base, and behind the tentacles. The dental
formula is 242, |

The shell is very minute, scarcely one-tenth of
an inch long, oblong, white, shining, and finely
striated transversely ; there are five whorls; the
aperture is oval, with two teeth on the pillar, the
margin is thickened and reflected, and presents
a tooth projecting inwards in the middle of the
outer lip.

, N

178 LAND AND FRESH-WATER MOLLUSKS.

The favourite abode of this minute species is
among decaying leaves in woods, among herbage
on mossy banks, and in moist places; it feeds on
Marchantia. It is commonly distributed through-
out Britain and Europe. In North America it
is represented by the closely-allied C. exiquum,
Say.

Though these very little snails are terrestrial,
yet, as they are attracted to the vicinity of water,
their minute shells occur, often abundantly, in
the alluvia of rivers. This species 1s common
as a fossil of the Newer Tertiaries. Among the
freshwater shells of the Purbeck beds at Villers-
le-Lac, Doubs, there is a single species of land
shell, Carychium Brotianwm, the bails of
the genus.

Genus CoNnovuLlus.

CoNnovuLus DENTICULATUS—(the Toothed Cono-
vulus) (Plate XI., fig. 134).—The shell is
oblong, brittle, smooth, and of a brown or
reddish-glossy colour; the spire is acute, with
fine hairs around the sutures of the higher
whorls ; the aperture is oblong’, rather thickened
with three or five plaits or folds on the pillar,
and a few denticulations on the outer lip; the
length is about three and a half-lines, the width
one and a-half. The lingual ribbon comprises

LAND SNAILS. 179

twelve transverse rows, containing fifty-one
teeth ; the central tooth is short and rounded;
the laterals at first are similar to the central
tooth, but gradually merge into the uncini,
which are short and bidentated.

The species varies considerably in size, colour,
and length of spire, and number of teeth. A
persistent variety is C. myosotis (Pl. XI., fig.137);
the shell is much thicker, and wants the tooth-
like protuberances on the outer lip ; it is a fossil
of the Red Crag at Sutton, and of the Mamma-
liferous Crag at Bramerton, associated with an
extinct species, C. pyramidalis.

OC. denticulatus inhabits brackish marshes, or
lives under stones immediately above high-water-
mark, near the mouths of rivers, often in com-
pany with Hydrobia ulve. It also frequents the
rejectamenta of rivers, feeding on the cast-up
matter. ‘The animal is active and irritable; it
does not hibernate. ‘Twelve eggs, or so, united
into a common mass by a viscid material, are
deposited among stones; they are hatched at the
end of a fortnight, and the young attain the adult
state in about a year.

The species is confined to the south and west
shores of England, and is rare in Ireland. It is
found in the interstices of a sea-wall in Portland
Harbour, Maine.

ConovuLus BipenTATUS—(the T'wo-toothed Cono-

N 2

180 LAND AND FRESH-WATER MOLLUSKS.

vulus) (Pl. XI., fig. 138).—The shell resembles
that of the last, but is more oval, and of a
yellowish, or brownish-white colour; it is more
ventricose, and has only two plaits on the pillar.
The foot is deeply transversely divided, whereas
that of C. denticulatus is entire.

Its habitats are the same as the last. It
occurs in the south and west parts of England, —
and is pretty general along the Irish coasts.

Orina OTIS, with a minute ear-shaped shell,
is a marine species of the family Auwriculide ;
it lives in the chinks of rocks at the margin of
the sea in the south and south-west of Britain.
The teeth resemble those of other Pulmonata,
and are similar to Conovulus. There are ten rows
of sixty teeth in each.

181

WATER SNAILS.
Famity Limnaipm (Water Air-breathing Snails).

THs very natural family comprises the fresh-
water pulmoniferous snails; they all have short
dilated muzzles, and two tentacles, with the eyes
sessile at their inner bases. Nearly all the pul-
monifera have only one jaw,* implanted supe-
riorly between the lips; but species of the
genera Limnea (excluding Amphipeplea) and
Ancylus, and Planorbis corneus, have three jaws
or, more properly, the labial armature is formed
of three pieces: the one large (the true jaw) is
placed transversely above the mouth, whilst the
other two, less in size, are placed vertically one
on the right and one on the left side. In the
remaining species the mouth is armed with a
single arched piece. The lingual dentition pre-
sents widely distinct characters in the several
genera. The stiff silky hairs, which are found
on the skin of Neritinee, have been found by
M. Claperéde to exist on most of our fresh-water

* This organ 18 composed of hardened mucus, and con-
tains a feeble quantity of carbonate of lime.

182 LAND AND FRESH-WATER MOLLUSKS.

mollusks. Their shells are extremely variable,
spiral and turreted, dextral or sinistral, discoidal
and limpet-like ; delicate, fragile, and of a uni-
form colour. They have no operculum, but
secrete a thin epiphragm when the pools, in
which they live, dry up.

They inhabit fresh-water, at a small depth,
as they are compelled to rise frequently to the
surface to breathe; many of them can lower
themselves in the water by a glutinous thread.
They lay their eges in a’ transparent jelly mass
on the leaves and stems of water plants, or on
stones. The early development of a Pulmo-
niferous snail can be most conveniently observed
in a [imneea. In an aquarium, the eggs are
often deposited on the sides of the glass, and in
that case a microscope can be brought to bear
on the object, without at all interfermg with the
course of nature. The egg sacs are dull at the
moment of laying, but after remaining in the
water a few hours they become transparent.
The form of the albuminous mass varies some-
what with the species ; it is usually an elongated
oval. The eggs are hatched in about 30 days.
The snail is usually infested with a species of hair
worm (Gordius inquilinus), numbers of which

attach themselves around the neck and beneath —

the tentacles, and are ever vibrating. They are

falsely-parasitic, for they appear to derive no

}

q

:

WATER SNAILS. 183

sustenance from the snail, but feed on animal-
cules.

From experiments made by Mr. Jennings and
Dr. Ball, some of the water-snails appear to have
the power of causing a peculiar sensation when
placed on the tongue. The experimentalists
operated upon the common pond-snail (Limnea
peregra) ; they allowed the foot of the animal to
remain for a few minutes on the tongue, when
the sensation was felt, varying in intensity ac-
cording to the size of the animal, and the length
of time it is allowed to remain. The sensation,
though not decidedly painful, is yet rather dis-
agreeable whilst it continues, frequently lasting
from one to two hours, bemg exerted with
greater energy during warm than cold weather.
The same painful sensation was experienced by
the contact of the river hmpet (Ancylus) with
the tongue. A few experiments were tried to
ascertain whether the power arose from an acid
secretion, capable of beimg emitted at pleasure
by the animal, but so far without success. Have
the pond-snails stinging or urticating organs of
the nature of those which have been recently
observed in the marine slugs (Holide) ? °

The family is represented in Great Britain by
four genera, which may be distinguished as
follows :—

184, LAND AND FRESH-WATER MOLLUSKS.

Shell oval, spiral—

(a) pillar with an oblique plait .... .... Limnea
(6) aperture sinistral... .., “es omeee Physa
ell comical... 2... 6s xs. ged” dec) ayer
phell'discoidal 0. fe.) see wee ‘ene ee

Genus Limnma (Pond Snails).

The generic word is derived from the Greek,
limne, a marsh or pool.

The animal is of a greyish colour; the head
is short and broad, with two flattened short
triangular tentacles bearing eyes at their bases ;
the foot is broad and short, with two lobes, or
simply notched in front. The jaw is composed
of three smooth pieces; the superior one is —
usually produced in front to form a slight beak.
The general character of the lingual ribbon is
such as is represented in fig. 24.

The shell is spiral, oval, or oblong, thin,
fragile, and translucent ; the last whorl is large ;
the aperture is longer than wide, oval, with a
thin edge and an oblique fold on the columella.
They inhabit still and shallow waters, crawl
slowly, float along the surface of the water with
the foot, in the fashion of a boat, and the shell
downwards, for the purpose of supplying them-
selves with air and collecting food. In a state of
repose they adhere by their foot to stones and
plants, and are capable of long immersion; in

WATER SNAILS. 185

drought they partially bury themselves in the
mud. The pond snails make a very audible
squeaking noise on being taken out of the water.
This arises from the expulsion of the water as
the animal retreats within its shell.

The food of the pond snails is animal and
vegetable matters in different states of putridity ;
they also feed on living aquatic plants, and the
green confervee encrusting their shells have been
observed to be objects of attraction among them-
selves. Dr. Bland noticed that the water snails,
by cleaning off the algal growth of the shells of
their neighbours, removed the epidermis, or
even made holes in them by this continued
rasping ; and thereby accounted for the decolla-
tion of the upper whorls of their shells, when
not attributable to chemical agencies ; formerly
this propensity was regarded as one of true can-
nibalism, because, in the absence of other food,
the snails devoured each other by piercing the
shell at the apex, and eating away the upper
parts of its inhabitant.

The water snails are very important elements
in an aquarium, where the removal of decaying
vegetable matter is necessary; they cannot,
however, keep in check the confervoid growth.

Hight species of the genus are known in Great
Britain, and are contained in three sections :—

186 LAND AND FRESH-WATER MOLLUSKS.

I. L. peregra, L. auricularia, and L. stagnalis,
have the last whorl much enlarged.

Il. L. palustris, L. truncatula, and L. glaber,
form another section, in which the spire is much
elongated and the whorls gradually increase im
size.

IIT. L. glutinosa and L. involuta are separated
by some authors from the true pond-snails, and
placed in a sub-generic group under the name of
Amplhipeplea, because they possess a globular
membranaceous shell, and the animal, though
hike Limnea, has the edges of the mantle, when
the snail is in motion, extended so as to cover
the shell.

A Inimnea is known in the Middle Purbecks,
and the genus is-represented by numerous spe-
cies in the fresh-water beds of the Upper Eocenes,
in the Isle of Wight; of the lving species,
LL. palustris, L. peregra, and L. truncatula, first
appeared during the deposition of the Mamma-
liferous Crag at Bramerton and Bulcham ; they,
with L. stagnalis and L. awricularia, occur in the
Pleistocene marls of Hssex.

LimnmA PEREGRA—(the Wandering Mud Snail)
(Pl. X., fig. 117).—This mollusk is the most
widely dispersed and abundant, and, at the
same time, the most variable of the fresh-water
snails.

The shell is ovate, thin, the colour varymg

Broo

recent

tr
Van lay

As

WATER SNAILS. 187

from a pale yellowish-grey to dark reddish-
brown; under a high magnifying power the
surface is seen to be striated spirally; the
whorls are five in number, convex; the last one
very large; the aperture is large and oval; the
inner lip is folded on the columella, forming
behind it a concealed narrow groove. The length
is from half-an-inch to an inch; the breadth
about two-thirds of the length.

The principal varieties which the shell of this
species presents, are the following :—

1. Var. ovata (Pl. X., fig. 118).—The spire
acute, extremely short; whorls exceedingly
convex, the last very large; aperture obliquely
produced, four-fifths of the whole length; shell
very thin and glossy. It is thus distinguished
by its ovate form, its dilated aperture, and
acute spire. It attais a larger size than the
normal form, and often equals the next species,
L. auricularia. It is common, and is the form
usually met with in still waters, especially if of
great extent ; whereas the smaller and narrower
form—the type of the species—inhabits running
waters, small brooks, and splashy pools.

2. Var. lacustris is an inhabitant of the moun-
tain lakes in Scotland, Ireland, and North of
England, and in the Shetlands. It has a small
glossy thin shell, strongly concentrically wrinkled ;
the spire is very short, and the aperture is large ;

188 LAND AND FRESH-WATER MOLLUSKS. >

this variety is intermediate in form between the
typical LD. peregra and L. glutinosa.

3. Var. Burnetht (Pl. X., fig. 116) differs from
the type in its involute spire, placed more
obliquely, in being regularly striated, and in the
darker colour of the animal. This variety was
detected by Mr. Burnett, in 1848, in the
stomachs of trout caught in Loch Shene, and
on a second visit he obtained many living ex-
amples. It occurs in a few other Scottish lakes
and also in North Wales.

This species shows greater activity than the
others of the genus; as implied by the specific
name—from the Latin peregrinor, “to travel
through strange places ””—it is widely dispersed,
everywhere abundant in ponds, ditches, and slow
running water, and is not unfrequently found
at some distance from the water, or walking on
the moist mud. It attains an elevation of 1742
feet on the Aberdeenshire mountains.

It is very prolific, and lays upwards of a thou-
sand eggs in a season; these are contained in
clusters of from 12 to 100; the gelatinous mass
in which they are imbedded is of an elongated
oval form.

The dispersion of the fresh-water mollusks is
chiefly effected by the agency of streams and
and-floods; but wherever a pool of water is
formed, L. peregra is the first to make its ap-

WATER SNAILS. 189

pearance, even in localities, such as a reservoir
on the top of a hill, where the ordinary agencies
will not account for its presence. Setting aside
the wonderful tales of ‘“ showers of snails,’ the
occurrence of shells in such localities is evidently
due to transportation by birds, the young snails
or capsules adhering to their feet. In elucida-
tion, here follows an experiment performed by
Mr. Darwin, and extracted from his ‘ Origin of
Species”? :—

““T suspended a duck’s feet, which might re
present those of a bird sleeping in a natural
pond, in an aquarium, where many ova of fresh-
water shells were hatching; and I found that
numbers of the extremely minute and just-hatched
shells crawled on the feet, and clung to them so
firmly, that when taken out of the water they
could not be jarred off, though at a somewhat
more advanced age they would voluntarily drop
off. These just-hatched mollusks, though aquatic
in their nature, survived on the duck’s feet, in
damp air, from twelve to twenty hours; and
in this length of time a duck or heron might fly
at least six or seven hundred. miles, and would
be sure to alight on a pool or rivulet, if blown
across sea to an oceanic island, or to any other
distant point. Sir Charles Lyell also informs
me that a Dytiscus has been caught with an
Ancylus firmly adhering to it.”

190 LAND AND FRESH-WATER MOLLUSKS.

LIMN@HA AURICULARIA—(the Wide-mouthed or
Har-shaped Mud Shell) (Pl. X., fig. 119).—A
large shell, and, without doubt, one of the most
beautiful of the genus, remarkable for its globose
form, and vastly expanded and roundish oval
aperture; the spire is very short and acute; these
characters serve to distinguish it from L. peregra.
The shell is moreover beautifully glossy and
semi-transparent ; the lines of growth are deep
and irregular. When the shell has lain dead for
some time in the water, it becomes opaque, pale
yellow externally and white within.

It has the habits of, but is less active than, the
former species. It is local and rare; usually
frequenting slow rivers, canals, and deep ditches ;
it 1s not uncommon in the valley of the Thames,
and in low districts of the Hastern Counties ; it
has not been observed in Scotland.

Limnma stagnatis—(the Lake Mud Shell) (Pl.
X., fig. 114).—The shell of this species is larger
and longer than that of any other Limnea, being
an inch and a-half long and nearly an inch wide ;
it is thin, brittle, of a greyish-white, brown or
red colour; the spire is composed of six or seven
rounded whorls, the last one occupying nearly
three-fourths of the length of the shell. The
shell varies in thickness, according to the nature
of the water and food; in ponds, the last whorl
is often much inflated; in clear running water,

WATER. SNAILS. 191

the shell is smaller, more slender, and tapering,
and is the variety fragilis; though variable in
its proportions, it always presents a very oblique
aperture, exceeding in height half the length
of the shell.

The dental formula of this species is 4235=
12,210; the central tooth is very minute; the
laterals are large with two unequal prominent
points, the outer the smallest. (See fig. 24.)

Ha a a

Fig. 24.— Portion of a transverse row of the lingual ribbon of
L. stagnalis (Lovén).

I. stagnalis prefers animal substances, and
plays the part of “scavenger of the waters” ;
its presence in aquariums is almost necessary.
It has been observed devouring the larva of
Dytiscus, a water-beetle.

Fig. 25.—L. stagnalis.

It is a sluggish animal, and may be seen on a

192 LAND AND FRESH-WATER MOLLUSKS.

summer’s day traversing the surface of the water
in an easy undulating line, or floating in luxurious
repose, perhaps

To taste the freshness of heaven’s breath, and feel
That light is pleasant, and the sunbeam warm.

When about to descend from the surface, it con-
tracts the pulmonary pouch, expelling the air,
and drops at once to the bottom, and regains the
surface by crawling up some solid body.

This species 1s distributed throughout HEng-
land, but is rare in the north; it inhabits Gulane
Loch, 17 or 18 miles east of Hdinburgh; it is
rare in Ireland. The variety is found in a few
canals. I have met with it very elongated in
the River Lea, at St. Alban’s.

I. stagnalis furnishes us with one of the pro-
blems of Natural History —its disappearance
in localities where it has been more or less
abundant for some years. Thus Dr. Johnston
recorded the presence, and after a short lapse
of time the total disappearance, of this snail in
Berwickshire. Having observed this phenomenon
in part, I am enabled to give the following pro-
bable explanation :—A pond in the neighbour- —
hood of Hastings was tenanted by many adults
of LD. stagnalis ; in the following year they were
not to be found; but in the summer of the suc-
ceeding year I found them again in plenty.

WATER SNAILS. 193

Now this snail is a favourite food of ducks and
geese, and the proximity of a farm, where these
birds were kept, to the pond with L. stagnalis
suggests to me the probable cause of their
disappearance; but the eggs having escaped
the general despoliation remained to replace
their predecessors, and after the end of the
first year attained to the adult condition. I had
no opportunities of determining whether in the
interval the pond was unfrequented by the geese,
which appears somewhat necessary to account
for the preservation of the young snails until
they arrived at maturity.

In other districts, to call in the aid of the
wild ducks and herons, which prey upon them,
as the agents of extermination, is quite fea-
sible.

Limnza paLustris—(the Marsh Mud Shell)
(Pl. X., fig. 113).—The shell of this species is
oblong, conical, and pointed; colour, yellow to
brown; whorls, six to seven, rounded, slightly
convex, with a rather deep suture; the last whorl
is large; the aperture is nearly half the length of
the shell, purplish and glossy in the inside; the
inner lip expanded, and partially covering the
slight umbilicus; the maximum length is about
three-fourths of an inch, but variable in size, as
-also in colour and form. Shells occur with spiral
narrow white bands. Not unfrequently the spire

Oo

194 LAND AND: FRESH-WATER MOLLUSKS.

is truncated or decollated from erosion or decay
of the first whorls.

It is a common and generally distributed
species, in ponds, marshes, and lakes, usually
about their margins.

It differs from LD. stagnalis, in the shell being
thicker and the whorls narrower.

LimnzA TRUNCATULA—(the Small Mud Shell)
(Pl. X., fig. 110).—The shell of this species
differs from that of LD. palustris, in its minute
size, not exceeding half-an-inch in length, and
in the more rounded and deeply separated whorls,
somewhat abruptly bent towards the suture.

The above specific name, given to it by Miller,
is derived from the truncated form of the whorls,
and not from the decollation of the spire; for
from its very habit it is not so lable to have
the apex of its shell eroded. It received the
name of fossaria from an English conchologist,
Montagu, from its inhabiting ditches, and also
that of minuta from Draparnaud, because of its
diminutive size, it being the smallest of the
genus.

IL. truncatula is extremely variable in size,
adult specimens being not unfrequently found
one-third less in size than ordinarily; these
inhabit high elevations and maritime marshes.
It also presents very great differences in form,
the degree of rugosity or smoothness, the pro-

- WATER SNAILS. 195

minence of the spire and the outline of the
mouth.

This little mollusk is generally distributed
throughout Britain and Europe, and extends
into North Africa, Afghanistan, and Siberia. It
inhabits the banks of ditches, canals, muddy
streams, and rivers; it is found on the stones
of pools at considerable elevation on mountains,
where it is preyed upon by the lapwing ;
it also frequents the moist mud and damp places
about springs and waterfalls. I have even taken
it in the rills at the margins of the high roads,
in which spots it was only occasionally bathed
in water, during and for a short time after rain.
L. truncatula, living as it does on the margins
of streams, pools, &c., differs in its habitats from
the species of the genus, which invariably pass
their days on submerged plants. In such spots
as indicated, this species deposits its eggs, which
are not fixed to the stems of aquatic plants, as
are those of its congeners, but are united in little
rounded masses, which rarely contain more than
from fifteen to twenty eggs.

In the heat of summer, the small mud-snails
bury themselves in the mud.

Limn#A GLABER—(the Smooth Mud Shell)
(Pl. X., fig. 115).—One of its synonyms is L.
octona, or “ the Hight-Whorled Mud Shell.”

The shell of this species is elongated, tapering,

02

196 LAND AND FRESH-WATER MOLLUSKS. -

composed of seven or eight rounded whorls, thin
and glossy, but with a few faint longitudinal
striations. The aperture is narrowed above, not
a third of the length of the shell, with a thick
broad white rib inside ; length of shell one inch

It is the rarest species of the genus, and is
found in ditches and shallow pools in some of the
eastern and south-western counties ; in marshes
on the coast near Swansea ; in Yorkshire, Durham,
and Staffordshire ; at Bowness, Westmoreland; in
Treland, Cork. It ranges into North and Central
Europe.

Limyaa (AMPHIPEPLEA) GLUTINOSA—(the Glutin-
ous Membrane Shell) (Pl. X., figs. 121, 122).—
L. glutinosa differs from the species of the genus
by the disposition of its mantle, which entirely
covers the shell when the animal is submerged,
and then resembles a ball of mucilage. It is this
character which induced Nilsson to found a new
genus, Amphipeplea, of it.

The shell of this beautiful and interesting
mollusk is semi-globular, thin, transparent, and
glossy amber-coloured; the spire is very short,
of three scarcely-produced whorls; the length is
about half-an-inch, and nearly as much wide.
When the shell remains in the water after the
death of the animal, it soon loses its transparency
and beautiful amber colour.

The animal of L. glutinosa is large, glossy,

WATER SNAILS. 197

and nearly gelatinous, very broad, obtuse at its
extremities. Its colour is greenish-yellow in the
thin parts, but of greenish-grey in the denser
parts. The foot is very large and truncated in
front. The tentacles are extremely thin and
transparent, slightly and irregularly veined with
bright-grey. The jaw is single, composed of a
slightly arched piece, with an indistinct median
projection, and covered by numerous striations.

It is not by the mantle that the shell is
covered, but by a simple dilatation of its border,
which is entire and very contractile, and is pushed
over upon the shell so as to envelop it like a
bag. The protection thus afforded to the test 1s
nearly always complete when the animals are
immersed. In the larger individuals, when the
water is deep and the sun shining, the mantle-
expansions do not quite cover the upper surface
of the shell, but a small round, oval, or irregular
space is left, which enables one to see the
speckled body. If the animal be disturbed by
touching the edges of its sac, it endeavours to
cover entirely the shell. The faculty of extension
of the mantle margin is a gift of Nature, to coun-
terbalance the extreme thinness and fragility of
the shell.

The animals cannot live out of the water, and
never voluntarily leave it; they are always on
the move, especially during sunshine, but their

198 LAND AND: FRESH-WATER MOLLUSKS.

walk is slow; they swim very well, with the shell
inverted, at the surface of the water, which, if
shallow and not sufficient, is soon rendered
glutinous with their mucus threads.

The egg-masses are large, about two inches
long, cylindrical, and shghtly curved ; the eggs are
disposed in the capsules m two rows of about
fifteen each, which are imbricated one on the
other, but the length of the capsule, and conse-
quently the number of eggs in each of them, are
variable.

It occurs in ditches and lakes on vadatles
plants, and-is abundant, though very local. It
is remarkable for its periodical appearance in the
same spots. It is recorded, from the neighbour-_
hood of Norwich on Stwms; near Oxford; Dun-
ster Castle, Somerset; Bala Lake, North Wales ;
and Windermere Lake; it ranges from Finland
to the Pyrenees.

Limn#A (AMPHIPEPLEA) INvoLUTA—(the Involute
Membrane Shell) (Pl. X., fig. 123).—It is easily
distinguished from the last species by the sunken
spire within the last whorl ;. the aperture of the
shell is very large, and extends to the apex.
‘The shell is small, polished, of a pale amber
colour, extremely thin and membranous, as in
L. glutinosa, with coarse longitudinal striz; its
maximum length is five and a-half lines, and its
greatest breadth three and a-half lines.

WATER SNAILS. 199

This beautiful mollusk was discovered by Dr.
Harvey, of botanical renown, in a small Alpine
lake, and in a stream which flows into it, on
Cromaglaun Mountain, near the lakes of Kul-
larney in 1832; not the smallest trace of its
existence in the many other tarns has been dis-
covered. It is one of the very few pulmoniferous
mollusks peculiar to Great Britain, which induced
the late Professer EH. Forbes to regard it as a
probable monstrosity of LD. glutinosa. Another
point of interest regarding this snail, is that the
shell partakes more of the form of the marine
Akera bullata than of the other Limneas; but the
structure of the animal resembles that of other
species of the genus. Accurate observations,
however, are required to satisfactorily set at
rest the disputed point as to whether the present
species has expanded lobes to the mantle or
not.

Dr. W. H. Evans communicated “ An Ascent
of Cromaglaun Mountain in Quest of Limnca
involuta,” to the ‘ Naturalist,’ of November,
1864; from which I extract the following most
complete account of the natural history of this
species :—

“Tts eastern side is almost overhung by the
perpendicular wall of the higher ridge of the
mountain, altogether precluding access in that
quarter; the remainder of the lake being sur-

200 LAND AND FRESH-WATER MOLLUSKS.

rounded for the most part by bog. The water,
impregnated by vegetable matter, is almost of a
coffee colour, but generally clear, and the whole
region has a wild and desolate aspect, strangely
contrasting with the charming scenery we have
just left. During the first quarter of an hour, I
searched diligently on the leaves and stalks of
the water-plants growing in the lake, and scooped
up quantities of mud, which I carefully examined,
but not a shell could I find. Water, rock, and
mollusk were nearly of one colour; but by
kneeling down beside the tarn, and putting
my face almost close to the surface, I was able to
see to some distance into the water. After
gazing steadily for a few minutes, I thought I
discovered two Limneas crawling up the side of
the rock, and a little careful manipulation with
the scoop soon put me in possession of the
prize. I spent about two hours at the lake, and
took eleven specimens of. the Limneea in addition’
to the first, which the guide had broken, and
in every instance the mollusk was either crawl-
ing on rocks or free; never attached to aquatic
plants, or found in the mud. Had the day been
bright and calm, I dare say I should have col-
lected a greater number; but where the breeze
rippled the surface of the water, it was impossible
to see anything accurately, even at the depth of
a few inches, unless it differed much from the

WATER SNAILS. 201

brown tint of the water. Owing to the un-
favourable state of the weather, and the con-
strained position I was forced to assume, it was
impossible to observe the animal very accurately
in the water; but although I looked for it, I was
unable to detect the mantle which is said to
cover the greater part of the shell. I kept them
in the box from Friday forenoon until late
on the following Monday evening; they were
then transferred to a tumbler of water, with a
little Anacharis in it, and they seemed as lively
and fresh as if they had been but an hour
caught. They moved about rapidly, and with a
continuous gliding motion over the sides of the
glass, sailing on steadily, so to speak, without
any of the jerking mode of progression so
common in most of the gasteropods. They
gradually died off, one surviving a fortnight.
During the time I had an opportunity of observ-
ing them in captivity I never could discover any
portion of the mantle expanded over the shell.”

Genus Puysa (Bubble Shells).

The animal is provided with two very long
slender tentacles, bearing the eyes at their bases
internally ; the jaw is single and slightly arched ;
the shell is sinistrally spiral, thin, and polished.
The two British species belong to two different

202 LAND AND FRESH-WATER MOLLUSKS.

groups: P. fontinalis to the typical section,
characterized by the oval shell; the mantle is
capable of being much extended, and its margins
are frmged with long filaments; P. hypnorwm, be-
longing to the subgeneric section Apleaa, has an
elongated spire, and themargin of the mantle plain.

Two species of Physa, the most ancient of the
genus, are known in the Purbeck formation;
many occur in Tertiary strata, and the two
living species are fossils of the newer Tertiaries.

PHyYsA FONTINALIS—(the Stream Bubble Shell)
(Pl. XI., figs. 133, 141).—This pretty and inter-
esting adjunct to an aquarium possesses an ex-
tremely thin, glossy, and semi-transparent shell
of a yellowish or brownish colour, of an oval
form, and nearly half-an-inch long, and about
half as much broad; the whorls are four, the
first three extremely small, the last one occu-
pies three-fourths or four-fifths of the shell.

This species is widely distributed, and common
on aquatic plants in brooks, ditches, canals, and
slow-running rivers.

It exhibits great activity, and its modes of
progression are various. The animal glides
rapidly along with a uniform quick motion, its
narrow and elongated foot apparently inadequate
to support the bulky body. The head, which is
obtuse in front, supports two long tapering and
very slender tentacles; the eyes are situated at

= et &
Plate Xi :

Vincent Brooks , Imp.

Ay ny

4 J |
BAS sera

WATER SNAILS. 203

the inner bases of the tentacles, and are very con-
spicuous, their black colour contrasting strongly
with the yellowish grey of the body. The
edges of the mantle are extended into about
twelve lobes, which can be spread over the shell,
nearly meeting above.

This little Physa can raise itself in the water
or sink at pleasure, without having recourse to
plants to assist its progress; in descending
through the water the movement is gradual and
uninterrupted, and is effected by means of a
thread affixed to the surface—a mode of pro-
eression analogous to that of some of the land
slugs which I have referred to, as spinning a line
of the gelatinous secretion from their skin; at
other times it rises rapidly hke a bubble from
the bottom; it floats, walking along, as it were,
immediately beneath the surface of the water by
a series of jerks. :

Puysa (ApLExa) HypNoruM—(PI. X., fig. 112).
—The mappropriate specific term signifies fre-
quenting Hypnum, a genus of the mosses.

The shell of this species is easily distinguished
by its elongated spire, and is half-an-inch or
more in length, of a reddish colour.

P. hypnorum is very gregarious and prolific;
it inhabits ponds and ditches, especially in the
southern and midland counties of Hngland; it
occurs in Scotland and Ireland, but is local.

204 LAND AND FRESH-WATER MOLLUSKS.

It is a very active creature, and ascends at
will to the surface in a direct line, or returns to
the bottom, or holds itself suspended in the
water, with facility; its habits may be well ob-
served in the aquarium. The above-mentioned
movements of this snail are, according to Mr. J.
Jones, effected in the following manner: “ The
edges of the foot are brought closely together,
converting that member into a tube, from which
the column of water therein enclosed is expelled
with considerable force, either upwards or down-
wards, as the animal may be disposed to ascend
or descend, being, in fact, a modification of the
mode of locomotion adopted by the cuttle-fish,
which effects its rapid movements by ejecting
water through a funnel.” The Pisidiums, the
glass-bubble shell, and some of- the pond-
snails, as previously stated, exhibit the same
powers; and it is the accepted explanation, that
the snail does so by means of glutinous threads.

Mr. W. Nelson charges the present species with
cannibalism; he writes, * * * * “on looking
again, three or four days after, I found some more
shells empty, but this time caught five or six of
the real delinquents busily feeding on the dead
body of one of their comrades, and one of the
empty shells had a rather large hole in the whorl
next to the body-whorl.”

WATER SNAILS. 205

FRESH-WATER LIMPETS.
Genus Ancytus (fresh-water Limpets).

THIS generic group is at once recognised by
the conical, limpet-like, thin shells; the apex is
posterior and sinistral. The animal is like Lim-
neea, but is more allied to Planorbis; its tentacles
are cylindrical and not triangular. The mouth
is armed with a jaw, composed of three rudi-
mentary pieces. ‘The lingual dentition presents
the following characters: the central tooth is
minute, the lateral teeth, thirty-seven in number,
have long recurved hooks, and are at first simple,
but becoming ultimately narrowed and minutely
toothed ; there are 120 transverse rows.

LLLPFUW

Fig. 26.—Portion of a transverse row of the lingual ribbon of
A. fluviatilis (Lovén).

In the subgeneric group, VELLETIA, Gray,
the animal and shell are dextral; the hngual
dentition is different, the central part of each row
being much arched and composed of a central

1 ae
¥
Ht

206 LAND AND .FRESH-WATER MOLLUSKS.

tooth with twelve similar laterals on each side;
next to which is a tooth of a different form, and
lastly, six more on each side, which latter are in
a slight curve; the number of transverse rows
is 75; the total number of teeth is 2,925.

To the type belongs A. fluviatilis ; to the sub-

genus, A. oblongus ; both species occur fossilized
in the newer Tertiaries. The genus Ancylus is
represented by one species in the Middle Eocene
of Hordwell.
- ANCYLUS FLUVIATILIS—(the River Iimpet) (Pl.
XI., fig. 136).—The shell of the common “ River
Limpet” is an elevated and regular cone, with
the point recurved and nearer the hinder end;
it is thin, of a yellowish-grey or horn colour, the
inside whitish and glossy; the exterior is orna-
mented with fine, close-set lines that diverge
from the apex to the margin, but is more distinctly
striated in the line of growth; the aperture of
the shell is oval, and nearly a fourth of an inch
in diameter; the height of the shell does not
usually exceed half-an-inch.

The shell varies somewhat in form, some ex-
amples being proportionately larger and higher,
others smaller and more swollen, and in the
prominence of its ridges; in colour, varying
from white to reddish-brown, and almost black.
The shells are often coated with a brick-red fer-
ruginous deposit. There is a pretty variety, with

WATER SNAILS. 207

the interior of the shell of a violet colour, the
aperture slightly elongated, and the epidermis
of a deep colour.

The species is widely distributed through the
length and breadth of Great Britain, and is
abundant in brooks and in the shallow parts of
rivers, fixed on stones or shells of fresh-water
mussels, and rarely attached to aquatic plants.
Tt is not unfrequently seen out of the water, on
the moist surfaces of rocks by waterfalls; in such
situations I have found the shells to be of an
unusually small size.

I have never been able to witness the act of
respiration in Ancyli, which appears to be only
very rarely necessary, for the animals remain a
very long time beneath the water, holding them-
selves with a perfect immobility to the submerged
stones. However, it must not be supposed that
such habits indicate any close affinity of Ancylus
to the marine limpets (Patella); because, though
the pond-snails frequently come to the surface
to respire, the coil-snails do so much more
rarely, and some Physas still less frequently
perform the act. The fresh-water limpet was
supposed to possess gills; and though since ascer-
tained, beyond doubt, to be air-breathing, yet
it 1s presumed to be capable of extracting air
from the water, for the purpose of respiration.

208 LAND AND FRESH-WATER MOLLUSKS.

Nevertheless, Mr. Clark suggests the follows
solution :—

“Tt is difficult to conceive how they can with
safety come to the surface to breathe pure air,
as, during the rainy seasons, the currents would
probably drive such light and delicate animals
down the stream, and cause them to perish, if
they ventured to quit their moorings; they must,
therefore, remain at anchor, unless they have the
power, when they wish to breathe the pure air,
of veering out a filamentary cable, by which they
can withdraw again, after respiration, to their
original site.”

From their small size and sedentary habits the
river limpets are not frequent denizens of our
aquariums. The jelly-like egg masses of this
species are attached to stones, and are ovate;
they contain from four to eight eggs placed in a
row. An annelid, Matzia heterodactyla, Vogt,
lives in the mantle cavity of this species.

AncyLus (VELLETIA) oBLoncus—(the Oblong
or Lake Limpet) (Pl. XI., fig. 139).— This
species, often termed Ancylus lacustris, or Vel-
letia lacustris, is at once to be distinguished
from the only other British species, A. fluvia-
tilis, by its oblong shell, and by the form of
the apex, which is twisted to the right, the
shell being thus dextral. Dr. Gray regarded
this difference of generic value, and consti-

WATER SNAILS. 209

tuted the genus Velletia for the reception of
the present species. The shell is an elongated,
subdepressed, and laterally compressed cone, of
a light horn colour, and coarsely wrinked.

A. oblongus differs from the river limpet in its
habitats; it lives attached to the under side of
leaves and stems of aquatic plants, as the yellow
water-lily (Nuphar lutea), Alisma, Potamogetons,
and Sparganiwms, and on the dead leaves of
trees that have lain some time in the water;
in still and gently flowing waters, as canals,
lakes, and ponds.

The present species is more active than its
ally; it gldes quickly, with a perfect appear-
ance of immobility in its plan of locomotion ; but
it may be observed turning its head from right
to left, under the shell, during its march. The
tentacles alone are capable of being extended
beyond the shell; they are cylindrical, obtuse,
slightly contractile, and, from their extreme
tenuity, appear white; but, seen through a lens
by the aid of sun-light, they are slightly tinged
with black. The eyes can be seen by viewing
the animal from the side; they are sessile, very
large, and black, somewhat angular or rounded.

They never leave the water, and occupy them-
selves with cleaning off the green matter which
is attached to submerged plants and bodies.

210 LAND AND FRESH-WATER MOLLUSKS.

Pianorsis (Coil Snails).

The shells of this genus are characterized as
orbicular, flat, and coiled nearly in the same
plane. The generic term signifies a flat coil.
Planus, flat ; orbis, coil or ball.

The animals inhabiting these discoidal shells
are very slender, elongated, and twisted in a
flat coil; they possess two very long and slender
tentacles, the eyes situated at their inner bases.
The foot is small; the lingual dentition is very
simple: the transverse rows extend straight
across the lingual membrane: the central tooth
is generally two-pointed, the laterals with three
points. ‘The jaw is single and slightly arched

(except in P. corneus), as in Physa, and in fact as
in Pupa, Balea, Clausilia, and Carychium. The
shells of this genus exhibit great tendency to
distortion.

The species that compose this genus are
numerous, inhabit slow running streams, ponds,
and ditches, feeding. on the aquatic plants,
and are very sluggish in their movements. A
peculiarity, possessed by all of the genus, may
be readily observed by irritating the animal of
P. corneus or P. marginatus, when a purplish
liquid is emitted, which is not the blood, for the
circulating fluid is colourless. The majority of

WATER SNAILS. 2%

the species are small: P. nautileus is the least,
and P. corneus the largest of the British species.
Monstrosities of the species occur with an ele-
vated spire. The prevailing colour of the shell
is greyish or reddish.

Coil shells are not known in a fossil state
before the epochs of the Purbeck and Wealden
deltas, two species of which occur in each of these
formations. Species of Planorbis are among the
most characteristic fossils of the Upper Eocenes of
the Isle of Wight. Those at present living in this
country are fossilized in the Upper Tertiaries of
Grays, Clacton, &c., and at Clacton are associated
with an extinct species, P. helicoides. P.margin-
atus, P. spworbis, and P. corneus are the most
ancient of the existing species ; they occur in the
Norwich Crag.

The British species are characterized as fol-
lows :—

L Whorls all exposed... lit Ags, ee ON
Last whorl embracing the rest, olossy staat rela» staat LAG

9. ANCES (CUT) OR a a ea ee
RPNeMACALINAUCE! fo ce. ces cee ac’ age we)

3. memeber Tone. i.) ng sce cee ese LP cOrmens
eee Mera 6 he) oe i RL Lae Mo

4, ) Whorls compact. ... ... LP. contortus
* ( Last whorl proportionately large ... Pe et oe
5 Shell covered with raised Tena stew P. albus
* ) Shell smooth Be dassel Use) (awl epee eames SCO Oe
6 Shell very depressed, of many narrow ae onallld i

Shell few-whorled ; last whorl rather large... 8
p 2

212 LAND AND FRESH-WATER MOLLUSKS.

: Shell very flat beneath, prone keeled ... P. vortea
* ( Shell subcarinated ee .. L. sprrorbis
8 Shell very small, imbricated se .. P. nautileus
" ( Shell large vo, Cee
9 Keel on the middle of the iy ... P. carimatus
" ( Keel on the lower side... ... ... P. marginatus
Bluntly keeled in the middle wi vee) ae
Septa in the last whorl... ... ... ... 2. lineatus

| PLanorBis cornEus—(the Horny Coil Shell)
(Pl. X., fig. 120).—The shell of this species, the
largest of the genus, is from half an inch to an
inch in diameter; an unusually large specimen
in my possession, from Tottenham, Middlesex, is
an inch and a quarter across. The colour is a
glossy, reddish-brown, sometimes white; the
test thick and irregularly striated by cone lines
of growth. ‘The whorls are five in number, with
a broad shallow umbilicus on the under side, the
upper surface a httle concave. The young shell
has its surface of a velvety appearance, on
account of the epidermis being clothed with a
fine down.

The body is nearly black; the tentacles are
long and curved. The jaw consists of three
pieces, but the lateral ones are very rudi-
mentary. A peculiarity of this animal, alike
possessed by all the coil-shells, is that of emit-
ting, when irritated, a purple-coloured fluid,
which is secreted by a gland at the sides of its
neck. It is a very sluggish animal, and on warm

WATER SNAILS. 213

summer days may be seen floating in the water.
When the ditches and ponds which it inhabits are
dried up inthesummer, the animalcloses the mouth
of its shell with a pellucid pellicle, and retires
into the interior ofits coil, and there remains in a
state of torpidity until the ditches are again filled
with water. This whitish filmy covering is analo-
gous to the epiphragm of the land-snails, and is
similarly pierced by a minute orifice, for the
access of air for the purpose of respiration. Te
observe this epiphragm-like protection, take
specimens of the P. corneus or any other species—
P. corneus being the larger, the pellicle is more
conspicuous—and place them in a dampish box,
or a botanical box with a few moist aquatic
plants ; at the end of two or three days all the
animals will be found to have taken this pre-
cautionary measure.

P. corneus is frequent in the ditches and ponds
in the eastern counties of England; it is in
great demand in the London markets for stocking
aquariums; in other districts it is very rare. It
occurs in a few localities in Ireland.

PLANORBIS contorTus—(the Contorted Coil Shell)
(Pl. X., fig. 108).—The shell resembles that of
the last species in its rounded whorls, but is very

.small, not being more than two-tenths of an inch
in diameter; the whorls are numerous and re-
markably compact and narrow, nearly flat above,

214, LAND AND FRESH-WATER MOLLUSKS.

and with a large and deep umbilicus; the colour
is bronzed-brown or horn ; albino varieties occur.
This minute snail possesses as many as 6,000
lingual teeth.

This is also a local species, though very
abundant, when met with, living on water-plants
in lakes, ponds, and ditches.

Pianorsis vorrex—(the Flat Coil Shell) (Pi.
XI., fig. 127).—The shell is extremely depressed,
thin, brown, pellucid, glossy ; concave above, and
flattish beneath, with from six to eight whorls ;
the outer whorl is rounded, but flattened under-
neath, so as to form a sharp keel or edge on the
lower margin ; the diameter of the shell is three-
eighths of an inch.

This species is very generally diffused. It
lives in shallow and stagnant waters, on the
stems and leaves of plants, or floating on the sur-
face, and rarely residing at the bottom. Its modes
of progression are various, and very characteristic
of the Coil Snails. It slowly glides along the
surface of a leaf by extending its foot, and pro-
ducing in it undulatory movements, by means
of which it is propelled forward. Now and then,
the shell, which is usually carried inclined at an
angle of from 20° to 30°, is suddenly jerked
forward by a semi-rotatory movement. Often:
the snail moves along with a continuous progress,
without jerking the shell at intervals. Some-

WATER SNAILS. pales

times the shell is laid flat, kept at an angle
of 50° or 60°, or even raised so as to be perpen-
dicular. When swimming along the surface of
the water, the shell lies flat on the surface.

PLANORBIS SPIRORBIS—(the Round-edged Coi
Shell) (Pl. XI., fig. 129)—The shell of this
species 1s very closely allied to that of P. vortea,
from which it differs in being thicker, less
flat, the whorls rounder, and the keel less
distinct. Its habits are similar to those of
P. vortex.

Jt is more widely diffused than the last.

PLANORBIS MARGINATUS—(the Flattened Coil
Shell) (Pl. X1., fig. 128).—The shell is of a
brownish colour, with close irregular striations,
concave above, and flat or slightly convex below;
whorls, six; the diameter of the last whorl is
equal to about one-fourth of the whole, and is
rounded above, and strongly keeled below. In
the young, the P. rhombeus of Turton, the shell
is more convex above, and with a deep AY
concavity beneath, and a blunt keel. -—~\
Monstrosities of this species occur with es =e
the volutions elevated into a spiral cone; Ss
as in fig. 27; or with the first few Fis. 27.
whorls coiled in the normal way, the others
spiral; or with open whorls.

This snailis prolific, and lays from eight to ten
capsules, each containing from six to twenty eggs.

216 LAND AND FRESH-WATER MOLLUSKS.

It can fix its shell without any apparent means of
attachment by its side to the flat surface of the
aquarium glass, where it may be often found
left high and dry by the loss of water in the
glass by evaporation. The flattened coil shell,
so frequent in the ponds and ditches of the south
and midland counties of England, becomes rare
northwards, and is unknown in Scotland; it
occurs throughout Ireland.

A well-known synonym ee this species is P.
complanatus.

PLANORBIS CARINATUS—(the Keeled Coil Shell)
(Pl. XI., fig. 1380)—The shell differs from that
of the et in its broader and more depressed
whorls, and the keel being situated on the middle
line of the whorl instead of below. It is of much
rarer occurrence, and never plentiful. It is
found somewhat generally in the eastern coun-
ties; it is doubtfully Scottish, but occurs in
Treland.

PLanorRBIS ALRUS—(the White Coil Shell) (Pl
XI., fig. 125).—The specific name albus is ap-
plied to this species from the greyish-white
colour of the animal and shell. The head of the
snail is thick and oblong in front, the tentacles
are long, slender, of a pale grey or white, with a
central brown line, dilated and transparent; at
the base on the inner side of each tentacle is a
small oval black eye. The foot is narrow, the

WATER SNAILS. PA a

length of which: is about one-third the diameter
of the shell. The animal, when walking in the
water, carries the shell inclined at an angle of
from 70° to 80°.

The shell is finely striated longitudinally ; the
epidermis is raised into deciduous bristles on the
striations, also minutely striated transversely ;
convex above and below, thin, pellucid, and
whitish; about one-fourth of an inch in diameter ;
the whorls five, the last one disproportionately
enlarged.

It is a common species.

PLANORBIS GLABER—(the Smooth Coil Shell) (Pl.
XI., fig. 126).—The nearest ally to this species
is P. albus, from which it differs in its smaller
shell, which is smooth; in the more rounded
whorls, the upper side being more convex ; and,
lastly, in being destitute of the strong spiral
strie.

P. glaber was first described by Mr. Jeffreys,
who states that he only knows about twenty
localities for it m England and Scotland; it is
rather a northern than a southern form; it has
been found in the neigbourhood of Belfast, Ire-
land, and in three other localities in the north-
east of the island. It is distributed throughout
the greater part of the continent, and ranges
from Sweden to Corsica and Algeria.

PLANORBIS NAUTILEUS—(the Nautilus Corl Shell)

218 LAND AND FRESH-WATER MOLLUSKS.

(Pl. X., fig.124).—This is the most elegant and
at the same time the smallest of our fresh-water
mollusks. The shell bears some general resem-
blance to that of P. albus; but its minute size,
dull appearance, and, above all, its sculpturations,
serve to distinguish it. It may be described as
—flat, rather concave in the middle, lower side
rather convex, thin, pellucid, dull, ight-brown
or grey; the whorls three, the last one enlarged,
strongly marked with transverse ridges, which
are more marked’in young individuals; the
diameter is two-twelfths of an inch.

The species is known by another name, P.
imbricatus, perhaps more characteristic than the
one adopted, which, however, has the priority.

P. nautileus is widely distributed, but is not
a common species.

The readiest plan to secure this species and
other minute fresh-water shells, is to collect the
conferve and plants on which they live, place
them in a basin, and pour warm water on them ;
the animals will then relinquish their hold and
fall to the bottom.

PLaNoRBIS NiITIDUS—(the Shining Coil Shell)
(Pl. XI., fig. 131).—This and the following
Species are associated together from the glossy
aspect of their shells, and from the last whorl
being very large in proportion to the rest, and
more or less embracing them. The shell of P.

WATER SNAILS. 219

nitidus is depressed, the upper more convex than
the lower side; of a dark horn colour, very
glossy, semi-transparent; the whorls are four in
number; the diameter of the shell is two and
a half lines; the outer whorl exceeding the rest
in size, with a blunt keel in the middle.

This small and pretty mollusk is not frequent,
' though dispersed throughout the British isles ;
it may be obtained generally on the fallen leaves
of trees, also on aquatic plants in ponds and
ditches.

PLANORBIS LINEATUS—(the Streaked Coil Shell)
(Pl. XI., fig. 182).—The shell of this species
closely resembles that of the last, but is of a
lighter colour, thinner, flatter, the keel sharper,
and the last whorl not so embracing; it is
markedly distinguished by the presence of from
two to five curved transverse plates inside the last
whorl; on the exterior these septa appear as
whitish lines. This peculiarity of structure in-
duced Lightfoot, m 1786, to call this shell a
Nautilus ; and subsequently Dr. Fleming regarded
the presence of the plates as sufficient to raise it
to the rank of a genus, under the name Seg-
mentina.

The present species is the rarest of the British
fresh-water mollusks; it is found chiefly in the
neighbourhood of London and in the adjacent
districts ; it occurs in the co. Tipperary, Ireland ;
and is distributed throughout Central Europe.

220 LAND AND FRESH-WATER MOLLUSKS.

OPERCULATED LAND SHELLS.
ORDER OPERCULATA.

THE Operculated Snails closely resemble the
plant-eating gasteropods, as Bithinia and the
periwinkle; and chiefly differ from them in their
habitats and the medium they respire. They
have a long muzzle, two slender tentacles, con-
tractile, but not retractile, like those of the
Helicide ; the eyes are sessile. The lingual ribbon
differs very widely in the aspect of its teeth from
the land-snails, and is narrow. ‘The teeth are
large ; three on each side of a central tooth, and
thus they very much resemble those of the fluvia-
tile gasteropods. ‘The sexes are distinct; the
aperture of the shell is closed by an operculum.

The order contains two families, each with a
single representative species in Great Britain ;
they may be distinguished as follows :—

Shell oval ; operculum shelly... ... ... Cyclostoma elegans
Shell cylindrical ; operculum horny ... ... Acme fusca

CycLostomaA ELEGANS — (the LHlegant Cirele-
mouthed Shell) (Pl. XI., fig. 140).—The shell is

LAND SHELLS. 221

about a fourth of an inch long, and four-tenths
wide, solid, of a grey or purplish yellow, with two
or three rows of darker spots; the whorls are five
in number, rounded, and strongly striated spirally ;
the aperture is circular, slightly angular above,
and closed with a hard shelly operculum.

The inhabitant of this beautiful shell has a very
striking appearance (see fig. 28); the muzzle
projects far beyond the body, and is used to

Fig. 28.—Cyclostoma elegans.

assist the snail in climbing; the tentacles are
annularly wrinkled, and terminated by brown
bulbs; the eyes, in place-of being situated at
the extremity of the upper tentacles, as in the
majority of the terrestrial mollusks, are placed on
each side of the head at the bases of the tentacles ;
the foot is short and broad, and divided in its
length by a groove; when the animal walks, the
portion on the one side is advanced, the animal
retaining its hold by the other, and then holds on
by the advanced portion as the other is gradually
brought in advance of it. ‘This species present
a most remarkable peculiarity in its anatomy,

papas LAND AND FRESH-WATER MOLLUSKS.

that of a brilliant white organ lodged among the
convolutions of the intestine ; it contains a mul-
titude of solid concretions, composed of an
organized skeleton and incrusting salts.” (Cla-
parede.)

This species is abundant in the localities where
it is found, but is always confined to calcareous
soils, especially those of the oolites and chalk.
It dwells in hedge-rows and on the margins of
woods, or more rarely on open downs and hills.
It ranges as far north as Yorkshire, is absent in
Ireland and in Scotland, and is distributed over
Central and Southern Europe, and extends to the
Canaries and Algeria.

The restriction of this species to limestone soils
is very marked. It occurs throughout the whole
of the chalk and oolitic ranges in great abundance,
more sparingly on the Mountain Limestone hills.
Dr. S. P. Woodward informs me, that in Norfolk
it is found in great profusion on the bosses of
chalk that appear among the overlaying Ter-
tiary gravels and clays, and is not met with
in the intervening areas. Notably also, the
junction of the chalk with the low alluvial plains
in the Wealden district is very accurately indi-
cated by this shell. Thus, although the hilly
districts of the Hastings Sands apparently seem
favourable to the existence of this snail, it does
not occur there, nor upon the plains of alluvium

LAND SHELLS. Aa

and weald clays that stretch up to the base of the
chalk downs of Hastbourne on the west, and those
of Kent on the east; but on passing on to the
chalk it is met with in extraordinary numbers.

In Gloucestershire, shells of this species con-
stitute a stratum, at a depth of 6 or 9 inches
beneath the surface, that I have traced over
several square miles. In the Isle of Wight and
in Dorsetshire it is found similarly in a sub-
fossilized state.

Acme Fusca—(the Brown Acme) (Pl. XI, figs.
142, 144).—The shell is scarcely one-tenth of an
inch long, cylindrical, and very polished ; under
a good lens it is seen to be marked with distant
longitudinal striations; the colour is glossy
brown ; the aperture is roundish oval, contracted
above and closed with a thin horny-whitish oper-
culum; the whorls six or seven; the umbilicus
is small.

It is rare in Great Britain, but widely dis-
tributed. It lives among decaying leaves and
tufts of moss, in moist situations, especially near
the sea. I was once successful in securing several
living specimens of this minute species, by collect-
ing dead leaves and shreds of bark into a heap ;
and upon turning over the mass, after a lapse of
a few weeks, my heart was gladdened with the
much-prized treasures and many other interest-
ing species. The above kind of bait I have

224, LAND AND FRESH-WATER MOLLUSKS.

employed very frequently and found it to answer
extremely well, naturally so, as it affords food,
shelter, warmth, and moisture to the snails.

A, fusca is known in a fossilized state at Cop-
ford, Essex.

FIG.

. Anodon cygneus : : : : : da

EXPLANATIONS TO THE PLATES.

PAGE
TITLE-PAGE.

Snail and Shell of Helix aspersa ; re

PuateE I. to face page 24.

Puate II. to face page 30.

2. Unio twmidus, the valves separated to show the

hinge, &. .. : : f : : 45 ah ee

3. Unio pictorum . F ; ‘ : 10, 26
4, Anodon cygneus, var. ae : : : = halk

5. Valvata piscinalis . ‘ : : . 3458
6. » eristata F : : ; : i BO

7. Hydrobia similis yx ; : : : <i stee

asammuaGrayona © 2... 8

Puate III. to face page 34.

9. Cyclas pisidioides : : , , eee Ss
TOs 5, oe heualis’, \. Eat ‘ : , ahhesG
ll. Pisidium amnicum . - : : : 2) hee
12. Cyclas lacustris . ‘ , : i ; aro
13. Bithinia Leachw. ; : : ‘ Cee 3
14. 49 tentaculata . y : : E ered (5
15. Unio margariuiferus . : : : : By eee

226 EXPLANATIONS TO THE PLATES.

FIG. PAGE
16. Cyclas cornea, var. flavescens . . 34
17. ,,_ ~-rivicola, with foot and suena protruded 33
Sr Gog, COTO. : : - - : . 34

PuatTe IV. to face page 54.

19. Pisidium Henslowianum . i ‘ , . 40
20. “3 obtusale .. ; : : ; . i
21. S cinercum . é : ; , >.

22, fe mitidum . : ; : , - at
23. Ss pusillum . : . : ‘ . 42
24, + pulchellum . F : : : opt ee
25, Driessena polymorpha ‘ : ‘ ; + ae
26. Paludina vwipara . : : : ‘ . 54
27. i Tnsteri : 56
28. Neritina fluviatilis, and inner cs of iposeiand 60

Puate V. to face page 72.

29. Arion hortenstis . , ‘ : : : eae:
30. Limaz agrestis . y ; : ‘ . tae
31. Arion ater. : ; : : ee
32. Iimax maximus and sielt ; ; ? ae |
33. 5 arborum. : ; ; ; ; . ge
Be. ys: eenellus ; é ; ; : a ae

35. ,, Sowerbir . : : ‘ : ; 2 ae

Puate VI. to face page 88.

36. Limax gagates, extended and contracted states,

and shell . 3 : ; ‘ -) nee
37. Shell of Testacella Manet. ; : ‘ «88
38. Testacella haliotidea . : : : ' ee
39. Lima flavus and shell . : 2 ; . 74
40. Geomalacus maculosus ; ; : ; ita
41. Oncidium celticcum : mer ee : « 82

42.
43.
. Snail of Succinea putris

45.
46.
47.
48.
49.
50.
51.
52.
53.
54,
55.
56.
57.
58.
59.
60.
61.

62.

62a.
63.

64.
65.
66.
67.

EXPLANATIONS TO THE PLATES.

Timasx brunneus
Vitrina pellucida, snail ae shell

Puate VII. to face page 112.

Helix nemoralis .
» rupestris
» hortensis
» auleata .
Snail and shell of Hale sp olitie
Heliz fusca
» lamellata .
Helicella excavata

a nitida
a nitida .
pura

¥ fulva .
Helix aspersa
Helicella crystallina .

ra alliaria
nitidula*
% radiatula
Helix arbustorum
5 pe var. hanine
Helicella cellaria

Puate VIII. to face page 134.

Helix Cantiana .
9 «sericea
5 Prsana
5 pulchella .

* The spire is too elevated, and the mouth too circular.
—R. T.

Q 2

EXPLANATIONS TO THE PLATES.

: Snail and shell of Helix ericetorum
. Helix pulchella, var. costata

» Cartusiana
» Pygnues
» revelata
» Lomatia .
» rotundata
» hismda
» vrufescens .
9 CONCINNGA .
» caperata
» lapicida
» vurgata

Puate IX. to face page 168.

. Bulimus montanus

ns obscurus
“: acutus .

. Zua lubrica

. Azeca tridens

. Balea perversa .

. Clausilia laminata
. Vertigo alpestris

. Achatina acicula

. Vertigo pygmea.

. Clausilia rugosa
partes var. dubia .

ah Rolphia

. Animal of Clausilia .
. Clausilra biplicata
. Pupa secale

» umbilicata
5 muscorum
» Anglica: :

PAGE

141
139
127
144
132
134
142
129
128
129
125
140
123

148
149
147
151
152
164
167
161
171
160
168
169
169
165
166
157
153
154
155

EXPLANATIONS TO THE PLATES. 229

PLATE X. to face page 186.

FIG. PAGE
100. Vertigo minutissima . : ; : : . 159
101. ,, ~ edentula : ; : ; A > oL59
102, ,, pusilla . ; : ; ; ; . AGB
103. . ,,. antwertigo. . : 7 : : - LG

104. 4, = substriata . . ; : , . 162
105. 4, Moulinsiana . ‘ . ; , . ez
106. Succinea putris . : : ‘ ; . 174
107. Snail and shell of S. ae SMD! i Pea ibs
108. Planorbis contortus . : . : : . BS
109. Succinea oblonga 3 : ; ‘ 2 . Av6
110. Limnea truncatula . : ; ‘ . 194
111. Vertigo angustior a : , a . 263
112. Physahypnorum- . ; : , ‘ . 203
113. Iimnea palustris. ; : ‘ ; ayes
114, » stagnalis : é : ; : 5 OO
115. 3 glaber . : : ; : . 195
116. 9» ~—s speregra, var. oe i : : « 2188
PEiat ay) = eregra.. aaa hts : : ‘ RBG
118. » var. ovata : : ; 2 EST
119. » auricularia . : P : ; » 290
120. Planorbis corneus . : 3 : : tr. pe
121, 122. Limnea glutinosa : ; : > 296
193. » wmnvoluta Z : : : . 198
124. Planorbis nautileus . ‘ ; - 3 ‘BEF

Puate XI. to face page 202.

125. Planorbis albus . : : : : 4 « 216
126. 5 glaber 2 4 : ; eet Ve
127. a vortex ; ; ’ : : . 214
128. 3 marginatus : : 3 : ea)
129. ‘ spirorbis . - 3 ; : 26
130. 3 carinatus . : : : ; . *216

230 EXPLANATIONS TO THE PLATES.

FIG. PAGE
131. Planorbis nitidus . “ : ‘ ‘ ae
132. 35 lineatus . ’ : ; ; . 219
133. Physa fontinalis : : : : : . 202

134. Conovulus denticulatus : : ; . 16S
135. Snail and shell of Carychium mumimum . : ie

136. Ancylus fluviatilis . ; A ; . 206
137. Conovulus denticulatus, var. myarcn ae : Tie
138. - bidentatus : 4 : . oS
139. Ancylus oblongus : : : : ; . 208
140. Cyclostoma elegans. ; : : : . 220
141. Snail of Physa fontinals . : ; ; . 208
142. Acme fusca e ‘ . 223

143. Snail of Valvata aes me lhe , . ee
144. Snail of Acme fusca, much enlarged . B . 223

INDEX,

Technical terms are wm italics, and will be found explained
at pages to which references are gwen.

A.

ACHATINA ACICULA, 171; pulsations of the heart of, 172 ;
subterranean habits of, 7b.

Acme fusca, 223 ; how to secure, 2b.

Adductor muscles of bivalves, 18.

Agate snails, 171.

Airbreathing snails, 65; relation of, to water-breathing
snails, 4b. ; orders of, 2b.

Alasmodonta margaritifera, 27.

Amber snails, 174.

Amphipeplea genus, 186.

— glutinosa, 196.

involuta, 198.

Amphistoma subclavatum, parasite of Cyclas, 35.

Anal opening in bivalves, 14.

Ancylus genus (fresh-water limpets), 205.

fluviatilis, 206 ; respiration in, 207; parasite of, 208.

— lacustris, 208.

—- oblongus, 208.

Animal kingdom, primary divisions of, 1.

Annulose animals, 2

Anodon anatinus, 31.

cygneus, 30; varieties of, 31 ; mite of, 32.

Boe INDEX.

Anterior margin, 10.

Aplexa hypnorum, 203.

Arion ater, 69 ; parasites on, 70 ; internal organs of, 2b.
hortensis, 71 ; jaw of, 7b.; phosphorescent eggs of, 1b.
Assiminia Grayana, 63 ; teeth of, <b.

Atax ypsilophora, mite of the Swan mussel, 32.
AURICULID& (family), 177.

Avicula margaritifera, pearls of, 28.

Azeca tridens, 152.

B.

BALEA PERVERSA, 164.

Bithinia Leachii, 57.

——- tentaculata, 56.

Bivalves, parts of shell of, 10-13 ; composition and structure
of shell of, 11; mantle of, 13; digestive organs of, 14 ;
circulatory apparatus of, 15 ; respiratory organs of, ab. ;
nervous system of, 17 ; organs of sense of, 7b. ; muscular
organs of, 2b.; reproduction of, 18; food of, 19; col-
lecting, 2.

Branchial opening in bivalves, 14.

Breadth of shell, 11.

Bubble snails, 201.

Bulimus genus, characters and species of, 146.

acutus, 147.

— montanus, 148.

obscurus, 149.

Byssus, nature of, 21.

C.

Cappis-worm case like Valvata piscinalis, 59.
Cardinal teeth, 12.

Carychium minimum, 177.

exiguum, 178.

Chrysalis snails, 152.

Circulatory system of bivalves, 15 ; in univalves, 52.

INDEX. 233

Classes of molluscous animals, 3.

Clausilia genus, 165 ; geological distribution and synoptical

list of species of, 166.

bidens, 167.
biplicata, 166.

— dubia, 169.

laminata, 167.

— Mortilleti, 170.

nigricans, 168.

—— perversa, 168.

— Rolphii, 169.

rugosa, 168.

Clausiwm, nature of, 165.

Ccelenteratous animals, 2.

Coil snails (Planorbis), characters of, 210; red fluid of, 2b. ;
geological distribution of, 211; synoptical table of
species of, ab. ; collecting small species of, 218.

Cold, effects of, on Paludina vivipara and Anodon cygneus,
56; on land snails, 97.

Collecting bivalves, 19 ; small water snails, 218 ; small land
snails, 223.

Colour, secretion of, in shells, 46.

Colourless blood of molluscous animals, 15.

Columella of shells, 44.

Composition of shell in bivalves, 11 ; in univalves, 46.

Concentric operculum, 46.

Conchiferous animals, 3.

Conovulus bidentatus, 179.

denticulatus, 178.

—— myosotis, 179.

—— pyramidalis, 179.

Corbicula consobrina, geographical distribution of, 43.

Crystalline style in stomach of bivalves, 14.

CycLapDIp& (family), 32; genera of, 33.

Cyclas (genus), 33.

calyculata, 36.

234 INDEX.

Cyclas cornea, 34; varieties of, 2b.; parasite of, ab.

flavescens, 34.

— lacustris, 36.

— ovalis, 36.

— pisidioides, 35.

rivicola, 33.

Cyclostoma elegans, 220 ; peculiar organ in, 221 ; restriction
of, to limestone soils, 222 ; in a subfossil state, 223.

D;

Decollation of spire of shells, causes of, 185.

Dextral shells, 45.

Digestive organs of, bivalves, 14 ; snails, 48-52, 93.

Dimyary bivalves, 18.

Disappearance and reappearance of water snails, 192.

Dispersion of water snails, 188.

Dissection of bivalves, 13.

Dorsal region, 10.

Driessena polymorpha, 20; foot, byssus, and apertures of
mantle of, 21; discovery of, «b. ; introduction of into
Britain, 22 ; action of light on, 23.

E.

EDIBLE SNAILS, 116, 134.
Entire aperture of shells, 45.
Epidernus of shell, 11.
Epiphragm of land snails, 96.
Equilateral shells, 11.
Equivalve shells, 10.
Eyes of bivalves, 17 ; of water-breathing snails, 52; of land
snails, 92.
F.
Foon of bivalves, 19 ; of water-breathing snails, 53.

Foot of bivalves, 17, 32; of Zebra mussel, 21 ; of water-
breathing snails, 46 ; of Cyclostoma elegans, 221.

INDEX. 23d

Fresh-water limpets, 205.
mussels, 25 ; extinct species of, ib.

G.

GANGLIA, 17.

Gasteropoda, structure and physiology of the, 44; shell of,
ab.; animal of, 46; digestive organs of, 48; lingual
ribbon of, 7b. ; respiration of, 52; nervous system of,
ab. ; reproduction of, 7b. ; food of, 53; habits of, 2.

Gasteropodous animals, 3.

Geological distribution of, the Unionide, 25; Helix, 145 ;
Bulimus, 147 ; Pupa, 153 ; Clausilia, 166 ; Carychium,
178 ; Limnza, 186 ; Physa, 202; Ancylus, 206 ; Pla-
norbis, 211.

Geomalacus maculosus, 83.

Glochidium, embryonic form of Anodon, 18.

Growth of, operculum, 46 ; of shells of land snails, 95.

H,
Heap of Gasteropods, 47. °
Helicella, characters of the genus, 103 ; species of, 10-4.
alliaria, 106.
cellacia, 105 ; teeth of, ab. ; jaw of, 104.
erystallina, 108.
excavata, 108.
fulva, 110.
nitida, 110.
nitidula, 107.
pura, 107.
radiatula, 109.
Helicidz. See Land Snails.
Helicine, 115.
Helix, synoptical list of species of, 111; geological distribu-
tion of, 145.
aculeata, 133.
arbustorum, 137.

Peseere

236 INDEX.

Helix aspersa, monstrosities of, 112; perforations of lime-
stone by, 117 ; poetical allusions to, 2b. ; hybernation
of, 118 ; amours of, 119.

— Cantiana, 126.

— Cartusiana, 127 ; confinement to chalk of, 2b.

caperata, 125.

concinna, 129.

— ericetorum, 141.

— fruticum, 145.

— fusca, 131.

hispida, 129.

— hortensis, 121 ; food of birds, 122.

——- incarnata, 145.

lamellata, 133.

—— lapicida, 140.

nemoralis, 120 ; jaw of, 2b. ; varieties of, 121.

obvoluta, 141.

— Pisana, 123.

— Pomatia, 134 ; jaw of, 2b. ; hybernation of, 135; growth
of shell of, 2b. ; experiments on, 136.

—— pulchella, 138 ; jaw of, ab. ; variety of, 139.

—— pygmea, 144,

—— revelata, 132.

—— rotundata, 142.

—— ruderata, 145.

— rufescens, 128.

——. rysa, 146.

—— sericea, 130.

virgata, 123 ; showers of, 124 ; eaten by sheep, 20.

Hinge of shells, 10.

Hinge-line, 12.

Hybernation of snails, 97, 135.

Hydrobia marginata, 146.

similis, 64. .

—— ventrosa, 64.

INDEX. 237

Imperforated shells, 44.

Incomplete aperture of shells, 45.

Inequilateral shells, 11.

Inoperculata, or typical Pulmonifera, 65 ; genera of, 66.
Intestines of bivalves, 14.

L.

LAMELLI-BRANCHIATA (class), 4.

Land snails (Helicide), characters of, 92; structure of ten-
tacle of, 2b. ; mouth of, 93 ; reproduction of, 94 ; growth
of shells of, 95; habits of, 96; epyphragm of, 2b. ;
hybernation of, 97, 135; geographical distribution of,
97 ; cleaning shells of, 98; genera of, 99 ; destructive
to vegetation, 113; how to destroy, 114; medicinal
properties of, 115; pomade of, 2b.; edible kinds of,
116, 134; perforation of limestone by, 117 ; poetical
allusions to, 2b. ; amours of, 119 ; showers of, 124; as-
sociation of to particular soils, 97, 127, 140, 157 ; food
for birds, 122; eaten by sheep, 124; enemies of, 114,
124,

Lateral teeth, 12.

Length of shell, 11.

Ligament of bivalves, 11.

Limacip& (family), 66.

Limax, generic characters of jaw of, habits of, 72.

agrestis, 75.

arborum, 78 ; suspension of, 1b.

—— brunneus, 77.

flavus, 74.

— gagates, 81 ; jaw of, 72.

—— maximus, 73.

— Sowerbii, 79.

— tenellus, 77.

238 INDEX.

Limnza (pond snails), characters of, 184; food of, 185 ;
species of, 186 ; geological distribution of, «b.

— auricularia, 190.

—— Burnetti, 188.

—— fossaria, 194.

—— glaber, 195.

—— glutinosa, 196.

—— involuta, 198.

—— lacustris, 187.

—— minuta, 194.

—— octona, 195.

—— ovata, 187.

— palustris, 193.

—— peregra, 186 ; varieties of, 187 ; dispersion of, 188.

—— stagnalis, 190; teeth of, 191; disappearance and re-

appearance of, 192.

truncatula, 194.

LiunaIp family (water snails), characters of, 181 ; habits
and reproduction of, 182; peculiar sensation produced
by, 183; decollation of spire of shells of, 185 ; dispersion
of, 188 ; disappearance of, 192 ; synoptical list of genera
of, 184.

Limpets, fresh-water, 205.

Lines of growth, 11.

Lingual ribbon or tongue, described, 48 ; methods of pre-
paration of, 49 ; mounting of, 7b. ; different sets of teeth
of, 50; numerical formula of, 51; value of in classifi-
cation, 2.

Lips of bivalves, 14.

Lirrorinip# (family), 62.

Longitudinal lines on shells, 45.

Lunule of bivalve shells, 11.

M.

Mantle of bivalves, 13.
Mantle-lobes, 13.

INDEX. 239

Marsh shells (family Paludinide), genera of, 53.

Maizia heterodactyla, 208.

Measurement of bivalve shells, 11.

Methods of collecting and preserving bivalves, 19.

Microscopic examination of, shells, 11, 12 ; cilia of bivalves,
16; tongues of snails, 49; pulsations of the heart of
Achatina, 172 ; development of pond snails, 182.

Molluscous animals, 2; characters of, 2b. ; classes of, 3.

Monomyary bivalves, 18.

Mother-of-pearl, 12.

Mouth of bivalves, 14.

Muscular impressions in bivalve shells, 12.

Muscular organs of bivalves, 17 ; gasteropods, 46.

Mussels, 20 ; fresh-water, 25.

Myvtitiv® (family), 20.

Mytilus edulis, 20, 21, 28, 29.

N.

Nacreous layer of shell, 12.

Nature of Zoological classification, 1.

NeritTip# (family), 60.

Neritina fluviatilis, 60; lingual ribbon of, 61; reproduc-
tion of, 62.

Nervous system of bivalves, 17 ; of water-breathing snails,
52.

O.

Oxsect of Zoological classification, 7.

Ocelli, 17.

OncrpiAD (family), 89.

Oncidium celticum, 89.

Operculated land snails, 220.

Operculum of shells, 46.

Organs of sense of bivalves, 17 ; of water-breathing snails,
52.

Otina otis, 180.

240 INDEX.

Pp.

PAINTERS’ MUSSEL, structure of, 10; description of, 26.

Paludina Listeri, 56.

vivipara, 54; effects of cold upon, 56.

Pearls of Unio margaritiferus, Mytilus edulis,28; Avicula
margariefera, vb. ; nature of, 2b.; artificial production
of, 2b. ; value of, 30.

Pedal muscles of bivalves, 18 ; of water-breathing snails, 47.

Peristome of shells, 45.

Physa (bubble snails), 201. .

fontinalis, 202 ; modes of progression of, 203.

hypnorum, 203 ; movements of, how effected, 204.

Pisidium (genus), characters of, 38.

amnicum, 38.

—— cinereum, 38.

—— Henslowianum, 40.

—— nitidum, 41.

—— obtusale, 42.

pulchellum, 39.

pusillum, 42.

Planorbis (coil snails), characters of, 210 ; red fluid emitted
by, 2b.; geological distribution of, 211 ; synoptical table
of species of, 2b.

—— albus, 216.

— carinatus, 216.

—— complanatus, 216.

—— contortus, 213.

—— corneus, 212; pellicle formed by, 213.

—— olaber, 217.

—— helicoides, 211.

—— imbricatus, 218.

—— lineatus, 219.

—— marginatus, 215.

—— nautileus, 217.

—— nitidus, 218.

INDEX. 241

Planorbis rhombeus, 215.

spirorbis, 215.

vortex, 214.

Pomade and syrup of snails, 115.

Pond snails (Limnea), characters of, 184; food of, 185;
species and geological distribution of, 186.

Posterior margin, 11.

Preparation of lingual ribbons for microscope, 49.

Preserving bivalves, 20; slugs, 90; land snails, 98.

Protozoan animals, 2.

Pulmoniferous animals, 3.

snails (class Pulmonifera), 65.

Pupa, characters of, 152; synoptical list of species of, 153 ;
geological distribution of, 2b.

— Angelica, 155.

—— muscorum, 154.

—— secale, 157.

—— umbilicata, 153.

—— vestuta, 153.

R.

Radiating lines on shells, 45.
Reflected lp of shells, 45.
Reproduction of bivalves, 18; of water-breathing snails,
52; of land snails, 94.
Respiration in bivalves, 15 ; in water-breathing snails, 52 ;
in air-breathing snails, 65 ; in Ancylus fluviatilis, 207. ef
Reversed shells, 45. g
f
S. ‘4
Scoop for collecting, 19.
Secretion of colour in shells, 46.
Seomentina lineata, 219.
Sense of hearing and sight in bivalves, 17 ; water-breathing
snails, 52.
R

242 INDEX.

Shell of bivalves, 10; of slugs, 67.

structure of, in bivalves, 11 ; in snails, 46.

parts of, in univalves, 44.

Sinistral shells, 45.

Sliggaun, 31.

Slugs (family Limacide), 66 ; differences between slugs and
snails, 7b. ; shell of slugs, 67 ; medicinal properties of,
ab. ; lingual ribbon of, 68 ; slime of, 2b. ; genera of, 2b. ;
glutinous suspending thread of, 78 ; preservation of, 90.

Snails. See Land Snails.

Species, definition of, 5.

Spiral lines on shells, 45.

operculum, 46.

Stomach of bivalves, 14.

Structure of shell in bivalves, 11; in univalves, 46.

Sub-kingdoms of animals, 2.

Succinea, genus, 174; characters and definition of, 2b.

elegans, 175.

oblonga, 176.

putris, 174; teeth of, 2b.

Suture, 44.

Swan mussel, 30.

Synoptical table of the families of the Pulmonifera, 66; of the
genera of the Helicidz, 99 ; of the species of Helicella,
104; of Helix, 111; of Pupa, 153; of Vertigo, 158 ;
of Clausilia, 166; of the genera of the Limneide,
184; of the species of Planorbis, 211.

T.

. Teeth of bivalves, 12.

— Tentacles of snails, 47 ; structure of, in Helix, 92.
Testacella haliotidea, 84; tongue of, 87; reproduction of,
88 ; hybernation of, 2.

Maugei, 89. .
Thickness of bivalve shells, 11.
Transverse lines on shells, 46.

INDEX. 243

Umbilicated shells, 45.

Umbo of shells, 11.

Umbonal cavity, 12.

Unio margaritiferus, 26 ; pearls of, 28 ; ms fisheries of, 29.

pictorum, 26.

tumidus, 26.

Unionide, character of the family, 25 ; genera of, 1b. ; ex-
tinct species of, 7b.

Univalve shells, 44.

Utility of classification, 7

V.

VALVATA CRISTATA, 59 ; gills of, 60.
piscinalis, 58 ; lingual ribbon of, 2b.
Valves, 10.

Varieties of species, 6.

Velletia, 205.

lacustris, 208.

Ventral region, 10.

Vertebrate animals, 2.

Vertigo, characters of, synoptical list of species of, 158.
alpestris, 161.

— antivertigo, 161.

— angustior, 163.

— edentula, 159.

—— minutissima, 159.

—— Moulinsiana, 162.

—— palustris, 161.

pusilla, 163.

—— pygmea, 160.

substriata, 162.

Vitrina, characters of the genus, 100.
pellucida, 100 ; voracity of, 101.

244 INDEX.

W.

WATER SNAILS, characters of, 181 ; habits and reproduction :
of, 182 ; peculiar sensation produced by, 183 ; synop-
tical list of genera of, 184; decollation of the spire of
the shells of, 185; dispersion of, 188; disappearance
and reappearance of, 192.

Water-breathing snails, 44.

Whorl, 44.

Whaorl snails, 158.

Z.

ZEBRA MUSSEL, description of, 20 ; foot, byssus, and apertures
of, 21 ; discovery of, ib. ; introduction of into Britain,
22; action of light on, 23 ; habits of, 24.

Zua lubrica, 151; distinction of from Zua lubricoidea, 7b.

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