EX LIBRIS

William Healey Dall

Division of Mollusks
Sectional Librat

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NATURAL HISTORY.

MOLLUS © A.

LONDON:
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NATURAL HISTORY.

MOLLUSCAy Buprnct itor

By P. H. GOSSE, A.L.S.

PUBLISHED UNDER THE DIRECTION OF
THE COMMITTEE OF GENERAL LITERATURE AND EDUCATION,
APPOINTED BY THE SOCIETY FOR PROMOTING

CHRISTIAN KNOWLEDGE. QMITHSON/ Ay

MAY 26 1998
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AND BY ALL BOOKSELLERS.

1854,

CONTENTS.

PAGE

CEPHALOPODA . . 58
DIBRANCHIATA . .. 65
SEPM 5. aw ite, (66
CMA” ice ge, lee Od
officinalis . . . w.
EPROLOWA . .
Siow eiges aie) Te
OGredite = sce. 60.
GASTEROPODA |. 7 |
PULMONIFERA. .. 80
CycLostomapDH . . . 81
Cyclostoma .. . 1%.
elegamse . sc « WD.
AUEICULADA. <<. . 82
Conovulus: 22... “26,
denticulatus . . w.
TLOMNEADAR ous %. 84
Linmens®@, . §. . 86
stagnalis) . . . w.
ELeLIeiag .. < iapsn: 4 88
Bieber aida ae 3) OL

pomutia.. . . - 92

LIMACIDA .
Limax .
agrestis .

NUDIBRANCHIATA
DoRIDIDE
Doris
bilamellata .
tuberculata .

TRITONIADE .
Tritonia
Hombergi

EoLIDIDZ .
Eolis
coronata

TECTIBRANCHIATA .
PLEUROBRANCHIADE .

Pleurobranchus .
plumula .

APLYSIAD

Aplysia .
leporina .
hybrida .

PAGE

. 144

vl
PAGE ,
BULLADE . . 145
Scaphander . 146
lignarius paler
Philine . , LaF
aperta ab.
CYCLOBRANCHIATA . 149
PATELLADE 2) 4.
Patella . 7 1 beS
cochlear . . 42.
vulgata . . 154
CHITONIDE - 58
Chiton . FOO
spiniferus ib.
fascicularis . . 161
PECTINIBRANCHIATA 163
CYPREADE . 164
Cyprea . . 165
tigris . . 166
exanthema . 167
moneta sik
Europea ab.
MoURICIDE . a hye:
Murex - 175
Purpura . 180
lapillus . Belts)!
VELUTINIDE . - 185
Velutina ib.
levigata th.

CONTENTS.

NATICADE
Natica .

monilifera .

Aldert

PYRAMIDELLADEZ
Stylifer .
Turton .
astericola

SCALARIADA .
Scalaria .

pretiosa .

communis

CERITHIADE .
Aporrhais .

pes carbonis .
pes pelicanr .

TURBINIDE
Phasianella

bulimoides .

Littorina
neritoides
rudis .
petra
littorea

PALUDINADE .
Bithinia

tentaculata .

NERITIDZ .
Neritina
fluviatilis

TROCHIDE
Trochus
granulatus .
striatus .
magus
cinerarius

FISSURELLADE
Fissurella .
reticulata

CALYPTRHADE
Calyptreea .
Pileopsis

Hungaricus .

DENTALIADE .
Dentalium .
Tarentinum .
entalis

CONCHIFERA
MONOMYARIA
OSTREADE
Ostrea
edulis

AVICULADE
Avicula.

margaritifera .

Pinna
pectinata

CONTENTS.
PAGE
. 206 DIMYARIA
207. ARCADE
ab. Arca.
ab. Noe .
out ae tetragona
. 209
MytTInip .
. 0. Mytilus
. 210 edulis
0b. choros
; ua UnIonip&
SMe Unio.
+ Le :
: prctorum
ab. AN
margaritiferus .
ale!
. 216 _CARDIADA
a ah Cardium
_ 217 rusticum .
edule .
aes CYPRINADA
, 225 :
; Cyprina
- w. Isocardia
SOBA!
cor.
ab. |
250)! VENERIDE
~ 240 Venus
2b. striatula .
. 249 ovata .
ab. CASING

MAcTRADA

Mactra .
helvacea .
stultorum

DoONACIDA
Donax
politus

TELLINADZ
Psammobia
vesper tina

SOLENIDZ .
Solen
siliqua
marginatus .

Myapa
Mya.
arenaria

GASTROCHZANADE
Gastrochena .
modiolina
Saxicava

CONTENTS.

PAGE
aah)
. 280

ab.
ab.

es
. 281
ab.

. 282
. 283
. 284

. 284
. 286
. 287
. 288

. 289
. 290
. 291

. 294
ab.
. 295
ab.

PHOLADIDE .
Pholas .
parva

dactylus .

BRACHIOPODA

Terebratula
psittacea

TUNICATA
ASCIDIADE
Ascidia .
virginea .

CLAVELINADZ
Perophora .
LTnstert

BotRYLLIDE .
Botryllus .
polycyclus

SALPADE .
Salpa
runcinata

. 313
. 314

NATURAL HISTORY.

MOLLUSCA.

THe four Classes of animals which have been
considered in the preceding volumes of this series
we have seen to have one character in common;
viz. the possession of a bony framework within the
body, of which a jointed spine is the most essential
element. This character, which unites those four
Classes into one great group, and gives to that
group the name VERTEBRATA, by which it is dis-
tinguished among naturalists, we have seen, how-
ever, by slow degrees, deteriorated, if I may use
such an expression, from bone to cartilage, and
gradually diminished in its development, until, in
the lowest of the Fishes, it can scarcely be recog-
nised at all.

I come now to treat of animals in which the
bony skeleton no longer exists. The conditions of
their existence do not require such a scaffolding on
which to build the constituent muscles: many are
habitually immersed in water, a fluid the density of
which supports their soft bodies; their motions
generally lack the precision, energy and variety of

B

24 MOLLUSCA.

those which belong to Vertebrate animals; and
where this is not the case, as in the Articulate
Classes, the skeleton which affords attachment to
the muscles, is not internal, but invests the body,
while its substance differs essentially from bone in
its chemical composition and its structure.

An immense assemblage of living creatures are
included in this category; creatures differing widely
from each other in the most important character-
istics, so that they cannot be grouped together.
The term INVERTEBRATA, by which they are some- °
times designated, indicates indeed only a negative
character, and we shall be greatly mistaken if we
suppose (misled by such a term) that the animals
which have a skeleton, and those which are des-
titute of one, constitute two primary divisions ot
living beings, of equal or co-ordinate importance.

Several divisions of INVERTEBRATE animals do,
in fact, exist, each one of which is equal in rank to
the VERTEBRATA. One of these will form the sub-
ject of the present volume, commonly known by
the name of MoLLusca; a term invented by the
illustrious Cuvier, from the word mollis (soft), and
evidently suggested by the softness of their bone-
less bodies. The appellation can scarcely be con-
sidered happy, for the character so indicated is
very trivial, and is shared by other animals of
totally different structure : — objectionable, how-
ever, as it is, it has been generally adopted, and
I shall not hesitate to make use of it.

As the great Vertebrate Division includes the
four distinct Classes of Beasts, Birds, Reptiles and
Fishes, so does the great Division of MoLLUscA
contain six Classes, distinguished by characters
which I shall presently enumerate. J must, how-

MOLLUSCA. 3

ever, first indicate those which they possess in
common, and by which they are naturally grouped
together.

The nervous system demands our first attention.
Instead of a great mass of nervous substance accu-
mulated in one place, and a lengthened spinal cord
_ proceeding from it, giving out threads to all parts
of the body, as in the VERTEBRATA, we find the
nervous centres numerous, unsymmetrical and dis-
posed in various parts of the system, no one having
so decided a predominance over the others in bulk,
as to merit the appellation of a brain. There is,
however, one mass larger than the rest, which is
always placed either above the gullet (wsophagqus),
or encircling it, in the form of a thickened ring;
and from this the nerves that supply the organs of
sense invariably originate. This mass, or ganglion,
must undoubtedly be regarded as the representative
of the brain; for in the most highly organized
animals of the Division, the Squids and Cuttles
(Cephalopoda), this encirling mass is enclosed and
defended by a case of cartilage, the lingering rudi-
ment of a bony skull.

The accompanying engraving, which is copied
from Professor Grant’s “ Outlines of Comparative
Anatomy,’ will give the reader an idea of the
system of nerves and ganglia, with some of the
other organs, as they appear in bulla liguaria, a
large and handsome shelled Mollusk found on the
British coasts.

In the above figure the chief ganglion forms a
ring, (marked ee,) ; anterior to this there is a small
ganglion, not seen, because situated below the bulb
of the gullet (a), just before the insertions of its
diverging muscular bands (c), and behind the

A MOLLUSCA.

salivary glands (b). The brain-ring (e) has on
each side a large three-lobed ganglion (f), whence
numerous nerves pass to the surrounding parts,

; and two long branches
| (h) extend backwards
along the sides of the
abdomen, to two gan-
aha (7,2), placed above
the muscular foot.
Behind these are two
sympathetic ganglia,
(k,k), which send
threads to the diges-
tive system, the ovary
(0), the oviduct (p),
the uterine sac (q), the
vulva (m),and the uri-
nary organs (n). This
may be considered as
fa fair average sample
| of the nervous system
fin the Mo.uusca,
being selected from
Ba Class presenting
ineither the highest,
B nor the lowest forms
| of organization.

The nervous centres
are, for the most part,
grouped without regard to symmetry, those of one
side not corresponding to those of the other; and
this irregularity is characteristic of the whole Di-
vision, not only in the nerves, but in the other
organs of the body. Some zoologists have derived
from this peculiarity, a name for the Division, suf-

NERVES OF BULLA.

~

MOLLUSCA. 2)

ficiently expressive, though too uncouth for general
adoption, that of HETEROGANGLIATA.*

All the senses common to the higher animals
are found in the Mouuusca, though some are,
doubtless, wanting in the humbler Classes of the
Division: In the Cephalopoda, the organs of sight
and hearing are distinct and well developed, and
Professor Owen is of opinion that the Nautilus, an
animal of this Class, possesses an organ of “passive
smell.” The Gasteropoda are almost invariably
furnished with eyes; and, according to M. Siebold
and other zoologists, with ears also, a pair of round
capsules, placed near the bases of the tentacles, and
enclosing one or more crystalline globules, called
otolites. Some of the Conchifera are furnished with:
numerous eyes, placed among the tentacles, ex-
amples of which are found in the Clams and
Scallops (Pecten) of our own shores. I scarcely
know a more beautiful sight of the kind, than is
presented by the edges of the mantle in one of our
Scallops. If you ever have an opportunity of pro-
curing a living specimen, which is not difficult to
find at low water, on most of our rocky shores,
place it in a glass of sea-water, and watch its
movements. Soon the beautiful painted shells will
begin to open, and the fleshy mantle will be seen
to occupy the interval, like a narrow veil extending
perpendicularly from each shell. The edge of each
of these veils will now be seen, if you examine it
with a pocket lens, to be fringed with long white
threads, which are the tentacles, or organs of touch ;
and amongst them lie scattered a number of minute
points, having the most brilliant lustre, and bearing
a close resemblance to tiny gems. Indeed, the

* That is, “having dissimilar nerve-knots.” .
to}

6 MOLLUSCA.

mantle has been aptly compared to one of those
pincushions which are frequently made between
pairs of these very shells, the eyes representing a
double row of diamond-headed pins, set round the
middle. It is observable that the Bivalves, which
are thus profusely furnished with eyes, are also

THE GREAT SCALLOP.

endowed with the faculty of precise and vigorous
motion. It does not appear clear that any of this
Class possesses a distinct sense of hearing.

The faculty of taste is plausibly conjectured,
rather than proved, to belong to the MOLLUSCca.
‘Jt seems necessary,” says Dr. Johnston, “to sup-
pose the existence of this sense in all Mollusca, for
they select particular articles of food in preference
to others; and we know no other sense which is
fitted to regulate the choice.” The organs appro-
priated to this faculty are probably the margins
and internal surface of the mouth, and the tentacles

MOLLUSCGA. i

which in some species are placed close to this
orifice.

Every one who has touched a crawling Slug or
Snail, must have had a practical proof of the deli-
cacy of its sense of touch. The whole surface of
the body, invested with a soft, flexible, and mucous
skin, contracts on the slightest contact with any
unexpected substance, and is, doubtless, an ex-
tended organ of feeling, probably much more sen-
sitive than the naked skin of our bodies. But,
besides this, most, if not all of these animals are
furnished with organs of special touch called tenta-
cles, which serve to collect and convey impressions
of the proximity, the form, the hardness, and per-
haps other qualities, of those bodies which the
animals may desire to investigate. ‘The mantle,
also, in many of the Casteropoda, is fringed with
a number of filaments, often curiously branched,
which are probably accessary organs of touch.

The sensitiveness manifested by some of the
large Casteropoda, the great Conchs of the West
Indies, for example, to the presence of other
bodies, even without contact, and which the Rev.
Lansdown Guiding attributed to the sense of
hearing, may, perhaps, rather be considered as a
modification of feeling, capable of appreciating the
pulsations of the atmosphere. The experiments
of this naturalist, not to be vindicated from the
charge of cruelty, are thus described. “I lately
suspended,’ he says, ‘“‘a number of large Strombi
by the spire, that the animal, when dead, might
fall from the shell. They had remained in this
situation several days, till the body, weak and
emaciated, hung down nearly a foot from the aper-
ture, and the eyes had become dim. I found that

8 MOLLUSCA.

even before my shadow could pass over them, they
were aware of my presence, and endeavoured to
withdraw into the shell. JI then cut off the eyes,
with the thick cartilaginous tentacula in which
they were lodged, but the animals still continued
to be sensible of my near approach, while hanging
in this mutilated and painful condition.” * Dr,
Johnston records a manifestation of feeling, some-
what analogous to this, in one of the common shell-
fish of our sandy shores. “On a summer evening,”
he remarks, “ I have observed the common Spout-
fish (Solen siliqua), extended along the surface of
the fine sand in which they burrow, enjoying, ap-
parently, the calmness and mildness of the season,
take alarm and instantaneously descend when I
was yet distant several yards: and I can explain
this and similar facts only on the supposition of
the existence of a sense of touch feelingly alive to
impressions impalpable to our grosser sense.” T
The respiration is aquatic in most of the Mot-
LuscA. ‘The breathing organs, in most cases,
resemble in essential points the gills of fishes, con-
sisting of a great number of leaves, often minutely
subdivided. ‘They are chiefly formed of blood-
vessels, covered with rows of vibrating cilia, by
the constant motion of which, currents of water
are perpetually hurled along the entire surface of
the breathing organ, communicating oxygen, the
vital principle, to the blood as they go, through
the thin walls of the vessels. In many species, as
the Bivalves, the gills form two large comb-like
plates; in others they are arranged in the form of
a feather; a beautiful tribe, known as naked-gilled,

* Zool. Journ. iv. 172.
¢ Introduction to Conchology, p. 199.

MOLLUSCA. 9

have these organs placed on the outside of the
body, sometimes forming prominent warts or pa-
pille, disposed in rows, or in tufts, sometimes
resembling little branching trees, and at others,
arranged as a number of elegant plumes, set, like
the petals of an exquisite flower, around a circle,

In the Tunicata, examples of which may be
found on our rocky beaches, closely adhering to
the under surface of stones at low water, and
looking like shapeless masses of a substance some-
thing between gristle and jelly,—the breathing
organ is developed to a very great extent. It
occupies a capacious chamber in the interior of the
animal, the two sides of which are studded on their
inner surfaces with little oval cells, arranged in a
regular pattern of rows. Each of these cells is
formed by an oval ring of cilia, which, when in
full play, present a most beautiful and interesting
spectacle. The accompanying figure, taken from
the life, is a magnified representation of a tiny
creature, not larger than a pin’s head, but as trans-
parent as the purest crystal. The oblong rings
conspicuously seen are the ciliary cells of the
breathing organ; but no figure can convey an ade-
quate impression of the beauty of the sight, when
the observer gazes upon forty or more of these
ovals, all set round their interior with what look
like the cogs on a watch-wheel, dark and distinct,
running round and round with an even, moderately
rapid, ceaseless motion.

One large tribe of the Gasteropoda comprises
animals, however, which breathe air, and are ter-
restrial in their habits. Of these the Slugs and
Snails of our fields and gardens afford familiar
examples. The delicately-formed, and often bril-

10 MOLLUSCA.

liantly-painted shells, which throng the damp
woods in tropical countries, likewise belong to this
group, and furnish the most highly prized treasures
of our conchological cabinets. In these the air is

°
<
a
9

eo vs 0

on eo
oad

PEROPHORA.

inhaled into an ample chamber, the interior of
which is lined with cilia. After parting with its
oxygen, it is again expelled; the common orifice
for both processes being situated on the side of the

-MOLLUSCA. #1

body. Any one may have ocular evidence of the
existence of this organ, by watching our common
Garden Snail. If you look at its right side, just
behind the tentacle, or horn, that carries a black
eye at its point, you will see a large hole suddenly
open, where before there was no trace of it. After
remaining open for a few moments, the margin will
leisurely contract again, until it is perfectly closed,
and as invisible as before. This is the breathing
orifice ; and during the interval that you saw it open,
the aerial contents of the chamber were expelled,
and a copious draught of fresh air was inspired.
The process is repeated with tolerable regularity
about once every fifteen seconds.

The blood in the MoLuusca is thin, transparent,
and colourless; or at most presents only a pale
bluish-white hue. It is, however, contained in a
system of distinct vessels, through which it cir-
culates, having for the source of its motion a well-
developed, complex, pulsating heart.

Besides the system of vessels which carry the
blood, there is another system, most conspicuous in
the aquatic tribes, which has been called the system
of aqueducts. They communicate with the ele-
ment in which the animal lives and moves, and are
filled with it at will, as the galleries and canals of
a sponge are filled with the liquid in which it is
immersed. The chief use of these water-canals
appears to be the distension and expansion of the
foot, to render it better fitted for locomotion, yet so
as not to interfere with the privilege, essential to
most of these animals, of withdrawing the whole
of the body within a shell. Some of the marine
Mollusca, when in a state of activity, protrude a
soft foot, far exceeding in dimensions the whole

1 -MOLLUSCA.

bulk of the shell; yet let the creature be disturbed,
and the whole is suddenly withdrawn into the ca-
vity, so completely that not a trace of it is visible.
* When shrunk within its shell,” observes Dr.
Johnston, “ you might well deem any animal that
could hide itself there, all too small and weak to
carry about a burden larger and heavier than it-

THE GIANT STROMBUS.

self, and that safety might be here advantageously
exchanged for relief from so much heaviness of
armour, and from such an impediment to every
journey. ‘There is in my small cabinet a fine spe-
cimen of Cassis tuberosa, which measures fully ten
inches in length, and upwards of eight in breadth,
another of Strombus gigas is nearly one foot in

MOLLUSCA. 13

length. The weight of the former is four pounds
two ounces; that of the latter, four pounds nine
ounces ; yet the snail creeps under this load at ap-
parent ease. Nor are you much surprised when
you see it actually in motion, for the seeming dis-
proportion between the contained animal and con-
taining shell has disappeared. On issuing from its
shell, like an Hastern Genii freed from his exorcism,
the animal has grown visibly,—has assumed a
portlier size and more pedestrious figure. The
body has suddenly become tumid and elastic, the
skin and exterior organs stretched and displayed,
the foot has grown in length and in breadth, and,
with additional firmness, it has acquired at the
same time the capability of being directed, bent,
and modified in shape, to a considerable degree, as
the surface of the road traversed may require.
Thus it is with nearly all the cephalous mollusca ;
and by a similar disposition of aqueducts, the foot
of the Bivalves is equally adapted to every act sub-
servient to their locomotion and more especially to
the act of burrowing; for had the foot not been so
framed as to permit of an enlargement superior to
the size of the shell, it seems obvious that the fur-
row could not have been made large enough to
contain the latter. The same, too, with many
Gasteropods which burrow in the sand when in
search of prey. The Luccina and most carnivo-
rous mollusca have this ability, dependent on the
system of aqueducts we have been describing ; and
you must observe, that from the manner in which
the shell is attached to the body by the large re-
tractor muscle, it so happens that this is drawn
into the furrow always with the notch in the
aperture uppermost, so that, when completely

14 MOLLUSCA.

buried, the animal is still enabled to communicate
with the water by its respiratory siphon.” *

Beyond the rudimentary strip of cartilage that
in some of the Cephalopoda represents the vanish-
ing spine of the VERTEBRATA, the MoLLuscA have
no internal skeleton. But in the great majority of
cases, the soft parts are protected and supported by
what we may call an external skeleton, of the sub-
stance familiar to us as shell. Lime is the es-
sential element of this substance, as it is also of
bone: but shell is a carbonate of lime, while the
earthy part of bone 1s a phosphate.

When we consider the beauty and variety that
are presented by shells, the important part they
play in the economy and habits of the animals,
and the use that is made of them in systematic
arrangement, it becomes a question of high interest
to inquire in what manner they are formed.

“The shells themselves are absolutely deprived
of vitality, permeated by no vessels, and as inca-
pable of expansion by any internal power as the
rocks to which they are not uncommonly attached;
so that the young naturalist is necessarily at a loss
to conceive either the mode of their formation, or
the origin of all the gaudy tints and external de-
corations that render them the ornaments of our
cabinets.

“The simple apparatus by means of which shells
are constructed, is the external membranous layer
that invests the body of the mollusk,—the mantle,
as it has been termed ; and, whatever the form of
the shell, it owes its origin entirely to this delicate
organ. : : ,

“Tt is the circumference, or thickened margin of
* Introduction to Conchology, p. 173.

MOLLUSCA. 15

the mantle alone which provides for the increase
of the shell in superficial extent. On examining
“this part, it is found to be of a glandular character,
and moreover not unfrequently provided with a de-
licate and highly sensitive frmge of minute tenta-
cula. Considered more attentively, it is seen to
contain in its substance patches of different colours,
corresponding both in tint and relative position
with those that decorate the exterior of the shell.

‘When the animal is engaged in increasing the
dimensions of its abode, the margin of the mantie
is protruded, and firmly adherent all round to the
circumference of the valve with which it corre-
sponds. ‘Thus circumstanced, it secretes calcareous
matter, and deposits it in a soft state upon the
extreme edge of the shell, where the secretion
hardens and becomes converted into a layer of solid
testaceous substance. At intervals this process is
repeated, and every newly-formed layer enlarges
the diameter of the valve. The concentric strata
thus deposited remain distinguishable externally,
and thus the lines of growth marking the progres-
sive increase of size may easily he traced.

“It appears that at certain times the deposition
of calcareous substance from the fringed circum-
ference of the mantle is much more abundant than
at others: in this case ridges are formed at distinct
intervals; or, if the border of the mantle at such
periods shoots out beyond its usual position, broad
plates of shell, or spines of different lengths, are
secreted, which, remaining permanent, indicate, by
the interspaces separating successively deposited
growths of this description, the periodical stimulus
to increased action that caused their formation.

‘« Whatever thickness the shell may subsequently

16 MOLLUSCA.

attain, the external surface is thus exclusively com-
posed of layers deposited in succession by the
margin of the mantle, and, seeing that this is the *
case, nothing is more easy than to understand how
the colours seen upon the exterior of the shell are
deposited, and assume that definite arrangement
characteristic of the species. We have already
said that the border of the mantle contains, in its
substance, coloured spots: these, when minutely
examined, are found to be of a glandular character,
and to owe their peculiar colours to a pigment se-
creted by themselves; the pigment so furnished
being therefore mixed wp with the calcareous mat-
ter at the time of its deposition, coloured lines are
found upon the exterior of the shell wherever
these glandular organs exist. If the deposition of
colour from the glands be kept up without remis-
sion during the enlargement of the shell, the lines
upon its surface are continuous and unbroken ; but
if the pigment be furnished only at intervals, spots
or coloured patches of regular form, and gradually
increasing in size with the growth of the mantle,
recur in a longitudinal series wherever the paint-
secreting glands are met with. ....

“While the margin of the mantle is thus the
sole agent in enlarging the circumference of the
shell, its growth in thickness is accomplished by a
secretion of a kind of calcareous varnish, derived
from the external surface of the mantle generally ;
which, being deposited layer by layer over the
whole interior of the previously existing shell, pro-
gressively adds to its weight and solidity. There
is, moreover, a remarkable difference between the
character of the material secreted by the marginal
fringe, and that furnished by the general surface

MOLLUSCA. 17

of the pallial membrane; the former we have found
to be more or less covered by glands appointed for
the purpose, situated in the circumference of the
mantle, but as these glands do not exist elsewhere,
no colouring matter 1s ever mixed with the layers
that increase the thickness of the shell, so that the
latter always remain of a delicate white hue, and
form the well-known iridescent material usually
distinguished by the name of nacre, or mother of
pearl,” *

This lucid description of the process specifically
applies to the Conchifera, or Bivalves; but the
formation of the shell in the Gasteropoda is not
marked by any important point of difference.

No species of this great Division of animals is
furnished with limbs, properly so called: unless
we may consider as such the long flexible ten-
tacular arms of the Poulpes and Cuttles (Cepha-
lopoda) which are used as instruments of an un-
gainly sort of crawling, as well as for seizing prey
and dragging it to the mouth: yet various modes
of locomotion are by turns practised among the
Mouuusca. In one extensive Class, the Gaster-
opoda, of which the Limpet and the Snail are
examples, an even gliding movement is that which
is most characteristic ; a broad expanded muscular
disk, called the foot, being applied to the surface
over which the animal crawls. Many of the
aquatic members of the Class are able to float at
the surface by the aid of the same organ. They
erawl to the top of the water up the stem of a
plant, or the side of a rock, and stretching out the
bottom of the foot along the surface, the back being
downward, it presently dries by contact with the

* Jones’s Animal Kingdom, p. 385.
CG

18 MOLLUSCA.

air. While it remains dry, it will float the animal,
which then glides along as if on a solid body,
crawling, in fact, on the inferior surface of the avr:
put if by any agitation of the water, or by the will
of the animal, the foot become overflowed, the state
of suspension is ended, and the creature falls to the

POULPE AND CALAMARY,

bottom. The Pond-snails (Zumneus), with olive-
coloured fragile shells, that inhabit every little
pool and lakelet, may be seen in a summer’s day,
by scores, enjoying the air in this manner.

The wide ocean between the tropics is inhabited

MOLLUSCA. 19

py a shell, resembling in appearance that of a
Snail, but tinged with blue (Janthina), which is
furnished with an elaborate apparatus for swim-
ming,—

“ Like little wanton boys that swim on bladders.”

To the hinder part of the foot is attached a kind of
float, consisting of many small bladders of thin
membrane, united in a group, and looking some-
what like coarse froth. By means of these, the
shell floats securely on the broad sea.

- Another bladder-swimmer, and like the former,
an ocean-species, 1s the Litiopa. “'This ‘is a small
snail, born amid the gulf-weed, where it is destined
topass the whole of its life. The foot, though
rather narrow and short, is of the usual character,
and, having no extra hold, the snail is apt to be
swept off its weed; but the accident is provided
against, for the creature, like a spider, spins a
thread of the viscous fluid that exudes from the
foot, to check its downward fall, and enable it to
regain the pristine site. But suppose the shock
has severed their connexion, or that the Litiopa
finds it necessary to remove, from a deficiency of
food, to a richer pasture, the thread is still made
available to recovery or removal. In its fall, acci-
dental or purposed, an air-bubble is emitted, pro-
bably from the branchial cavity, which rises slowly
through the water, and as the snail has enveloped
it with his slime, this is drawn out into threads as
the bubble ascends; and now, having a buoy and
bladder whereon to climb to the surface, it waits
suspended until that bubble comes into contact
with the weeds that everywhere float around.” *

* Johnston’s Conchology, p. 134.

b

20 MOLLUSCA.

A species of Certthium, found at the mouths of
rivers in tropical countries, has the silkworm-like
habit of spinning threads, by which it suspends
itself from the mangrove-roots; and our own
freshwater Snails have the power of suspending
themselves in the same manner. Mr. Warington,
in an interesting paper on the habits of some
aquatic animals kept in confinement, thus records
the curious fact :—

“In watching the movements of the Limnet,
I was for some time under the impression that they
had a power of swimming or sus-
taining themselves in the water,
as they would rise from the bottom
of the pond, a portion of the rock-
work, or a leaf of the plants, and
float for a considerable period,
nearly out of their shells, with-
out any apparent attachment, and
by the contortions and gyrations
of their body and shell, move
some little distance, inahorizontal
direction, from the point which they had left.
On more carefully watching this phenomenon,
however, I found they were attached by a thread
or web, which was so transparent as to be alto-
gether invisible, and which ae could elongate in
a similar way to the spider: they also possessed the
power of returning upon this thread by gathering
it up, as it were, and thus drawing themselves
back to the point which they had quitted. These
facts were clearly proved in the following manner :
A Limneus stagnalis had glided its way along a
young and short leaf of the Vadlisneria, which ter-
minated below the surface of the water, and having

LIMNEUS AURICULARIS,

MOLLUSCA ye

reached the extremity, launched itself off from it ;
after moving about with a sort of swimming or
rolling motion in a horizontal direction for some
time it lowered itself gradually, and in effecting
this, the long flexible leaf of the Vallisnerta was
bent with an undulating motion, corresponding
exactly with every movement of the snail, clearly
showing that it had a firm attachment to the ex-
tremity of the leaf. On another occasion a LZ.
glutinosus gradually rose from the surface of a piece
of submerged rock, and when at the distance of
about three or four inches from it, stayed its pro-
gress, floating about in a circumscribed horizontal
direction for some time; at last it rose suddenly
and rapidly to the surface, evidently from the
rupture of its thread of attachment. The most
convincing proof, however, of this fact, that I can,
perhaps, adduce, and one that I have often repeated
with all the before-mentioned Limnez, is that when
the snail has been some inches distant from the
supposed point of attachment, a rod or stick has
been carefully introduced, and slowly drawn on
one side between them in a horizontal direction,
and by this means the snail can be made to un-
dulate to and fro, obeying exactly the movement
of the rod: this requires to be done very gently,
as, if too much force is used, the web is broken,
and the snail rises rapidly to the surface.’’ *

The wide expanse of ocean from the equator to
the poles is tenanted by a class of swimmers,
small, indeed, in the number of its species, but
countless in the hosts of individuals of which they
are composed; the Pteropoda. Some of these in-
habit shells, which for delicacy and transparency,

* Annals of Natural History. October, 1852.

22 MOLLUSCA.

exeel the thinnest glass. They possess a pair of
large membranous fins, which closely resemble the
wings of a butterfly, and by using these organs in
a flapping manner, the little animals swim briskly
about.

Perhaps some of my readers will expect me to
include the beautiful Paper Nautilus (Argonauta),

PAPER NAUTILUS.

among swimming Mollusks; seeing that the poets
have claimed for it the honour of teaching navi-
gation to man :—

“Learn of the little Nautilus to sail,
Spread the thin oar, and catch the rising gale.”—PopE.

Montgomery, the poet of the ocean, thus beauti-
fully expresses the popular notions concerning
it:—

MOLLUSCA. 23

“Tight as a flake of foam upon the wind,
Keel upward from the deep, emerged a shell,
Shaped like the moon ere half her horn is fill’d ;
Fraught with young life, it righted as it rose,
And moved at will along the yielding water.
The native pilot of this little bark
Put out a tier of oars on either side,
Spread to the wafting breeze a twofold sail,
And mounted up, and glided down the billow,
In happy freedom, pleased to feel the air,
And wander in the luxury of light.”—-Prtican ISLAND.

The accuracy of modern research, however, has
proved this to be but a pleasant fable. ‘The Ar-
gonaut is a Cuttle-fish, and crawls along the bot-
tom, like its fellows, by means of its slender,
flexible, tentacular arms, as represented in the pre-
ceding engraving, (fig. 2); while the pair that are
furnished with a broad fleshy disk, have an office
very different from that of sails, namely, that of
forming, repairing, and protecting the thin and
papery shell. (See fig. 3.) Its only swimming.
power appears to be that which it possesses in
common with all Cephalopoda, of shooting along in
a backward direction, by the force of a jet of water
from the funnel, as shown at fig. 1, where it is re-
presented as swimming towards the point a.

Among the TunicaTa there are some singular
tribes which swim freely in the sea. “The Salpe,
translucent as their native waters, and often united
in chains, after a pattern peculiar to each species,
are driven along the surface with considerable
quickness by alternate contractions and expansions,
and by the propulsion they receive from a current
of water, which is made continually to traverse the
long diameter of the body, sucked in by the pos-
terior aperture, and issuing im a stream through
that on the side of the mouth. Hence the body is

24 MOLLUSCA.

always pushed backwards—a circumstance that
has misled some naturalists to describe the posterior
aperture for the true mouth. The Pyrosomata are a
still more singular family of the same order. Hach
seeming individual of this genus is, in fact, a
numerous colony of little mollusca, every one in
its own cell, distinct, yet inseparably connected
with its fellows. Collected imto the figure of a
gelatinous cylinder, open at one extremity and
closed at the other, and roughened externally by a
multitude of tubercles disposed sometimes in rings
and sometimes irregularly, they float in the Aus-
tralian seas like stars of this lower world, shedding
around them a halo of light, brilliant indeed, but
surpassed in beauty by those other colours of the
creatures which it serves to disclose; colours which
come and go at pleasure, glorying as it were, in
their subtle changes, passing rapidly from a lively
red to aurora, to orange, to green, and to azure
blue; a magic scene, compelling more than the
admiration of every beholder.” *

Bivalve Mollusca in general have much less
power of shifting their locality than Univalves.
Many appear to be absolutely stationary, at least.
during their adult existence. But others, as the
Cockle, have a most versatile organ, known as the
foot, capable of being protruded from between the
valves, which, among its various uses, serves the
purpose of locomotion. It is in general applied in
this manner. Being stretched out to its utmost
extent, its point is made to hook downward into
the sand or mud, and the body with the shell is
then dragged down by the muscular contraction of
the foot. In most cases, this mode of progression

* Johnston’s Intr. to Conch. p. 124.
*

MOLLUSCA. 25

is sufficiently slow and awkward, but some of the
sand-borers are able to conceal themselves thus
with surprising rapidity.

Others of this Class are vigorous leapers; and
of some the bounds are so vivacious, forcible and
sudden, that they might almost be compared with
the flight of a bird, or the shooting of a fish. The
Clams or Scallops (Pecten) and their elegant re-
latives the Lime, are eminent among our native
species for this faculty. The mode in which the
leaps are effected is always described as being the
opening and sudden closing of the valves or shells;
but, in the case of the former genus, I have re-
cently found that the real organ of motion is the
mantle. The edges of this being firmly closed,
when the interior is filled with water, the fluid is
forcibly ejected from the lips, which are relaxed for
the purpose at any point according to the will of
the Scallop; and by the jet of water striking on
the surrounding element, the whole animal is shot
to a considerable distance in the opposite direction.

Most of the Mouiusca are, as I have already
intimated, inhabitants of the waters, and these are
divided between the seas and the freshwaters, in a
ratio somewhat like that which these divisions of
the waters of our globe bear to each other. Of
the marine kinds some dwell permanently and ex-
clusively at the bottom of the deep sea, whence
they are to be procured only by dredging. A
species of Crania has been brought up from a
depth of 255 fathoms. Others inhabit the open
ocean, habitually or occasionally swimming on
the top of the waves, or resting on the floating
sea-weeds of warm latitudes. Many species con-
fine themselves to the vicinity of the shore, where

26 MOLLUSCA.

each peculiar situation and locality has its proper
kinds. The sands, the ooze and mud of harbours,
the boulders and loose stones of the wave-washed
beach, the sides, ledges, and pools of rocks, un-
covered at the recess of every tide, are all inhabited
by species peculiar to the respective locality. Some
species strictly marine are able to endure protracted
exposure to the air, as the Periwinkle and the
Limpet, the most familiar of shell-fish, which every
visitor to the sea-side habitually sees clustered on
the rocks close to the limits of high-water mark.

The fresh-water Mollusca manifest a similar
choice of situation, though a less latitude is per-
mitted for its exercise. Some are peculiar to large
rivers, some to estuaries, others to lakes, and yet
others to small ponds and ditches.

In general the habits of one species of a genus
when ascertained, are found to indicate those of all
its fellows of the same genus; as for instance not
only is our common Cockle (Cardium edule) a
burrower in the ooze at the margin of the sea, but
all other species of the genus Cardiwm have simi-
lar habits of life. Yet Mr. Gray has enumerated
a considerable catalogue of species, which break
this rule, classimg them under four divisions.
1st, where. species of the same genus are found in
more than one kind of situation, as on land, in
fresh and in salt-water; 2nd, where one or more
species of a genus, most of whose species inhabit
fresh-water, are found in salt or brackish water ;
3rd, where, on the contrary, one or more species of
a genus, whose species generally inhabit the sea,
are found in fresh-water; and 4th, where the same
species is found both in salt and fresh-water.” *

* Philos. Trans. 1835; Part ii.

MOLLUSCA. 27

Of those species which dwell upon the land and
breathe the air, most affect moist situations. The
common Garden Snail, as is well known, retires to
crevices and corners in continued dry weather,
where it closes its shell with a temporary door to
prevent the evaporation of its vital juices, and
patiently waits the return of congenial humidity.
The first shower prompts the sensitive creatures to
venture abroad, and we see them crawling by
dozens over our borders and garden walks, im-
bibing from the steaming surface the grateful mois-
ture. The damp woods of warm countries are the
situations which most reward the researches of the
laborious collector of land-shells; but there are
some which are found in the driest places, as stony
plains, and the summits of arid hills.

GARDEN SNAIL.

Many terrestrial Mollusca which ordinarily in-
habit moist places, are enabled, by a precaution
similar to that adopted by our own Snail in

28 MOLLUSCA.

drought, to sustain life, in such a state of retirement
and suspension of their usual habits, not for a few
days or weeks only, but even for many years.
Numerous examples have occurred in which the
land-shells of distant countries have been brought
to England, alive but torpid, and have been kept
shut up in drawers for twelve, eighteen, and even
twenty months; manifesting no signs of life until
moistened, when they presently crawled about, and
began to eat. But the most singular example of
this protracted sleep on record, is that of Mr.
Simon’s Snails, which must surely have been the
veriest Rip Van Winkles among Mollusca. The
following account is from the Philosophical Trans-
actions; and the facts seem to have been carefully
investigated, and well authenticated :—

“Mr. Stuckey Simon, a merchant of Dublin,
whose father, a fellow of the Royal Society, and a
lover of natural history, left to him a small col-
lection of fossils and other curiosities, had among
them the shells of some snails. About fifteen
years after his father’s death (in whose possession
they continued many years), he by chance gave to
his son, a child about ten years old, some of these
snail-shells to play with. The boy put them intoa
flower-pot, which he filled with water, and the
next day into a basin. Having occasion to use
this, Mr. Simon observed that the animals had
come out of their shells. He examined the child,
who assured him that they were the same he had
given him, and said he had also a few more, which
he brought. Mr. Simon put one of these into
water, and in an hour and a half after, observed,
that it had put out its horns and body, which it
moved but slowly, probably from weakness. Major

MOLLUSCA. 29

Vallancy and Dr. Span were afterwards present,
and saw one of the snails crawl out, the others
being dead, most probably from their having re-
mained some days in the water. Dr. Quin and
Dr. Rutty also examined the living snail several
different times, and were greatly pleased to see
him come out of his solitary habitation after so
many years’ confinement. Dr..Macbride and a
party of gentlemen at his house, were also wit-
nesses of this surprismg phenomenon. Dr. Mac-
bride has thus mentioned the circumstance :-—
‘After the shell had lain ten minutes in a glass
of water that had the cold barely taken off, the
snail began to appear, and in five minutes more
we perceived half the body pushed out from the
eavity of the shell. We then removed it into
a basin, that the snail might have more scope than
it had in the glass; and here, in a very short time,
we saw it get above the surface of the water, and
crawl up towards the edge of the basin. While it
was thus moving about, with its horns erect, a fly
chanced to be hovering near, and, perceiving the
snail, darted down upon it. The little animal
instantly withdrew itself into the shell, but as
quickly came forth again, when it found the enemy
had gone off. We allowed it to wander about the
basin for upwards of an hour, when we returned
it into a wide-mouthed phial, where Mr. Simon
had lately been used to keep it. He presented me
with this remarkable shell, and I observed, at
twelve o’clock, as I was going to bed, that
the snail was still in motion; but next morning I
found it in a torpid state, sticking to the side of the
elasa,’!.*
* Phil. Trans. (abridged) xiii. 566.

30 MOLLUSCA.

In treating of the food of the Mollusca, Dr.
Johnston divides them into three classes; first,
those which take their food in a liquid form, or
suspended in water; secondly, those which are
more properly carnivorous; and, thirdly, those
which feed on vegetable matter.

Under the first division are comprised all those
which have no distinct head, including the three
classes, Zunicata, Brachiopoda, and Conchifera.
None of these have any power of pursuing prey,
nor any organs for mastication. Yet any one who
has ever examined with a microscope, either the
sea-water, which appears to the naked eye pure
and simple, or the impalpable sediment which lies
upon the bottom, will be at no loss to discover
abundant organic matter fitted to supply nutriment
to these headless, generally stationary, and appa-
rently helpless creatures. Countless millions of
Infusorial animalcules sport in the clear water,
altogether unappreciable by our senses, while vege-
tables clothed with flinty shells, the Diatomacee
of botanists, equally numerous and equally minute,
crowd the mud on the floor of the sea.

In order that these minute bodies should afford
nutriment to the headless Mollusca, a simple but
effective contrivance is provided. The currents
which ceaselessly play over the breathing organs,
produced by the cilia which cover them, not only
bring water to be respired, but come charged with
the various organic particles, both animal and
vegetable, that occur in the vicinity. It is, there-
fore, merely necessary that the orifice of the
stomach, which for convenience sake may be
called the mouth, be situated in the course of
the currents, and be endowed with the power of

MOLLUSCA. 31

selecting and retaining such substances as are
suitable for digestion.

The remaining classes divide themselves into
flesh-eaters, and those which live upon vegetable
diet, the preponderance, however, being, as well as
ean be estimated, rather with the former. Not
a few of the Univalves feed upon their Bivalve
relatives, not seizing the opportunity, as has been
pretended, of killing their victim as it lies in-
cautiously with gaping shells; but by drilling
a small hole through one of the valves, and ex-
tracting the fleshy parts, particle by particle.
Some species devour dead fishes and other putri-
fying animal matters with avidity. Many of the
elegant naked-gilled tribes prey on each other,
though their proper food consists of zoophytes.
I have found the large Holis papillosa tear away
the tentacles of different species of sea-anemones,
which seemed to be its natural food.

The Cephalopoda, including the Cuttles, the
Poulpes, and the Squids, are fierce and predatory,
the tyrants of the deep. Furnished with many long
arms, stretching in all directions, and studded with
rows of adhesive suckers, they seize with ruthless
grasp any passing fish or other animal, whose
strength is inferior to their own, and drag it toa
hard and sharp horny beak, the mandibles of which
_ resemble those of a parrot’s bill, and being moved
by powerful muscles are enabled either to crush
the shells in which their victim may be enclosed,
or to tear it to pieces if it be a fish, or other animal
of muscular or sinewy tissues.

In speaking of the vegetable-feeding Mollusca, the
ravages committed by those pests of our gardens,
the Slug and Snail, will occur to every one. Other

32 MOLLUSCA.

species of the same genera are never or rarely seen
in gardens, but devour the herbage of the roadside,
the bank, or the hedge. Many, particularly those
which inhabit the woods of foreign countries, de-
vour the leaves of trees. The plant-eaters among
the marine tribes live upon the various kinds of
sea-weeds, of which there is a sufficient variety to
gratify a taste much more epicurean than it pro-
bably is in reality. The common Periwinkle and
the Limpet are both vegetable feeders, and there is
a pretty little species of the latter genus which
invariably, I believe, confines itself to one plant:
this is the Patella pellucida, distinguished by having
on its summit three or four lines of blue, most
brilliantly gemmeous. It feeds on the tangle,
(Laminaria digitata) eating away a cavity for
itself, just large enough to contain its body, in the
substance of the cartilaginous stem, commonly be-
neath the shelter of the arching roots. [have pulled
up the tangles by dozens at low spring-tide, and
have scarcely ever found one that had attained
certain dimensions without finding a little parasitical
Limpet embedded in its substance.

If we measure the interest which we take in any
section of created beings by their powers of con-
ferring benefit or inflicting injury on our own race,
we shall find the Mollusca not unworthy of our
regard in both these respects. Many of them are
used as human food, and that not by savage nations
only, but by ourselves and by all classes of society.
The Limpet, the Periwinkle, the Whelk, the
Mussel, and the Cockle, are commonly sold in the
streets of our sea-port towns and large cities, though
these are certainly more prized by the lower classes
of society than by those of more cultivated tastes.

MOLLUSCA. oe

There is no doubt that many if not all of our larger
Bivalves might be added to the list, and probably
some of these might prove not unworthy of a place
among more delicate viands. I have myself tried
the large Pholas dactylus, that bores the sandstone,
and have found its substance tender, and its taste
agreeable.

The Cuttle-fishes, though but little used among

PHOLAS.

ourselves, are prized by most other nations. Mr
Couch, speaking of the common Squid, declares
that it is excellent, and compares it to tripe, a re-
semblance to which the kindred genus owes its
name, for Kuttel in German signifies tripe. Among
the people of Southern Europe the Cuttles are in
high repute for the table, and this taste has been
D

34 MOLLUSCA.

handed down from the ancient Greeks and Romans.
The classics frequently allude to them as among
the greatest delicacies. At the nuptial feast of
TIphicrates a hundred Polypi and Sepie were served
up. Among the Greeks generally they were dis-
euised with various condiments and sauces; and
the Poulpe, or Many-feet, (Polypus, the Octopus
of modern zoology) was the most highly esteemed.
Dr. Johnston quotes the “ good old story” of Phil-
oxenus in illustration of the gourmand taste for

this ill-looking Cephalopod.

“Of all fish-eaters,
None, sure, excell’d the Lyric bard, Philoxenus.
"Twas a prodigious twist! At Syracuse,
Fate threw him on the fish call’d ‘ Many-feet.’
He purchased it, and drest it; and the whole,
Bate me the head, form’d but a single swallow.
A crudity ensued—the doctor came,
And the first glance inform’d him things went wrong.
And ‘ Friend,’ quoth he, ‘if thou hast aught to set
In order, to it straight ;—pass but seven hours,
And thou and life must take a long farewell.’
‘T’ve nought to do,’ replied the bard, ‘all’s right
And tight about me. , é :
: : ; : : I were loath, howe’er,
To troop with less than all my gear about me ;—
Good doctor, be my helper then to what
Remains of that same blessed Many-feet.

> 99

Snails appear to have found equal favour with
the ancients. The Romans were accustomed to
keep these animals in snail-sties, or Cochlearia,
where they fattened them with nutritive pastes
artificially made. The species was probably the
Helix pomatia, which is considerably larger than
our garden snail, but the dimensions which they
are said to have attained under these favourable

MOLLUSCA, 35

circumstances are so enormous as to be utterly
incredible. The Illyrian snails were most esteemed
for their size, and Pliny informs us that it was a
matter of emulation among the amateur snail-feeders
of that day to excel each other in the bulk to which
their pets should attain; vaunting their most pro-
digious specimens, as prize pigs and oxen are boasted
of among ourselves: “ And in time men grew to
take such a pride and glory in this artificial feat,
namely, in striving who should have the biggest,
that in the end one of their shells ordinarily would
contain eighty measures called quadrants.” *

Our continental neighbours still enjoy a dish of
snails, and several attempts have been, from time
to time, made to introduce them at English tables,
but with very little success.

But among all the edible Mollusca, there is
none that can compete with the Oyster. To speak
of the universality of the esteem would be super-
fluous ; but some statistical particulars may not be
uninteresting, as showing the importance of this
shell-fish in a commercial view. “The number
of vessels immediately employed in the dredging
for oysters on the Essex coast are about 200, from
twelve to forty or fifty tons burden each, employing
from 400 to 500 men and boys. The quantity of
oysters bred, and taken, and consumed annually,
mostly in London, is supposed to amount to 14,000
or 15,000 bushels. All the fisheries connected
with this part of the coast, are stated to employ a
capital supposed to amount to from £60,000 to
£80,000.” T

It is, however, not only as supplying food that the

* Holland’s Pliny, vol. i. p. 267.
+ Encyc. Brit. Supp. vol. iv. p. 269.

36 MOLLUSCA.:

benetits of the Mollusca are to be estimated: they
are useful also in the arts. The pearl, that splendid
auxiliary to costume in all ages, glittering on the
tiara of the Assyrian monarchs and on the diadem of
our own sovereign, is a production of this class of
animals, This, it is true, has no merit beyond
its beauty, but the substance called mother-of-

CAMEO CUL IN A CASSIS.

pearl is, as is well known, much used in the arts.
{t consists of the interior layers of many species
of shells, principally Bivalves; but some among
the Univalves have an interior brilliantly nacreous.
The Top-shells (Trochus), several species of which

MOLLUSCA. ot

occur on our own shores, are very rich in this
respect, and the widely-gaping Har-shells (Haliot?s)
are most gorgeous.

The elegant articles called cameos, so much used
as clasps and brooches, are formed out of the
substance of large shells: the ponderous Helmets
(Cassis) of the West Indies are chiefly used for this
purpose. A great excellence in the art consists in
the careful cutting away of the material so that the
ground shall display one colour, commonly a dark
hue, while the design is carved in another, commonly
the pure white, which overlays the brown.

Shells, being composed of carbonate of lime, are
capable of being burned to a quick-lime, having all
the essential properties of that made from stone.
On some parts of our own shores where limestone
is scarce, shell-lime is extensively burned; but in
other countries, as Holland and the United States
of America, scarcely any other is used, either for
building purposes or for manuring land.

Among the subordinate uses of shells may be
mentioned that in China
and Japan the valves of
a sort of Oyster (Placuna),
which are as large as a
plate, flat, and transparent,
are used in windows and for
other purposes where we
employ glass; and among
the semi-barbarous nations
of Africa, a little species of Cowry (Cyprea moneta)
is universally recognised as a money currency.

The natural secretions of the Mollusca are not
much used among us. The Indian ink used by
artists is generally understood to be in part, at least,

MONEY COWRY.

38 MOLLUSCA.

composed of the black liquor of some species of
Cuttle; and an ink is prepared in Italy from this
liquor, which, according to Cuvier, differs from the
genuine China ink only in being a little less black.
Among the ancients this secretion was certainly
the basis of the ordinary writing ink, and the soft
blackish-brown colour, known as sepia, is at this
day manufactured from it.

The Tyrian purple, the most celebrated manufac-
ture of that famous crowning city whose merchants
were princes, was the juice of a shell-fish. Several
species were employed to communicate various tints,
but the principal was the Murex trunculus, one of
the commonest shells of the Mediterranean, which
may be compared for size and general appearance
to our familiar Whelk. But there is a shell oc-
curring by myriads on our own rocky shores, which
has a like property ; it
is the Purpura lapillus,
a small white univalve,
surrounded by one or
more bands of brown
more or less distinct. I
have myself been en-
tertained with making
experiments on the
purple dye of this shell-fish, which, perhaps, some
of my readers may like to imitate. In order to
this, having collected a few of the animals, which
adhere to the rocks between tide-marks, break the
shells with the blow of a hammer, taking care not
to crush the animals: throw them then into a basin
of fresh water, in which they will die in a few
minutes. Examining them now, you will find, just

behind the head, under the overlapping edge of the

PURPURA.

MOLLUSGCA. 39

mantle, a thick vein of a yellowish white hue, filled
with a substance resembling cream: this is the
dye in question. It is thick and glutinous, so that
you cannot well apply it with a pen; but with a
camel’s-hair pencil you may paint, as it were, upon
linen or cotton cloth any lines, the initials of your
name, for example. When you have done this
you will perhaps be disappointed, for the marks as
they dry will be but just discernible, displaying
only a pale yellow tint with not the slightest
approach to purple, but exhaling an insufferable
odour of garlic.

Place your linen in the light of the sun, and look
at it again in half-an-hour, or, if you please, watch
its changes. ‘The marks have by this time passed
from yellow into pea-green, and are now of a full
grass-green; under the influence of the light the
change proceeds rapidly, the yellow element gradu-
ally disappearing, and the blue element becoming
more and more prominent, until through the stages
of deep-green, sea-green, and greenish-blue, the
colour at length appears a full indigo. The red
element now begins to be apparent, and rapidly
increases in intensity until the hue is a dull,
reddish purple. In my own experiments this was
the ultimate tint obtained; a tint perfectly indelible
as long as the texture of the material remained,
neither light, nor time, nor washing, nor the appli-
cation of chemical agents having now the least
influence either in changing its hue or causing it
to fade. I have seen it stated that if the cloth be
washed in scalding water and soap, it comes out
from the lather changed from the reddish purple
hue to a fair bright crimson; with me, however,
the soap and the hot water had no appreciable in-

40 MOLLUSCA.

fluence in brightening the colour. My experiments
were performed in winter, and I will not affirm that
the intensity of a summer’s sun would not in some
degree have modified the result. ‘There appears
to me one objection to this material ever having
been used to dye large surfaces of uniform colour ;
for from the admixture of mucus with the colouring
matter, when any quantity of the latter is collected,
the hue is found to imbue the cloth in a mottled
or blotched manner, some parts being much darker
than others. What method the ancients had of
avoiding this appearance [ do not know.

I have seen it repeatedly stated that the slimy
liquor remaining in the shell of the common snail,
when the animal is crushed, is an admirable ce-
ment for glass or china, resisting both heat and.
moisture. I have tried it both simple, and mixed,
as sometimes directed, with quick-lime in powder,
but am compelled to confess, that I found it ut-
terly worthless, the adhesion being in every case
no greater than if I had used spittle for the
purpose.

Let us now see what rank the Mollusca can
assume among those creatures which inflict di-
rect injury upon man. ‘The ravages committed by
various species of snails and slugs are often an-
noying, and sometimes serious. There are pro-
bably few of my gentle readers who have a garden
at their disposal, who have not been disappointed
of their crops of spring flowers by the nightly
depredations of these pests. The border has been
well dug and smoothed, the seed has been carefully
sown, and the spot has been eagerly watched from
day to day; but no sooner have the tender seed-
leaves appeared above ground in a slender green

MOLLUSGA. 41

line or circle, than night after night they are
gnawed away, until nothing remains but the brown
earth, and the label which tells where the seed had
been. But to the farmer the consequences are
often much more important. In wet seasons the
slugs increase with such rapidity in the fields, that
a wheat-crop after one of clover, tares, or beans, is
very uncertain, and may be said generally to fail.
The damage annually done to corn, clover, and
turnips, by these apparently insignificant creatures,
is very great. In France and the South of Europe,
the vineyards are subject to similar attacks from
the vine snail (Helix pomatia). The buds and
opening leaves of the vine are gnawed off by them
as they appear, and the hopes of the autumnal
vintage are often blasted.

But much more lameutable than any of these
are the injuries inflicted upon shipping, and the
piers and defences of maritime towns, by the ship-
worm (TZeredo navalis). Ranging over extensive
seas trom the tropics to the shores of Northern
Europe, this boring worm, or rather Mollusk with
a worm-like form, is incessantly engaged in de-
vouring and destroying all kinds of woodwork that
is immersed in the sea. Linneus long ago styled
it the calamity of ships, and there is no maritime
nation which has not confessed the formidable
power of this subtle enemy. In the years 1731
and 1732, the United Provinces were under a
dreadful alarm; for it was discovered that these
mollusks had made such depredations on the piles
which support the banks of Zealand and Freis-
land, as to threaten them with total destruction,
reclaiming from man what he had with unex-
ampled labour wrested from the ocean. A few

42

MOLLUSCA.

years after they fortunately abandoned the dikes ;
but fearful of the return of an enemy more power-

TEREDO.

ful than even the Grand
Turk, who boasted that
he would exterminate
them with a host armed
with spadesand shovels,
the Dutch offered a re-
ward of value, to any
one who should dis-
cover a remedy to ward
off their attacks, and
ointments, varnishes,
and poisonous liquors,
were recommended by
the hundred. The exact
amount of the damage
done at this visitation
—which Sellius, unable
to discover any natural
cause for it, says was
sent by the Deity to
punish the growing
pride of the Hollanders
—TI have not been able
to ascertain. Writers
in general speak of it
as “very great ;”’ and

Dr. Job Baster mentions the Teredo as an animal
“which has done so many millions damage to

these countries.”

In our own country it has done,

and continues to do, extensive mischief. The
soundest and hardest oak cannot resist these
noxious creatures; but in the course of four or
five years, they will so drill it as to render its

MOLLUSCA. 43

removal necessary, as has repeatedly happened in
the dockyard of Plymouth. To preserve the tim-
bers used there, and exposed to them, the plan now
adopted is to cover the parts under water with
short broad-headed nails, which, in salt water, soon
invests the whole with a strong coating of rust im-
penetrable by their augers. ‘The plan appears to
have proved effectual, for, in the harbours of Ply-
mouth and Falmouth, where the Teredo was once
abundant, it is now rare or not to be found; but
in other parts it has still a residence, and within
these few years it has materially injured or de-
stroyed many of the piles used in the construction
of the pier at Port Patrick, on the coast of
Ayrshire; and the Limnoria terebrans, a crus-
taceous insect, co-operating with it, the result
of their united efforts can hardly fail to be the
utter and speedy destruction of all the timber in
ihe pier.’ *

Another kind of injury is dependent on the fact
that certain species, which are generally eatable
and even wholesome, become at certain times highly
poisonous. Some foreign species are liable to this
fatality, particularly oysters, both in the East and
West Indies. But we need not go to distant coun-
tries for cases in point. The Mussels of our own
rocks, though generally sold and eaten by many
persons without fear, are well known to be fickle in
their qualities, and many cases are on record in
which their use has proved fatal. One of these,
well authenticated, and investigated by scientific
medical men, occurred at Leith in June 1827. Many
of the poor of this town were poisoned by eating
mussels which had been collected in the docks.

* Tntroduction to Conchology, p. 11.

44 MOLLUSCA.

“The town,” says Dr. Combe, “was in a ferment, and
the magistrates
with great propri-
ety issued a warn-
ing against the use
of the mussels.
; Many deaths were
pi, veported, and hun-
dreds of indivi-
duals were stated
to be suffermg
under the effects
vy of the poison.
# Luckily, matters
were not so de-
plorable; but we
ascertained that in
addition to the
man mentioned
before, the com-
panion of our pa-
tient, an elderly woman, had died. In all about
thirty cases occurred, with great uniformity of
symptoms, but varying very much in severity;
but none, so far as I know, have left any permanent
bad effects.’”’* 7

The cause of this occasional liability to become
poisonous seems involved in almost total obscurity.
Dr. Johnston, who discusses at some length the
many loose and vague conjectures that have been
hazarded on the subject, has shown, that not one of
them is tenable, unless it be that in some cases the
poisonous principle proceeds from some particular
food which, not fatal to the Mollusks, yet gene-

* Edin. Med. and Surg. Journal, xxix. p. 88.

MUSSELS,

MOLLUSCA. 45

rates a diseased condition of the body, deadly to
other creatures. The Leith mussels, he adds, were
living in a dock, where we may presume they were
nurtured and fattened amid putrescent matters; and
Dr. Coldstream, than whom no one is better quali-
fied to decide the point, gave it as his opinion that
the liver was larger, darker, and more brittle than
in the wholesome fish, and satisfied Dr. Christison
that there was a difference of the kind. It must
be confessed, however, that these observations leave
the question pretty nearly where 1t was before.

Some peculiar secretions of the Mollusca remain
to be noticed. And first the black liquor or ink of
the Cuttles and Squids, which has already been
mentioned as useful to man, but which is doubtless
much more useful to the animals themselves. These
animals, when in danger, are known to pour forth
from a funnel-like orifice a liquor of a blackish-
brown colour in considerable abundance ; this fluid,
readily diffusing itself and mingling with the sur-
rounding water, produces such a cloud of obscurity
as frequently enables the crafty animal to escape,
enveloped in the mist of its own making,—as the
deities in Homer are represented as concealing
their favourite heroes.

Somewhat analogous to this is a secretion of a
rich purple hue produced and poured forth under
excitement, by those large and naked mollusks, the
Aplysiec. I have found one of these animals, on
being put into a vessel of clean sea-water, change
the whole to a brilliant purple in a very few
minutes; and on the water being renewed even
again and again, produce the same result. This
was a West Indian species, but there is one found
occasionally upon our own coasts which has the

46 MOLEUSCA.

same property. This liquor must not be con-
founded with that which constitutes the purple dye
of Murex, Purpura, &c. already mentioned, for it
is so volatile as to be unsuitable for the purposes of

APLYSIA.

dyeing. According to Cuvier, the secretion in dry-
ing assumes the beautiful deep hue of the sweet Sca-
bious, and remains unaltered by long exposure to
the air. Nitric acid, in small quantity, heightened
the tint, but a larger dose changed it to a dirty.
orange colour, while potash turned it to a dingy
vinous grey. Both the acid and the alkali preci-
pitated many white
flakes from the fluid.
The purple tintis readily
transferred to spirit when
the animal is immersed
in 1t; the tincture retains
this colour for awhile,
but at length becomes
PLANORBIS CORNEUS. of a deep clear red,
like that of port wine.

A very common shell in ponds and ditches,
(Planorbis corneus,) coiled up like a ram’s horn, is

MOLLUSCA. 47

said to have the same property ; a purple fluid is
poured out from beneath the mantle, but it is so
fugitive that no application can prevent its speedily
turning to a dull rusty colour.

Colonel Montagu mentions one of our marine
shell-fish (Scalaria clathrus) as secreting a purple
juice. ‘‘It may be collected either from the recent
or dried animal, by opening the part behind the
head; and as much can be procured from five in-
dividuals as is sufficient, when mixed with a.few

SCALARIA.

drops of spring-water, to cover half a sheet of paper.
Neither volatile nor fixed alkali materially affects
it; mineral acids turn it to a bluish green, or sea-
green; sulphuric acid renders it a shade more in-
clining to blue; vegetable acids probably do not
affect it, since cream of tartar did not in the least
alter it. These colours, laid on paper, were very
bright, and appeared for some months unchanged
by the action of the air or the sun; but, being ex-
posed for a whole summer to the solar rays, in a
south window, they almost vanished. The appli-
cation of alkali to the acidulated colour always
restored it to its primitive shade, and it was as
readily changed again by mineral acid.” *

I have already mentioned some thread-spinners
among the Mollusca; there are others which have

* Test. Brit. Supp. p. 122.

48 MOLLUSCA.

the power of forming threads of silky substance
much stronger and more durable than those of our
pond snails. The Common Mussel (Mytilus edulis)
is one of these marine silk-worms; and we have a
good many others. The bundle of threads, familiar
to many of my readers as the beard of the shell-fish,
is the substance in question, termed by naturalists
byssus, a Greek word originally signifying silk ; and
the use to which it is applhed by the animal itself
is that of a cable to moor itself to the solid and
immovable rock, that it may not be washed away
by the violence of the waves. The mode in which
the threads are formed, and the organ by which
they are secreted, are thus described by Professor
Rymer Jones :—

“The foot in the Mussel is of small dimensions,
being useless as an instrument of progression. By
its inferior aspect it gives attachment to the horny
threads of the byssus, which are individually about
half an inch in length, or as long as the foot
itself, by which, in fact, they are formed, in a
manner quite peculiar to certain families of Con-
chifera; no other animals presenting a secreting
apparatus at all analogous, either in structure or
oftice, to that with which these creatures are pro-
vided. The manner in which the manufacture of
the byssus is accomplished is as follows: A deep
eroove runs along the under surface of the foot, at
the bottom of which thin horny filaments are formed
by an exudation of a peculiar substance, that soon
hardens and assumes the requisite tenacity and
firmness. While still soft, the Mussel, by means
of its foot, applies the extremity of the filament,
which is dilated into a kind of little sucker, to the
foreign substance whereunto it wishes to adhere,

MOLLUSCA. 49

and fastens it securely. Having accomplished this
the foot is retracted; and the thread, of course,
being drawn out of the furrow where it was secreted,
is added to the bundle of byssus previously ex-
isting, all of which owed its origin to a similar
process.” *

Whoever has attempted to wrench up a Mussel
from one of those shallow rock-pools, in which they
lie as closely packed as paving stones, will have
had proof of the great strength of these threads, no
small violence being required to detach one. But
there is an example on record, where the strength
of the threads has been turned to such account
as to give this Mollusk a second claim to be in-
cluded in the list of such species as are beneficial
to man.—‘‘ At the town of Bideford, in Devonshire,
there is a long bridge of twenty-four arches across
the Torridge river, near its junction with the
Taw. At this bridge the tide flows so rapidly that
it cannot be kept in repair by mortar. The Cor-
poration, therefore, keep boats in employ to bring
mussels to it, and the interstices of the bridge are
filled by hand with these mussels. It is supported
from being driven away by the tide entirely by the
strong threads these mussels fix to the stonework ;
and by an act, or grant, it is a crime liable to
transportation for any person to remove these
mussels, unless in the presence and by the consent
of the corporative trustees.”

There are bivalve shells allied to the mussel,
called Penna, usually of very large size, but of thin
and delicate structure. ‘The threads spun by these
are long, fine, glossy, and produced in great abun-
dance; they are capable of being twisted like silk,

. * Animal Kingdom, p. 383.
E

50 MOLLUSCA.

and the inhabitants of Sicily weave them into a
sort of cloth remarkable for its softness and warmth,
but which refuses to take any dye. In the British
Museum, together with some very fine specimens
of the shells of this Mollusk, there is a pair of
gloves made of its byssus; but articles made of this
material are very costly, and cannot be considered
in any other light fhan that of curiosities. Pope
Benedict XV, in 1754, had a pair of stockings
presented to him which were woven from the silk
of the Pinna. These were the subject of general
admiration, from the extreme delicacy of their
texture—well shown by the minuteness of the box
in which they were enclosed.

The mention of the ship-worm naturally presents
to the mind another tribe of bormg Mollusca,—
those which perforate hardened clay, and even stone.
These, belonging to various genera, are sufficiently
common on our own coasts. Different species of
Pholas excavate their burrows, which resemble the
holes bored by augers or large gimlets in wood,
clay, and sandstone; the Venerwpis in shale and
similar friable rocks, the Lithodomi and Saxitcave
in the limestone, and the Gastrochena in limestone,
fluor, and granite. A curious example of the boring
powers of one of these species, the Modiola:litho-
phaga, occurs at Pozzuolo, in the Bay of Naples,
where a colony of these Mollusks had settled
themselves in the pillars of the temple of Jupiter
Serapis during the period of its submersion. At
the height of ten feet above the base of the three
standing pillars which remain, and in a position
exactly corresponding in all, is a zone of six feet
in height, where the marble has been scooped into
cells by these Mollusca. The holes are to the

MOLLUSCA. 51

depth of four inches; and it is observed that the
nodules of quartz and feldspar, which sometimes
occur in the hard limestone of the pillars, are un-
touched.

Many theories have been invented to account for
the singular power exercised by these animals, such
as the following; that the animals entered the rock
while it was in a soft and plastic state, and that it
afterwards hardened around them—that the animal
poured out some peculiar fluid which had the
chemical property of dissolving the rock—that the
latter was ground away by the roughnesses on
the shells as they revolved, as if by the action of
a rasp or file—that the minute particles of the stone
were one by one separated and driven off by the
force of currents of water, produced by vibrating
cilia: but all these theories appear to be set aside
by the discovery of Mr. Albany Hancock, one of
the highest living authorities on the subject. This
gentleman finds that the excavating instrument is
the anterior portion of the animal, either the foot
and the edges of the mantle, or the edges of the
mantle solely. These organs are fitted for the
office they are to perform, not only by their position
and figure, and their phiability and muscular struc-
ture,—made more than commonly muscular for the
duty,—but also by being armed with a rough layer
of numerous crystalline particles of various sizes
and shapes, chiefly five- and six-sided, and all
having one or more elevated points near the centre.
These crystals are imbedded in the surface of the
boring foot and thickened edges of the mantle ;
and, consisting, probably, of silex or flint, either
pure or in combination with some animal matter,
they form a sort of file—superior, however, to any

52 MOLLUSCA.

of our workmen’s files in this, that the surface keeps
itself always in a proper state of roughness for
trituration. This is done by an organic law, which
causes the crystals to be constantly shed, and. as
constantly renewed.*

All the borers above alluded to are Bivalves,
and I know of no other Mollusk which can pro-

LIMPET,

perly be classed with them. A common Gastero-
pod, however, the familiar Limpet (Patella vulgata),
excavates the rock on which it lives to the extent
of making a depression, more or less deep, exactly
corresponding to the shape and size of the margin
of its shell. When one removes a Limpet from
its firm adhesion and finds a hollow beneath it,
evidently made to contain its body, one is ready to
conclude that the animal is a permanent tenant of
the spot, never moving from it; and when we learn
that the food of the Limpet consists of sea-weeds,
we wonder how it is possible that a stationary
animal can find vegetable food. But the truth is,

* Ann, and Mag. N. H. Oct. 1848.

MOLLUSCA. 58

I believe, that the Limpet wanders away from its
hollow during the night, returning to it as a home
by an infallible instinct on the approach of morning.
The mode in which the excavation is performed is
the same as that just mentioned in the case of the
borers, the whole under surface of the foot being
furnished with sharp crystals of flint imbedded in
its substance.

In general the stony shells of the Mollusca
afford them,,a sufficient protection, but a few
species construct for themselves nests. A native
example of this instinct is described in eal
terms by the Rev. D. Landsborough, who obtaine
it in Lamlash Bay :—

“The most interesting, though not the rarest,
thing we got was Lima hians. I had before this
some specimens of this pretty bivalve, and I had
admired the beauty and elegance of the shell; but
hitherto [ had been unacquainted with the life and
manners of its inhabitant. Mr. and Miss Alder
had got it in the same kind of coral at Rothesay,
so that when Miss Alder got a cluster of the coral
cohering in a mass, she said, ‘ O, here is the Lima’s
nest!’ and breaking it up, the Zima was found
snug in the middle of it. The coral nest is
curiously constructed, and remarkably well fitted
to be a safe residence for this beautiful animal.
The fragile shell does not nearly cover the Mollusk,
the most delicate part of it, a beautiful orange fringe-
work, being altogether outside of the shell. Had
it no extra protection, the half-exposed animal
would be a tempting mouthful—quite a bonne-bouche
to some prowling haddock or whiting; but He
who tempers the wind to the shorn lamb, teaches
this little creature, which He has so elegantly

54 MOLLUSCA.

formed, curious arts of self-preservation. It is not
contented with hiding itself among the loose coral,
for the first rude wave might lay it naked and
bare. It becomes a marine-mason, and builds a
house or nest. It chooses to dwell in a coral
grotto; but in constructing this grotto it shows
that it is not only a mason, but a rope-spinner, and
a tapestry-weaver, and a plasterer. Were it merely
a mason, it would be no easy matter to cause the
polymorphous coral to cohere. Cordage, then, is
necessary to bind together the angular fragments
of the coral, and this cordage it spins; but it spims
it as one of the secrets of the deep. Somehow
or other, though it has no hand, it contrives to
intertwine this yarn which it has formed, among
the numerous bits of coral, so as firmly to bind
a handful of it together. Externally, this habi-
tation is rough, and therefore better fitted to elude
or to ward off enemies. But though rough exter-
nally, within all is smooth and lubricous, for the
fine yarn is woven into a lining of tapestry, and
the interstices are filled up with a fine slime, so that
it is smooth as plaster-work.

“When the Lima is taken out of its nest, and
put into a jar of sea-water, it 1s one of the most
beautiful marine animals you can look upon. The
shell is beautiful; the body of the animal within
the shell is beautiful ; and the orange fringe-work,
outside of the shell, is highly ornamental. Instead
of being sluggish, it swims about with great vigour.
Its mode of swimming is the same as that of the
scallop. It opens its valves, and, suddenly shutting
them, expels the water, so that it is impelled
onwards or upwards ; and when the impulse thus
given is spent, it repeats the operation, and thus

MOLLUSCA. 5D

moves on by a succession of jumps. When moving
through the water in this way, the reddish fringe-
work is like the tail of a fiery comet. The filaments

LIMA.

of the fringe are probably useful in catching its prey.
They are very easily broken off, and it is remark-

56 MOLLUSCA.

able that they seem to live for many hours after
they are detached from the body, twisting them-
selves like so many worms.’’*

Thus we have slightly touched a few of the
details of the history of this great division of
animated beings; and we discover that they are
not less rich in interesting endowments and tacul-
ties, In various contrivances and compensations, in
singular habits and instincts, than other animals
higher in the scale of organization. But it is only
when we study the Mollusca as living beings, that
we discover these points of varied interest. The
mere collection of shells, however curious their
forms and brilliant their colours, would impart
but a small amount of knowledge when separated
from the animals to which they belong. ‘The
shell-collector of former days looked upon his
drawers, if they were rich in rare species or
varieties, as containing an assemblage of gems ;
and, indeed, the enormous prices given for fine and
scarce shells, joined with the surpassing beauty of
the objects themselves, almost justified the view
which the possessor took of his cabinet of treasures.
They were to him really ‘les delices des yeux et
de l’esprit ;’ and the energetic zeal with which he
collected, and the sacrifices that he made to procure
a fine and perfect Many-ribbed harp, a Gloria
maris, or Cedo nulli, among the cones; an Aurora
or Orange-cowry, a Voluta aulica, or Voluta
Junonia, &c., were only comparable to the extrava-
gances of those visited by the tulip mania when it
was at its height. But though they were the
delight of his eyes, they were, in nine cases out of
ten, little more to the owner of them: they were

* Excursions to Arran, p. 319.

MOLLUSCA. ot

mere trinkets on which he looked dotingly, without
knowing, and scarcely wishing to know, the
organization of the animal whose skeleton only
was before him.” *

In these days, however, the examination of the
shell is considered by all who possess any claim to
science, as subordinate to the history of the entire
animal.

Naturalists arrange the MoLLusca im six classes,
named Cephalopoda, Pteropoda, Gasteropoda,
Conchifera, Brachiopoda, and Tunicata. Of these
the first three are sometimes distinguished as Hn-
cephala, or furnished with a head ; the last three as
Acephala, being destitute of that organ.

* Penny Cyclop., art. MaLacoLoey.

58 CEPHALOPODA.

CLASS I. CEPHALOPODA.

(Head-footed Mollusks.)

Ir we were to takea Poulpe or a Cuttle-fish from
some hole or tide-pool in the rocks, and look upon
its many flexible arms studded with sucking disks,
its sack-like body, its green staring eyes, and its
bird-like beak, we should be ready to say that such
an animal presents but a shght analogy with the
sluggish and almost shapeless creatures familiar to
us under the name of shell-fish. And, in truth, the
former do possess a higher rank in the scale of
animal life, having their senses developed into
greater perfection, and forming, indeed, the link by
which the latter take hold of the races which, from
their elaborate organization, are placed at the summit
of the scale—the VERTEBRATA.

We shall better understand the connexion between
the present Class and other Mollusca, by considering,
with Cuvier, that “the mantle unites beneath the
body, and thus forms a muscular sac which enve-
lopes all the viscera. This body, or trunk, is fleshy
and soft, varying in form, being either spherical,
elliptical, or cylindrical, and the sides of the mantle
are in many of the species extended into fleshy fins.
The head protrudes from the muscular sac, and is
distinct from the body: it is gifted with all the
usual senses, and the eyes, in particular, which are
either pedunculated or sessile, are large and well
developed. The mouth is anterior and terminal,

CEPHALOPODA. 59

armed with a pair of horny or calcareous mandibles,
which bear a strong resemblance to the bill of a
parrot, acting vertically one upon the other. Its
situation is the bottom of a subconical cavity,
formed by the base of the numerous fleshy tenta-
cular appendages which surround it, and which have
been termed arms by some naturalists, and feet by
others.”

These fleshy flexible feet are characteristic of the
Class, and give to it its systematic appellation of
Cephalopoda, signifying head-footed. They are
instruments of locomotion; the animal being enabled
to crawl awkwardly upon this circle of feet, head
downwards. But their chief use to the animal is
as organs for the seizing and holding of prey;
and for this purpose they are eminently qualified.
Each arm is furnished with a double row of sucking
disks, each of which on being applied to any surface
adheres to it at the will of the animal with immense
force, so that it is easier to tear away the substance
of the limb while the creature maintains its hold,
than to release it from its attachment; and even
after death, the suckers continue to retain a con-
siderable power of adhesion.

The manner in which these suckers act, will be
understood by a reference to the principle of a
cupping-glass. Hach one consists of a firm fleshy
or cartilaginous ring, across which a disk of
muscular membrane is stretched, with a circular
aperture in the centre. A cone-shaped mass of
flesh fills this aperture, like a piston, capable of
being drawn backward. The membranous disk
itself can also be drawn in. Now, let us suppose
that one of the sucking disks of a tentacle touches
any object fit for prey, such as a fish, for example,

60 CEPHALOPODA,

gliding by. ‘The instant that the Cuttle feels the
contact, instinctively, and with the speed of light-
ning, it retracts the fleshy piston; a vacuum is
thus created, and the edges of the disk are pressed
against the surface of the victim, with a force equal
to the weight of the water that is above it, added
to the weight of the atmosphere. If need be, as
when the victim makes strenuous efforts to escape,

STRUCTURE OF SUCKER.

the vacuum, and consequently the adhesion, is in-
creased by the withdrawal of the membranous disk.

This apparatus, powerful as it is, is but one out
of a thousand instruments of the same kind with
which the animal is furnished. Our common
Poulpe ( Octopus vulgaris) has eight tentacular arms,
and every one of these carries one hundred and

CEPHALOPODA. 61

twenty pairs of sucking disks. The struggles of
the unhappy victim once touched by the fatal spell,
only ensure its speedy destruction ; for as it writhes
and darts to and fro, it ever comes into contact with
others of the disks in succession, each of which
adheres. Others of the arms now entwine them-
selves about it, and thus it is surely dragged to the
central mouth, where the sharp and horny beak
soon cuts it to pieces in spite of its scaly armour.
The effective power of this apparatus is graphically
described by Mr. Broderip:—

‘We well remember, in our youth, going far out
with an old fisherman of Dawlish, to visit his
floating nets which he had laid for the pilchards.
As we looked down into the clear blue water, we
could see that the number of fish entangled was
great; but, to the great discomfiture of the fisher-
mau, who was eloquent on the occasion, almost
every other fish was locked in the embraces of a
cuttle-fish, plying his parrot-like mandibles to some
purpose. The fisherman, who seemed to regard
these unbidden guests as an incarnation of ail evil,
carried a capacious landing-net, but so quick was
the sight of these Cephalopods, so ready were they
in letting go, and agile in darting back or sideways
clear of the net, that, though the greedy creatures
held on to the last moment, the fisherman did not
secure above three out of the crowds that had
spoiled his haul. Upon mentioning this to Mr.
Owen, he informed us that the muscular arrange-
ment enabled the animal, when it was disposed to
let go its hold, to push forward the piston, and thus
in a moment destroy the vacuum which its retrac-
tion had produced.” *

* Penny Cyclop. art. CEPHALOPODA.

62 CEPHALOPODA.

These highly endowed and repulsive creatures
are formidable even to man. We may pass by,
until better authenticated, the stories told by old
naturalists, of Cuttles inhabiting the Indian Seas,
with tentacles as long and thick as a ship’s mast,
which they are said to throw over vessels and drag
them under water. But Mr. Beale, who has so
largely increased our knowledge of the Sperm
Whale, recountsa sufficiently fearfulrencontre which
he had with a species of Octopus, while searching
for shells upon the rocks at the Bonin Islands.
He was much astonished at seeing at his feet a
most extraordinary looking animal crawling towards
the surf, which it had only just left. It was creeping
on its eight legs, which, from their soft and flexible
nature, bent considerably under the weight of its
body; so that it was lifted by the efforts of its
tentacula only a small distance from the rocks. It
appeared much alarmed at seeing him, and made
every effort to escape. Mr. Beale endeavoured to
stop it by pressing on one of its legs with his foot;
but although he used considerable force for that
purpose, its strength was so great that it several
times liberated its member, in spite of all the
efforts he could employ on the wet and slippery
rocks. He then laid hold of one of the tentacles
with his hand, and held it firmly, so that the limb
appeared as if it would be torn asunder by the
united efforts of himself and the creature. He then
gate it a powerful jerk, wishing to disengage it
rom the rocks, to which it clung so forcibly by
its suckers. This effort it effectually resisted ; but
the moment after, the apparently enraged animal
lifted its head with its large projecting eyes, and,
loosing its hold of the rocks, suddenly sprang upon

CEPHALOPODA. 63

Mr. Beale’s arm, which he had previously bared to
the shoulder for the purpose of thrusting it into
holes in the rocks after shells, and clung with its
suckers to it with great power, endeavouring to
get its beak, which Mr. Beale could now see, be-
tween the roots of its arms, in a position to bite.
Mr. Beale declares that a sensation of horror per-
vaded his whole frame, when he found that this
monstrous animal had fixed itself so firmly on his
arm. He describes its cold slimy grasp as ex-
tremely sickening; and he loudly called to the
captain, who was also searching for shells at some
distance, to come and release him from his disgust-
ing assailant. The captain quickly came, and
taking Mr. Beale down to the boat, during which
time the latter was employed in keeping the beak
of the cuttle away from his hand, quickly released
him by destroying his tormentor with the boat-
knife, when he disengaged it by portions at a time.
Mr. Beale states that this Cephalopod must have
measured across its expanded arms about four feet,
whilst its body was not bigger than a large clenched
hand.*

In one genus of this Class the action of the
suckers is Increased by a strong and sharp hook
which projects from the centre of each. During
action these hooks are plunged into the flesh of the
victim, securing a yet firmer hold; added to which
the two long arms, which are so endowed, and which
are over and above the eight possessed by the
Poulpe, are capable of being firmly locked together,
and thus can be made “to cooperate in dragging
to the mouth such powerful or refractory prey as
singly the arms might be unable to subdue.”

* Hist. of the Sperm Whale.

64 CEPHALOPODA.

Most of the species of the Class are destitute of
any external covering, but a few are protected by
a shell. An immense number of fossil species,
however, belonged to the latter division, known by
the names of Belemnites, Nummulites, Orbulites,
Ammonites, &c. The most important existing

species possessing a shell, are te Pearly Nautilus of
the tropical seas, and the Paper Nautilus of the Medi-
terranean. The former of these possesses four gills,
a peculiarity which distinguishes it from all its
fellows: Professor Owen, therefore, proposes to
divide the Class into two Orders ; the one ineluding
the Pearly Nautilus, called Tetrabranchiata, or four-
gilled; the other including the rest of the existing
species, named Dibranchiata, or two-gilled.

As the animals belonging to the Molluscous
Division are very numerous, I propose to limit this
volume to those families which are represented by
species existing in and around the British Islands,
contenting myself with an occasional slight notice
of such foreign kinds as have anything particularly
interesting in their history. I shall therefore at
onee proceed to the second of these Orders.

TWO-GILLED CUTTLES. 65

ORDER DIBRANCHIATA.

(Two-gilled Cuttles.)

THE creatures composing this order approach
nearest to the Vertebrate animals of all the Mollusca.
They have a distinct brain included in a box of
cartilage—the vanishing remains of a bony skull;
they have large highly-coloured and complex eyes,
protected in some species by eyelids; and ears of
simple structure, hollowed in the cartilage of the
rudimentary skull. They are remarkable for having
three separate and well organized hearts, one for
the circulation of the arterial blood through the
body, the others for the projection of the venous
blood through the two gills.

Any person who has had an opportunity of ex-
amining one of these animals in a living state, must
have been struck with a very curious phenomenon.
Over the whole surface of the body there are
coloured spots which are perpetually changing their
position and figure, running into each other and
separating, playing hither and thither, contracting
and dilating, appearing and disappearing, with great
velocity and in the most singular manner. On
close examination, it appears evident that these
changes are owing to a fluid which moves iregu-
larly within the substance of the skin. Even after
death the spots continue to play for a considerable
time, and that on small portions of the skin cut
‘away from the rest.

The cause of this curious appearance is not yet

F

66 DIBRANCHIATA.—SEPIADA,

thoroughly understood. Milne-Edwards, whose
opinion is entitled to the highest respect, gives the
following explanation of it:—‘ The skin of these
animals is furnished with a number of differently-
coloured spots, which alternately appear and dis-
appear, and if a portion is put under a microscope,
it may be perceived that these changes depend on
the contraction of small vesicles filled with a
coloured liquid, which reach from the surface of
the skin to a considerable depth. When one of
these spots appears, the liquid, corresponding here
to the pigment in the other case, is propelled
towards the superficial part of the vesicle, and there
displays itself; whilst during its disappearance it
is forced into the deeper parts by the contraction
of this superficial point itself, which then becomes
almost invisible.’ *

FAMILY SEPIADA.
(Cuttles and Squids.)

The lingering rudiment of a vertebrate skeleton
in these animals has been already noticed ; their
body encloses, however, a solid support of quite
another nature, which represents the true shell
so characteristic of Mollusca generally. Within
the substance of the mantle, if we slit it up along
the line of the back, we find an oblong cavity,
within which lies loose, and unconnected with it a
large plate, horny in some species and shelly in
others. The pen of the common Squid (Loligo
vulgaris) is of the former texture; the substance
called cuttle-bone, so often found on sandy beaches,
is of the latter; but both are strictly analogous to

* Edinb. New Phil. Journ. XVII. 319.

lord

CUTTLES AND SQUIDS. 67

the shell of the slug, which is also enclosed within
the mantle; and both are formed in the same
manner, namely, by a deposition of horny or shelly
matter in a fluid state from the sides of the con-
taining cavity.

The animals of this Family have ten arms, two
of which, greatly longer than the rest, are very
slender except near their tips, which are dilated ;
these extremities alone are furnished with suckers.
The other eight arms are short, thick, and fur-
nished throughout their whole length with suckers,
forming a double row along their under surface.

The body is generally lengthened, more or less
flattened, with the skin dilated on each side so as
to form a pair of wings or fins. It is probably by
means of the impetus afforded to the body by these
expansions, that some species of the I‘amily are
enabled to throw themselves out of the water, and
to shoot along through the air to a considerable
distance with a motion that resembles flight. These
are commonly called Flying Squid.

Mr. F. D. Bennett describes a portion of the
Northern Pacific as peculiarly animated by the
presence of various oceanic creatures. ‘The Albacore,
the Sword-fish, the Barracuda, the Bonita, the
Flying-fish, are mentioned, and among them the
Squid, whose movements closely resembled those
of the last-named volatile fish. ‘“ During a calm,
in lat. 30° N., the Flying-squid appeared in larger
fights than we had ever before witnessed; per-
secuted probably by the Albacore (which select
this tranquil time to descend deep in the water, and
to rove far from the ship in quest of food) they rose
from the sea in large flocks, leaping over its smooth
surface, much in the same mayner, and to the same

68 DIBRANCHIATA.—SEPIAD”.

height and distance, as the Flying-fish. Many of
them were captured by birds during their leaps,
and one individual, in making a desperate effort to
escape some aquatic pursuer, sprang to a consider-
able height above the bulwarks of the ship, and
fell with violence upon the deck.” *

GENUS SEPIA.
(The Cuttle.)

In this genus, which contains our commonest
species of the Order, the body is oblong and flat-
tened, with the side-tins extending along its whole
length. The mantle is free at its
front margin; the suckers are sup-
ported by horny hoops with entire
edges. The internal support is
shelly, and is composed of a suc-
cession of extremely delicate plates,
sustained by slender columns, regu-
larly arranged, the spaces between
the plates being filled with air.

Many of my readers are doubtless
familiar with the object here repre-
sented, so frequently cast up by the
Waves upon our smooth sandy
beaches: it is the shell of the com-
mon Cuttle-fish (Sepra officinalis).
Its use is not only to give firmness
to the soft and jelly-like body of the animal, but to
aid it in swimming by its buoyancy ; for though
the material of which it is composed is stone, from
the delicacy of its texture and the peculiar arrange-
ment of the plates, the large proportion of | air

“ Whaling Voyage round the Globe.

CUTTLE-BONE.

THE CUTTLE. 69

enclosed within it renders the whole lighter than
water.

The Cuttle is about a foot in length, of an oblong
form. Its colour is a dull, dirty white, mottled and
spotted with those
changing veins of
fluid, already de-
scribed, of a reddish
brown hue. ‘The
texture of the body
is soft and flabby,
but, notwithstanding
its unpleasing ap-
pearance, it forms
a wholesome and
agreeable dish wher-
ever prejudice does
not preclude its use. |
When well cooked
the flesh is tender and
digestible, bearing
considerable resem-
blance to tripe.

I have already al-
luded to the inky
fluid secreted in an
internal reservoir
within the body of
the Cuttle. It is
poured forth in co-
pious quantity from a funnel-like tube beneath the
mantle, and is intended as a means of concealment,
and of annoyance to its pursuers. “A gallant officer
who was inconsiderately collecting shells in a pair
of immaculate white trowsers, came suddenly upon

CUTTLE.

70 DIBRANCHIATA.—-SEPIADA,

one of the naked Cephalopods snugly harboured in
a recess in the rock. They looked at each other,
and the Cuttle, who had his eyes about him, and
knew well how to use them, upon seeing the enemy
advance, took good aim, and shot so true that he
covered the snowy inexpressibles with the contents
of his ink-bag, and rendered them unpresentable
either in drawing-room or dining-room.” *

Entangled among the sea-weeds washed up on
the sea-beach in the latter part of summer, we
occasionally see what at first sight we are ready to
take for a bunch of purple grapes. ‘The fisherman
indeed calls them sea-grapes, so close is the like-
ness in colour, size, and aggregation. But if we
take the cluster into our hand and examine it, we
shall see that their texture is leathery, or somewhat
like India-rubber, that the extremity of each berry
runs out to a point, and that its base springs from
a fleshy cord which clings and entwines irregularly
around the marine plants. ‘These berries are the
eges of the Cuttle-fish, and if we were to open the
tough skin of one, we should find either the white
yolk and clear glaire, or else the infant animal,
perhaps fully formed and ready to take advantage
of this premature opening of his prison, by darting
out, with all his organs perfected and all his wits
about him.

The parrot-like beak presents a strong exception
to the general softness of this animal ; it is so hard,
stout, and stony, and moved by such powerful
muscles, that the strong shells of bivalves and uni-
valves are not able to resist its force: even the hard
and stony limpet is dragged from its attachment,
and crushed to pieces in these powerful mandibles.

* Penny Cyclop. art. SEPIADZ.

PTEROPODA. 4

CLASS II. PTEROPODA.
(Fin-footed Mollusks.)

THIS is a very small Class, comprising a few
species of curious structure. They are all of di-
minutive size, and all swim in the open ocean,
rarely approaching the shore, except when washed
thither by accident. They are all characterised by
having a membranous expansion, resembling a
large fin, on each side of the head. By means of
these organs, the little Pteropod rows itself about
in the open sea perpetually; beg unfurnished
with any means of crawling, or of affixing itself to
any solid body. Some of these animals, as the ge-
nera Hyalea (a) and Cleodora (b), for example, have
the body enclosed in a shell of elegant form, and of

GLASS SHELLS.

a texture resembling the thinnest glass, for delicacy
and transparency. The Cleodora pyramidata, one of
the species of the latter genus, is of extreme delicacy
and beauty. The shell is glassy and colourless ;

72 PTEROPODA.

very fragile; nearly in the form of a triangular
pyramid; with an aperture at its base, from which
proceeds a long and slender glassy spine; and a
similar spine projects from each side of the middle
of the shell. The hinder part of the animal is
globular and pellucid, and in the dark vividly
luminous, presenting a singularly striking appear-
ance, as it shines through its perfectly transparent
lantern. Both of these are found floating in great
numbers on the surface of the tropical sea.

Others are entirely destitute of a shelly covering,
as is that little species which occurs in enormous
profusion in the Arctic Seas, and which we now
proceed to describe.

GENUS CLIO.
(“ Whale-food.”)

These little creatures have an oblong mem-
branous body, without a mantle; a head formed of
two rounded lobes, each of which is furnished with
three long tentacles, capable of being withdrawn
into a fold of skin, or protruded at pleasure. The
mouth, which is terminal, has two small fleshy lips ;
and two eyes, of elaborate structure, are placed at
the back of the neck.

The species best known is that which is com-
monly called by our northern voyagers, Whale-food
(Clio borealis). Though not more than an inch in
length, it occurs in such countless millions as to
form the principal part of the nourishment required
by the most gigantic of living creatures. The Clio.
bears some slight resemblance to a butterfly just
emerged from the chrysalis, before the wings are

WHALE-FOOD. 73

expanded. Near the head there is on each side a
large fin or wing, by the motions of which it changes
its place. These motions are amusing; and as the
little creatures are so abundant, they
make the dreary sea quite alive with
their gambols as they dance merrily
along. In swimming, the Clio brings
the tips of its fins almost into con-
tact, first on one side, then on the
other. In calm weather they rise to
the surface in myriads, for the pur-
pose of breathing ; but scarcely have
they reached it before they again
descend into the deep. Mr. Scoresby
kept several of them alive in a glass
of sea-water for about a month,
when they gradually wasted away
and died. The head of one of these little creatures
exhibits a most astonishing display of the wisdom
of God in creation. Around the mouth are placed
six tentacles, each of which is covered with about
three thousand red specks, which are seen by the
microscope to be transparent cylinders, each con-
taining about twenty little suckers, capable of being
thrust out, and adapted for seizing and holding
their minute prey.

Thus, therefore, there will be three hundred and
sixty thousand of these microscopic suckers upon
the head of one Clio: an apparatus for prehension
perhaps unequalled in the creation.

CLIO.

74 GASTEROPODA.

CLASS III. GASTEROPODA.

(Crawling Mollusks.)

lr we examine the manner in which the common
Garden Snail crawls, and especially if we look at
it through a pane of glass as it glides up on the
outside of the window, we shall see that the whole
of the under-part of the body forms a wide fleshy
disk, which is applied to the surface upon which
the animal moves. Carefully watching this, we
perceive that there are minute muscular move-
ments constantly taking place over the whole disk,
by means of which the animal advances with an
uniform gliding progression. This disk, and its
peculiar action, afford the most important character
by which this Class of animals is distinguished,
and hence they have been named Gasteropoda,
which signifies belly-footed.

The upper surface of the body is covered with
a fleshy cloak, the edges of which usually project
in a greater or less degree, overlapping the foot-
disk and other organs. This is called the mantle.

There is a distinct head, more or less conspicu-
ous, according as it more or less projects from
beneath the edge of the mantle; it is furnished
with tentacles, varying in number from two to six,
arranged in pairs on each side. ‘These are pro-
bably delicate organs of touch, and perhaps they
may be connected with other senses also. The
majority of species are furnished with eyes, com-

GASTEROPODA. 75

monly placed either at the bases or at the tips of
one of the pairs of tentacles. Every one is familiar
with their appearance in the snails and slugs of
our gardens, i which they are placed as minute
shining black points at the tips of the upper ten-
tacles. Many of the marine Gasteropoda, as the
great Conchs (Strombus) of the tropical seas, have
eyes well developed and of elaborate structure.
Mr. Swainson says—“ In the typical Strombz, these
organs are so much developed that the iris is richly
coloured, and the eyes of some of the larger species
have been described to us as particularly beau-
tiful.”* According to the Rev. Lansdown Guilding,
a naturalist who has enjoyed the advantage of
familiarity with these fine Mollusca in their native
seas, they have a distinct pupil and a double iris,
equalling in beauty and correctness of outline those
of birds and reptiles ; and he discovers in the organ
a vitreous and an aqueous humour, and the black
pigment.+ And Mr. J. E. Gray affirms, that “the
eyes of the marine carnivorous Mollusca, Buccinum
undatum, or Husus despectus, and more especially
some of the larger Strombz, are as fully developed as
in the cuttle-fish, showing the cornea and the
nearly orbicular crystalline lens almost perfectly
formed, as may be seen by any person simply cut-
ting the cornea across, and slightly pressing it,
when the crystalline lens will protrude.” {

Some species of this Class, few as compared with
the great body, are naked, but the majority are
protected by a shell, in some cases very thin,
brittle, and glassy, in others somewhat horny, but
more generally of a stony texture, and of great

* Malacology, 136. + Zool. Journ. iv. 172.
* Edin. Journ. iii. 52.

76 GASTEROPODA.

solidity and hardness. The chemical composition
of these shells, however, varies very little; they
consist of carbonate of lime deposited in cells of
animal albumen. In the porcelain shells, of which
the Cowries (Cyprea) afford familiar and beautiful
examples, the lime is compact, with so small a
portion of animal matter, that when immersed in
acid the shell is completely dissolved, no sensible
trace remaining. In the pearly shells, such as the
genus Zrochus, the calcareous matter is deposited
in layers; and these, when submitted to acids, leave
behind an insoluble membrane of albumen which
retains the form of the shell.*

The shell is secreted by the mantle. In one
family, that of the Chitons, it consists of several
pieces, but in general it is simple, and takes the
form of a hollow cone produced in various degrees.
In the Limpets, which we see adhering so abun-
dantly to our sea-side rocks, the cone is low and
nearly symmetrical; but in the great majority of
this class, the cone is greatly lengthened and twisted
upon itself, so as to form a spire.

The mode in which the shell is formed has been
well investigated by Mr. J. EX. Gray, whose obser-
vations on the subject I shall here take occasion to
cite :—

“The shell, which is peculiar to this division of
the animal kingdom, may be seen covering the
young animal in the egg before it has gained all its
organs, as was observed by Swammerdam, and
verified by the more extended observations of
Pfeiffer, Turpin, and others. They are easily seen
in the egg of the Limnat, Physe, Ancyli, and
Bithinie, which have a transparent coat.

* Thomson’s Chemistry, v. 54.

GASTEROPODA. Te

“ The shells of the newly-hatched animals have
been frequently considered as distinct species, and
some very thin shells of land Mollusca, such as
Vitrine, have been taken for the young of other well-
known species, as Helix hortensis. ‘These young
shells are easily known by their always being of
a pale horn colour; the whorls are generally rather
irregular, and enlarge very rapidly; and the apex
of the whorl, which was first formed, is generally
large and blunt compared with the size of the shell.
They are always destitute of colour, for the animal
does not deposit the colouring matter until after it
has been hatched; and it is therefore generally
easy to distinguish, in the young shell, (and some-
times also in the adult,) that part of the top of the
spire which formed the shell of the animal when in
the egg. |

“The shell is formed by the hardening of the
animal matter, which is secreted by certain glands
on the surface of the body, by means of chalky
matter, which is also secreted by similar glands.
It has been stated that the unhatched animal, very
shortly after it is formed, begins to make its shell;
and when it is hatched, deposits on the edge of the
mouth of the little shell, which covered its body in
the ege, a small quantity of the mucous secretion.
This dries, and is then lined with some mucous
matter, intermixed with calcareous particles; and
when this hardens, it again places on its edge an-
other very thin layer of the mucous secretion, and
again lines it as before. The mucous secretion
first deposited forms the outer coat of the shell, and
is of use in protecting it from injury, while the
mucous matter mixed with lime, which is placed
within it, forms the substance of the shell itself.

78 GASTEROPODA.

This deposition of mucous, and of mucous mixed
with calcareous matter, goes on as the animal grows
and feels the want of a larger shell for its protec-
tion. The shell is, in fact, moulded on the body of
the animal itself, as the body grows; and, for this
reason, any irregularity in the body is moulded in
the shell.

“The animal has the faculty, also, of mending
any break or injury that its shell may have re-
ceived, if it is not of such a magnitude as to de-
range all the functions of the animal itself; and it
mends them in the same manner as it forms its
shell,—that is to say, by depositing first a coat of
animal matter, and then lining it with mucous
matter, mixed with chalk, to harden it. But as
the animal is usually very desirous of getting the
repairs done as quickly as possible, and is most
probably damaged by the injury it has received,
these repairs are generally much more roughly ex-
ecuted than the shell itself, and commonly destitute
of regular colour.

“The particles, which vary the colour of the sur-
face of the shell, are deposited while the shell is
being increased in size, immediately under the
outer mucous coat; and as these particles are also
secreted by peculiar glands, the colour is always
situated in a particular manner on each species,
the glands being gradually enlarged, and gradually
separated, but not changed in position by the
erowth of the shell. All the variations exhibited
in the colouring of the different species, or in the
different individuals of the same species, are pro-
duced by the permanent or temporary interruption
of the action of these glands.’”*

* Land and'Fresh-water Shells, 73.

GASTEROPODA. 79

The part upon which the spire turns is called
the pillar. It is sometimes solid, but sometimes it is
hollow ; in the latter case the perforation is named
the umbilicus. When the spire is long, the shell
is said to be turbinated, which is the common form ;
but in some genera, as Planorbis, the convolution
takes place in the same plane, and the shell is flat,
or even concave. Such shells are termed discoid.
When the upper part of each turn or whorl envelopes
or covers that which preceded it, the spire is said
to be concealed.

In almost all species the convolution is towards
the right side. There are a few, however, which turn
to the left; these shells are termed reversed. The
end of the latest whorl, where the animal protrudes,
is termed the mouth or aperture. In order to close
this, when the animal withdraws itself into its
shell, the hinder part of the foot is usually furnished
with a horny or shelly plate, called the operculum,
which, when the animal contracts, is brought into
such a situation, as more or less completely to close
the mouth of the shell, when the animal is drawn
into its cavity. It has hitherto been observed only
in those Mollusca which have pectinate branchiz,
and in two genera, Cyclostoma and Helicina, among
the air-breathing land-shells. The form of the
operculum is in general either that of a very low
cone, made by successive layers, each one a little
larger than its predecessor, or that of a flattened
spire, and the texture is either horny or shelly.

The species of Gasteropoda are very numerous,
and are arranged in five orders, viz.—Pulmonifera,
Nudibranchiata, Tectibranchiata, Cyclobranchiata,
and Pectinibranchiata.

80 -PULMONIFERA.

ORDER PULMONIFERA.

(Lung-breathing Mollusks.)

Tus extensive Order contains Mollusca which
differ from all the rest of the Class, by breathing
atmospheric air. There is an orifice situated on
the right side, beneath the margin of the mantle,
which opens into a chamber lined with a delicate
net-work of vessels. This lined cavity is analogous
to the lungs of vertebrate animals, and its muscular
floor is said to perform alternate motions, answering
to those of the diaphragm, by which the lungs are
filled and emptied by turns.

Many of the species inhabit fresh waters ; but the
greater number are denizens of the land, requiring,
however, a damp atmosphere, to preserve them in
health and vigour. The close, humid forests of
tropical countries sustain the terrestrial species in
immense number and variety: the shells of many
of these—distinguished by their curious forms, by
their large size, by their rich and brilliant colours,
often arranged in finely-contrasted bands, and by
their delicately sculptured surfaces,—are among the
most precious ornaments of conchological cabinets.
The aquatic species form, notwithstanding the
element in which they live, no exception to the
leading character of the Order; they also breathe
air, which they obtain by coming periodically to
the surface.

In general, the subjects of this Order are protected
by an ample spiral shell ; but in some this appen-

LUNG-BREATHING MOLLUSKS. Sl

dage is very minute, concealed within the substance
of the mantle, or altogether wanting. Our own coun-
try furnishes examples of each of these kinds. All
the native species are comprised in five families, —
Cyclostomade, Auriculade, Limneade, Helicide,
and Limacide.

FAMILY CYCLOSTOMADA.

This is an extensive family, though represented
in Britain by but a single species. The great majority
of its members are elegantly formed and beautifully
sculptured shells from warm countries. The shell
is spiral, ample in its dimensions, with a circular
aperture, generally surrounded in the adult with a
frill-like, shelly expansion ; it is closed by a spiral,
shelly operculum.

The animal has a broad foot, divided longitu-
dinally ; a central spiral body, enveloped in a single-
edged mantle. There are two tentacles, which are
lengthened and. contractile, with an eye placed on
the outer side of the. base
ofeach. The sexes. are
distinct. All the species
are terrestrial, and are ge-
nerally found on trees, on
the leaves of which they
feed. The only British
species (Cyclostomaelegans)
is a little shell, about half an inch in length, and
rather less in width, of a grey or purplish yellow
hue, often marked with two rows of dark spots.
The spire is composed of five rounded whorls,
marked with numerous close-set, raised lines, run-
ning spirally, with finer longitudinal ones between

G

THE ELEGANT CYCLOSTOMA.

82 PULMONIFERA.—~- AURICULADZ.

them. There is an umbilicus behind the pillar ;
the operculum is hard, horny externally, and marked
with a single, depressed, spiral line.

This Mollusk lives on vegetable matter, like the
snails, and is found in damp places, on a chalky
soil. It is not very generally distributed, but is
said to be abundant on the warm chalk hills,
covered with brushwood, at Caversham, near
Reading, in Berkshire. It is common also in
the Isle of Portland, where I have seen it numerous
in April, crawling on the twigs of shrubs, with the
operculum carried behind, in a curious manner.

FAMILY AURICULADZ.

The characters of this family are the following :—
The animal has a lengthened foot, a lengthened
ringed muzzle, two somewhat cylindrical tentacles,
with eyes near their bases on the inner side. The
body is spiral, placed on the centre of the foot, and
invested with a thin mantle, with a thickened edge.
There is an ample spiral shell, the pillar of which is
plaited at all periods of its life.

Mr. Gray observes of these Mollusca, which are
feebly represented in Britain by some three or four
small species comprised in three genera, that they
appear, by their habit and character, to be exactly
intermediate between the land and the fresh-water
Univalve Mollusca. They have the sessile eyes
of the Pond-snails, placed behind instead of
in front of the tentacles, and the subcylindrical
tentacles of the Land-snails; but the tentacles are
not retractile under the skin of the neck. In the
same manner, the Carychia and the Acmea are ter-
restrial, living in damp moss; the Conovuli live in

LUNG-BREATHING MOLLUSKS. 83

the mud at the mouths of rivers, or in the sea:
they seldom leave salt, or at least brackish water.
There are some foreign species which live in ponds,
and have all the habits of our Pond-snails, only
that their pillar is more distinctly plaited.

The family may be represented by Conovulus
denticulatus, an oblong, spiral shell, rarely exceed-
ing half an inchin length, of a brown or purplish hue.
Its last whorl is long and compressed ; the pillar is
grooved, with several spiral plates; the throat is
also grooved. A remarkable character of this shell
is, that the pillar extends no further than the upper
part of the last whorl, the upper whorls being des-
titute of any pillar or internal spiral division.
This character is common to most species of the
family, and forms, as Mr. Gray observes, one of
its best technical distinctions. It is attributed to
the animal’s absorbing the partitions which separate
the upper whorls, and thus converting the spire into
a single cavity.

This little Mollusk is by no means common ; it
has been found in the marshes near Faversham, at
the roots of rushes. It )
is said also to inhabit
the clefts of rocks, near
high water-mark, as well
as the mud left bare by
the tide, at the mouths
of rivers. The animal A
feeds, according to M. THE DENTICULATED CONOVULUS.
Bouchard Chantreux, (Nat. size and magnified.)
on the detritus of marine plants and rotten wood.
It lays twelve or thirteen eggs in the months of
June and September, united by a viscid matter
into a small mass, which is fixed under the more

84 PULMONIFERA.—LIMNEAD&.

humid stones. The eggs are globular, yellowish,
and quite diaphanous: they are hatched about the
fifteenth day, and the animals reach their full size
about the end of the second year. They do not
hybernate.

Famity LIMNEADA,
(Pond-Snails.)

The Fresh-water Snails were scattered by Lin-
neus and his followers among various marine and
terrestrial genera, on account of the diversity which
is found in the shape and appearance of their shells.
Since more attention has been paid by conchologists
to the structure of the animal inhabiting a given
shell, the close similarity which subsists between
them has prompted their union into one family,
and that one of the most natural of all those into
which the Mollusca are divided. ‘They are distin-
guished by the following characters :—

The animals have a lengthened foot, a spiral
body, a short, broad muzzle, two large tentacles,
triangular and compressed, or awl-shaped, with the
eyes near their outer bases. The tongue is fur-
nished with rows of hooked teeth. The mantle,
which is ample, has a thin edge, and is protected
by a shell of exceedingly variable form, being
spiral, turreted, discoid, or simply conical. Those
which are spiral are sometimes regular, and some-
times reversed. The colour is generally pale
brown, uniform in hue, and the surface is closed
with a hard olive skin, technically called the
pertostraca, or that which is around the shell. |
They are destitute of an operculum.

The habits of these Mollusca are as identical as

POND-SNAILS. 85

their structure. They inhabit lakes, ponds, and
ditches of fresh water; are found, but less commonly,
in rivers, and still more rarely in brackish water.
They crawl on the mud at the bottom, or on the
stems and leaves of aquatic plants, always coming
to the surface, at intervals, to take in a fresh
supply of air into the lung chamber for respira-
tion. They may frequently be seen floating, at the
surface of still water, by the expanded foot, the
shell being downward and submerged.

They lay their eggs in round or oval masses ot
consistent jelly, each mass containing a number of
egos, varying from three to upwards of a hundred,
according to the genus. The masses are attached
to plants or stones beneath the surface, and are
hatched in about a fortnight after they are de-
posited.

The Pond-snails are very numerous, and widely
distributed, species being found in almost all parts
of the world. Twenty-four are reckoned by Messrs.
Forbes and Hanley as British.

“Jt had been supposed that the shells of flu-
viatile Mollusca could be distinguished from those
of the terrestrial kinds, by the edge of the mouth of
the shell never being furnished with a thickened
internal rib, and not being in the shghtest degree
reflexed, and that the animal never closes it with
an epiphragm; however, further examination has
shown that when the Pond-snails and the Whirl-
shells are left nearly dry by the evaporation of the
water, either by the heat, or by dryness of the
weather in winter, these animals assume the cha-
racter of terrestrial Mollusca, thicken and reflect
their mouth, and form an epiphragm to prevent
themselves from being destroyed by the drying up

86 PULMONIFERA.—LIMNEAD&,

of the fluid necessary for their respiration and
lige.

GENUS LIMNEUS.

In this genus the shell is ovate, oblong, or tur-
reted, thin and horny, and transparent. The aperture
is ovate or expanded, the margin entire, and the
pillar marked with a single oblique plait running
into the axis.. The animal has a short broad foot; the
head and snout, and the ten-
tacles, are also all charac-
terised by peculiar breadth ;
the two eyes are placed in
front of the base of the last-
named organs. ‘he mantle
has an even edge sometimes
reflected upon the shell, but
never covering it. The tongue
is armed with many trans-
verse rows of short, hooked
teeth. :

The largest British species
is the Lake Mud Shell (Zim-
neus stagnalis), which attains
a length of two inches, and a
diameter of one. In the

ah See large rivers of Kastern Europe

it grows to a much larger

size. The shell is thin and brittle, of a greyish
hue, often covered with an extraneous coat; the
spire is composed of about seven whorls, tapering
toa fine point ; the last whorl is striated lengthwise,

* Gray’s Land and Fresh-water Shells, 229.

POND-SNAILS. S7

and generally crossed by transverse raised lines,
giving it an angular appearance ; this whorl is large,
and often greatly swollen. The pillar fold is
strongly marked, almost forming an umbilicus.
The animal is of a yellowish hue, paler beneath.
In stagnant and slow moving waters this species
is not uncommon; and, on a warm summer’s day,
numbers of this and other species may be seen tra-
versing the mud, climbing the aquatic plants, or
mounting to the top, and floating on the unruffled
surface in a reverse position. ‘The principle by
which an animal, heavier than water, is thus enabled
to float, is not very easy of explanation ; a parallel
to it, however, is afforded by the familiar experiment
of carefully laying a needle on still water, where
it will float as long as it remains unshaken. The
swimming body must, of course, be considered as
in contact with the incumbent air, the cohesive
power of which to the body, and among its own
particles, is probably sufficient to overcome the
force of gravity. But the Pond-snail not only
floats, but swims at the surface, traversing its pool
with a smooth, gliding motion, in an undulating
line. M. de Quatrefages is of opinion that the
progression of Mollusks, in this reversed position
on the surface of the water, cannot be made by
any muscular action of the foot; and he ascribes
the motion to the action of the vibratile cilia, which
cover the entire body as well as the sole of the foot.:
Dr. Johnston,* however, sets in opposition to this
opinion the fact, that an Hols crossing a basin can
at once stop and remain there for any time, though,
during all this period of rest, the cilia are in as
. * Introd. to Conchol. 130.

88 PULMONIFERA.—HELICIDA.

active a state as when the creature was in motion.
I would add, also, as adverse to the opinion of the
French naturalist, that in the Holis and other floating
species I have distinctly observed the action of the
foot muscles ; the animal, indeed, literally crawls
on the under surface of the stratum of air, just as if
it were a plate of glass.

The curious habit which these Water-snails have
of rising perpendicularly through the water, and
the still more curious power of spimning a thread,
by the help of which this feat 1s accomplished,
have been already described in the earlier pages of
this work. I shall merely add to these particulars
of their history, that they lay in summer large oval
masses of clear jelly, which they affix to the stalks
and leaves of submerged plants. Hach mass con-
tains from 100 to 130 eggs, which are hatched in
sixteen days.

Famity HELIcip&é.
(Snails.)

This is an immense family. Between sixty and
seventy species belonging to it are enumerated as
natives of the British isles, and those which inhabit
foreign countries are far more numerous. The tech-
nical characters may be thus described. The head
and tentacles are capable of being wholly withdrawn
into the body, in which state they are covered by
the infolded skin as with a sheath ; the end of the
tail tapers to a point, and is destitute of a gland.
The lung chamber is generally in front of the
body, with the breathing hole at its hinder part.

SNAILS. 89

The body is spiral, the mantle thin, with a thickened
edge lining the inside of an external shell.

The indigenous members of this extensive family
are familiar to every one. Some of them are de-
structive and voracious’ tenants of our gardens;
others occur to us in our summer walks, swarming
by scores on the banks and hedgerows; and not a
few attract our admiration by their clean globose
shells, and by the beauty of the colours, frequently
disposed in spiral bands, with which they are
adorned. But the beauty of our native species is
far surpassed by many of those from the tropics,
many of which, especially those of the genus
Bulimus, shine in the most gorgeous colours,
crimson, scarlet, orange, yellow, green and blue;
and many of them are of gigantic size.

All the members of the family are voracious
vegetable feeders; many of them devour indis-
eriminately the leaves of various plants, especially
such as are tender either from youth, or from
incipient decay. ‘lo aid them in crushing down
the vegetable fibre, the mouth, which is situated on
the under part of the head, is armed with a cutting
instrument of beautiful contrivance. The upper
one of the two fleshy contractile lips is armed
with a broad horny plate, the lower edge of which
is free, very sharp, and slightly curved, forming
in fact a knife, admirably adapted to divide the
leaves and soft parts of vegetables, when they are
pressed by the action of the lips against its cutting
edge. The floor of the mouth is provided with a
small cartilaginous tongue, covered with delicate
transverse striz, and so disposed that by its move-
ments it is well calculated to assist in propelling
the food into the cesophagus.

SO PULMONIFERA.—HELICIDA.

A moist state of the atmosphere combined with
a certain degree of warmth, though not essential
to life, is necessary to the healthy performance of
its functions in the Snails. On the approach of
winter in cold or temperate climates, they hide
themselves in protected situations, where they con-
struct, in a manner presently to be described, a
tight chamber, within which each individual sleeps
away the cold season in a torpid state. During
the summer, a continuance of dry weather will
induce a similar retirement and a similar torpidity,
though more brief in its duration.

The great majority of the species deposit a
number of eggs glued together into a mass, and
concealed under rubbish, the bark of decaying
trees, dead leaves, or moss, or beneath the surface
of the ground. Those of the Garden Snail (Helix
aspersa) are soft, semi-transparent, and about as
large as small peas; those of many foreign species
are oval, and are enclosed in a firm, white, calcareous
shell, like those of birds. Some of these are ,of
considerable size. That of the magnificent Bulimus
hemastoma, from the West Indies, is as large as a
blackbird’s egg, and that of Bulimus ovalis trom
Brazil still larger. The latter species has pro-
duced eggs in England. <A specimen had_ been
presented to the Horticultural Society, and was
kept in their conservatory at Chiswick. At first it
appeared rather sickly; but after it had been kept
in the hot-house for some time, it recovered, and
began to move about. Mr. Booth, who was on
the spot, says—‘It cannot now be correctly ascer-
tained when it produced the first egg, but it was
very shortly after its arrival—I should think about
the beginning of November. This egg was sent

SNAILS. 91

by the desire of Mr. Sabine to the Zoological
Society. About the same time this year (1829)
it produced a second egg, and three weeks after-
wards a third; the latter was unfortunately broken
by the animal itself, but the former is still in pre-
servation. It fed upon lettuces, and the tender
leaves of cabbages; the former seemed to be its
favourite food. Sometimes it would devour two
large lettuces, and then remain for days afterwards
Without touching food, or moving from its place, ex-
cept when cold water was sprinkled upon it. During
the day, it was usually in a dormant state in the
shade; but towards the evening, when the house
was moist and warm, it would spread itself out,
and move from one part to another. It seemed to
like moisture, and I have no doubt that it might
have been preserved for years, if it had not been
accidentally killed. On Saturday last, it was at the
end of the house where the fire comes in, and
ventured too far upon the hot bricks after they had
been watered ; in the morning, it was found fixed
to them quite dead.” *

GENUS HELIX.

The animal in this well-known genus has a
lengthened, depressed foot, and a large produced
central spiral body, covered with an ample shell.
The form of the shell is generally more or less
globose, but sometimes depressed or flattened ; the
mouth is large and rounded, but the swelling of
the last whorl intruding into it renders the interior
of the aperture crescent-shaped; the mouth is
strengthened by an internal thickened rib, and its

* Zool. Journ. v. 102.

92 PULMONIFERA.—HELICIDA.

margin, when the animal is full grown, is turned
outwards.

Mr. Gray, in his “ Land and Fresh-water Shells
of the British Islands,” has enumerated twenty-six
species of this genus as natives of this country and
its adjacent isles. By far the finest of these is the
Edible Snail (Helix pomatia), which inhabits woods
and hedges in chalk districts, in the southern and
midland counties of England. The shell of this
fine species attains a diameter of two inches, and a
height of the same; the last whorl is very large
and globose, and all are strongly striated across
with close-set lines; the colour is commonly pale
brown, with four spiral bands of dark brown; the
interior is tinged with violet.

The animal is ofa pale greyish-brown, the body
studded with warts, the tentacles are long, the foot
dilated, marked with impressed lines, forming a
network.

Among ourselves these animals are occasionally
eaten, and, when pro-
perly cooked, are said
to be not unpleasant
to the taste. Lister
tells us how they
were dressed in his
\ time. “They are
) boiled in spring
water, and when sea-
soned with oil, salt,
and pepper, make a

Bete eRe dainty dish.” But

on the Continent,

as I have before intimated, snails have been from
the earliest times an admired luxury. “ The

SNAILS. 93

ancient Romans kept these animals in what were
called cochlearia, or snail-stews. These were gene-
rally formed under rocks or eminences, the bottoms
of which were watered by lakes or rivers; and, if
a natural dew or moisture was not found, an artifi-
cial one was formed by bringing into the place a
pipe, bored full of holes like a watering-pot,
through which it was continually sprinkled. The
snails required little attendance or food, supplying
themselves, in a great measure, as tuey crawled
about the sides or floor of their habitation. To
fatten them, however, they were fed with bran and
sodden lees of wine.

“‘These snails are at this day much admired in
some parts of the Continent, and are not always
used from economical motives ; for at Vienna, but
a few years ago, seven of them were charged the
same price in the inns as a plate of veal or beef.
The usual modes of preparing them for the table
are by boiling, frying them in butter, or sometimes
stuffing them with force-meat ; but, in what manner
soever they are dressed, their sliminess always
remains.

“The greatest numbers, and the finest snails,
are brought from Suabia.

“ Dr. Townson was shown at Erlau a snailery,
which the proprietor informed him was constructed
on an improved plan. In our island, he says, this
might have had the denomination of a patent
snailery, or philosophical snail-sty. It consisted
only of a large hole, two or three feet deep, dug in
the ground, having a wooden house as a cover.
The animals were fed on the refuse of the garden,
which was thrown to them.” *

* Bingley’s Anim. Biography, iv. 335.

94 PULMONIFERA.—HELICID&.

In the latter part of summer, the Edible Snail
lays beneath the surface of the earth from sixty to
eighty eggs, which are of a globular shape, covered
with a white leathery skin, and about as large as
dried peas. In from twenty to thirty days, ac-
cording to the state of the weather, the young
snails are hatched, each enclosed in a delicate shell,
of a single whorl. A period of thirteen months
from the time of hatching suffices, according to M.
Bouchard Chantreux, to bring the animal to its full
growth.

The name pomatia, derived from the word me@a,
which signifies a lid, refers to the curious covering
with which the animal closes the mouth of its shell,
to exclude the air during its residence in winter
quarters. All the circumstances connected with its
hybernation are so interesting that I shall describe
them at length from a memoir on the subject by
M. Gaspard, condensed in the Zoological Journal,
with some valuable notes by Professor Bell. .

M. Gaspard remarks that in our temperate
climate, as soon as the first autumnal chills are felt,
about the commencement of October generally,
felix pomatia becomes indolent, loses its appetite,
and associates in considerable numbers on hillocks,
the banks of ditches, in thickets, hedges, and such
places. In a day or two the animals cease feeding,
expel the last contents of the intestines, and then
hide themselves under moss, grass, dead leaves, or
the like rubbish. Here each forms for itself, with
the anterior part of its muscular foot, a cavity suffi-
ciently large to contain at least its shell. ‘This
cavity it enlarges and excavates by turning itself
round on every side, then raising itself against
the sides of the cavity, and at last against the

SNAILS. 95

roof formed of moss or leaves, or a small quantity
of earth, brought there by its motions. When
it has succeeded in bringing the aperture of the
shell to nearly a horizontal position, it stops.
The foot is soon contracted within the shell; the
snail then expands, so as completely to cover
it, the collar of the mantle, which is at this
period very white ; and then inspires a quantity of
air, after which it closes the respiratory hole.
When this is done, a fine transparent membrane is
formed with its mucus, and interposed between
the mantle and any extraneous substances lying
above. ‘The mantle then secretes a quantity of
very white fluid over its whole surface, which sets
uniformly, like plaster of Paris, instantly forming
a continuous covering about half a line thick.
When this is hardened, the animal separates its
mantle from it by another and stronger mucous
secretion; and after a few hours, expelling a
portion of the air it had previously inspired, it is
enabled to shrink a little farther into the shell.
It now forms another lamina of mucus, expires
more air, and thus retires farther into the shell.
In this way sometimes a fourth, fifth, and even
sixth partition are formed, with intermediate cells,
filled with air.

Such is M. Gaspard’s account; but Mr. Bell
remarks that it does not completely explain the
manner in which the excavation is formed. “It
is not by the pressure of the foot,” says the last-
named zoologist, “and the turning round of the
shell, that this is principally effected. A large
quantity of very viscid mucus is secreted on the
under surface of the foot, to which a layer of
earth or dead leaves adheres; this is turned on

96 PULMONIFERA.—HELICID&.

one side, and a fresh secretion being thrown out,
the layer of earth mixed with mucus is left. The
animal then takes another layer of earth on the
bottom of the foot, turns it also to the part where
he intends to form the wall of his habitation, and
leaves it in the same manner, repeating the process
until the cavity is sufficiently large, and thus
making the sides smooth, even, and compact. In
forming the dome or arch of the form, a similar
method is used, the foot collecting on its under
surface a quantity of earth ; and the animal turning
it upwards, leaves it by throwing out fresh mucus,
and this is repeated until a perfect roof is formed.
As I have very often watched this curious process,
I am certain of the facts. On removing very care-
fully a portion of the roof soon after its completion,
I was enabled to see the formation of the operculum.
In about an hour, or even less, after the hyberna-
culum is covered in, the whole surface of the collar
of the mantle instantaneously pours out the calca-
reous secretion in considerable quantity. ‘This is
at first as fluid as thick cream, but very soon
acquires exactly the consistence of bird-lime, being
excessively adhesive and tenacious, and in about
an hour after it is poured out, it is perfectly solid.”

M. Gaspard states that the labour of each indi-
vidual continues for about two or three days, but
that the whole of the month of October is occupied
by the general closing of the shells of the species.
He adds that, about the beginning of April, the
hybernation ceases. ‘The mode by which their
escape from confinement is effected is simple and
easily comprehended. ‘The air which 1s contained
in the different cells, and which had been expired
on the animal withdrawing itself farther and

SLUGS. 97

farther into the shell, after the formation of the
operculum, is again inspired, and each separate
membranous position broken by the pressure of the
hinder parts of the foot, projected through the
mantle. When it arrives at the calcareous oper-
culum, the animal, making a last effort, bursts and
detaches its most obtuse angle; then, insinuating
by littleand little the edge of the foot between the
shell and the operculum, it forces the latter off, or
breaks it away.’’*

Famity LImMAcIDé.
(Slugs. )

In general, the animals of this family resemble
those of the preceding. The body, however, is
lengthened and slender, attached to the foot by its
whole length, instead of rising into a spire. The
mantle is generally small, not nearly covering the
body. ‘The shell is minute and rudimentary, some-
times concealed within the substance of the mantle,
and sometimes altogether wanting.

In general the Slugs are, like the Snails, herbi-
vorous ; but the curious genus Testacella, of which
a species has been found in the neighbourhood of
London, feeds almost exclusively on earth-worms.

GENUS LIMAX.

Our common Slugs, but too familiarly known,
have a lengthened body, with a granular surface,
keeled behind. The mantle is small, covering like
a shield the fore part of the body. Its substance
encloses a small, flat, transparent, oval shell, some-
what resembling the human nail.

* Zool. Journ. i.
H

98 PULMONIFERA.—LIMACID&.

Slugs proper are widely distributed, species being
found in various parts of both hemispheres; but
the temperate regions of the northern hemisphere
are principally troubled with them. The common
Grey Slug (Limazx agrestis) commits great ravages
every year in our fields and gardens, notwith-
standing the number of birds which make this
species their prey; and various means have been
devised to get rid of the pest, or at least to diminish
its intensity. Quicklime, soot, coal-ashes, and
saw-dust, are in turn sprinkled on the ground
around tender plants ; but the effects of these and
similar substances depend upon their dryness, and
the inability of the Slug to crawl upon powdery
substances. The first shower of rain, however, and.
even the dews of night, break the spell.

This species varies much in size and colour,
being by turns white, pale reddish-grey, and nearly
black ; but it may be easily distinguished by its
body being furrowed with interrupted lines, with
a short keel, which is always placed obliquely.
The mantle is comparatively large, marked with
circular lines; the enclosed shell is very minute,
thick, hard, and irregular.

The Grey Slug is very prolific, continuing to lay
its groups of eggs from April to the end of No-
vember, and depositing from thirty to seventy eggs
at each time. ‘The young increase in size rapidly,
and reach their full growth in three months from
their birth. When uritated, the Slug pours out
from the whole surface of its body a copious white
mucus, of the consistence of thick white cream,
which dries into a white membrane.

NAKED-GILLED MOLLUSKS. 99

ORDER NUDIBRANCHIATA.
(Naked-gilled Mollusks.)

SCARCELY any of the animals which the marine
naturalist meets with in his dredging voyages, or
his sea-side excursions, are so attractive as those
of this Order. They are remarkably elegant in
their forms, which present great variety. Their
motions are graceful and lively, their colours
peculiarly brilliant, and their history and economy
marked by points of great interest. Nor is it
rarely that the zoologist is gratified with an oppor-
tunity of observing these very attractive Mollusks,
for the species are numerous, the British shores
alone yielding more than a hundred.

These are not air-breathers, like the members of
the preceding Order; they are all marine, and re-
spire by means of gills, which are not enclosed
within the body, but (at least during action) ex-
posed freely to the surrounding medium. Some-
times these organs are capable of being partially
withdrawn into a cavity, situated on the medial
line of the back ; but more commonly they take the
form of simple or branched warts, arranged along the
sides. The foot is large and broad. The mantle
is ample, and projects above the foot on all sides.
None of the species are protected by a shell, except
in early infancy. ‘The young, on emerging from
the egg, is enclosed in a shell, which closely re-
sembles that of a nautilus, and bears very little
resemblance to the parent in its form; it has,

100 NUDIBRANCHIATA.

therefore, to pass through a metamorphosis before
it attains its permanent condition.

The eggs in all the species are numerous.
They are deposited, during the spring and summer,

LARVA OF EOLIS.

commonly in the form of a broad ribbon of clear
jelly, attached by one of its edges to some solid
substance, and generally coiled, or irregularly
twisted, or frilled. The eggs themselves are
arranged in close-set rows, crossing the gelatinous
belt, and giving an opaque white appearance to the
mass, which would otherwise be colourless.

In general each egg-shell (chorion) contains but a
single yolk, but in some of the Dorides each con-
tains two or three; and in the elegant Antiopa
cristaia, a specimen of which lately spawned in
my possession, I found, upon the average, the
extraordinary number of sixty yoiks in each egg
shortly after deposition. The yolk, which is con-
tained within a delicate, transparent, membranous

NAKED-GILLED MOLLUSKS. 101

shell or chorion, may be observed changing form.
The time required to mature the embryo varies in
different species, and probably in the same species
under different circumstances; in general from ten
to fifteen days is sufficient for this purpose.

The development of the embryo is highly in-
teresting, especially as, owing to the transparency
of all the organs, nothing is easier than to watch its
progress. I have kept many specimens in glass vases
of sea water; and as all the species of this Order
are hermaphrodite—that is, the sexual functions are
united in the same individual—every specimen ob-
tained is pretty sure to spawn during the season.
The yolk, which at first nearly fills the egg-shell,
soon becomes a little elongated, with one end
diagonally truncated, or, as it were, cut off ob-
liquely; the truncated end then becomes two-
lobed, ‘‘ each lobe exhibiting an imperfect spiral,
and having its margin ciliated. The now animated
being is seen to rotate within its prison. Shortly
the lobes enlarge, and a fleshy process, the
rudimentary foot, is observed to develop itself
a little behind them, on the medial line; a shell
closely investing the inferior portion of the embryo,
the lobes and rudimentary foot being uppermost.
The shell rapidly increases, and assumes a nautiloid
form; afterwards the foot displays, attached to its
posterior surface, a circular operculum, which is
opposed to the mouth of the shell. The lobes now
expand into two large, flattened, ovate appendages,
with very long vibratile cilia around the margins,
and the larve are at length mature. The whole
mass of spawn now presents the utmost animation.
Hundreds of these busy atoms are seen, each within
its transparent, membranous cell, rotating with

102 NUDIBRANCHIATA.

ereat agility and ceaseless perseverance, the cilia
all the while vigorously vibrating on the margins
of the outstretched lobes. The membranous chorion,
which by this time has become enlarged, ultimately
gives way, no longer able to resist the perpetual
struggle within; and the liberated larva, wending
its way through the shattered shreds of the general
envelope, boldly trusts itself to the open trackless
water, where, doubtless, thousands and tens of
thousands perish ere they find a fitting resting-
place, some being swept away by resistless cur-
rents, others fallg a prey to ever-watchful and
innumerable enemies.’’*

As the larva increases in age, the foot acquires
considerable dimensions. ‘The operculum becomes
delicate and transparent, so as to be with difficulty
examined; it is, however, seen to be circular, and
concentric lines seem to indicate that its growth
takes place in the ordinary manner. Besides the
long cilia of the lobes, the action of which is under
the control of the larva, ‘‘ the whole surface of the
exposed parts is covered with minute cilia, whose
vibrations never cease. ‘These cilia serve most pro-
bably for respiratory purposes, and may also assist
in bringing food to the mouth.

‘When the larva is at rest, the oral lobes are
pulled back into the shell, and the foot being
drawn down, brings along with it the operculum,
which closes the orifice. But when in action, the
whole of these parts preject beyond the opening of
the shell, the foot lying back against the spire;
and the oral lobes inclining forward, their cilia
commence to vibrate, and the larva, with the mouth
of the shell upwards, moves through the water with

* Alder and Hancock’s Monograph. (Doris.)

NAKED-GILLED MOLLUSKS. 103

lively action, sinking, or rising, or advancing on-
wards at its pleasure.”

Messrs. Alder and Haneock, from whose beau-
tiful “Monograph of the British Nudibranchiate
Mollusca” I cite these particulars, “‘ have not suc-
ceeded in tracing the development of the larva into
the mature form; but it is not difficult to under-
_stand how this change is effected. When the
larva is placed with the mouth of the shell down-
wards, the oral lobes in front, (speaking particularly
of Holis,) the anal termination of the intestine, and
the oval sac representing the generative organs,
will be found on the right side, close to the base of
the oral lobe, and the operculigerous lobe or foot
will be seen to extend backwards in a median
position, occupying the place of the crawling disk.
Thus it is evident that the principal organs of the
larva only require to be slightly modified in form,
and it is changed into the mature animal, the shell
and operculum being cast off, and the oral lobes
either absorbed or altered into a veil or oral ten-
tacles.”’

The food of the Nudibranch Mollusca is for the
most part animal. Various kinds of zoophytes are
devoured by many species, some are even cannibals,
preying upon their own kind; but some of the
Dorides appear certainly to be herbivorous, feeding
on the fronds of sea-weeds. Professor Grant has
often found their stomachs completely filled with
minutely divided portions of coarse marine plants,
filling not only that organ, but also the cavities of
the liver, which in these animals is very large.
The mouth and its various parts are very efficiently
adapted for the seizing and devouring of food.
Various parts are armed with points and cutting

104 NUDIBRANCHIATA.

edges in different genera; but the tongue is, I
believe, in all most elaborately armed with spinous
teeth, arranged in numerous rows.

The mouth has large fleshy lips prolonged into
an internal tube, within which is a muscular

TONGUE-TEETH OF EOLIS.
(Magnified.)

inner lip, capable of being pushed forwards, and
bringing with it the mouth and jaws when the
animal is in the act of seizing its prey. The mouth
contains two large horny jaws placed vertically,
and armed with cutting edges. The tongue is
shaped like a strap, and can be moved in different
directions, or thrown forwards to assist the animal

&
NAKED-GILLED MOLLUSKS. 105

in seizing and securing its prey. It is covered
with numerous transverse plates, armed with spines
or teeth directed backwards. These teeth differ
in number and in form; those of Holis papillosa,
figured above, are very numerous and minute,
being not more than one-sixth part of the thickness
of a human hair. Their arrangement is in trans-
verse arched rows, but in E. coronata, there is one
large central tooth on each plate with denticulated
sides; and in #, alba, a central tooth only, without
denticulations.

FAMILY DORIDID&.

The members of this extensive family are cha-
racterised by having the anal orifice placed in the
medial line of the back, towards the hinder part,
and the respiratory organs arranged around it in
a more or less complete circle of leaf-lke plumes,
so as to resemble the petals of a beautiful flower.
The mouth is a small conical proboscis placed under
the front edge of the mantle, where this latter
organ is distinct, and sometimes guarded by two
simple tentacles ; another pair of tentacles is placed
on the front part of the back. These are peculiar
in their structure, being beset with numerous
narrow plates, arranged diagonally, parallel to each
other. These tentacles, for the most part, are capa-
ble of being withdrawn into proper cavities, the
edges of which, in many cases, are raised into
tubular sheaths to protect them.

The Doridide are found on the shores of every
sea. Many species are common on our own coasts,
crawling on sea-weeds, or concealed beneath stones
between tide-marks; some kinds, however, confine

Z

106 NUDIBRANCHIATA.—DORIDID&.

themselves to deep water, and are to be obtained
only by dredging.

GENUS DORIS.

The body in this, the principal genus, is usu-
ally of a semi-oval form sometimes very convex,
‘but more generally depressed, and occasionally
almost flat. The mantle is ample, projecting over
the head, and on all sides; its surface is generally
rough, with numerous warts, and its texture is stif-
fened with calcareous spicula or crystals of lime im-
bedded in its substance. The mouth is commonly
without jaws, but is frequently furnished with a pre-
hensile collar, armed with minute spines. ‘The tongue
is covered with rows of teeth curved backwards.

The breathing organs consist of flat plumes,
sometimes small and
simple, sometimes large
and branching, either
united at the base mto
a flower-like expansion,
or placed separately in
a circle more or less
perfect. In some species
these plumes are capable
of being withdrawn into
a common cavity, the
margin of which can be
closed completely over
them, but in others there
is no cavity ; and when
danger threatens, the

BRANCHIAL PLUME OF DORIS. plumes are merely con-
tracted, curled up, and bent down towards the
centre of the circle.

DORIS. 107

The upper or dorsal tentacles are generally short
club-shaped organs, with the upper portion fre-
quently bent into an angle. This
portion is always set with narrow,
oblique plates, usually ten or
twelve in number, pointing be-
hind and downward. They are
always retractile, but for the most
part not sheathed.

The species of this genus de-
posit their spawn in the spring ;
the eggs, as already described,
being generally arranged intrans-
verse rows, imbedded in a trans-
parent gelatinous ribbon. Doris
bilamellata, which I have kept
in captivity, always deposited
its ribbons on the side of the
vessel just beneath the surface of the water. It
adheres by one edge, and forms an imperfect spire
or cup, the ribbon being bent upon itself, the upper
edge or brim leaning a little outward, and being
puckered. That of D. tuberculata is very large, the
ribbon being three-fourths of an inch high, and
wound round in many spiral coils. I have observed
it, on the Devonshire shores, depending in a flaccid
manner from the under surface of rocks, durimg
the recess of the tide. The embryos in such coils
of spawn are immensely numerous. Mr. Darwin
thus describes the contents of a spawn-coil of a
species of this genus, which he found at the
Falkland Isles. ‘‘ From two to five eggs [yolks],
each 75pths of an inch in diameter, were con-
tained in a spherical little case [chorion]. These
were arranged, two deep, in_ transverse rows,

TENTACLE OF DORIS.

108 NUDIBRANCHIATA.—DORIDIDA,

forming a ribbon. The ribbon adhered by its
edge to the rock in an oval spire. One which
I found measured nearly twenty inches in length,
and half in breadth. By counting how many balls
were contained in a tenth of an inch in the row,
and how many rows in an equal length of the
ribbon, on the most moderate computation there
were six hundred thousand eggs. Yet this Doris
was certainly not very common; although I was
often searching under the stones, I saw only seven
individuals.” *

When we meet with accounts like this of the
exceeding multitude of eggs produced by some
species of animals, we are apt to wonder that the
world is not filled with them, and to ask what be-
comes of these immense hosts. The fact is, they
form the food of other creatures, a vast multitude—
perhaps nine out of every ten—being devoured as
soon as they are born. What Mr. Peach says of
these very embryos, I have myself often observed
in those that I have endeavoured to rear. The
‘“‘have myriads of enemies in the small Jnfusoria,
which may be noticed with a powerful microscope
hovering round them, and ready to devour them
the instant weakness or injury prevents their keep-
ing in motion the cilia, which serve both for loco-
motion and defence. Let them cease to move, a
regular attack 1s made, and the animal is soon de-
voured ; and it is interesting to observe several of
the scavengers sporting in the empty shell, as if in
derision at the havoc they have made.’’ ft

The largest British species of this genus is
D. tuberculata, often called the Sea Lemon. It

* V oyage of Adventure and Beagle, iii. 258.
{¢ Annals of N.H. xv. 446.

DORIS. 109

attains three inches in length, is of a yellow
colour, with the mantle covered with small round
warts. Hence in size, form, hue, and surface, the
animal bears no small resemblance to the half of a
lemon cut through lengthways, especially when
the branchial plumes and the dorsal tentacles are
concealed by being withdrawn into their respective
cavities. But the colour is not always plain

SEA LEMON.

yellow ; it sometimes verges to grey, and is fre-
quently marked in the most beautiful manner
with large spots and clouds of crimson or purple.
The branchial flower is composed of eight plumes,
which are large, tripinnate, and of a_ bluish
white hue.

This species is said to be more common on the
east coast of Scotland and England than on the
west. I have, however, found it on the shores of
Dorset and of north and south Devon; it lives
among the rocks, in the zone bounded by the
limits of high and low tide, as well as in deep
water. In captivity, the habit of this, as of some
other species of the genus, is to glide slowly round
and round the vessel in which it is kept, just beneath

110 NUDIBRANCHIATA.—TRITONIADA.

the surface of the water, now and then lifting and
puckering up the edges of the mantle, and allowmg
the air to bathe the sides of the body.

FAMILY TRITONIADZ.

This is a small group considered in the number
of its component species, though some of these are
of unusually large size. Its distinctive character-
istics are that the gills, which are either laminated,
plumose, or papillose, are arranged down the sides
of the back, and that the stomach is simple. By
the former character it is distinguished from the
Doridide, the feathery gill-leaves of which are
retained in several of these, but never arranged
in the form of a flower around the vent. By
the latter it is severed from the Holidide, in
which the stomach sends off branching tubes on
each side.

There is no proper mantle distinguished as such
from the general surface of the body ; but there is
often an elevated ridge running down each side,
along which the gill-tufts are placed. In the
Scyllea, an oceanic genus found crawling among
the stems and weeds of the floating gulf-weed,
there are two or three erect, square lobes of flesh,
projecting from each side of the back, and on the
imner side of these the small tufted gills are
scattered. In Glaucus, another oceanic animal of
exquisite beauty, the gills take the form of fan-like
ae: of filaments, diverging from the tips of long
oot-stalks.

The head, in most of the species, is protected by
a veil or expansion of membrane, sometimes cleft

GLAUCUS. 111

into tentacular processes, at others margined with a
fringe. Tethys, another beautiful genus inhabiting
the Mediterranean, has this veil enormously de-
veloped, and profusely fringed. The animal is
said to use this organ to aid it in swimming, but
this is hardly probable.

So little has been recorded concerning the
habits and economy of the marine, and especially
the oceanic Mollusca, that I with pleasure quote the
observations of Mr. George Bennett, on a species of
Glaucus taken in the tropical part of the Atlantic
ocean. The accompanying figure will convey an

GLAUCUS.

idea of the form of the animal, the colour of which
is a vivid blue or purple on the upper surface, and
silvery white beneath :—

“These little animals were very delicate and

ie NUDIBRANCHIATA.—TRITONIADA.

fragile in their structure, and although many—in-
deed I may say numbers—were caught, yet very
few in comparison were found to be in a perfect
condition, some being deficient in one, two, or more
fins, and others being completely crushed. Not
one of the specimens caught on this occasion, or
during the voyage, had the silvery line or streak
running down the back, from the head to the ex-
tremity of the tail, branching off also to the fins,
and along the centre of each of the digitations.
Several Porpite were also captured in the net at
the same time with these animals, and served as
food for them.

“Tt caused much regret to see the change death
produced in the beauty of these interesting little
animals, and all means of preserving them were
found to be useless. When placed in spirits, the
digits of the branchial fins speedily became re-
tracted ; the beautiful purple gradually faded, and
at last disappeared, and the delicate pearly white
of the under suriace of the body and fins peeled off
and disappeared. Thus did this beautiful Mol-
lusk become decomposed in less than the space of
an hour. Some Mollusks quickly lose their colour
after death, but retain their form for a long time;
but these speedily change after death, both im form
and colour, and the beauty before so much admired
perishes, never to be regained.

‘¢ When taken in the hand, the under surface of
the animal soon becomes denuded of the beautiful
pearly white it previously had, and at that time
appears like a small transparent bladder, in which
a number of air-bubbles are observed, together with
the viscera. On the abdomen being laid open, a
large quantity of air-bubbles escaped; and perhaps

GLAUCUS. Lie

a query may arise how far they assist the animal in
floating upon the surface of the water.

“JT again placed several of the specimens in a
glass of sea-water; they were full of life, sometimes
moving about, not very briskly, however, and at
other times remaining floating upon the surface of
the water, merely gently moving the fins. As they
floated upon the surface of the water in the glass,
the sides of the head, back, tail, fins, &c. exhibited
at the time a light silvery blue colour, which was
admirably contrasted with the deeper blue of the
upper surface, and falling into the elegant pearly or
silvery white of the under surface of the animal,
displaying an exceedingly rich and elegant appear-
ance. Often, when at rest, the animal would drop
one or more of the fins; but on touching them, they
would be immediately raised to the former position,
and that organ was turned back as if to throw off the
offending object, followed at the same time by a
general movement of the whole body. On touching
the animal upon the back, it seemed to display more
sensitiveness in that than in any other part of the
body, judging from the effects produced in com-
parison with similar experiments on other portions
of the body. For instance, the centre of the back was
touched lightly and rapidly with a feather, which
caused the little creature to sink, as if under the
pressure of the touch, throwing at the same time the
head, tail, and all the fins upwards, followed by a
general distortion of the whole body of the animal.
As if the gentle touch had been productive of severe
pain, I invariably found every part of the upper
surface of the body very sensitive when touched,
displaying a general movement of uneasiness
throughout the whole of the body of the creature,

iz

114 NUDIBRANCHIATA.—TRITONIAD&.

“These creatures have a peculiar manner of
throwing the head towards the tail, and flouncing
the tail towards the head, when they are desirous
of removing any object of annoyance ; it 1s at that
time these animals seem to recover from their tor-
pidity, and evince the greatest activity in their
movements. When much annoyed, they throw
the body about with great activity, coiling up the
head, tail, fins, &c. in a somewhat rotundiform
position, and if the tormenting object is not re-
moved, dash out again in full activity of body,
then return to the rotundiform position, and there
remain for a short period, apparently exhausted
by their efforts; but on the cessation of the iri-
tating cause, the animal quietly resumed its original
position, perhaps dropping one or two of its wearied
fins, according as its own sensations of ease or
comfort might dictate.

‘When nothing irritated this tender Mollusk, it
would remain tranquilly floating upon the surface
of the water, with scarcely any movement but that
which proceeded from the undulating motions of
the digitated extremities of the fins, as well as
an occasional slight twisting action of the same
organs.

‘““T placed some small specimens of Porpita in
the glass of water containing the Glauci, to observe
if they would attack them. or some time one of
the Glauci was close to a Porpita, and was even
annoyed by the tentacles of the latter touching its
back ; yet the Glaucus bore this, although with the
usual characters of impatience, yet without at-
tempting to attack it. At last it seized the Por-
pita between its jaws, and by aid of a powerful
lens, an excellent opportunity was afforded me of

GLAUCUS. 115

closely watching the devouring process, which was
effected by an apparently sucking motion; and at
this time all the digitated processes of the fins
were floating about, as at other times, when the
animal was atrest. But I did not observe, in one
single instance, that they were of any use to the
animals, either to aid in the capture, or to securely
hold their prey when in the act of being devoured ;
for the animal seems to depend merely upon the
mouth in capturing its prey, as, in this and other
instances which I had opportunities of observing,
they seized their prey instantly with the mouth,
and held it by that power alone, whilst by a kind
of sucking motion the prey was devoured. The
digitations may, therefore, only be regarded as
appendages to the fins, to aid the animal, perhaps,
in the direction of its movements, as it was observed
that they turned and twisted them about during
the progressive motion—that is, when this tardy
animal is pleased to progress,—as if in some way
or other to direct the movements of the animal.

“The Glaucus, after eating the tentacles, and
nearly the whole of the soft under surface of its
prey, left the horny portion, and remained tranquilly
reposing upon the surface of the water after its
meal, the only motion visible in the animal being
the playing of the digits of its fins. The mutilated
remains of the Porpita sank to the bottom of the
glass.

“Soon after, another Glaucus began a devouring
attack upon another Porpita which had been placed
in the glass, eating a little of it, and then ceasing
after a short meal, occasionally renewing the
attack at short intervals. On examining the Porpita
which had been partially devoured by the ravenous

116 NUDIBRANCHIATA.—TRITONIADA.

Glaucus, I found the disc had been cleared of
the tentacles and other soft parts, a small part of
the fleshy portion only remaining upon the disc.
Only one part of the horny disc exhibited any
injury, and that appeared to be the place where
the animal was first grasped by the Glaucus.

‘When any of these animals came in contact
with another in the glass, they did not display any
annoyance, nor coil themselves up, nor did they
evince any savage propensities one towards the
other; and they would often float about having
their digitated processes in contact one with the
other, without exhibiting any signs of annoyance.
Even when placed or pushed one against the other,
they did not manifest any irritation, but remained
undisturbed as in their usual moments of quiet
repose.

“Qn the back of the animal being seen in a
strong light, a black line could be discerned on
each margin, and passing down the centre of each
fin; and sometimes varied by having two black
lines on the upper part of one fin, although the
opposite fin may display but one.

“The margin between the falling of the purple
colour of the back into the silvery white of the
abdomen, often exhibited beautiful tints of a golden
green; but these variations were probably produced
by the effect of different rays of ight. These ani-
mals soon perished; I could not preserve them for
any length of time in the glass of sea-water, although
the water was changed as often as it was thought
necessary. The digitated processes of the fins were
observed to shrink up on the death of the animal,
and the process of decomposition rapidly took
place, the whole body becoming a shapeless mass,

GLAUCUS, 119

having a bluish colour of deadly hue for a short
period, and then becoming of a blackish or brownish
black colour. I have seldom seen a gelatinous
animal which appeared so firm whilst in the water,
that proved so speedily to decompose when removed
from it. ven the beautiful purple of the back,
the silver or enamel of the abdomen, and the
silvery blue of the sides, all speedily vanish, indeed
instantly disappear, upon the death of the animal, as
if it had been washed off; the expansive, delicate,
and beautiful fins, and digitated processes, are no
longer seen; they shrink up to nothing.

“ Even on taking the animal alive out of the
water, and placing it upon the hand, that instant
almost, from its extreme delicacy, it was destroyed.
The digitations of the fins fell off, the least move-
ment destroyed the beauty of the animal, it speedily
lost all the purple and silvery enamelied tints, and
became a loathsome mass. ‘Thus do we too often
find animals, beautiful in external adornments,
eurious in their habits and organization, and
calculated in every respect to supply us with
inexhaustible sources of intellectual gratification,
doomed speedily to perish—brief in the period
allotted to them in the busy theatre of animated
existence: but, doubtless, with the gift of existence,
they have received from the bounteous hand of their
Creator, the means of enjoying their fleeting lives.

“To place these little animals in the glass of
water from the towing net, without injury to their
delicate structure, required care; so that as soon as
they were captured in the net, attached to the
meshes, they were not handled, but carefully washed
off, which was effected by dipping the meshes in the
glass of water, when the animal soon detached

118 NUDIBRANCHIATA.—TRITONIADA.

itself without sustaining any injury, and floated in
the water.

“Although these animals are so fragile, so easily
destroyed on being taken out of their natural
element, yet they fling themselves about in the
water without sustaining any injury, without even
the loss of any of the digitated processes of the
fins; yet when there is much movement of the
water, in carrying the glass from one place to
another, they are evidently disturbed and restless,
and the fins are dropped. If, therefore, a slight
motion of the water disturbs them, what can
become of these delicate Mollusks durmg tempes-
tuous weather? Can they be similar to the delicate
ephemera, doomed to live merely for the space of
a day, and perish in myriads? From the immense
number seen only from the ship,—and how many
myriads more extended beyond ourrange of vision !—
it conveyed to the mind some idea of the profusion
of living beings inhabiting the wide expanse of
ocean, and a feeling of astonishment at the incon-
ceivable variety of forms and constructions to
which animation has been imparted by creative

ower.

“The tail of this animal has been described as
resembling that of a lizard. The comparison is good,
not only with regard to form, but also (with, perhaps,
a little more flexibility) to motion when in action.
Sometimes the animal throws its tail up to the
body, as if intended to brush off any annoying
object, and at other times it has been observed to
turn the head towards the side, as if for a similar
purpose ; it seems in the action of eating to resemble
a caterpillar.” *

* Proc. Zool. Soc. for 1836.

TRITONIA. 119

GENUS TRITONIA.

The body is prismatic ; that is to say, lengthened
with ridges or angles running along it; it is often
thick and firm. There are two tentacles, consisting
of several branched filaments arranged in the form
of a bundle or brush, and capable of being with-
drawn into tubular sheaths. The head is protected
by a veil sometimes cleft into filaments. The gills
are small branching plumes, arranged in a single
series along a ridge bordering each side of the
back.

The largest British species of the whole Order
is a member of this genus, Zritonia Hombergi,

TRITONIA HOMBERGI.

which grows to six inches or more in length. It
varies considerably in colour, being generally of a
pink or purple hue, often varied with blue, but
sometimes the entire animal is of an amber
yellow.

This very fine species occurs all round our coast,

120 NUDIBRANCHIATA.—TRITONIADA.

but is considered somewhat rare. It seems to be
a deep water species: I have procured it by trawling
off Portland. It is remarkable for a power pos-
sessed only in a very limited degree by any of the
Mollusca, that of producing an audible sound.

Professor Grant, to whom we are indebted for
a record of the curious fact, says “that the sounds
resemble very much the clink of a steel wire on
the side of the jar, one stroke only being given at
a time, and repeated at intervals of a minute or
two. When placed in a large basin of water, the
sound is much obscured, and is like that of a watch,
one stroke being repeated as before at intervals.
The sound is longest and oftenest repeated when
the Tritonie are lively and moving about, and is
not heard when they are cold and without any
motion. Inthe dark, [have not observed any light
emitted at the time of the stroke; no globule of air
escapes to the surface of the water, nor is any ripple
produced on the surface at the instant of the stroke.
The sound, when in a glass vessel, is mellow and
distinct.”

The Professor has kept these Tritoniw alive in
his room for a month; and during the whole period
of their confinement, they have continued to pro-
duce the sounds, with very little diminution of
their original intensity. In a still apartment, they
are audible at the distance of twelve feet. ‘“ The
sounds obviously proceed from the mouth of the
animal, and at the instant of the stroke we observe
the lips suddenly separate, as if to allow the water
to rush into a small vacuum formed within.
As these animals are hermaphrodites, requiring
mutual impregnation, the sounds may possibly be
a means of communication between them; or if

TRITONIA. 125

they be of an electric nature, they may be the
means of defending from foreign enemies one
of the most delicate, defenceless, and beautiful
Gasteropods that inhabit the deep.” *

The mouth in this animal forms, according to
Cuvier’s elaborate description, a cutting instrument
of peculiar efficiency. “It Gifs: aang
consists of a large oval iS irae ht
and fleshy mass enclosing a
the jaws and their mus-
cles, as well as a tongue
covered with spines, and
its opening is guarded by
two fleshy lips. The jaws
form the basis of all this
apparatus. Their substance is horny, their colour
a yellowish brown, and their form very extraordi-
nary, for an organ of this kind cannot be better
described than by comparing it to the shears used
in shearing sheep. They differ, however, in the
following particulars: instead of playing upon a
common spring, the two blades are formed to work
upon a joint, and instead of being flat, they are
shghtly curved.

“The two blades are very sharp, and there is
nothing that has life that they cannot cut, when
the animal causes the cutting edges to glide over
each other. For this purpose muscles of great
strength are provided, the fibres of which are trans-
verse; and their office is to approximate the two
blades that are again separated by the natural
elasticity of the articulation, whereby they are
united at one extremity.

“The aliment, once cut by the jaws, is imme-

* Edin, Phil. Journ. xiv. 186.

MOUTH OF TRITONIA.

122 NUDIBRANCHIATA.—EOLIDIDA.

diately seized by the papille of the tongue, which,
being sharp and directed backwards, continually
drag by a kind of peristaltic movement the alimen-
tary materials into the cesophagus.”’*

FAMILY EOLIDIDZ.

The animals of this family have a_ peculiar
elegance, delicacy, and beauty. ‘They have the
branchiz arranged along the sides of the back. In
one genus, which links this family with the pre-
ceding, these organs are branched, resembling little
leafless trees; but in general they are warts of a
long oval or spindle shape, pointed at the extremity.
Their surface is covered with strong cilia, which con-
stantly maintain a vigorous vibration, by the action
of which currents of the surrounding water are
continually poured along each of the papilla, as
these organs are named, affording the necessary
oxygen for renewing the vital power of the blood.
There is reason to believe, however, that the whole
surface of the body, which is also covered with
cilia, assists in respiration.

The papillee are permeated by a canal, which in
many of the species is brilliantly coloured, con-
tributing largely to the exquisite beauty of these
little animals, This canal is connected with the
stomach and the digestive function, supplying the
place of the liver in other animals. In the prin-
cipal genus of the family, each papilla is furnished
with a curious organ; it is a little oval bag placed
at the extremity of the papilla, and opening by a
very minute aperture at its tip. Within the bag

* Jones’ Anim. Kingd. 410.

EOLIDID. 125

there are closely packed a vast multitude of clear
oblong capsules, within each of which a narrow
body is discerned running through its length. At
the will of the animal, a number of these oblong
capsules are ejected from the aperture, and at the
same instant each capsule shoots forth with great
force from one end a long thread or hair. These
thread capsules are found in the Actiniw and Coral
animals, as also in Medusw ; and there can be little
doubt that they are weapons of defence, and that
the propulsion of the thread is the immediate cause
of the stinging power possessed by many of these
animals; probably, indeed, by all, though not
appreciable by us.

The structure of the mouth and of the tongue
with its numerous teeth has been already described.

PAPILLZ OF EOLIS,

A short gullet leads into a large membranous
stomach, sending off on each side branches which
subdivide and lead by smaller tubes into the canals,
which I have already mentioned as running through

the branchial papille.

124 NUDIBRANCHIATA.—EOLIDID A.

GENUS HOLIS.

A vast number of species are comprised in this
genus, and nearly fifty have already been discovered
on our own shores. Their body is somewhat slug-
like, sometimes broad, but more generally slender
and much lengthened, without the least trace of a
mantle. The skin is smooth, and not stiffened with
spicula; the head is prolonged into two smooth
tapering tentacles, which are apparently organs of
touch, being waved about with great vivacity when
the animal crawls ; besides these there are two dorsal
tentacles, situated as in Dorzs. Their surface is
sometimes smooth, but sometimes set with mem-
branous rings or oblique plates ; the eyes are placed
behind them. The branchie are lengthened, cylin-
drical, spindle-shaped, or flattened papillee, arranged
in transverse rows or clusters along the sides of the
back, often very numerous. ‘These organs usually
project outwardly, leaving an open space down the
middle of the back; they are commonly carried
inclining backwards, and overlapping each other ;
but when the animal is alarmed or irritated, and
particularly when it seizes its prey, they are stif-
fened, erected, and brought forward like tlie quills
of a porcupine.

All the species are carnivorous, fierce, and vora-
cious; some prey upon their weaker fellows, and
even devour their own spawn. ‘The ordinary food
of most of the species appears to be the various
kinds of zoophytes; some of the minuter sorts,
creatures of great beauty, are almost invariably
found nestling in the tiny shrubs of Sertularians,
and there can be no doubt that they devour the
polypes. Mr. Alder has seen /. coronata feed upon

EOLIS. > fee

a Lucernaria, and I have found the largest of our
native species, 4. papillosa, eagerly gnawing the
tentacles of Actinie more bulky than itself.

One of the most lovely of the species is the
Crowned Eolis (Z. coronata), which is seattered
over most parts of our rocky shores; I have taken
it in considerable number at Babbicombe, Devon,
and likewise at Weymouth, clinging to the under
surface of flat stones at extreme low water. When
the stone is turned over, an inexperienced collector
might readily overlook it, for it takes the appearance

THE CROWNED EOLIS.

of a shapeless knob of jelly about as large as a pea.
On detaching it, however, and dropping it intoa glass
of clear sea-water, its beauty becomes apparent. It
quickly unfolds itself into a slender, tapering animal,
about an inch long, and of a clear pellucid appear-
ance, tinged with pink. The papille are arranged
in six or seven clusters on each side; they are
slender, with the central canal of a rich crimson
hue, the surface reflecting a brilliant metallic blue,
and the tips opaque white. The tints of these
organs are exceedingly beautiful; and as the animal

126 NUDIBRANCHIATA.—EOLIDID A.

moves them irregularly about, they shine with a
radiance resembling that of rubies and sapphires.

These elegant branchiz seem very easily dis-
lodged; the specimens I have kept have usually
lost one or more tufts, which, however, soon begin
to sprout again. They are liable to be lost through
the pugnacity of the animals themselves, as their
predaceous habits frequently impel them to tear off
each other’s papille.

In captivity, this Holis is very active, continu-
ally gliding with a uniform motion around the
sides of the vessel, or climbing about the numerous
branching sea-weeds that are growing in it. They
frequently crawl close to the edge of the water, but
never come actually out, though they occasionally
float at the surface, by means of the expanded foot,
back downwards.

Another species (Z. punctata) has been heard to
make that peculiar clicking sound, already men-
tioned as produced by Tritonia.

COVERED-GILLED MOLLUSKS. 19%

ORDER TECTIBRANCHIATA.
(Covered-gilled Mollusks.)

In general form and appearance, many of the
animals contained in this Order resemble those of
the preceding ; but they differ from them in having
the gills attached along the right side, or upon the
back. These organs assume the form of a single
plume, or of leaflets more or less divided, but not
symmetrical ; they are always more or less covered
by the mantle, whence the name applied by Cuvier
to the Order. The mantle encloses within its sub-
stance, in almost all cases, a small shell to protect
the vital parts. In some of the genera, the shell is
developed to such a degree as to cover the animal ;
as in the fresh-water limpet (Ancylus), found in some
of our streams. For the most part, however, the
species are marine ; they are widely scattered, but
appear to be most numerous in the Indian and
Mediterranean Seas. ‘The sexual functions are
united in each individual, in which particular, this
Order agrees with those which I have already con-
sidered; but in the form of the breathing organs, it
manifests a closer affinity with the following Order.

The Covered-gilled Mollusca may be grouped in
five families, three of which are represented by
British species.

FAMILY PLEUROBRANCHIDZ.

‘The members of this family a cursory observer
would at once associate with the Nudibranchs ; but

128 TECTIBRANCHIATA.—PLEUROBRANCHIDA. °°

an examination of their structure reveals particulars
in which we see an evident departure from that
model. The mantle is large, projecting on all
sides over the foot, which is also ample; thus a
deep furrow runs all round between these parts.
Within this furrow, on the right side, les the
branchial plume, resembling a series of pyramids,
divided into triangular leaflets. The plume is
attached to the body at its base, but its tip, which
points backwards, is free. ‘The organs of repro-
duction and of excretion are also situated on the
same side, the former before, the latter behind the
gill-plume. ‘The head is distinct, concealed by a
broad veil, which is furnished with four tubular
tentacles. The mouth consists of a simple mus-
cular proboscis, or fleshy tube, which is capable of
considerable elongation and contraction; it is en-
tirely destitute of teeth or any cutting instru-
ment, but is, nevertheless, fully able to seize and
force into the stomach such materials as are used
for food. The stomach is greatly developed, and
in the principal genus is divided into four cavities,
of which the second is muscular, and armed with
shelly teeth; the internal surface of the third is
increased by longitudinal plates.

In the typical genus, there is a small thin shell
enclosed within the mantle, and situated in the
middle of the back, so as to cover and protect the vis-
cera. In the curious genus Umbrella, from the Indian
ocean and the Mediterranean, the shell is com-
paratively large, external, and shaped somewhat
like that of a Limpet ; but in Plewrobranchea, there
is no trace of a shell either internally or ex-
ternally.

COVERED-GILLED MOLLUSKS. 129

GENUS PLEUROBRANCHUS.

A not unapt comparison has been made of these
Mollusks to a tortoise, the mantle representing the
back shield, and the foot the breastplate. They are
more or less oval in outline, flattened, with the
back convex; the mantle is fleshy, and projects
considerably on all sides ; the head is placed beneath
its front margin, and carries two superior tentacles
with a pair of minute eyes, sunk beneath the skin
at the outer part of their bases. The upper part of
the head is developed into a ‘7
broad triangular veil, the lateral “iff (iy
edges of which carry another (/, 7
pair of tentacles. These organs,
as well as the superior pair, are
imperfectly tubular, and are
formed by the bending together
of their sides, which meet and &
overlap, but do not unite. The s
mouth is a short, fleshy pro- \s
boscis, provided with horny jaws ‘&
and a long ribbon-like tongue,
armed with teeth, as in the Nu-
dibranchs. The branchial plume
projects from between the mantle
and foot; in crawling it 1s trans-
verse, and appears, when viewed
from above, to be composed of Ab
many triangular lamine, over- Sth PLUME OF FLEURO-
lapping and pointing backwards.

Each lamina shows transverse wrinkles. Viewed
laterally, it is seen to consist of a central stem,
with about eighteen pinne on each side, each pinna
being again pinnated on each side The stem,

130 TECTIBRANCHIATA.—PLEUROBRANCHIDA.

pinne, and pinnulee, are all dilated inwardly, so that
the stem, which is narrow and slender in one aspect,
is wide in another ; and the pinne are the triangular
lamine, whose wrinkles are in fact the pinnule.
The organ is connected with the bottom of the
lateral groove, for about two-thirds of its length,
by a membrane. The plume can scarcely be
recognised in its two aspects, even though examined
again and again in quick succession. It appears
very sensitive, and changes much in appearance by
its various degrees of contraction and expansion.

The mantle contains in the centre of its sub-
stance an oval shallow cavity, within which hes,
quite free and unattached, a shield-like shell of the
same form, so delicate in its texture as to be
almost membranous, with a very slight indication
of a spire at one extremity. The position of the
shell is indicated externally by a dark cloudy spot
in the middle of the back ; and on an incision being
made in this part, the shell falls out.

The warmer seas produce the largest and most
beautiful species of this genus, some of which are
marked with bright colours. They are found
swimming in the open ocean, and crawling on the
rocks or weeds of the coast, and specimens have
been dredged, from various depths to thirty fathoms,
on stony bottoms and beds of sea-weed. We
have two native species, neither of which can be
considered common. The rarer of these, Pleuro-
branchus plumula, is found on our south-western
coast, where it was first discovered by that eminent
zoologist, Colonel Montagu. I had recently the
good fortune to find two specimens in a rocky cove
near Torquay, both of which lived in captivity for
some weeks.

COVERED-GILLED MOLLUSKS. 1S

The species is usually described as yellowish
white; but my specimens were both of a rich golden
yellow, with the central cloud brown, tinged in
front with red, the underside of the foot of a light

PLEUROBRANCHUS PLUMULA.

(1. Viewed from above; 2. from beneath.)

flesh colour. The length of the larger was an inch
and two-thirds when crawling, the breadth three
quarters of an inch.

In captivity they were sluggish, fond of hiding
among the fronds and leaves of sea-weeds, but
at times gliding freely like a Doris. They
swam on the surface by the foot reversed, and
then left behind a great wake of clear -viscid
jelly. They were beautiful animals. After keep-
ing them in health about a fortnight, I put one
into fresh water to kill it, for preservation. This,
however, was not so readily fatal to it as I had
supposed, for at the end of half an hour I found,
by its contraction when touched, that it was still
alive. Probably the mode in which it had con-
tracted, on being put in—the foot being narrowed,

132 TECTIBRANCHIATA.—PLEUROBRANCHIDA.

and the edges of the mantle being incurved on all
sides around the foot—may have in some measure
prevented the access of the water to the vital
parts. At the end of that time I replaced it in
sea-water, where it soon partially recovered its
activity, relaxed its mantie, and contracted it
dorsally so as to expose the groove between it and
the foot, greatly protruding the tentacles and veil,
and the branchial plume ; thus I was enabled to get
a much better sight of these parts. As soon as it
was replaced in the sea-water, a quantity of white
mucus was discharged from the whole surface,
most copiously from the foot, which as it lay on
its back was uppermost. This mucus gradually,
by the contractions of the animal, was accumulated
in a knob at the posterior end of the foot, and then
thrown off. The reticulate structure of the mantle
integument was much more distinct than in health ;
it was seen to form a delicate lacework of yellow
fibres all over the surface, covering and enclosing
a peliucid parenchyma.

The animal evidently had been injured by its
bath of fresh water; for it lay on its back, ex-
panding and contracting its various parts, without
the power of turning over to crawl, or even of
adhering by the foot when turned, but rolling
helplessly back. The form and appearance, too,
were very different from those of health; the
groove being widely exposed by the contraction of
the mantle, in which state the animal resembled
some published representations of it more closely
than when in health.

The student of nature, one who really delights
to contemplate the wonderful works of God, as they
appear in the conditions and under the circum-

COVERED-GILLED MOLLUSKS. 138

stances in which He has placed them, and not
merely their dried and shrivelled remains, techni-
cally labelled and arranged in the drawers of a
cabinet, can scarcely have a greater treat than a
ramble on a summer’s day along the margin of the
sea, on some one of our rocky shores.

‘Tis pleasant to wander along on the sand,
Beneath the high cliff that is hollow’d in caves,
When the fisher has put off his boat from the land,
And the prawn-catcher wades thro’ the short rippling waves;

While fast run before us the sandling and plover,
Intent on the crabs and the sand-eels to feed;

Or on a smooth rock which the tide will soon cover,
To find us a seat that is tap’stried with weed.”

But still more pleasant is it to peer into those
wells of pure water which are hollowed out in the
living rock, frmged with waving sea-plants, and
stocked with animals of various kinds, all pursuing
their natural avocations, and disporting themselves
in a thousand ways, under the umbrageous shade
of what to them is a marine forest. As we gaze
down into these clear, quiet depths, we almost
unconsciously repeat the words of one of our
noblest poets, who has selected such a scene for the
embellishment of the wildest of his romances :—

‘“‘ And here were coral-bowers,
And grots of madrepores,
And banks of sponge, as soft and fair to eye
As e’er was mossy bed
Whereon the wood-nymphs lie
With languid limbs in summer’s sultry hours.
Here too were living flowers,
Which, like a bud compacted,
Their purple cups contracted,
And now, in open blossom spread,
Stretch’d like green anthers many a seeking head.

134 TECTIBRANCHIATA.—PLEUROBRANCHIDA.

And arborets of jointed stone were there,
And plants of fibres fine as silkworm’s thread ;
Yea, beautiful as mermaid’s golden hair
Upon the waves dispread.
Others that, like the broad banana growing,
Rais’d their long wrinkled leaves of purple hue,
Like streamers wide outflowing.”*

A hundred times might you fancy you saw the
type, the very original of this description, tracing,
line by line, and image by image, the details of the
picture; and acknowledging, as you proceed, the
minute truthfulness with which it has been drawn.
For such is the loveliness of nature in these
secluded reservoirs, that the accomplished poet,
when depicting the gorgeous scenes of eastern
mythology; scenes the wildest and most extra-
vagant that imagination could paint; drew not
upon the resources of his prolific fancy for imagery
here, but was well content to jot down the simple
lineaments of nature, as he saw her in plain
homely England.

It is a beautiful and fascinating sight for those
who have never seen it before, to see the little
shrubberies of pink coralline,—the “arborets of
jointed stone,’—that fringe these pretty pools.
It is a charming sight to see the crimson banana-
like leaves of the Delesseria waving in their
darkest corners; and the purple fibrous tufts of
Polysiphonie and Ceramia, “fine as silkworm’s
thread.” But there are many others which give
variety and impart beauty to these tide-pools.
The broad leaves of the Ulva, finer than the finest
cambric, and of the brightest emerald-green, adorn
the hollows at the highest level; while at the
lowest wave tiny forests of the feathery Ptilota

* Southey. Curse of Kehama, xiv. 5.

COVERED-GILLED MOLLUSKS. 135

and Dasya, and large leaves cut into fringes and
furbelows, of rosy Lthodymenie. All these are
lovely to behold; but I think I admire as much as
any of them, one of the commonest of our marine
plants, Chondrus crispus. It occurs in the greatest
profusion on our coast, in every pool between tide-

CHONDRUS.

marks, and every-where,—except in those of the
highest level, where constant exposure to light
dwarfs the plant, and turns it of a dull umber-
brown tint,—it is elegant in form, and brilliant in
colour. The expanding fan-shaped fronds, cut

136 TECTIBRANCHIATA.—PLEUROBRANCHIDZ.

into segments, cut, and cut again, make fine bushy
tufts in a deep pool, and every segment of every
frond reflects a flush of the most lustrous azure,
like that of a tempered sword-blade.

I have said that animals of various kinds inhabit
these rock-pools. They are cavities of irregular
shapes and diverse dimensions in the surface of the
rock, covered by the sea at every incoming tide,
and left full when it recedes. The water, therefore,
presently becomes as clear as crystal, and the
surface being too small to be ruffled by ordinary
breezes, the eye can easily penetrate even to the
bottom, and mark all that is goimg on within.
There are little fishes, with bright eyes and silvery
sides, peeping from under the shelter of the broad
leaves, or darting out with vibrating fins from be-
neath one projection of the rock to another.
Elegantly painted prawns are swimming leisurely
to and fro, and hundreds of other smaller Crus-
tacea are playing about. Sea anemones of dif-
ferent species stud the rocky sides, and attract the
eye with their brilliant colours—crimson, purple,
scarlet, green, and white—resembling gorgeous
flowers, or ripe and mellow fruits, according as the
are expanded or contracted. The shelled Gas-
teropods are not wanting; the little Cowry, the
Purpura, the various species of Trochus, to say
nothing of limpets and periwinkles. And here we
may often see the lovely Nudibranchs and Tec-
tibranchs, crawling with graceful elegance about
the fronds of the waving Algz, or floating at the
surface of the still water in that reversed position
already described.

Many more objects of like kind the observant
naturalist will find from time to time, to gratify his

SEA-HARES. 137
curiosity and reward his diligence; twining Sea-
worms and Star-fishes; little Medusz, like active
bells of the clearest glass; the Beroé, a tiny
ball of crystal; slender, shrub-like Zoophytes ; and
multitudes of other creatures, all shewing forth the
glory of the great Workmaster, ‘for whose plea-
sure they are and were created.”’ (Rev. iv. 11.)

H'amMILY APLYSIADZ.
(Sea-Hares.)

In such rock-pools as I have just described, or
among sea-weeds growing at low water-mark, a
large fleshy Mollusk may occasionally be found,
with two erect tentacles somewhat resembling the
ears of the hare. It is the representative, the only
British one, of the family Aplystade.

The most prominent characteristics of this group
are the following :—The mantle is greatly developed
and dilated at the sides into large flexible crests,
which can be turned up, and, surrounding the back
on every side, can be reflected over it. The head
is distinct, and separated from the body by a neck
of greater or less length; its front forms a broad
lip, drawn out at the corners into a pair of flattened
tentacles ; another pair is carried erect on the top
of the head. The gills, in the form of complicated
leaflets, are placed upon the back, and are gene-
rally covered with a convex, horny, or shelly plate,
irregular, and varying in shape.

The Sea-hares are vegetable feeders, and, by a
curious analogy with the herbivorous Mammalia,
the digestive apparatus is highly complicated.
According to Professor Grant, there are three
stomachs; a short narrow gullet dilates into a large

138 TECTIBRANCHIATA.—APLYSIADZ.

membranous crop; a curved bag, which is generally
found filled with pieces of coarse sea-weed. This
large crop or paunch occupies the right side of the

ee
Mae é
ee 3

”

a Wy Wi

* oa

ee

INTERNAL ANATOMY OF SEA-HARE,

body, and opens laterally into the middle stomach,
which is the smallest of all, and performs the part
of the gizzard. Its coats are thickened; and the

SEA-HARES. 139

interior callous lining is beset with firm, horny
processes, in the form of rhomboidal plates or
molar teeth, which serve to compress the softened
vegetable matter transmitted in small portions from
the first stomach. The third cavity of this com-
plex apparatus is placed on the left side of the
body ; its interior surface is studded with sharp,
horny spines, resembling canine teeth, to pierce and

SECOND AND THIRD STOMACHS OF SEA-HARE LAID OPEN.

subdivide the coarse food, and thus prepare it for
the action of the gastric juice, and other fluids ac-
cessory to digestion, which enter the stomach from
adjacent organs.

The complexity of this structure has reference to
the coarseness of the materials on which the animal
subsists—the leathery fronds of the olive sea-weeds,
which slowly and with difficulty yield their nutri-
tive elements to the digestive functions.

The circulation of the blood in these animals
has been considered, on the high authority of Cu-
vier, to present extraordinary peculiarities. ‘The

140 TECTIBRANCHIATA.—APLYSIAD A.

large vessel which collects and receives the venous
blood from all parts of the system, and carries it
forward to the gills, was believed to have nume-
rous perforations in its walls, through which a free
communication existed with the general cavity of
the abdomen, so that the fluids contained in the
one could readily permeate the other.* But it has
been since proved that these supposed perforations
are merely depressions, and that the lining mem-
brane of this great blood-vessel is entire, as in other
animals.

The Mollusca of this Order undergo a metamor-
phosis exactly similar to that already described in
the Nudibranchs; there is, in fact, scarcely any
appreciable difference in the form of the newly-
hatched young in either of these Orders, in that
of the Pectinibranchs, and in the Class Pteropoda.
How long the infant animal remains in this, its
first condition, is not yet ascertained. Arrived at
the second stage, we find it still enclosed in its
transparent and nautilus-like shell; but the mantle
has become detached, and covers tightly the mass
of the viscera. The foot is so enlarged, that it
forms a considerable projection beyond the margin
of its operculum ; and the veils have also grown
in size, while the eyes have altered to a violet
colour. The head has now two short, conical,
ciliated tentacles, and the little animal swims
with surprising quickness.

In the third stage the shell has fallen off, and the
general shape is that of the parent, but the veils
still remain. In the fourth stage, the creature
begins to crawl in the gasteropod fashion, and the
branchie and ceca begin to sprout. ‘There are now,
* Mem. sur les Mollusques, ix. 14. + Grant’s Comp. Anat. 465.

SEA-HARES. 141

also, visible pulsations in the heart ; and the mouth
is armed with jaws, and with a spinous tongue.
Another stage is marked by the fall of the veils,
and by the budding forth of the anterior tentacula,
as well as of the branchiz; and the full evolution
of these organs completes the metamorphosis and
entitles the animal to the privileges of maturity.*

GENUS APLYSIA.

Most of the characters which distinguish this
genus liave been already enumerated in those of
the family. The peculiarities by which it is sepa-
rated from its fellow genera are chiefly the presence
of an internal shell, and the position of the gill-
plume. The latter organ assumes the form of
complex leaflets, attached to a broad membranous
footstalk, and concealed beneath the shell.

The genus is truly marine; yet M. Rang has
observed specimens of A. dolabrifera inhabiting
marshes in the island of Bourbon, where the water
was almost fresh, and where Neritina and Melania,
both essentially fresh-water genera, were its com-
panions. }

They swim freely, by means of the large fin-like
expansions of the mantle, which are waved with an
undulating motion. They have been seen also
floating at the surface, suspended like Pond-snaiis
from the inverted foot.

All the species, I believe, are remarkable for the
power of pouring out, in copious profusion, a fluid
of a brilhant purple hue, which readily diffuses
itself through the surrounding water. I have
already mentioned my own experience of this phe-

_* Jchnston’s Introd. to Conchol. 373.

142 TECTIBRANCHIATA.—APLYSIADA.

nomenon in a West Indian species, and Mr. Patter-
son thus speaks of it in our native species, 4. hy-
brida. “The first which our dredge brought up
was placed on one of the rowing benches of the
boat, and in a very short time emitted a rich
purplish fluid, so copiously, that it ran along the
board. Being transferred to a phial of sea-water,
the purple dye was still given off in such abun-
dance that the creature soon became indiscernible.
It was not until the water was again changed that
we had the opportunity of observing the ease and
grace with which it moved about, elevating and
depressing its mantle, altering the outline of its
body, and extending and retracting its tentacula so
incessantly, that an artist would have found a dif-
ficulty in catching its characteristic figure.”* This
fluid is said by Professor Goodsir to be secreted by
the edge and internal surface. The secreting sur-
face of the mantle consists of an arrangement of
special nucleated cells, which are distended with a
dark purple matter.T

Besides the purple secretion, the Sea-hares
occasionally discharge, from an orifice situated
behind the oviduct, a milky fluid highly acrid, and
probably containing stinging thread capsules similar
to those already described in Holis. The Sea-
hares have in all ages sustained the imputation of
being highly offensive and injurious to man, and
though in modern works it has been the custom to
ridicule the charge, there is reason to think it may
not be altogether groundless. Barbut declares that
a sailor, in the Mediterranean, happening to take
hold of an Aplysia, it gave him such instantaneous
and excruciating pain, as to cause inflammation and

* Zool. for Schools, i.179. + Anat. and Pathol, Obs. 23.

SEA-HARES. 143

the loss of his arm. A better authority, Mr. Charles
Darwin, found a species at St. Jago, the secretion
trom which caused a sharp stinging sensation similar
to that produced by the Physalza or Portuguese man
of war.*

_ The account given by Bohadtch is remarkably
clear and circumstantial. He tells us that the
Lerneea (A. /eporina) abounds in the Bay of Naples,
where the fishermen excused themselves for not
bringing it to him, saying it was a filthy thing
which stank abominably. When removed from
the sea, and placed in a vessel, there exuded a
large quantity of a limpid, somewhat mucilaginous
fluid, exhaling a sweetish, sickening, peculiar
smell: but besides this, and distinct from its purple
secretion, the Aplysia excretes also a milky
liquor, formed in an internal conglomerate gland,
which seems to be analogous to the kidney of ver-
tebrate animals. As often as he took the Aplysia
from the vase of sea-water, and placed it on a plate
with the view of more narrowly examining its
structure, the room was filled with a most feetid,
nauseous odour, compelling his wife and brother
to leave the room, lest sickness and vomiting should
follow. He himself could scarcely endure it, and
during the examination had repeatedly to go out anc
breathe a purer air. His hands and cheeks swelled
after handling the creature for any length of time,
and as often as it ejaculated its milky secretion ;
but he is uncertain whether the swelling of the
face proceeded from the halitus merely, or from
having accidentally touched it with the hand
besmeared with the liquid: probably the latter
was the real cause, for when he purposely applied

* Voy. Adv. and Beagle, iii 6.

144 TECTIBRANCHIATA.—APLYSIADA.

some of it to the chin, some hairs fell from the
part.*

For myself, however, I can state, that I have
freely handled many specimens of A. hybrida, both
young and adult, when newly taken out of the
water, without perceiving the least unpleasant sen-
sation, either of feeling or smell.

Among the ancient Romans, the Sea-hare was
esteemed highly venomous, and it certainly formed

SEA-HARE.

one ingredient in the poisonous draughts that were
used in the corrupt ages of the empire for the vile
purpose of assassination. Locusta used it to destroy
such as were inimical to Nero; it entered into the
fatal potion which she prepared for the tyrant
himself, and which he had not resolution to
swallow; and Domitian was accused of having

‘iven it to his brother Titus. 'T’o search after the
Sea dias was to render one’s self suspected; and

* De Anim. Marin.

BULLAS. 145

when Apuleius was accused of magic, because
forsooth he had induced a rich widow to marry
him, the principal proof against him was that he
had hired the fishermen to procure him this fearful
animal. He averred, however, that his only object
in procuring the Sea-hare was the gratification of
a laudable curiosity.

Our native species (A. hybrida) is about three
inches in length, of an olive or dark green hue,
often marked with dark rings enclosing white areas;
the mantle is sometimes clouded with purple or

blue.
Famity BULLADA.

The shell, which in the preceding families is
thin, small, and rudimentary, is in this family much
more developed. The spiral character is distinct,
and the general form and texture show a consi-
derable approach to that condition in which it is
more familiar to us, viz. that of an ample, tur-
binated covering, for the inhabitation of the animal,
of stony hardness. Yet in none of the genera of
this family does the shell perform the function ot
a dwelling-house for the animal: it is still more or
less concealed by the flesh; not, indeed, imbedded
in the substance of the mantle, but invested more
or less completely by fleshy lobes or wing-like ex-
pansions, that turn up on each side and embrace it.
In the genus Scaphander, however, which includes
the largest British species of the family, the shell
is entirely exposed, the wing-like lobes being
smaller than usual.

In its texture the shell is generally thin, pellucid,
and colourless, or nearly so, though in some of the
species in which the family characters are be-

L

146 TECTIBRANCHIATA.—BULLADZ.

ginning to disappear, pale colours are displayed
by the shell, and its texture is stony. Its form is
more or less rolled upon itself, but without a salient
or produced spire, and the mouth is usually ample
and widely expanded.

The animal is large, fleshy, and often slimy.
The gills are concealed, the tentacles are so much
shortened, widened, and separated, that their form
is well-nigh obliterated, and they constitute a large
square fleshy veil, beneath which are placed the
eyes. ‘The stomach is complicated, and in some
species there is a shelly gizzard, with a peculiar
erinding apparatus of great strength, needful for
the demolition of the shells of other species of
Mollusca on which the bullade feed. They are
very voracious, and sometimes swallow bivalves so
large as quite to distort their own form, and render
it almost unrecognisable. The shelly gizzard of
Scaphander lignartus, a large species not uncommon
on our coasts, was described by Gioeni, a Sicilian
naturalist, as a new genus of multivalve shells, to
which he gave his own name, calling it Goenza.
He even went so far as to describe the habits of the
pretended animal, which was actually received into
the catalogues of science by some of the most
eminent names in conchology, until at length the
imposture was detected and exposed.

‘The animals of this family generally inhabit
deep water, that is to say, below the range of low

tide. Occasionally, however, they stray within
tide-marks.

BULLAS. 147

GENUS PHILINE.

In this genus the shell is thin, fragile, and
colourless, of a broad rounded outline, with the
aperture very wide, and a small spire, frequently
concealed. The animal is proportionally large,
slug-like, and slimy, with the power of secreting
and of throwing off an adhesive mucus in copious
abundance. ‘he shell is partially covered by the
mouth, the side lobes of which are well developed.
The head disk is obscurely four-sided, without
eyes or distinct tentacles.

Of the six species of this genus which are found
in the British seas, the largest .
is P. aperta, the Gaping Bulla.
It is an unpleasing, almost shape-
less slug, very soft and slimy to
the touch, of an opaque white
hue, sometimes tinged with pale
orange. Looked at from above,
it appears to be composed of four
portions,—the square head-disk,
the body partly enclosing the
shell, and the lobes or wings of
the mantle turned up on each
side and investing it. It is
usually about an inch and a THe Garine suina.
quarter in length, but individuals are found of a
larger size.

The shell, on being dislodged, is transparent and
colourless, but on drying loses somewhat of its
clearness, and becomes of a lustrous white hue. Its
surface is smooth, except for the concentric lines,
which mark its progressive increase. The aperture

148 TECTIBRANCHIATA.—BULLADA.

is so open as to display the whole interior even to
the summit.

The Gaping Bulla is common on our coasts, es-
pecially in the south, inhabiting muddy and sandy
ground at afew fathoms’ depth. I have dredged
it abundantly in Weymouth Bay, a mile or two
from shore. In captivity it is sluggish, remaining
inert at the bottom of the vessel in which it is kept,
so as to be an uninteresting subject of observation ;
added to this it continually secretes and discharges
a viscid slime, which stretches through the water
in long tenacious strings, and envelopes and dis-
tresses any other marine animals which may be its
fellow-captives. Some of the Nudibranchs discharge
mucus in the same manner; but I know of none
that possesses the disagreeable quality to the same
extent as this Bulla.

LIMPETS. 149

ORDER CYCLOBRANCHIATA.

THE breathing apparatus in this small group
consists of a great number of little conical leaflets,
arranged in a circle, more or less complete around
the body, and attached beneath the margin of the
mantle. The animal is covered by a shell varying
much in dimensions and in structure in the different
genera. They are all somewhat sluggish animals,
adhering for many hours together to the surface of
rocks, or other bodies, by means of the foot, which
is large and muscular. All of the species inhabit
the sea.

FAMILY PATELLADZA.
(Lampets.)

A conical shell is the distinctive character of
this family; showing no trace of a spire, and
destitute of any aperture or notch, by which other
genera are known, which have shells of similar
form and appearance. The shell, which is made
out of one entire piece, quite covers the body; it is
in the form of a widened cone, the apex of which
is higher or lower, nearly central, or more ap-
proaching one end,—in different species. The
animal is large in proportion to the shell, with
a mantle, under the projecting edge of which, is
a fringe of small leaves, that perform the oftice of
respiration. The head is furnished with a large
but short proboscis, and with two pointed tentacles,
each of which carries an eye at the outer side of

150 CYCLOBRANCHIATA.—PATELLADA.

its base. The mouth is fleshy, and contains a long
slender tongue, armed with spinous teeth, for the
rasping down of the sea-weeds, of which the food
of these animals consists. This organ in the
common Limpet is described as a narrow ribbon-
like-body, fully three inches long, of nearly equal
breadth throughout, except at the tip, where it is
soft and somewhat dilated. The width of this
singular appendage is not more than one-twelfth of
an inch; but the surface is armed through its whole
length, with three parallel rows of spinous teeth,
pointing backwards. The teeth of the middle row
are cut into four points, but those of the external
rows, which are not exactly opposite to, or con-
tinuous with, those of the middle series, but alter-
nate with them, are cut into two points only.
“The first time,” says Mr. Patterson, ‘we

TONGUE OF LIMPET.
(The upper figure represents a portion of the surface magnified).

chanced to see this, we mistook it for some strange
species of worm; but on examining several Lim-
pets, the supposed worm was seen in all; and
great was our astonishment when we discovered
that we had, in every case, been looking at the

LIMPETS. 151

tongue of the Limpet, and not at any intruder into
the privacy of his conical fortress.” *

This curiously toothed tongue ‘is never pro-
truded beyond the margin of the lips. It seems to
be used for rasping down the food; and in pyro-
portion as the anterior prickles are worn away in
this operation, and absorbed, another portion of the
tongue is brought forward to supply its place; but
that there may be no deficiency in its length, we
find the apex soft and vascular, where in fact
a continual growth and addition are going on.

‘“‘ When a phytophagous Gasteropod is about to
eat, it thrusts forward, and to a certain extent,
evolves, the spinous tongue, protruding at the same
time the lip on each side, by which the tongue is
compressed and forced into the form of the bowl of
a spoon. The food is now taken hold on by the
lips, drawn forwards, and retained by the prickly
tongue, and simultaneously pressed against the
upper horny jaw, by which means a portion is
bitten off, sometimes with a very audible noise.
The detached morsel is then passed along the
tongue, torn and rasped down by its sharp prickles,
and forced on by the peristaltic motion of the organ,
and by the retropulsive action of the adjacent
muscles, the mass is made to enter the gullet. At
the entrance of this canal, there is an uvular ca-
runcle, which is probably the seat of the animal’s
taste ; and on its side a pair of lobulated salivary
glands, or sometimes two pairs, which have each
a single excretory duct to convey their peculiar
secretion into its upper part, to lubricate and soften
the mass. The gullet is a muscular canal, lined
interiorly with a mucous coat, presenting, indeed,

* Introduction to Zool. i. 178.

152 CYCLOBRANCHIATA.—PATELLADZA.

the same structure as the whole alimentary canal,
and is generally plaited in a longitudinal direc-
fon,

M. De Blainville considered that the organ of
respiration in the Limpets was a vascular network,
spread over the interior of a cavity, situated above
the neck, with a wide opening in front. Hence he
constituted the family into an order, which he
named Cervicobranchiata, or neck-breathers. The
opinion of so eminent a zoologist, adverse as it was
to the received judgment of his fellow labourers in
science, demanded a close investigation, which has
_ been given by M. Deshayes and others. The result
has been to show that such a cavity exists, with
a structure similar to that of the Limpets, in many
other Gasteropoda, which possess distinct and un-
doubted gills of the pectinate form, which I shall
presently describe; and that there is no sufficient
reason for believing that this chamber in the neck
has any respiratory function at all: this office being
fulfilled by the fringe of floating leaflets that en-
circle the body, as had been maintained by Cuvier
and others.

In order to fit these little organs for the office
which has been assigned to them, they are fur-
nished with a multitude of célia, microscopically
minute, covering all parts of their free surface. By
means of the constant undulating movements of
these célia, a perpetual current of sea-water 1s made
to roll along each leaflet, communicating the requi-
site oxygen to the blood-vessels, of which it is
mainly composed. The currents flow from the
outer towards the inner edge, across the surface of
each leaflet.

* Johnston: Introduction to Conchology, 328.

LIMPETS. 153

The doubts occasionally cast on what are received
as established truths in science, though they may
seem to unsettle our knowledge, and give a cha-
racter of vagueness to it, must not be considered as
inimical either to its progress or its solidity; not
even when, as in the case just cited, they are found
to be without foundation. They give rise to new
and more careful examinations; to extensive com-
us of species with species, or of fact with
act; to satisfactory inductions of principles from
observations ; and often to the discovery of laws
before unsuspected.

GENUS PATELLA.

As the family consists but of this single genus,
the characters already enumerated need not be
repeated. ‘The species are numerous, widely dis-
tributed over the globe, scarcely any sea being
destitute of some, with the exception of the Arctic
Regions, where none have been observed by voy-
agers. As usual, the largest species are found in
the seas of the tropics. Deshayes in his Tables
enumerates 104 living species, and ten fossil ;
several others have becn added by subsequent
naturalists, but as the genus is peculiarly liable to
variation in the form, colour, and surface of the
shell, it is very likely that many of these de-
scribed species are merely varieties.

The animals of this genus have the power of
wearing away, or of absorbing the surface of other
shells, or of the rocks to which they adhere, and of
thus forming sunken pits or depressions on them.
The Patella cochlear of the Cape of Good Hope, is
often found attached to a large species of the same

154 CYCLOBRANCHIATA.—PATELLADZA.

genus, on the surface of which it forms a flat disk,
exactly agreeing in size with the circumference of
its own shell. ‘To form these depressed disks, (of
which there are so generally two on each larger
Patella, one on each side of the apex, as almost to
form a character of the species,) and to assist in
the increase of its size, the animal appears also to
absorb the coralline or other similar substances
with which the larger shells are abundantly
covered.*

But we need not wander to the southern hemi-
sphere for illustrations of this power. The most
familiar shell-fish of our shores, the common Lim-
pet (P. vulgata), will afford one equally good.

ho has not seen the oval pits, sometimes but
just discernible, at others sunk to the depth of an
eighth of an inch or more, on the rocks of our
coast, each accurately corresponding in shape and

COMMON LIMPET.

dimensions with a Limpet which inhabits it? I
have wondered at them many times, not being then
aware of the habits which have been ascribed to
these animals, of wandering away from these pits,
(which they have chosen for a home,) and of re-
turning to them regularly again.

* Gray, in Phil. Trans. 1833.

LIMPETS. 155

These habits were first made known by Mr.
Lukis, a naturalist of Guernsey, to whom we are
indebted for other interesting notes on the economy
of animals. “The locomotion of the Limpet,” he
observes, ‘may be ascertained by marking one
individual to avoid mistake, and then observe its
cautious roaming and regular return to its favourite
place of rest, where the shell will be found exactly
to correspond with the surface of the rock to which
it is attached. Here it will rest or sleep, and only
relax its strong adhesion to the rock, when the
muscular fibre becomes exhausted by long con-
traction, in which state a sudden blow, horizontally
given, will easily displace it. A fact known to the
fishermen and poor, who use them for food, is, that
they are more easily collected in the night time
than in the day. May not this be the period of
roaming for food as well as when covered by the
tide ?

“The march of the limpet is slow and formal ;
and whenever the cupping process is renewed, the
posterior end of the shell is brought in contact
with the rock, which is of a soft nature, and will
receive the impressions of its denticulations. The
track of an individual placed under surveillance
was thus made visible over a space of several
yards, possessing the same regularity and dis-
position, and was further remarkable for the con-
stant revolution on its left.

“The tracks of the limpet on granite and other
hard rocks, present, at first sight, the same appear-
ances; but, on a closer examination, they are
found to differ. When first observed in 1829, a
large portion of a fine-grained sienitic rock was
traced over by these shells; the remainder was

156 CYCLOBRANCHIATA.—PATELLAD ZA.

plain, and appeared varnished with a thin coating
of some kind of fucus, without any markings upon
its surface. As no patellee were at first discovered,
and the isolated situation of the rock prevented
any from reaching it, I was at a loss to explain
these appearances ; but, after some search, a fissure
was found at the north end, where five or six lim-
pets had fixed themselves, each having a direct
road leading to their pasturage-ground. By the
help of a glass, the markings visible on the rock
were discovered to be the remains of the above
fucus, which had been eaten through or trodden
down by these animals in their excursions, and
which retained the indentures of their shells. The
edge of the vegetable surface was then examined,
and found to be nibbled in a circular manner re-
sembling the anterior margin of the shells.” *

The force with which a limpet adheres to the
rock is very great, especially when it has had
warning of assault, and has had time to put out its
muscular strength. Réaumur found that a weight
of twenty-eight or thirty pounds was required to
overcome this adhesive force. His experiments
seem to prove, however, that its power is mainly
owing, not to muscular energy, nor to the produc-
tion of a vacuum in the manner of a sucker. If an
adhering limpet were cut quite through perpen-
dicularly, shell and animal, the two parts maintained
their hold with unabated force, although of course a
vacuum, if there had been one, would have been
destroyed by the incision. ‘The power is said to
reside in a very strong glue, a very viscid secre-
tion, deposited at the will of the animal. “If,
having detached a patella,’ says Dr. Johnston,

* Mag. Nat. Hist. iv. 347.

LIMPETS. 157

“the finger be applied to the foot of the animal, or
to the spot on which it rested, the finger will be
held there by a very sensible resistance, although
no glue is perceptible. And it is remarkable, that
if the spot be now moistened with a little water, or
if the base of the animal be cut, and the water
contained in it allowed to flow over the spot, no
further adhesion will occur on the application of
the finger,—the glue has been dissolved. It is
nature’s solvent, by which the animal loosens its
own connexion to the rock. When the storm
rages, or when an enemy is abroad, it glues itself
firmly to its rest ; but when the danger has passed,
to free itself from this forced constraint, a little
water is pressed from the foot, the cement is
weakened, and it is at liberty to raise itself and be
at large. The fluid of cementation, as well as
the watery solvent, are secreted in an infinity of
miliary glands, with which the foot is, as it were,
shagreened ; and as the limpet cannot supply the
secretion as fast as this can be exhausted, you may
destroy the animal’s capacity of fixation, by de-
taching it forcibly two or three times in suc-
cession.” *

This common limpet, though hard, coarse, and
unsavoury, is largely eaten by the poorer classes on
our rocky shores. It is easily procured in almost
any quantity, between tides, and therefore is a
good deal resorted to by those who have little or
nothing better. The wretched inhabitants of the
isles of Scotland, and of the Atlantic shores of
Ireland, in particular, have often been preserved
from actual famine by this miserable food. The
quantity eaten as a regular part of diet is immense.

* Introd. to Conch. p. 147.

158 CYCLOBRANCHIATA.—CHITONIDZA.

Mr. Patterson, when residing, in July, 1837, near
the town of Larne, in the county of Antrim, en-
deavoured to form some calculation of the quantity
of limpets alone taken from the rocks about that
part of the coast, and used as food. He had reason
to believe that the weight of the boiled “ fish ” was
above eleven tons! The weight, as carried from
the beach, was, however, much greater, as there
was to be added that of the shell, and the sea-
water which it contained. This, too, was exclusive
of a probably equal quantity of periwinkles and
whelks. *

FAMILY CHITONIDA.

We find in this family a group of mollusca,
which, possessing in their anatomical structure
nothing very peculiar, present, in the covering by
which they are protected, a form of shell quite
anomalous, and such as to have given rise to a
conjecture that in this family we have the link that
connects the MoLuusca with the ARTICULATA.

The shell in the chitons consists of eight narrow
transverse calcareous pieces, overlapping each
other, and strongly implanted in a thick and fibrous
border of the mantle, which surrounds the whole.
The mantle itself is of a stiff leathery consistence,
and though sometimes smooth, is more commonly
covered with small scales, spines, or hairs. The
elasticity of this investiture allows the animal to
stretch and contract itself in crawling, and even to
roll itself in a ball, in the manner of an oniscus or
a hedgehog, the shelly pieces moving freely upon
each other. To effect the various motions required,

* Introd. to Zool. i. 171.

CHITONS. 159

there are three muscles given off from each piece to
the succeeding one, one in the line of the back, the
others at each side. Thus the animal may be con-
sidered as enveloped in a coat of plate armour, and
the name of coat-of-mail shell is sometimes applied
to it by collectors.

SHELL-PLATES OF CHITON

The chiton has no projecting head, nor any ten-
tacles, but a kind of veil that surrounds the mouth;
the eyes also are wanting. There is a very long
ribbon-like tongue, armed like that of the limpet,
with horny teeth. The gills consist of small tri-
angular leaflets, set in a fringe, which runs along
the furrow between the mantle and the foot. The
foot is large, and extends the whole length of the
animal.

In the family are comprised two genera, differing
in the development of the shelly plates.

160 CYCLOBRANCHIATA.—CHITONIDZ.

GENUS CHITON.

The character which distinguishes the chitons
proper from the Oscabrelles (Chitonellus), is that
the dorsal plates of shell are comparatively large,
much wider transversely than longitudinally, and
all in contact with, and overlapping each other.
This genus includes a large number of species,
which are scattered over all seas, except in the
very rocky shore, in greater or less abundance,
fast adhering by the broad foot, exactly in the
manner of limpets. The largest species are found
on the tropical coasts of America, where some
attain the gigantic dimensions of four, five, and
even six inches in length. The Chiton spiniferus
of Chili is said to reach the size last mentioned.
The shells are much prized by conchologists, and
they are consequently sought by collectors in fo-
reign countries, though the operation is sometimes
attended with danger. I have myself collected
some kinds, of large size, on the shores of Jamaica,
among sharp and rugged rocks, where the surf
dashing in breaks over the naturalist at almost
every wave, drenching him, of course, and often
buffeting him against the rocks, and washing his

rize from his hands the very moment he has
Actuched it from its hold.

The mode in which Chitons are procured re-
quires some skill and practice, as if they are
touched without being detached in an instant, they
increase their adhesion so greatly as to defy all
efforts to remove them without lacerating the
edges of the mouth, and thus spoiling them as
cabinet-specimens. An old knife, that has the tip

CHITONS. C6he

blunt and rounded, is the best adjunct. The
operator must apply the point of this close to the
extremity of the Chiton, without actually touching
it; then, striking a smart blow with the palm of
his other hand on the handle of the knife, the
animal is dislodged by the shock, before it has any
opportunity to confirm its hold. To prepare it now
for the cabinet, it must be thrown into fresh water
for several hours, and when quite dead, which may
be known by the relaxation of muscular rigidity,
the foot and all the soft parts must be cut out
of the concavity of the mantle. The latter must
then be placed on a narrow strip of board, exactly
as if the animal were crawling, to which it must
be tightly bound by threads passed round and
round in every part, and laid to dry in the shade.
Specimens prepared in this way will possess a
natural appearance, and will never curl up in any
state of the weather.

The flesh of the larger chitons is red and coarse;
it is, however, eaten by the negroes of the West
Indies, who compare it, by a certain exercise of
imagination doubtless, to beef. ‘There is a species
found in the same locality, reported, I know not on
what foundation, to be poisonous.

We have about fifteen species of this genus
enumerated as British,
of which one of the
largest, as well as most
common, or at least most
generally distributed, is
the Tufted Chiton (C.
fascicularis). Itis about
three-fourths of an inch
in length, with the shelly plates striated and granu-

M

TUFTED CHITON.

162 CYCLOBRANCHIATA.—CHITONIDZ.

lated, and the margin of the mantle studded with
little bundles of bristles, about nine or ten on each
side. It varies in colour, but is generally greyish,
or dusky olive. I have dredged it of large size
in Weymouth Bay, attached to oyster-shells. A
much smaller species is also common in that locality
(C. cinereus), which occurs in the pools and on the
ledges of the shore, near low-water mark.

When put into a glass of sea-water, the Chitons
are sluggish, often remaining for days rolled up
before they begin to adhere, and then remaining
a long time inert on the same spot.

COMB-GILLED MOLLUSKS. 163

ORDER PECTINIBRANCHIATA.
(Comb-gilled Mollusks.)

WE have now arrived at the most numerous
division of the GASTEROPODA, which comprehends
nearly the whole of the spiral univalves, and many
with simply conical shells. Their distinctive cha-
racter is the possession of gills composed of nu-
merous leaflets, or fringes, ranged in parallel order,
like the teeth of a comb, and attached, in one, two,
or three lines, (according to the genus) to the ceiling
of the breathing-chamber, a cavity opening by a
wide orifice between the edge of the mantle and
the body. All the members of the Order respire
water, and nearly all are marine.

A pair of tentacles are always present, accom-
panied by a pair of eyes, often highly organized,
carried, sometimes, on spinal footstalks, and some-
times seated, as it were, on the side, or at the base
of the tentacles. ‘The mouth takes the form of a
proboscis more or less lengthened, and: conceals a
tongue armed with small recurved hooks, which
wear down the hardest bodies by slow and repeated
friction. ‘The sexes are always separate.

The shell is in general turbinated, or twisted
spirally into a cone more or less regular; the aper-
ture of which is sometimes entire, sometimes
notched, sometimes drawn out into a canal. The
orifice is in general capable of being closed by an
operculum, a horny or shelly disk, attached to the

164 PECTINIBRANCHIATA.—CYPREADA.

posterior part of the foot of the animal, and fitting
the interior of the mouth of the shell when the
animal retreats within the cavity.

The most important difference between the
animals of this order consists in the presence or
absence of a canal, formed by a lengthening of the
lung-chamber of the left side, which is carried
along a similar canal in the shell, or through a
simple notch, to enable the animal to respire with-
out the need of quitting its shelter. The presence
or absence of an operculum is also a distinction ;
and the filaments, fringes, and other ornaments,
which are occasionally carried on the head, the
foot, and the mantle, afford other characters for the
subdivision of this extensive Order.

FAMILY CYPREHADA.
(Cowrves.)

Of this extensive group of shells, the majority
of which are so exquisitely beautiful that they form
the ornaments of cabinets, and the pride of collec-
tors, a single British species is a sufficient warrant
for noticing, in this volume, so attractive a family.
Most of them are inhabitants of the tropical seas,
residing chiefly near the shore, on reefs, and among
rolled masses of broken coral; hence archipelagos
and smaller groups of islands are peculiarly rich in
the lovely Cowry-shells. There the brilhancy and
variety of colour displayed both by the shells
themselves and by the animals, accord with the
glories of those latitudes, where the hght and heat
of a vertical sun give the greatest stimulus to
animal and vegetable life.

COWRIES. 165

The characters of the family are the following:
the form is oval, flattened on one side, on which is
placed the aperture; this is as long as the shell,
narrow, and open at each end: the spire in the
adult state is entirely concealed: the outer lip is in
general bent inward and thickened. The surface
of the shell is often highly polished, with a glassy,
or porcelain-like enamel, with no trace of an epi-
dermis, or investing coat of skin.

The animal is large ; the mantle is developed
into widely-expanded lateral lobes, which are,
during activity, turned upward on each side, so as
closely to embrace the shell. These lobes are gene-
rally gaily coloured, and are often adorned with
various fringes and other appendages. The head is
furnished with a retractile proboscis, and with a
muzzle. The gill-plume is single. The sexes are
separate. ‘There is no operculum.

“The difference of aspect,” observe Messrs.
Forbes and Hanley, “between these mollusks
when crawling, with all their beautifully-coloured
soft parts exposed, often completely concealing
their enamelled shells, and their appearance when,
after being seized, they suddenly and instan-
taneously withdraw their bodies and mantle-lobes,
and expose the shell only, is very curious and
surprising.’ *

GENUS CYPRZA.

As specimens of some or other of the numerous
species that compose this beautiful genus may be
found on almost every mantlepiece, sideboard, and

* Brit. Mollusca, iti. 493.

166 PECTINIBRANCHIATA.—CYPREADZ.

chiffonier, my readers will be at no loss for the
means of actual comparison of the following cha-
racters by which it is distinguished. he shell is
oval, more or less swollen, and flattened on the
inferior side: its surface is polished or enamelled,
commonly smooth, but sometimes marked with
parallel grooves: the aperture is as long as the
whole shell, narrow, forming a canal at each extre-
mity ; the outer lip is in full age bent inward, and
much thickened, and as well as the inner lip, (or
that edge of the aperture which faces it,) in almost
all the species marked with numerous parallel
tooth-like ridges.
The animal has large smooth, or warted mantle-
lobes, capable of entirely embracing the shell
between them, their edges meeting along its sum-
mit. The head is broad, with a retractile pro-
boscis, and long, pointed tentacles, at the bases of
which are the prominences which carry the eyes.
The jaws are horny, and there is a long nibbon-
like tongue, armed with rows of minute-teeth.
Some species appear to have the faculty of
changing the colours with which the mantle is
vividly adorned. Mr. Stutchbury, who had an
opportunity of examining many individuals of
C. tigris at the Pearl Islands, has stated that those
cowries lived there in very shallow water, and
always under rolled masses of madrepore. They
never were to be seen exposed to the sun’s rays.
On lifting one of those masses a tiger-cowry was
generally observed with its shell entirely covered
by the large mantle, which was mottled with dark
colours, the intensity of which the animal seemed
to have the power of changing; for the colours
varied in the same light and in the same medium,

COWRIES. 167

after the manner of the spots on the cephalopodous
mollusca, or, to use a more familiar instance, some-
what in the same way that the hues of a turkey-
cock’s wattle vary.*

Mr. Arthur Adams, however, remarks on this
statement: ‘“ Although I have examined hundreds
of Cyprea tigris in a living state, I never saw
those changes of colour in the mantle of the animal
described by Mr. Stutchbury.” T

The form of a cowry-shell is so peculiar, that no
one, on first taking it into
the hand, would suspect that
it is modelled on the same
plan as the cones and olives
with which it is frequently
associated. Yet the structure
is essentially the same, and
in the youth of the shell the
resemblance is manifest, a
young cowry being so like
an olive as to present no
peculiarity worth notice. In
the course of growth, however, important changes in
the external shape occur, chiefly by the development
of the outer lip, and the deposition of the surface-
enamel. Mr. Gray defines three stages in the growth
of Cyprea exanthema. In the first the shell is
generally smooth, of a pale greyish colour, or with
three transverse bands, and the upper part of the
inner lip is smooth and convex, the lower part flat
or concave ; the owter lip is thin. The accompany-
ing figures represent this stage.

In the next stage the shell begins to assume

* Zool. Journ. iv. 163.
T Zoology of Samarang, part iii. p. 24.

YOUNG COWRY.

168 PECTINIBRANCHIATA.—CYPRAEADA.

more of the character of the genus, the outer lip
beginning to be bent in, or rather thickened, and
the mantle beginning to
secrete and to deposit
the coat of enamel,
which is studded with
white spots. The figure
displays this state: the
spire is sinking behind
the elevated lips, which
are thickening; while
the spotted coat is seen
at one side, creeping
along over the back of
the shell, which it is
destined to cover.

At length the thick-
ening of the lips proceeds
to such an extent as
almost to conceal the
spire, and to reduce the
aperture to a narrow
line, the edges of which
are now thickly plaited with the tooth-like ridges
so characteristic of the genus. The lobes of the
mantle protrude through this aperture, and ex-
panding on each side, have deposited all over the
exterior of the shell a coat of glassy enamel,
studded with pale round spots, which entirely con-
ceals the transverse bands that were formerly visible
across it. ‘The appearance, therefore, is now such
as is represented in the following figures, which
most of my readers will readily recognise as those
of a familiar shell.

The deposition of enamel is the last process of

HALF-GROWN COWRY.

COWRIES. 169

the change, and one to which so much of the
beauty of these shells is indebted. It sometimes
happens that the glassy coat envelopes, while soft,

FULL GROWN COWRY.

any accidentally-intruding body adhering to the
shell, and, quickly hardening, detains it there.
Specimens of cowries are tound in collections, on
which other shells are fixed, firmly imbedded in
the enamel. As such accidents are rare, however,
it may be supposed that the frequent use of the
mantle-lobes to embrace the shell has a tendency to
prevent the adhesion of other shells.

170 PECTINIBRANCHIATA.—CYPRAEADA.

Some naturalists have supposed that the cowries,
precluded, as it appears, (beyond a certain point)
from enlarging their shells in the usual manner by
the increase of the last whorl, have the power of
forsaking their shells, and of forming new ones of
larger size, as a crab or lobster sloughs its crust.
Others believe that a process of gradual absorption
and deposition will meet the necessities of the case,
which, however, it must be confessed, presents con-
siderable difficulty.

The earliest stage of life im these animals, as,
we believe, in all the Gasteropoda, however diverse
their adult condition may be, appears under the
form of a nautilus-like shell, the inhabitant of
which is furnished with two large-winged lobes, by
which it is able to swim freely. Mr. Arthur Adams
thus describes the young of one of the cowries :—
‘“ While staying at Singapore, I had an opportunity,
in conjunction with Dr. Trail of that place, of ob-
serving the fry of Cyprea annulus, the species being
then in spawn. Several specimens collected by us
at low water, were seen to have conglomerated
masses of minute transparent shells, adhering to
the mantle and other parts of the animal, which
masses, when placed in a watch-glass of salt water,
under the microscope, became disintegrated, and
detached individuals were perceived quitting the
rest, and moving in rapid gyrations, with abrupt
jerking movements, by means of two rounded
flattened alar membranous expansions, reminding
one of the motions of some of the Pteropods.
When at rest, they jomed the principal mass, or
adhered, by means of their dilated expansions, to
the surface of the watch-glass.” *

* Zool. of Samarang, Part III. p. 23.

COWRIES. 171

According to the same observer, the minute

snail-hke shell of the young cowry forms the
nucleus of that which afterwards grows, and under-
goes the changes in form already described. The
young are very active, whirling giddily about
through the water, and occasionally adhering to
foreign bodies, not by any disk for the purpose,
but by means of the dilated expansions of the
mantle. In the course of growth, these fleshy ex-
pansions become entirely absorbed, and do not
ultimately constitute the lobes of the mantle which
embrace the shell in the adult.
_ One of the species (C. moneta) possesses an
interest, as forming a recognised currency in some
parts of Africa, and of further India. Their value
in Bengal is said to be as follows: 3,500 cowries
are equal to one rupee, or about 2s. 3d. sterling.
They are procured chiefly from the Maldives, and
the coast of Congo. After the spring-tides, women
collect the sea-sand in baskets; the cowries are
then picked out, and heaped up in the sun; the
animals soon dry up, and the shells, being cleaned,
are ready for the money-market.

Many of my readers are doubtless familiar with
our little native cowry
(Cyprea Europea). It
varles in size, from that
of a split pea to that of a
large horse-bean. It is
elegantly marked all over
with transverse ridges.
These ridges are por-
cellanous white, and the alternate furrows between
are purplish, or flesh colour. The larger specimens
commonly display three spots of dark brown,

CYPRHEA EUROPA,

172 PECTINIBRANCHIATA.—CYPRAHEADA.

arranged lengthwise. But probably few are aware
how very elegant a creature it is when tenanted by
its living inhabitant, and crawling at ease in clear
water. The foot, on which it glides with a slow
but smooth motion over the surface of the rock on
which it habitually dwells, or, if you please, on
the bottom of the saucer of sea-water in which you
are examining it, is a broad expansion spreading
out to twice the superficies of the base of the shell.
Above this is the fleshy mantle, which is so turned
up as closely to invest the shell, conforming to its
shape, and even fitting into the grooves between
the ridges. This mantle can be protruded at the
will of the animal, so far that the two sides meet
along the top of the shell, and completely cover it ;
or can be completely retracted within the wrinkled
lips beneath ; and it is capable of all gradations of
extension between these limits. From the front
of the shell protrudes the head, armed with two
straight and lengthened tentacles, answering in
function and appearance to the upper part of horns
in a snail; except that the little black points which
constitute the visual organs are not in this case
placed at the tips, but on a little prominence on
the outside of the base of each tentacle. Above
and between these, which diverge at a considerable
angle, projects the proboscis, a rather thick, fleshy
tube, formed by a flat lamina, with its edges bent
round so as to meet along the under side. The
interior of this proboscis is lined with delicate
cilia, by whose constant vibrations a current of
water 1s drawn into the tube, and poured over the
surface of the gills for the purpose of respiration.
This current may be readily perceived by any one
who will take the trouble to watch with a pocket-

COWRIES. 173

lens, as I have been this moment doing, a Cowry
crawling up the side of a phial filled with sea-
water. By placing the vessel between your eye
and the light, and fixing your attention on the
front of the proboscis, you will presently perceive
the minute particles of floatmg matter (always
held in suspension even in clear water) drawn in
various directions towards the tube, with a motion
which increases in velocity as they approach, and
at length rapidly sucked in and disappearing one
after another within. It is an interesting sight to
see, and one that cannot be looked on without
delight and admiration at this beautiful contrivance
of divine wisdom, for the incessant breathing of
the respiratory organs, in water charged with vivi-
fying oxygen.

Let us now look at the vivid hues of all these
organs. The foot, which expands to so great a
length and breadth behind the shell, is of a buff,
or pale orange-ground colour, delicately striated
with longitudinal undulating veins of yellowish
white. The mantle which embraces the shell is of
a pellucid olive, thickly mottled and spotted with
black, and studded with glands protruding through
its substance of light yellow; and it is edged with
a narrow border of red. The proboscis is ver-
milion-red, varying in brilliancy in different indi-
viduals. ‘The tentacula are of a paler tint, of the
same colour, speckled with yellow.

Such, then, is the beauty of the animal which
inhabits this familiar and plain little shell; a
beauty, of which those who know it only in cabi-
nets can hardly form an idea; while as one gazes
on it placidly gliding along, one cannot avoid an
emotion of surprise that such an amplitude of

174 PECTINIBRANCHIATA.—MURICID&. |

organs can be folded within the narrow compass of
the shell, and protruded through so contracted an
aperture.

Famity Muricipaé.
(Whelks, &c.)
The Rock-shells and the Whelks, with their

numerous allies, have commonly been considered
as constituting two families, the Muricide and the
Buccinide, or, to use the terms of Professor De
. Blainville, the Stphonostomata and the Entomosto-
mata. But by Messrs. Forbes and Hanley all
these mollusca are united in one family, under the
name first mentioned ; and this appears to be their
true relation to each other; for even De Blainville
confesses that his two families differ evidently very
little, whether in the soft parts or the shell.

The species which, thus united, are very nu-
merous, have the following characters in common :
The shell is very variable in form, but always dis-
tinctly spiral, often turreted, with an aperture vary-
ing im size from excessive width to excessive
narrowness, but always provided with a canal,
which is sometimes produced into a long gutter, at
others is contracted to a mere notch.

The animals are distinguished by a spiral body,
with the foot, which is shorter than the shell,
rounded in front. The mantle is furnished in front
of the breathing-chamber with a long canal,
always uncovered, which is used as an organ of
prehension. ‘I'he head is crescent-shaped, with a
protrusile, proboscis-like mouth, whence is unfolded
a ribbon-shaped tongue, armed with teeth arranged
in triple rows, of three in arow. ‘The breathing

WHELKS, ETC. 175

apparatus consists of two unequal plumes, the
leaflets of which are arranged like the teeth of a
comb. An operculum is for the most part present,
horny in texture, marked with lines which show
the layers of progressive growth, but varying much
in form, according to the different genera.

Some of the more prominent, or more interesting
of the genera composing this important group, I
shall slightly notice; and first of all, that fine
series of shells which gives name to the family,
the genus Murex. Many of the species are remark-
able for their brilliancy of colouring, and for the
beauty and singularity of the forms which they
assume. ‘The siphonal canal is sometimes greatly
lengthened, as in the species called the Wood-
cock’s-head (J. haustellum), and is occasionally
beset, as well as other parts of the shell, with long
shelly spines, as the Thorny Woodcock (M. tennis-
pina): often the progressive stages of growth are
marked by beautiful shelly foliations, as in the
magnificently-hued Royal Murex (J. regius) of
South America.

It was from various species of this family, but
preeminently from those of the genus Murex, that
the ancients obtained the purple dye which made
Tyre the “ crowning city.” This rich hue was of
great costliness ; its beauty has been celebrated by
poets and historians, and the very finest kinds were
reserved for the hangings of temples, and the robes
of kings and priests. In the reign of Augustus,
double-dyed purple wool was sold for about 36/.
sterling per lb. But as wealth would not hesitate
at any price to obtain that which was fashionable,
laws were enacted, rendering it penal for any one
but the emperor to wear cloth of this sort.

176. PECTINIBRANCHIATA.—MURICIDA.

The observations of Mr. Wilde have thrown a
confirmatory light on the accounts handed down to
us by ancient writers of the mode of procuring the
dye. ‘This gentleman, when visiting the ruins of
Tyre in 1838, found on the shore a number of
round holes cut in the solid rock, varying in size
from that of an ordinary metal-pot to that of a
large boiler. In these cavities, and scattered on
the beach around, lay large quantities of shells,
broken, apparently, by design, but subsequently
agglutinated together. It was evident that the
shells had been collected in quantities, and de-
posited in the cavities in order to be pounded in
the very mode described by Pliny, for the purpose
of extracting the purple dye contained in the
animal. ‘he broken shells proved, on examination,
to be all of one species, Murex trunculus, which
was known to have yielded the Tyrian purple, and
recent specimens of the same species were found.
on the adjacent beach.

In this family are placed the largest of univalve
shells, such as the Trztonium, of which one species,
richly clouded with brown and red like tortoise-
shell, is sometimes found two feet in length; and
the genus Cassis, well known as Helmet-shells, of
triangular form and ponderous structure. All these
are highly ornamented, especially the massive kinds
from the West Indies and the Indian Ocean. The
use of the helmets for the cutting of cameos has
been noticed in a former page of this volume ; but
some statistical details on the same subject may
not be uninteresting to my readers. They were
communicated by Mr. J. E. Gray to the Society of
Arts, in 1847.

Mr. Gray observed that numerous attempts have

WHELKS, ETC. 177

been made to substitute various materials, such as
porcelain and glass, for the ancient cameos (which
were cut in onyxes and other precious stones);
but their great inferiority has caused them to be
neglected. The best and now most-used substi-
tutes are shells, several kinds of which afford the
necessary difference of colour, and at the same
time are soft enough to be worked with ease, and
hard enough to resist wear. The shells used are
those of the flesh-eating univalves, which are pe-
culiar as being formed of three layers of calcareous
matter, the layers being;perpendicular lamine placed
side by side.

The cameo-cutter selects those shells which have
the three layers composed of different colours, as
they afford him the means of relieving his work ;
but the kinds now employed, and which experience
has taught him are best for his purpose, are the
Bull’s-mouth (Cassis rufa) from the Indian seas,
the Black Helmet (C. Madagascariensis), a West
Indian shell, the Horned Helmet (C. cornuta), from
Madagascar, and the Queen Conch (Strombus gigas),
a native of the West Indies. The first two are the
best shells.

After detailing the peculiarities of these shells,
Mr. Gray proceeded to give an account of the pro-
gress of the art, which was confined to Italy until
within the last twenty years, at which period an
Italian commenced the making of cameos in Paris ;
and now about three hundred persons are employed
in this branch of trade in that city. The number
of shells used annually, thirty years ago, was about
three hundred, the whole of which were sent from
England, the value of each shell in Rome being
30s. The increase of the trade is shown by the

N

178 PECTINIBRANCHIATA.—MURICIDZ.

following account of the number of shells used in
France in the preceding year :—

80,000 Bull’s-mouth, valued at . . . . £6,400
8,000 Black Helmet . J) i. (A ie ae
500 Horned Helmet _,, oe ipa ad ee Ve 60
12,000 Queen Conch 2 Sarat te 5 700
100,500 shells. Total Value . . . £8,960

The average value of the large cameos made in
Paris is about six francs each, giving a sterling
value of £32,000, and the value of the small
cameos is about £8 ,000, giving a total value of the
cameos produced in Paris for one year of £40,000,
while in England, not more than six persons are
employed in this trade.*

Those glories of a conchological cabinet, the
Harp-shells (Harpa), are also members of the
present family. The number of species is but
small, and they are all found in the Indian Seas,
especially around the Mauritius and neighbouring
islands, whence the finest specimens of the com-
mon species, as well as of the more valuable
Many-ribbed Harp, are procured for the European
collectors. The animal is brightly coloured, and
beautiful. The fishing for these shells is carried
on at low water, with a small rake, to which a net
is attached, on sand-banks, at night and at sunrise,
when the Harps principally roam about to feed.
They have been known to take the bait on the
fishing-lines laid for Olive-shells.

“The shells when in fine condition are great
favourites with collectors, and indeed a drawer of
fine Harps, in all the freshness of their beauty, 1s

* Atheneum, May 1, 1847.

WHELKS, ETC. Mies.

a sight worth seeing. Care should be taken to
keep them with their mouths downwards, and from
the sun and light, or their brilliant colours will
soon fade.” *

I must not omit to mention also, the more
homely, but at the same time, more useful Spindles
and Whelks of our own shores. The former genus
(Fusus) is remarkable for the size of its members.
F’. antiquus, the largest of British univalves, being
frequently found six and occasionally seven inches
in length. This shell is used by the mhabitants

WHELK.

of the Shetland Isles as a lamp, suspended horizon-
tally by a cord, the ample cavity being made to hold
the oil, and the wick projecting from the canal, The

* Penn. Cyclop.; art. ENTOMOSTOMATA.

180 PECTINIBRANCHIATA.—MURICIDA.

Whelk (Buccinum undatum), as many of my
readers well know, is extensively sold on stalls in
the streets of London. Hard, indigestible, and
unwholesome as it is, there are multitudes of the
poorer classes to whom it is a delicacy ; it is simply
boiled, and seasoned with vinegar and pepper.
With our ancestors it seems to have found a place
at tables of more pretension, for Dr. Johnston men-
tions, that at the enthronization feast of William
Warham, Archbishop of Canterbury, in 1504, no
fewer than 8,000 Whelks were supplied, at five
shillings a thousand. Whelks are caught in
creels or pots, baited and sunk in shallow water.
The genus, however, which I select specially to
exemplify the family is the following :—

GENUS PURPURA.

It was included by Linneus and his followers
under the great genus Buccinum, but has now been
separated to include a considerable number of
species having the following characters :—

The shell is oval, with the spine usually much
shorter than the aperture, which, in most of the
species, is very wide; the surface is sculptured
spirally, often forming fringed edges, or rows of —
knobs: the outer lip is rarely thickened, but is
commonly notched; the inner lip is ill defined,
covered with a glassy enamel; the pillar is broad,
flattened, and sometimes hollowed ; a short, strongly
notched canal is present, and a horny operculum.

The animal has a broad flattened head, with
two tentacles, the bases of which are thickened
by the union with them of the eye-stalks; a
reticulate proboscis, a long tongue, armed with

WHELKS, ETC. 181

teeth placed three in a row, of which the middle
one is three-pointed, and the outer ones hooked.
The mantle is produced into a short siphon; the
foot is ovate, notched in front and obtuse behind.

Nearly a hundred species of the genus are found
in the warmer seas, some of them of large size,
and almost ail with a very wide-spread aperture
and short spire. Our own common Dog-Winkle
(Purpura lapillus) approaches more nearly the
form of Buccinum: it is an exceedingly variable
shell in size, colour, and sculpture; its most com-
mon appearance is white or pale yellow, sometimes
banded with light or dark brown, and sometimes
wholly of a deep chocolate hue. The figure on
page 38 will enable my readers to recognise it,
especially as it is one of the most abundant of our
native shells, occurring by thousands on every
rocky shore.

I have already described in the introductory
chapter of this volume, the purple secretion
possessed by this mollusk, and the mode of apply-
ing it; the dye is common to the genus, and in a
greater or less degree to many genera of the same
family.

The Dog-Winkle is to be found attached to
rocks and stones between tide-marks, and few who
behold it sluggishly clinging to its hold, would
suppose that it is as ravenous and ferocious a
tyraut among its fellow mollusks, as the lion or
leopard among the flocks. Yet abundant evidence
exists to show that it habitually preys upon other
shell-fish, both univalves and bivalves. Mr. Hanley
has “seen a Purpura devour a Periwinkle in the
course of an afternoon, when placed in the same
vessel of sea-water, sucking its prey as it were out

182 PECTINIBRANCHIATA.—MURICID&.

of the shell, after placing the orifice of its own
body-case against that of its victim.”

From Mr. Stevenson’s interesting account of the
erection of the Bell-Rock Lighthouse, we learn that
the valves of the Mussel are no defence against
the Dog-Winkle.

‘When the workmen,” says this gentleman,
“first landed upon the Bell-Rock, limpets of a
very large size were common, but were soon
picked up for bait. As the limpets disappeared,
we endeavoured to plant a colony of mussels from
beds at the mouth of the river Eden, of a larger
size than those which seem to be natural to the
rock. These larger mussels were likely to have
been useful to the workmen, and might have been
especially so to the light-keepers, the future in-
habitants of the rock, to whom that delicate fish
would have afforded a fresh meal, as well as a
better bait than the limpet; but the mussels were
soon observed to open and die in great numbers.
For some time this was ascribed to the effects
of the violent surge of the sea, but the Buccinum
lapillus | Purpura| having greatly increased, it was
ascertained that it had proved a successful enemy
to the mussel. The Buccinum being furnished
with a proboscis capable of boring, was observed
to perforate a small hole in the shell, and thus to
suck out the finer parts of the body of the mussel ;
the valves of course opened, and the remainder of
the fish was washed away by the sea. The per-
forated hole is generally upon the thinnest part of
the shell, and is perfectly circular, of a champhered
form, being wider towards the outward side, and
so perfectly smooth and regular as to have all the
appearance of the most beautiful work of an expert

WHELKS, ETC. 183

artist. It became a matter extremely desirable to
preserve the mussels, and it seemed practicable to
extirpate the Buccinum. But after we had picked
up and destroyed many barrels of them, their
extirpation was at length given up as a hopeless
task. The mussels were thus abandoned as their
prey, and in the course of the third year’s opera-
tions, so successful had the ravages of the Buccinum
been, that not a single mussel of a large size was
to be found upon the rock, and even the small
kind which bred there, are now chiefly confined to
the extreme points of the rock, where it would
seem their enemy cannot so easily follow them.”
The mode in which the Purpura actually per-
forms the operation, has been described by Mr. Spence
Bate from observation. ‘The Whelk,’’ he observes,
*“* attacked the Mussel, but it bored where there
was no epidermis. I pulled it off, and turned the
Mussel upside down (the other valve having more
epidermis upon it), but in a short time I returned,
and found that the Whelk had turned over the
Mussel, and had resumed its operation at its old
bore. This I did twice or thrice, with the same
result. Giving up the idea of its boring at any
other point, I next thought I should like to see
how it managed to devour its prey. For this pur-
pose I divided the muscles of the Mussel, so that
the valves parted, so as to enable me to observe
the work of gormandizing as it proceeded, but to
my surprise, the-animal gave up all idea of boring,
when there was an easier method of obtaining food,
and so passed its proboscis between the valves.
I think this shows that the Whelk, when it attacks
its prey, seeks out for the part most suitable for its
operation, and I believe invariably chooses a point

184 PECTINIBRANCHIATA.—MURICIDA.

from which the epidermis has been removed pre-
viously. A section of the bore, taken during
the operation, shows that it is convex, and con-
tradicts the received notion of the operation being
performed by the action of the ribbon, which
being in the centre of the proboscis, would perforce
wear the middle of the bore deepest, but this is
not the case. The animal makes no movement of
a rotatory kind or otherwise, during the operation.
It takes about two days to get through the shell,
when it eats about two-thirds of a moderate-sized
mussel, which seems to satisfy hunger for about
three weeks.” *

The curious inquirer after the many natural
objects which the receding tide reveals, may occa-
sionally see in the spring months as he peeps into
the crevices of the rocks, a number of little urn-
like bodies crowded together, and standing erect
from the rock. They are about the size of a grain
of wheat, to which they bear no small resemblance,
being of a yellow colour, but tinged as they
approach maturity with reddish-purple. ‘These are
the egg-capsules of the Dog-Winkle. Réaumur
states, that the purple dye is obtained from these
vesicles with less trouble than from the animal;
an assertion which by no means agrees with my
experience. ‘he membrane of which they are
composed is very tough, but if we cut it open we
find that each contains many infant mollusks, all
inclosed, as the period of birth draws nigh, in-their
tiny shells.

Mr. Peach, who bred the animals from the cap-
sules, observed that the latter change form as the
included young ones ripen, the apex of the cup

* Forbes and Hanley’s Br. Moll. iii. 385.

WHELKS, ETC. 185

becoming thinner and more convex. He found
that so long a time as four months elapsed before
the vesicle opened, and then the included whelklings
did not quit their cradle all at once, but took their
time in coming out, according to their individual
dispositions ; doubtless, the quick-minded and more
curious commencing their travels first, whilst those
of slow and studious constitutions would remain
as long as a fortnight before resolving to see the
world, which with young Purpurew is no very
dangerous adventure, since the neighbouring bar-
nacles enable them to look about with safety,
before making a long journey from their birth-
place.*

FAMILY VELUTINIDA.

A small and unimportant group is indicated by
this name, represented in Britain by two genera,
each consisting of two species. ‘They have a shell,
the aperture of which is very broad and open, and
the spire minute ; in texture it is thin, sometimes
pellucid, and sometimes even membranaceous. In
one genus it is entirely included within the sub-
stance of the mantle, as in Pleurobranchus: in the
other it is external, but partially invested by the
edges of the mantle, and covered with a skin
(epidermis).

The animal is large, with a short broad head,
furnished with two tentacles, and eyes at the
exterior of their bases. ‘There are two gill-plumes.
The operculum is wanting.

Our most common species is Velutina laevigata,
reckoned by Linnzeus among the snails, and long
supposed to be a fresh-water mollusk ; it is, how-

* Cited in Forbes and Hanley, iii. 384.

186 PECTINIBRANCHIATA.—NATICADA.

ever, exclusively marine, and generally inhabits
deep water. It is an open-mouthed shell, about
half an inch in diameter, of a dull reddish hue,
covered with a furry epidermis. Messrs. Forbes
and Hanley distinguish it from its fellow species
by affirming that it is not membranaceous, but this
does not agree with my own experience; the
specimens that have fallen under my notice having
been quite flexible and membranaceous, especially
near the margin. Nothing is known of its habits.

Famity NATICcADé.
(Naticks.)
The shell in this family is globose, with the

spire minute and scarcely raised; the surface is
generally smooth, and often covered with a porce-
lain-like polish; the aperture is large and semi-
circular; the pillar is always thick and solid, and
its exposed part, constituting what is technically
known as the inner lip, is often very broad.

The animal is large in proportion to the shell,
yet capable of being wholly withdrawn into it.
The mouth is not extended into a proboscis, but is
concealed beneath a broad hood or veil. When
the eyes can be recognised, they are placed at the
bases of the tentacles. The mantle is entire, that
is, its edges are not cut into filaments. An oper-
culum is always present, sometimes horny in
texture, sometimes shelly, but invariably closing
the wide aperture of the shell.

Though the genera comprised in this family are
few, the constituent species are numerous, and
widely scattered in geographical distribution. For

NATICKS. 187

the most part they are marine, but some inhabit
rivers and lakes of fresh water; and M. Lesson
affirms of one species which is found in Australia,
that it lives abundantly on trees. Some of the
Neritine are ascertained, on indubitable authority,
to live indifferently in the sea and in fresh-water.

GENUS NATICA.

Handsome globose shells, with a smooth surface
as if varnished, and with a very wide aperture,
compose this genus, which is technically distin-
guished by having the inner lip smooth, not
depressed; the umbilicus open, with a central
gibbous ridge or prominence, and the operculum
formed of shelly substance.

The animal is large, slimy, and slug-like, with
the foot so enormously developed as to communicate
to the creature a most remarkable aspect when
seen crawling. It is a long oval plate of soft flesh,
commonly squared in front, and rounded or notched
behind. ‘The forepart, where it is widest, forms a
thick sort of shield, somewhat eared, which is
turned up on the front of the shell, partially
covering it, and hiding the whole head of the
animal, except the tentacles, which project from
behind it. The hind part of the foot, and the
sides also, partially envelope the shell, of which
only the summit is seen, apparently embedded in
an immense mass of white flesh. The operculum,
notwithstanding its large size, is not visible when
the animal is in motion, beimmg hidden by the
extremity of the shell.

When one beholds the great volume of fleshy
substance which the animal displays when crawling,

188 PECTINIBRANCHIATA.—NATICAD A.

we can scarcely believe that it can possibly be
withdrawn into the shell ; yet this is easily effected,
and that so completely, that the closely-fitting

NATICA,

operculum is seen, shutting the aperture consider-
ably within the margin. It is performed, however,
if I may judge from my own experience of several
British species, with some difficulty, and by a
succession of efforts; and the animal when once
forced by annoyance to retire, is often ill-disposed
to protrude again, at least for a considerable time.

The species of the genus are widely distributed,
and are most numerous within the tropics. Several
of them are of large size. Seven or eight species
are found on the British shores, of which the finest
is Natica monilifera.

In this large and handsome shell, the form is
globose, nearly as broad as long; it is strong
but not solid, smooth and glossy, though with a
few fie sunken lines, which mark the progressive
growth. ‘The ground-colour is whitish, sometimes
tinged with flesh-red, or with bay, and each whorl
is marked along its upper margin with a line of
oblique but parallel dashes of rich chestnut.

NATICKS. 189

The animal, in such specimens as I have seen,
is almost wholly of a pure milk-white hue. It is,
as already stated, very large, the long oval foot
extending far beyond the outline of the shell on
every side, and partly inclosing it. Messrs. Forbes
and Hanley state that this is a local species, found,
however, on most parts of our coast where sand is
plentiful. I have taken it by dredging in Wey-
mouth Bay, where it seems a common species,
together with N. Alderz. Both of these animals
have a curious habit, which I have not seen
noticed. ‘They are said to live burded in sand, but
I believe this is only to a partial extent. When
put into an aquarium with a sandy bottom, they
soon begin to crawl just beneath the surface of the
sand, the foot alone being immersed in it; and this
organ as it slowly moves along, deposits and leaves
behind a broad belt of clear mucus, of slight
density. The progress of the creature through the
fine soft sand,-is very curious to witness.

In places where this Natica is common, the
dredge not unfrequently brings up its spawn-masses.
Professor Harvey in his delightful ‘“ Sea-Side
Book,” thus speaks of them.— “ These ege-clusters
are really very curious and elegantly formed objects,
which must often have attracted the notice of a
rambler, who felt puzzled to know what they
were. They are firmly gelatinous, or of the
consistence of gristle, transparent, or nearly so,
slightly coated with fine sand, and in shape
resemble the hoof of an animal. When dry, they
look not unlike pieces of thin Scotch oaten bread.
The surface is marked with little hexagonal spaces,
which define the eggs. But what is most to be
admired in the structure, is the form of the curves

190 PECTINIBRANCHIATA.—NATICAD.

which the hoof-like body assumes, which fit it for
lying on loose sand, without becoming deepl
buried in it.”** I am inclined to believe that the
original form of this egg-mass is that of a very
broad ribbon, attached by one edge to a rock, like
that of a Doris, in a spiral curve, the upper edge
of the ribbon leaning outwards a little, so as to
resemble a cup, and that the likeness to a horse-
hoof which Professor Harvey alludes to, and which
I have myself observed, is seen only when the
ribbon is torn away by the dredge, and turned
upside-down. This curious mass of eggs was
considered to be a zoophyte by the earlier natu-
ralists, and was characterised as such by Gmelin,
under the name of Flustra arenosa. Its true
nature was first suspected by Mr. Boys, and was
fully proved by Mr. Hogg, in 1833, who hatched
the Natica from it.

The species of this genus are all carnivorous,
boring holes into other shells and devouring their
contents. Dr. Gould asserts that they are very
voracious, and play a conspicuous part in devouring
the dead fish and other animals which are thrown
up by the tide. The small circular holes with
which bivalve shells are often drilled, are the work
of these snails, and made by them to gain an
entrance to the animal apparently so well secured
against such a foe. The foot can be expanded so
as to envelope completely the objects on which they
prey, for a long retention of it in its grasp is
necessary, from the slowness with which they work
their auger or spiniferous tongue.

* Sea-Side Book, p. 33. + Linn. Trans. 18338.
+ Invertebr. of Massachusetts, 232.

STYLIFER. 191

FAMILY PYRAMIDELLADA.

This is an extensive group of small, and for the
most part, minute shells, which often display much
beauty to the close observer; their forms being in
general elegantly turreted, their surfaces smooth,
often polished, or ornamented with the most beau-
tiful and elaborate sculpture. The aperture is
entire, and not lengthened into a canal; the pillar
or inner lip is often plaited.

The animals are furnished with a retractile
proboscis, and with tentacles of varying form,
with the eyes not set on footstalks, but immersed
in the bases. The tongue is remarkable for being
unarmed with teeth.

As the fossil remains of a former world present
the extinct forms of this family in great numbers
and variety, the group is one of much interest to
the geologist.

GENUS STYLIFER.

I select the genus Stylifer to illustrate the
family, because of its singular form and still more
curlous economy, rather than for its abundance in
these latitudes, for it is represented on the British
coast by a single species, and that of very rare
occurrence.

The shell is somewhat globose, with the tip
slender, and projecting in the form of a little
point or style; its surface is smooth and polished ;
its whorls are numerous. ‘There is no operculum.

The animal has slender tentacles, and eyes
immersed at their bases; the mantle has been
described as thick, fleshy, cup-shaped, enveloping

192 PECTINIBRANCHIATA.—PYRAMIDELLADA.

the last whorl of the shell, but Mr. Adams from
observation on the living animal, informs us that it
is entirely enclosed and covered by the thin shell,
while the foot is narrow, slender, and very much
produced beyond the head in front.

The habits of this teresting mollusk are most
singular, for it is found to live parasitically upon
the animals of the class Hchinodermata (Star-fishes
and Sea-Urchins). Three species are known, one
of which (Stylifer Turton?) is a rare inhabitant of
the British seas. Dr. Turton, how-
ever, its discoverer, found no fewer
than a dozen attached to the spines
of Hchinus sphera, dredged in 'Tor-
bay. It has since been found in
several localities, as on the coasts
of Northumberland, Durham, and
Cork, always under similar circum-
stances. Mr. Alder states, that it occurs on young
Sea-Urchins.

A fine species was discovered in the Indian
Archipelago by Mr. Hugh Cuming, and named
S. astericola. He found this elegant parasite
burrowing in different parts of the oral dise of
Asterias solaris. It was almost hidden from sight,
so deeply does the animal penetrate into the sub-
stance of the star-fish, in which it makes itself a
comfortable cyst (or cell) for itself, and wherein it
most probably turns by aid of its rudimentary foot.
All the specimens infested with these testaceous
mollusks appeared to be in the best health, though
there is reason to believe that they feed upon the
juices of the Star-fish. Mr. Broderip observes that
Stylifer (with that instinct of self-preservation which
is imparted to all parasites whose existence depends

STYLIFER.

WENTLETRAPS. 193

upon that of their nidus) appears, like the larve of
the ichneumon tribes among insects, to avoid the
vital parts; for in no instance did Mr. Cuming find
it imbedded anywhere save in the rays, though
some of the individuals had penetrated at their
base, and very near the disc. When extracted, the
older shells have the appearance of a milky-clouded
glass bubble: the younger shells Mr. Broderip

found of an unclouded transparency.

FAMILY SCALARIADA,
(Wentletraps.)

Though very limited in numbers, this family is
interesting to the conchologist as containing some
species of singular form and remarkable beauty,
one of which was formerly valued so highly as to
command enormous prices, and to have acquired
the name of the Precious Wentletrap. “ In this
family a spiral shell with an entire aperture is
combined with an animal whose head is not pro-
duced into a muzzle, but furnished with a retractile
trunk. The sexes are distinctly separated. The
eyes are immersed at the external bases of subulate
(awl-shaped) tentacles.” The dentition of the
ribbon-like tongue is very peculiar; there is no
central tooth differmg from the rest, but all are
alike, arranged in transverse rows, ‘and forming
simple claw-like hooks. The animals are probably
predaceous like the Whelks, &c. Most of the
species, which amount to nearly a hundred, inhabit
the seas of warm climates, though a few are found
on our own shores.

O

194 PECTINIBRANCHIATA.—SCALARIADA.

GENUS SCALARIA.

The shell is spiral, consisting of many whorls,
assuming a turreted form, ornamented with many
elevated ribs, which cross the whorls in the same
direction as the length of the shell; the aperture is
rounded, with the lip thickened and entire. There
is a horny operculum.

The animal has an angularly lunate head, with
two long pointed tentacles, and eyes immersed at
their bases; the mouth, which opens below, has a
retractile proboscis; the’ mantle is rudimentary ;
the foot is triangular, grooved beneath, and fur-
nished in front with a fold.

In the principal section of the genus, confined to
the warmer parts of the globe, the whorls or turns

PRECIOUS WENTLETRAP.

of the spire do not touch each other in any direc-
tion: these are designated trwe Wentletraps, In
this division is placed the shell above alluded to,

WENTLETRAPS. 195

the Precious Wentletrap or Royal Staircase (Sca-
laria pretiosa), a large shell, twisted into a loose,
untouching spiral, of a pale yellow hue, ornamented
with ribs of pure white. ‘This is always a prized
addition to a cabinet, for it is undoubtedly a shell
of extraordinary beauty ; but the value which was
attached to it in former years can only be considered
as a phase of insanity, analogous to the well-known
tulip mania, and other fantasies of a like kind. In
1753, at the sale of Commodore Lisle’s shells at
Longford’s, four Wentletraps were sold for seventy-
five pounds twelve shillings: viz. one not quite
perfect, for sixteen guineas; avery fine and perfect
one for eighteen guineas; one for sixteen guineas ;
and one for twenty-three pounds two shillings.*

But higher prices than these have been given.
That in Mr. Bullock’s museum, supposed to be the
largest known, brought at his sale the sum of 271.,
and was estimated in 1815 at double that value;
and there is a tradition that a specimen was sold
in France for 2,400 livres, or 100 louis!

Another section, known as false Wentletraps,
have the whorls contiguous; and many of these
species are European. Some of them secrete a

COMMON WENTLETRAP.

purple liquor, as has already been noticed in these

pages respecting our commonest native species, S.

communis. This shell is turreted, usually about
* Da Costa’s Elements, 204.

196 PECTINIBRANCHIATA.—CERITHIADZ.

an inch and a quarter in length, of a pale bay or
drab hue, with prominent ribs, spotted with purple.
The animal is blackish-grey speckled with white.
The Wentletraps inhabit rather deep water, and
affect a sandy or muddy bottom: hence they are
obtained only by dredging. The species just de-
scribed has been procured at various parts of our
coast, but principally on the shores of Devonshire.

FAMILY CERITHIADA.

This group, as defined by our latest malacolo-
gists, includes shells which at first sight appear to
be very dissimilar, as the slender turreted Cerathium
and the broad-lipped Pelican’s foot. ‘The genera
are ‘remarkable for the muzzle-shaped heads and
corresponding features of organization of the animals
which construct them.” ‘They seem to constitute
a group intermediate between those comb-gilled
Gasteropoda which have entire mouths, and those
which are furnished with siphons, partaking of and
mingling many of the characters of both.

GENUS APORRHAIS.

A thick, massive, many-whorled shell marks
this genus, subject to much alteration in form as it
advances in age. In youth the aperture is simple,
slightly angular, with a moderate canal; in adult
age the canal becomes lengthened, and the outer
margin of the shell is produced into a wide wing-
like expansion, the edge of which projects in di-
verging lobes or finger-like processes.

The animal has a long muzzle; cylindrical ten-
tacles, with the’ eyes placed on prominences at

PELICAN’S FOOT. 197

their bases; the mantle digitated, loose, with a
rudimentary siphon; the foot short, angular in
front, and obtuse behind; the branchial plume
single; the operculum horny.

We have two native species, called the Cormo-
rant’s foot (A. pes carbonis), and the Pelican’s foot
(A. pes pelicani). Of these the former is exceed-
ingly rare, the latter very common. The name in
both cases is derived from the wing-like expansion
of the adult shell resembling the webbed foot of a
sea-bird. The Pelican’s foot is the larger shell,

PELICAN’S FOOT.

measuring commonly about two inches in length,
and nearly an inch and a half in width, when full
grown. Its colour is yellowish, with clouds and
spots of chestnut brown. ‘The animal is yellowish-
white, marked with scarlet spots, especially about
the head and on the tentacles. It is commonly
brought up by the dredge, particularly from a
gravelly bottom. In captivity it is uninteresting,
as it remains sluggish and inactive, obstinately

198 PECTINIBRANCHIATA.—TURBINIDA.

keeping its body contracted within the shell.
Though I have kept many specimens, I have
never seen one crawl.

FAMILY TURBINIDZ.
(Winkles.)

An immense assemblage of species, some of
which are of large size and great beauty, is com-
prised in this family. The animal is spiral, with
the sides occasionally ornamented with tentacular
appendages differmg in number and form; the
head is protruded somewhat in the form of a pro-
boscis, furnished with slender thread-like tentacles;
the latter carry at their bases’a pair of eyes, usually
raised on footstalks; the mouth has no tooth on
the lip, but is provided with a ribbon-shaped tongue
of great length, rolled up spirally when not in use,
and carried in the cavity of the body. A furrow
passes across the foot near its front border; the
gills consist of two fringes.

The shell is thick and solid, often more or less _
pearly on the inside, forming a spiral cone, with
the opening round or slightly depressed. ‘There is
an operculum, which is calcareous (shelly) in some
species, horny in others; in the latter the spiral
formation is visible on the outside, in the former
on the inside.

All the members of this family are believed to
be vegetable feeders, subsisting on the sea-weeds,
the substance of which they rasp down by the
action of their rough tongue. Yet the large and
beautiful Phastanella bulimoides, an Australian
species assigned to this family, is said by MM.
Quoy and Gaimard to be taken in nets baited with
flesh, and let down into the sea.

WINKLES. 199

GENUS LITTORINA.

The shell in this common and well-known genus
is spiral with but few whorls, generally more or
less oval in form, and thick and solid in substance.
The spire is sometimes pointed, as in the common
Periwinkle (Z. littorea) ; sometimes obtuse or round,
as in the equally common Yellow Winkle (L. ner?-
toides). ‘The aperture is round and entire; the
outer lip is sharp-edged, thickened within. The
operculum is horny and elastic; its spire consists
of a few turns, rapidly enlarging, with a central
nucleus.

In most of our seaport towns, and in many of
our inland cities, the Periwinkle is sufficiently
familiar, from its being so commonly sold by mea-
sure as human food. ‘The animals are found by
thousands on rocks at low-water, or on the mud
left exposed by the receding tide in harbours and
estuaries; they are collected by the children of
fishermen, boiled, and hawked about the streets at
alow price. They are eaten not infrequently by
persons above the lowest grade of society, not
from necessity, but from choice; though to most
uneducated palates they are coarse, tough, and
indigestible.

The Periwinkles are able to bear long-continued
exposure to the air with impunity. The species
just mentioned may be observed adhering to the
rocks by hundreds under a hot sun, and that for
hours together; but a smaller kind (ZL. rudis),—
which may be recognised by its being frequently
found white, pale-green, yellow, and orange in
eolour,—habitually resides in hollows of rocks that
are elevated many feet above the range of high-

200 PECTINIBRANCHIATA.—TURBINIDA.

water. But their gills are constantly moistened
by a minute quantity of sea-water contained in the
cavity of the body; and this is prevented from
evaporation, partly by the close adhesion of the
margin of the shell to the rock, and partly by the
tightly-fitting operculum.

Indeed there is reason to believe that this and
some other species of the genus spend the winter
in the air, hybernating, like the Snails. ‘“ Mr.
Gray found that many individuals of L. petrwa, and
some of LZ. rudis, were in this condition, during his
stay at Dawlish. They were attached to the rocks
several feet above the reach of the highest autumnal
tides ; the foot was entirely retracted ; and a mem-
branous film was spread between the rock and the
edges of the outer lip of the shell; the gills were
only moist, the branchial sac being destitute of
that considerable quantity of water which exists in
it in those of the same species which are adherent
to it by their expanded foot. In this torpid con-
dition the individuals observed by Mr. Gray con-
tinued during the whole of his stay, which lasted
for more than a week. On removing several of
them, and placing them in sea-water, they recovered
in a few minutes their full activity.”’*

In Sweden the common people affect to prognos-
ticate the weather by the position of the Periwin-
kles ; when these ascend the rocks, it is considered
as a sure sign that a storm is near, as their instinct
leads them to place themselves out of the reach of
the dashing of the waves; on the contrary, when
they descend upon the sands it is supposed to indi-
cate calm weather. I much doubt, however, the
fact of any such connexion between the habits of

* Proc. Zool. Soe. iii. 116.

WINKLES. 201

the Winkle and the state of the atmosphere, and
still more, the philosophy of the reason assigned
for the habit.

The plant-eating Gasteropoda are said to “lay
their eggs merely enveloped in a mass of jelly, just
firm enough to retain its form in the water, and
which, deposited on the fronds of sea-weed, or on
the surface of rocks and stones, adheres to them
with tenacity. The form of the mass is roundish,
oval, or oblong, and it may be more complex in
some. ‘The ova are always immersed in the mass,
which forms a common bed to the whole; but
besides this, each egg (or at most three or four
eggs) has its own proper globule of jelly, con-

SPAWN OF PERIWINELE,
(magnified).

tained within a skin or pellicle of the greatest
tenuity, and which isolates it from the rest.””*
_ The accompanying figure, which is copied from
Dr. Johnston, represents the mass of spawn laid
* Johnston’s Introd. to Conch, 351.

202 PECTINIBRANCHIATA.— PALUDINADZ.

by the common Periwinkle, in which each of the
infant animals is seen enclosed in its proper
globule, and covered already with a shell of a
single whorl.

The Periwinkle (L. littorea) is
subject to much variation in
form, colour, and markings; it
is generally about an inch in
height, globose, very thick, with
the margin thin; the colour is
russet brown, or olive, sometimes
yellowish, with spiral bands of
black. The ground colour oc-
casionally becomes a rich orange
: or scarlet, with or without black
PERIWINKLE. bands; and these varieties are

very handsome.

FAMILY PALUDINADA.
(Marsh Snails.)

This is a group of fresh-water Mollusks, so
closely resembling the Periwinkles in many of
their characters as to have been confounded with
them by Cuvier and other zoologists. ‘Those cha-
racters are as follows :—

The shell is conical, spiral, thin in texture,
covered with an olive-coloured skin; the orifice is
ovate, entire, but angular behind. The animal
has a muzzle-shaped head, and long, slender ten-
tacles, with eyes seated at the outer side of their
bases ; the gills are always enclosed in the breathing
cavity. An operculum 1s always present, generally
horny, but sometimes shelly, formed of concentric

MARSH SNAILS. 203

lamine ranged round a nucleus commonly placed
in or near the centre.

Unlike the great majority of the Comb-gilled
Mollusca, the members of this family are confined
to fresh waters, inhabiting lakes, streams, and
marshes. ‘They are distributed all over the world;
and occur in a fossil state as far back as the oolitic
series. The fine globose shells which are found in
the rivers of tropical countries, known as Apple-
snails (Ampullaria), are but slightly separated from
this family.

GENUS BITHINIA.

In addition to the family characters, those which
distinguish this small group are, that the opercu-
lum has a thick shelly coat on the inner surtace,
and has the nucleus nearly central; and that the
aperture of the shell has a slightly thickened rb,
along the interior of the margin.

Two species of this genus are found in the
streams and ditches of this
country, the more common of
which is the Tentacled Bi- ==
thinia (Lithinia tentaculata).
It is about half an inch in
length; the shell is often
covered with a blackish foul
coat; the spire is composed of
five whorls, the lowest of which

: é : wy
is swollen. The animal is =
purplish black, with brillant BITHINIA TENTACULATA,
yellow specks. eee genied).

This genus, like the Mollusca generally, pro-
duces eggs, while its fellow-genus Paludina is
viviparous. The mode in which the eggs are laid

204 PECTINIBRANCHIATA.—NERITID A.

is curious, and has been particularly described by
M. Bouchard Chantreaux. According to this careful
observer, the Tentacled Bithinia lays from May to
August.

Famity NERITIDA.
(Nerits.)

A single British species represents a family
which, in warmer climates, plays a conspicuous
part along the shores of the ocean, and in their
rivers and lakes. ‘The members have solid shells,
more or less oval, the last whorl so greatly de-
veloped as to occupy by far the principal portion,
the aperture very open, somewhat crescent-shaped,
with an expanded and flattened inner lip.

The animals have broad muzzle-shaped heads,
with awl-shaped tentacles, and eyes on short foot-
stalks; the foot is somewhat three-sided, without
any lateral filaments. An operculum is always
found, which is spiral, semi-oval, and furnished
with two internal processes on its front edge, form-
ing a sort of hinge on the sharp edge of the inner
lip of the shell. Dr. J. HE. Gray thinks that this
peculiar structure of the operculum ‘“ makes this
family more closely resemble the bivalve shells :
the processes appearing to answer the same purpose
(that of keeping the two parts in their proper situ-
ation) as the teeth of the hinges in the bivalves.”

GENUS NERITINA.

The shell in this genus is semi-oval, without
any perforation; the inner lip is slightly toothed,
sharp-edged ; the surface is smooth, or striated, or
spinous, covered with a skin.

NERITS. 205

The animal has two slender tentacles; a rather
short foot, three-sided in outline, with the angles
rounded. The tongue is armed with rows of teeth,
differing much in form and size. The operculum
is semi-oval, slightly shelly, with a sharp, flexible
outer edge, and a tooth on its lower margin.

Many species are assigned to this genus, the
greater number of which inhabit fresh-water rivers,
especially of tropical countries, where they adhere
to stones with considerable tenacity. Yet there is
a species which inhabits one of the great North
American rivers, through a range of two hundred
miles, from the mouth, where the water is quite
salt, to beyond the reach of the tide, where it is
perfectly fresh. Another species is found only in
the sea.

When the animals have arrived at their full
size, they have the power of absorbing the shelly
matter of the divisions which separate the whorls
of the spire, so as to allow more room for the spiral
body, without increasing the size of the shell.
This reduction of substance is accomplished with-
out endangering the strength of the shell, as only
a very small part of the whorl is exposed on the
outside.

Our single native species (Neritina fluviatilis)
is about three-eighths of an inch long, and two-
eighths broad; usually of a pur-
plish hue, banded or chequered
with spots of white; but the
colouring of different specimens
varies exceedingly. ‘The animal
is white, with the head and neck
black. Itisfound chiefly in slow- “*277*4 FUUVtAtTIEIS:
running streams, adhering to stones. The shells are

206 PECTINIBRANCHIATA.—TROCHID A.

often covered and disguised by irregular incrusta-
tions of calcareous matter, deposited by the water,
which may serve as a protection to the animals,
causing them to take the appearance of rough
stones or masses of earth. This species, like all
its fellows, displays very little of its body when
crawling.

FAMILY TROCHIDA.
(Top-shells.)

An extensive group of very fine shells is in-
cluded under the above appellation, many of which
are of considerable size, of very regular and ele-
gant shape, and of exquisite beauty of colour, and
sometimes of sculpture. Our own shores possess
many species, among which are some of the finest
of our univalve shells, and specimens distinguished
by all of these characteristics. Yet the finest
species are, as usual, exotic, and tropical; for the
great Pearly Top (Zrochus pica) of the West
Indies, the Imperial Sun (Imperator imperialis)
of Australia, and the Perspective Staircase (Sola-
rium perspectivum) of the Indian Seas, belong to
this family.

The shell in this large group varies considerably
in form, but is always spiral; the spire sometimes
is drawn out to great length, at other times so
much depressed as to be nearly flat; but it always
forms a large portion of the shell. The aperture
is entire, without notch or canal, as the animals
are destitute of a siphon.

The animal has a head terminating in a broad
muzzle, and often ornamented with head-lobes ;
side-lobes greatly developed, and furnished with

TOP-SHELLS. 207

lappets and tentacular filaments, a pair of true
tentacles, and eyes fixed on footstalks behind their
bases; the gill-plume is single; and an operculum
is always present, spiral in structure, commonly
circular in shape, and either horny or shelly in
texture.

GENUS TROCHUS.

Even a glance at the British species of this
genus would show the great diversity that subsists
in the external form of the shell, from the regular
pointed cone, in which the whorls do not break
the uniformity of the outline, as in the beautiful
T. granulatus and T. striatus, &c., to the tubercled,
almost hemispheric form of 7. magus, in which the
swollen and knobbed whorls project like a winding
staircase round a pictorial ‘“‘ Tower of Babel.”

The aperture is entire, usually angular, and ap-
proaching to a four-sided figure, and opens on a
plane which is oblique with respect to the axis of
the spire. The interior of the shell is pearly.

The animal is considerably developed; it is
furnished with a pair of tapering tentacles, and
two eyes set at the ends of stout footstalks. Be-
hind these, on each side, is a large lappet, which
merges into a broad wing-like expansion of the
mantle, bearing commonly three, sometimes more,
tentacular filaments, which are probably delicate
organs of touch. ‘The foot is oblong, more or less
lengthened, carrying on its posterior part an oper-
culum, which is composed of many spires, of horny
texture.

Of the sixteen species which are enumerated as
inhabitants of the British seas, one of the most
beautiful, and certainly the largest, is the Granu-

208 PECTINIBRANCHIATA.—TROCHIDA.

lated Top (Trochus granulatus). It is esteemed a
local and rather rare shell, being confined to our
southern shores and the Irish Sea. I find it

TL

(t Mah ly

HG NA OOl

a) \ )) yr <h

PE gE Vn 7 Wel Mil
“Tay i

GRANULATED TROCHUS.

quite common in Weymouth Bay, in from eight
to twenty fathoms. It not unusually attains a
height and a breadth of an inch and a quarter,
and has been taken of an inch and a half. Its
shape is elegantly conical, with the base rounded ;
the whorls scarcely break the regularity of the
outline ; they are sculptured with spiral raised lines,
each of which is composed of a number of minute
rounded knobs, like a string of beads. The texture
of the shell is thin and rather fragile; its ordinary
tint is a pale flesh-colour, or yellowish white, with
a few scattered dashes or short streaks of purple,
that run parallel with the spiral lines.

The animal is large and handsome, with the
lobes and wing-like appendages much developed.
It is white, speckled with brown, especially about
the head.

KEYHOLE-SHELLS. 209

All the species of the genus feed on marine vege-
tables: I have watched with pleasure the little
Grey Top (Z. cinerarius), the commonest species
of our weed-clad rocks, rasping down with the
teeth of its ribbon-lke tongue the minute Con-
ferve that grow on the inside of my glass vases.
With a pocket lens it is easy to see the process,
which I can compare to nothing else than the mode
in which a cow licks up, as it were, the grass, as she
moves along, by successive sweeps of her tongue.

FAMILY FIsSURELLADZ.
(Keyhole-shelis.)

In external form and appearance, the shells
which compose this group bear the closest resem-
blance to the Limpets (Patellade). All of them,
however, have the peculiarity of an orifice in the
shell, either at the summit of the cone, or in the
form of a slit at the front edge.

The characters of the included animals dis-
tinguish them at once; they have well-developed
heads, with short muzzles, and tapering tentacles,
at the outer bases of which the eyes stand on short
footstalks. Beneath the mantle on each side is a
series of short tentacular filaments, similar in cha-
racter to those of the Zvochide. ‘There are two
gill-plumes, which are large, pectinated, and equal;
they are placed in an ample cavity, which commu-
nicates with the aperture of the shell, whether
this be situated on the summit, or in the front
margin.

All the mollusks of this family are marine, and
are distributed through the seas of most parts of
the world; but principally those of warm climates.

P

210 PECTINIBRANCHIATA.—FISSURELLADZ.

GENUS FISSURELLA.

From the usual form of the orifice in the shell
of this genus, which resembles that of a key-hole,
the species are familiarly known by the appellation
of Keyhole Limpets. Itis placed at the summit
of the shell, which is very regularly conical, and
not otherwise to be distinguished from that of a
Patella. .In the very young condition the orifice
is placed more forward. The animal has been
already sufficiently described.

We have but a single native species, the Netted

FISSURELLA RETICULATA.

Keyhole Limpet (Fissurella reticulata). It attains
an inch in length, is of an oval form, and of a dirty
white hue, with dusky rays. - Its surface is sculp-
tured with a raised network, formed by radiating
and circular ridges.. The animal is large, and of
« yellow colour, varying in shade from cream-
white to a rich deep orange; the latter hue being
seen only in those specimens that are found ad-
hering to shells incrusted with a scarlet sponge.
It is obtained only on our western and southern
coasts.

CAP-SHELLS. 214

FAMILY CALYPTREADA.

Another group of Limpet-like shells are associ-
ated under this title, represented poorly in the
British seas, but numerous and much varied in
their details in those of the tropics. They are
commonly more or less circular in outline, rising
into a cone, the tip of which sometimes is pro-
duced into a spire, which falls over. In the interior
of the shell, there is in some of the genera a
variously shaped shelly plate, which is quite want-
ing in others.

The animal has a distinct head furnished with
tentacles, and eyes placed at their bases; the
muzzle is not produced into a proboscis. The
tongue is armed with teeth, arranged in rows of
seven each, the central one differing in form from
the others. The gill plume is single, and the foot
is unfurnished with lateral filaments.

Some of the genera, at least, sit on and hatch
their eggs. According to Audouin and Milne
Edwards, the parent Calyptrea “ disposes them
under her belly, and preserves them as it were
imprisoned, between the foot and the foreign body
to which she adheres, her patelloid shell thus
serving not only to cover and protect herself, but as
a shield to her offspring. These eggs are oval
bodies of a yellow colour, enclosed in membranous
capsules, which are elliptical, flattened, translucid,
and filled with an albuminous matter. The num-
ber of these little capsules varies from six to ten;
they are connected among themselves by a foot-
stalk, so as to represent a sort of rosette; each of
them contains from.eight to ten eggs. It appears

212 PECTINIBRANCHIATA.—CALYPTREADAL

that the young Calyptree are developed under
this sort of maternal roof, and do not quit it until
they are in a condition to affix themselves, and
are provided with a shell sufficiently hard to pro-
tect their own bodies.” *

Our other native genus of this family is said to
manifest an instinct similar to this.

GENUS PILEOPSIS.

The Fools-cap Limpets, as the mollusks of this
genus are called, have the shell shaped like a
somewhat high cone, with the summit a little pro-
duced, and turned over backwards. The surface
is commonly marked with lines (ste), and covered.
with a horny skin, which is sometimes invested
with a short velvety down. The interior has no
plate or partition of any kind. The place of the
attachment of the muscle is marked by a horse-
shoe impression. ‘The animal has been already
described.

The only British species is commonly known by
the appellation of Torbay Bonnet (Pileopsis Hun-
garwus) ; it also bears the names of Fools-cap
Limpet, Cap of Liberty, and Hungarian Bonnet,
all of which designations, as well as both of its
scientific ones, have an obvious reference to its
form. It isa rather large shell, being frequently
more than an inch and a half in diameter, and an
inch in height. Its substance is rather thin, though
strong, and somewhat translucent; its colour is a
delicate pink, or flesh-white, though this is con-
cealed, especially around the lower part, by an
olive-coloured skin, covered with shaggy down.

* Litt. de la France, i, 138.

CAP-SHELLS, 213

The interior of the shell is delicately smooth, and
of the same roseate hue as the exterior.
The animal is usually pale yellow, with a pink

4
S
Ore

TORBAY BONNET.

mantle bordered with a fine orange-coloured
fringe. The head, which is large and swollen, is
tinged with brown.

Though generally distributed, the Fools-cap
must be considered a rare shell. Torbay, as one of
its familiar names indicates, is the locality in
which it occurs in greatest abundance. I have
had several specimens brought to me from Wey-
mouth Bay, and the West Bay of Portland.
Messrs. Forbes and Hanley state that it “ chiefly
inhabits rocky ground, and oyster and scallop
banks, adhering to shells living in various depths
of water, from fifteen to as deep as eighty fathoms,
and extending its range to considerable distances
from land. It is finest in from fifteen to twenty-
five fathoms, and usually small in very deep
water.” *

It has been proved, says M. Deshayes,t .by
observation, that the animals of this genus are

* Br. Moll. ii, 461. + Annales du Muséum.

214 PECTINIBRANCHIATA.—DENTALIADA.

still more sedentary than the true Limpets, for
there may be seen in certain individuals of the
P. Hungaricus irregularities, proceeding from the
body on which it has lived when young, continu-
ing exactly the same to adult age; irregularities
whose traces may be observed on the lines of
growth, and which prove, in the opinion of M.
Deshayes, that during its whole life the animal
has never changed its place. But, probably, M.
Deshayes was not aware of those interesting facts
which have been observed in the habits of the
true Limpets, already described in these pages;
for, if a similar habit of roaming for food, and
returning with precision to the exact spot which
it has chosen as its home, be common to the Fools-
caps also, it appears to me that the phenomena
alluded to by the eminent French zoologist would
be siafficiently accounted for without his hypo-
thesis.

FAMILY DENTALIADA.
(Tusk-shells.)

On many a pebbly beach upon our coasts there
is frequently found, among other shells washed up
by the sea, one which bears the closest resemblance
to an elephant’s tusk in miniature. It is the re-
presentative of a family, comprising but a single
genus, which is interesting because rts characters,
as well those of the shell as of the animal, manifest
a decided approach to those of another great divi-
sion of organized beings, the ARTICULATA. Indeed
it was formerly considered by the best zoologists
to be a genus of Annelida, allied to those which
form the shelly tubes so commonly seen on sub-

TUSK-SHELLS. 215

merged shells and stones, known as the family
Serpulade ; and this position was assigned to the
tusk-shells by Cuvier, even in his last edition of
the “Régne Animal.”

The shell, in this family, is a tube more or less
curved, wider at one extremity than at the other,
and open at both ends. It is, in fact, a very
lengthened cone, with an open apex, as in Fissu-
rella, a genus with which it has been considered to
have some alliance.

The animal is of the same form as the shell, and
presents not only in this respect, but also in many
details of its structure, peculiarities which distin-
guish it from all the rest of the Glasteropoda.
According to Mr. Clark, of Exmouth, to whose
elaborate and skilful dissections our knowledge of
the anatomy of the Mollusca is so much indebted,
the gills are two symmetrical organs, hanging
from the sides of the animal, a little behind its
middle. The heart is placed at the front of the
gill-cavity ; a peculiarity of position which is de-.
pendent on the curious fact that the water to be
respired flows into the gills from the posterior
aperture of the shell. The front orifice is occupied
and stopped by the thick collar of the mantle,
through the centre of which
the tip of the foot protrudes.
The mantle invests the body ar ee
like a tube; but if this be (vratural size.)
slit down the back, a minute Ree ci
head is discovered near the middle of the body,
furnished with horny jaws, and bearing on each
side a large tuft of filaments, which are considered
to be salivary glands. ‘There are neither eyes nor
tentacles.

Ov
Ze :

= SEEN a
_—_——_—_————_
Para

216 PECTINIBRANCHIATA.—DENTALIADA.

The animal is attached to its shell only at its
posterior end; the fore parts are capable of being
protruded or withdrawn at the pleasure of the
animal. When fully expanded the foot is thrust
out in the form of a thickened and pointed tongue,
surrounded by a trumpet-like lobe; the whole of
which has been compared to the expanded corolla
of a flower, with a very thick and pointed pistil.

Genus DENTALIUM.

As the family includes but this one genus, it is
needless to repeat the characters by which it is
distinguished. The species are rather numerous ;
M. Deshayes enumerates twenty-three living and
thirty-four fossil, and several have been added to
both lists since he wrote. Their geographical
distribution is extensive, few seas being without
some representatives of the genus; and they range
from deep water to within tide-marks. In their
habits they are carnivorous, feeding on those minute
animals with chambered shells called Foraminifera,
as well as on small bivalves. Mr. Clark has found
species of as many as eleven distinct genera in the
pouches on the two sides of the mouth, or in the
stomach, of our commonest Tusk-shell (Dentalium
Tarentinum). 'The same acute naturalist has the
following observations on the affinities of the genus,
already slightly alluded to :—

“The symmetrical, subventral position of the
branchie, the posterior flow of water to them, and
the resemblance of the foot to that of some of the
bivalves, combined with the similar character of
its action, appear in a striking manner to show
its connexion with the Conchifera: whilst by its

TUSK-SHELLS. 207

cesophageal cerebral ganglions, and completeness
of the circulation, it has established its claims as a
Gasteropod. There are also traces of alliance with
some of the inferior classes. The red blood and
vermiform configuration of the posterior part of the
animal show some of the characters of the Anne-
lida.”
Two species of the genus
are recognised as British, D.
entalis, the Smooth Tusk, and
D. Tarentinum, the Grooved
Tusk. Of these the former is
common around the shores of
Scotland and the north of Eng-
land; the latter on our southern
coasts. Though possessing much
resemblance to each other, they
may be distinguished by the
small end of the latter being
finely grooved lengthwise, while |
the former is quite smooth and |
shining
The Smooth Tusk, here re- 3
presented, grows to a length of 4
nearly two inches, with a dia-
meter of about a quarter of an
inch at the larger end. It is
opaque, of a shining white sur-
face, like porcelain, never tinged
(asits southern congener usually
is) with pink, and never marked
with sculpture, but often with IX
rings indicating the progress Of pewratium TARENTINUM,
growth. (magnified).

It is a deep-water species, living “ buried in sand

pMjreifl p)))NH yy

218 PECTINIBRANCHIATA.—DENTALIADA,

or sandy mud, in from ten to one hundred fathoms;”’
but obtained most abundantly in from forty to
seventy fathoms.

Dr. Gray remarks that the apices of the British
specimens often appear to be either broken off, or to
have fallen off of themselves, like the tips of those
shells called decollated, as some of the Helicide ;
and he adds that when the tip is broken, the
animal forms a slight tube within, which is more or
less produced beyond the tip. Specimens in this
condition have been described as distinct species.
A parasitical worm, of the class Echinodermata,
the Sipunculus Bernhardus, is frequently found
inhabiting old and dead shells of the Dentalium,
the mouth of which it closes, except a minute
orifice, with a sort of mortar made with sand.
This parasite has sometimes been mistaken for the
original inhabitant of the shell.

BIVALVE MOLLUSKS. 219

CLASS IV. CONCHIFERA.

(Bivalve Mollusks.)

It needs but a glance at a Cockle or an Oyster,
to perceive that it is an animal lower in the scale
of existence than a Snail or a Periwinkle. The
absence of anything like a head, of any distinct
mouth, of jaws, or tongue, or other apparatus for
selecting and seizing food, as well as of the organs
of sensation, together with the limited power of
locomotion, proves its inferiority ; and this position
is fully borne out by an investigation of its
anatomy.

The first character that strikes us on looking at
one of these Mollusks is, that it is enclosed, more
or less completely, within a shell composed of two
pieces, called valves, which commonly bear a close
resemblance to each other. They are united at one
portion of their outline by a hinge, which allows
them to separate to a certain extent, while they
can be, during the life of the animal, brought to-
gether with accuracy, and held in this position
with great force.

If, now, we open the shelly valves, and examine
the interior, of the common Scallop (Pecten), for
instance, we see that each is lined with a delicate
membrane, the edges of which meet in the same
manner as those of the valves. These edges are
slightly thickened, studded with coloured glands,
and fringed with rows of close-set, thread-lke,
contractile tentacles. Proceeding now to separate

220 CONCHIFERA.

these membranous leaves, which together compose
the mantle, we find two pairs of other leaves, com-
posed of radiating fibres of exquisite structure,
attached to the body in one part, but elsewhere
floating freely, so as to allow the surrounding water
to bathe every part of their surface. These organs
are the gills, and, on being examined with the
microscope, show how beautifully their exquisite
structure 1s contrived for the maintenance of a con-
stant current of water over them. Lach of the
four leaves is then seen to consist of a vast number
of straight slender transparent filaments, evidently
tubular, arranged side by side, so that 1,500 of
them would be contained within the length of an
inch. Strictly, however, these are but one filament,
excessively long, bent upon itself again and again,
at both the free and the attached end of the gill-
leaf, throughout its whole extent. This repeated
filament is armed on each of two opposite sides
with a line of vibrating cilia, the two lines moving
in contrary directions; by the action of which a
current of water 1s made continually to flow up
and down each of these delicate filaments; so that
the blood which circulates in their interior (for they
are doubtless blood-vessels) is continually exposed
throughout this its long and tortuous course to the
action of oxygen.

Like all organic functions, the action of these
cilia is not under the will of the animal. It is
said that if, during life, a small portion of the gills
be cut off, the motion of the cilia will convey the
fragment swiftly away, with a smooth easy motion,
through the surrounding fluid in a definite direc-
tion. It does not even cease with the life of the
animal, A specimen which I examined had been

BIVALVE MOLLUSKS. 99T

dead at least fifteen hours, yet when I placed the
torn fragments of the branchiz, one after another,
beneath the microscope, the energy of the ciliary
action, as the wave flowed with uniform regularity
up one side and down the other of every filament,
filled me with astonishment. [ven the next morn-
ing, twenty-six hours after death, when the tissues
of the filaments were partially dissolved, the ciliary
motion was still going on, on portions that pre-
served their integrity.

In a sort of hood formed by the union of the
gill-leaves at their basal part, is placed the en-
trance of the stomach; a simple orifice without
jaws, teeth, or tongue, but bordered by four thin,
membranous lips.

The force with which the valves resist our
attempts to open them, during the life of the
animal, depends on the presence of a large and
powerful muscle, which is very apparent when
they are opened, as it occupies a considerable
portion of the interior, stretching directly from
one valve to the other, and inserted by a broad
base into each. By the contraction of the fibres
which compose this muscle, the valves are strongly
pulled together, and it is by cutting across this
with an inserted knife that an oyster is commonly
opened. When death ensues, the valves open spon-
taneously from another cause; muscular contrac-
tion then ceases, and the relaxed fibres can no
longer resist the expansive force of a dense and
highly elastic substance placed at the back of the
shell close to the hinge, and known as the ligament.

Around this great muscle are grouped the
stomach, liver, intestine and other vital organs;
while in the neighbourhood of the mouth there is

279 CONCHIFERA.

usually found a fleshy organ capable of being pro-
truded beyond the limits of the shell, and of assuming
various forms, suited to the different offices which it
has to perform. This organ, which is small in the
Pecten, is, in other genera, as the common Cockle, for
example, developed to a very large size; while in
others, as the Oyster, no trace of its presence is to be
found. It is commonly known as the tongue or foot.
The current which plays over the gills subserves
also another purpose, not less necessary to lite, I
have already said that the Bivalve Mollusca are
unprovided with any organs for pursuing or seiz-
ing prey; and yet their food is largely animal.
It consists principally of those minute creatures
belonging to the Class Jnfusoria, which, invisible
to the unassisted eye, swarm in innumerable
millions in the waters both of the sea and of rivers.
The currents which pour across the gills are crowded
with these minute creatures, and the parts that
surround the mouth lyimg in their course, and
being themselves also clothed with vibratory cilia,
a portion of the stream is drawn into the gullet
and passes into the stomach, carrying with it the
tiny prey, on which the Mollusk fattens, without
any exertion of its own, for the ciliary action is
doubtless, to a considerable extent, involuntary.
As far as is at present known all the members
of this class are hermaphrodite; that is, the repro-
ductive organization, instead of being assigned to
two sexes, is perfect in every individual animal.
In the Oyster, the ovary may be seen through the
mantle, resting, as a whitish mass of considerable
size, upon the muscle. It occupies the whole upper
part of the animal, and creeps down along the sides
and lower parts, being filled, at the time of repro-

BIVALVE MOLLUSKS. 223

duction, with a milky fluid containing multitudes
of small granules of a whitish colour. These are
the eggs; and in many of the family they are not
at the time of their exclusion abandoned at once,
but are deposited between the membranes of the
gill-leaves, where they undergo a kind of incuba-
tion. In some, the shell is developed in the egg
before it quits this receptacle. This fostering of
the eggs seems to be analogous to the gestation of
the eggs in the Crustacea and the Pipe-fishes.*

I have hitherto spoken of but a single adductor
muscle, but in a large number of species there is
a second, placed near the front part of the animal.
This variation naturalists have used to divide the
Class into two Orders, denominated Dimyaria and
Monomyaria, or respectively. Double and Single-
muscled Bivalves. ‘l'hese characters can be de-
termined at a glance by looking at a single valve
of any shell; for the place of attachment of the
adductor muscle is marked by a distinct sunken
impression in the interior of each valve. From
this circumstance also, these impressions, by the
differences in their form, position, and dimensions,
afford excellent characters for the discrimination
of genera.

The accompanying figure, representing the
interior of one of the valves of a common shell,
will serve to illustrate the appearance of the mus-
cular impressions, as well as of some other parts
that are commonly mentioned in technical deserip-
tion. ‘The oval mark on the left-hand side of the
figure is the front muscular impression ; the pear-
shaped mark on the opposite side is the hinder
one; the bending line which connects them is

* Penny Cyclop. vil. 432.

224 CONCHIFERA.

called the pallial impression, or that which marks
the attachment of the mantle. On the upper side

VALVE OF CYTHERZA.

is seen the hinge, an apparatus of shelly teetli
alternating with cavities, which fit, with the most
accurate precision, corresponding cavities and
teeth in the opposite valve. ‘The very summit of
the shell, which often, as in this instance, pro-
jects into a blunt point, bending towards one side,
is termed the beak or umbo; beneath this, on the
anterior side, or that towards which it turns, there
isa depressed space, often very conspicuous, termed
the lunule; while on the hinder side of the wmbo
is spread the dense elastic leathery igament. The
lunule, umbo, and ligament, constitute the dorsal or
superwor border, the lower side (in the figure) is the
ventral or inferior border; a line drawn from one
to the other of these measures the length of the
shell, the width being, of course, at right angles to
this, while the thickness is determined by a line from
the centre of one valve to that of the opposite.

OYSTERS AND SCALLOPS. 225

ORDER I. MONOMYARIA.
FAMILY OSTREADZ.
(Oysters and Scallops.)

On account of the beauty possessed by many
members of this family, (a beauty comprising
elegance of form, elaborate sculpture, and the
most rich and brilliant colours,) their high de-
velopment of organization, and, above all, the esti-
mation in which they are held, and the extent
to which they are consumed as human food, this
must be considered as the most important of all the
families of the Conchifera, or even of the Mollusca.
Considerable variation, indeed, is found in the
anatomy of these animals, and some of them
entirely lack those organs which are found well
developed in others; yet they possess so many
characters in common, and glide into each other
by gradations so close, that it is difficult to divide
the group. All the tribe have the mantle widely
open, no siphonal tubes, a single adductor muscle,
and a ligament either entirely or in part con-
cealed in the edge of the shell, lodged in a cardinal
groove, and sometimes accompanied with teeth.
In most cases there is a minute foot capable of
spinning those threads which are called byssus,
but this power is for the most part exercised only
while the animal is young.

The Limes (Zima) and the Scallops (Pecten) are

Q

226 MONOMYARIA.—OSTREAD A.

among the most active members of this Class of
animals; they have been called the butterflies of
the shell-fishes, a comparison not less apt on ac-
count of the delicacy and beautiful colouring of
the wing-like shell, than of the agile motions which
they exhibit. Though inhabitants of the deep
sea, these bivalves take long and rapid leaps,
shooting hither and thither, and fluttermg about
through the water with an irregular zig-zag move-
ment, produced by the alternate opening and shut-
ting of the valves with great force. The motions
thus performed appear to be without any determinate
direction, and to depend upon the impact of the
valves upon the water; but these animals (the
Pectens at least) have the power of effecting a more
deliberate and precise locomotion, in the perform-
ance of which the mantle is the principal agent.
The following observations, which I had recently
an opportunity of making upon a young specimen
of the Common Scallop or Quin (P. opercularis)
which I was keeping in captivity, will serve to
illustrate the form and office of the foot, as well as
the faculty more immediately under consideration.

My attention was attracted to the Pecten by
this curious circumstance, that it was adhering by
one valve (the flat one) to the side of the glass
phial, at some distance from the bottom. On close
examination with a lens, I discovered that it was
attached by a very delicate byssus. Curious to
ascertain how it contrived to mount from the bot-
tom to this position, I touched it slightly, and
caused it to loose its hold. In the course of half
an hour I found that it had resumed the same
position again. I again disturbed it, and began to
watch its motions. It was lying with the convex

OYSTERS AND SCALLOPS. 227

valve downwards on the bottom of the phial. The
first thing I observed was the thrusting forth of
the delicate little foot, an organ which seemed to
me appropriately named, when I marked its close
resemblance in form to a human foot and leg, en-
veloped in a white stocking. What I may call
the sole of this tiny foot was pressed against the
side of the glass, feeling about from place to place;
while with the lens I could distinctly see, im the
part corresponding to the toe, the opening of the
fleshy lips, or sides of the grooves, in which the
threads of byssus are said to be formed. While it
was thus engaged my surprise was excited by
seeing it suddenly throw itself with a jerk into an
upright position; but the action was too startling
to allow me to see how it was performed. I again
laid it prone, and though for a moment it closed
the valves, it presently opened them again, and
performed a similar feat. This was followed by
several leaps in different directions, in quick suc-
cession; but I was still at a loss to know the
modus operandi. It appeared to me certain, that
the ordinary supposition, viz. that the action is
performed by the vigorous opening and shutting of
the valves, was not the correct one. At length a
favourable observation gave me a suspicion of the
truth. I perceived the lips of the mantle (which
were held in contact, though the valves were con-
siderably separated) suddenly open to a partial
extent, as if by a blowing from within. At this
instant there was a leap in the opposite direction,
attended with a considerable agitation in the water.
With. this clue I observed more definitely. Having
rendered the water a little turbid, in order the
more distinctly to see any motion of the particles

228 MONOMYARIA.—OSTREAD A.

suspended in it, several leaps confirmed the notion
that had suggested itself tome. The mode of pro-
ceeding is as follows: when the Pecten is about to
leap, it draws in as much water as it can contain
within the mantle, while the lips are held firmly in
contact. At this instant the united edges of the
lips are slightly drawn inward, and this action
gives sure warning of the coming leap. The mo-
ment after this is observed, the animal, doubtless
by muscular contraction, exerts a strong force upon
the contained water, while it relaxes the forced
contact of the lips at any point of the circumference,
according to its pleasure. ‘The result is, the forci-
ble ejection of a jet of water from that point ; which,
by the resilience of its impact upon the surrounding
fluid, throws the animal in the opposite direction,
with a force proportioned to that of the jet d'eau.
The action may be well imitated by the human
mouth blowing a stream of air from any determined
point, while the lips are held firmly together at all
other points. The resemblance, indeed, of the
mantle to the human lips performing such an
action, (a resemblance perhaps more close than
flattering,) struck me as ludicrously faithful. Nor
was the appearance less suggestive of a pair of
bellows without a nose, of which the valves were
the covers, and the mantle the leathers, discharging
their contents from any part of their sides.

The Oysters (Ostrea), on the other hand, are
stationary ; never moving from the spot where the
ege is first deposited. very one is aware that
the shells are frequently found adhering in the
firmest manner to rocks or stones, or to each other;
the substance of the shell having been deposited
upon the foreign body, so as to conform perfectly

OYSTERS AND SCALLOPS. 229

and minutely to every irregularity of its surface.
“ The shelly case of the Oyster,” observes Sir
Anthony Carlisle in his eloquent oration, “ is its
sole security, and a superior delicacy of touch,
diffused over the whole of the living surfaces,
warns the creature of every danger, and bids the
closing of senseless valves. The inward organi-
zation is equally simple with the exterior forms,
and both are suited to a passive life; for locomo-
tive beings demand evidences of distant things,—
sometimes to supply their wants, and on other
occasions to inform them of danger; but a sta-
tionary creature, being doomed to rely on its fixed
resources, would only be tantalised by evidences
placed beyond its control.” *

In the Pectens, the edges of the mantle are
furnished with eyes and tentacles; the Limes have
the latter greatly developed, but the former organs
are wanting, or very minute; the Oysters are
destitute of both eyes and tentacles. The ap-
pearance of the eyes of the common Pecten has
been already described (see p. 5). If we examine —
one of these organs under a microscope, say with
a power of 220 diameters, we distinctly perceive
it to be composed of a large globose lens, invested
in a transparent coat, which is buried for more
than half its volume in a socket of granular sub-
stance, and of a yellowish brown colour, having an
ill-defined circle near its front part, of a blackish
hue. This last, under continued pressure, bursts,
and discharges a deep crimson pigment.

The genera composing this family are very ex-
tensive, and widely spread; particularly in the
seas of warm and temperate climates. In general

* Hunterian Oration, 1826.

230 MONOMYARIA.—OSTREADA.

they are eaten wherever found, and are highly
sapid and delicate. The common Scallop (P. oper-
cularis) is said to have derived its local name of
Quin from the partiality which the celebrated
epicure of that name manifested for it; and the

PECTEN.

Great Scallop or Frill (P. maximus), a much. rarer
species, is sought after for the London markets.
‘Scalloped with bread crumbs in its own shell,
or fried with a little vinegar and pepper, it forms
a very delicious morsel; it has the sweet flavour

OYSTERS AND SCALLOPS. 231

which characterizes all the scallops. The deep
valves of this shell are much used to contain
scalloped oysters, and in fishermen’s huts for rude
but useful lamps.” *

GENUS OSTREA.

The Oysters have a shell composed of two
unequal valves, usually thick and irregular, con-
nected by a hinge of the simplest character, with-
out teeth. Externally the surface is rough, and
composed of a great number of foliations loosely
plaited, or marked with radiating furrows. ‘he
lower valve is more or less hollowed, the upper
one flat.

The animal is shaped like the shell, having an
open mantle with double edges, bordered by short
fringes; the eyes, the tentacles, and the foot, are
wanting.

We have but one British species, the Oyster,
par excellence (Ostrea edulis), but the abundance
and renown of this species compensate for the
absence of others. The British Oysters were held
in the highest estimation by the ancient Romans,
who were even at the expense of bringing them to
Rome for their luxurious feasts.t ‘ Excellent as
the oysters of Britain undoubtedly are, there are
many degrees of that excellence, the animal vary-
ing much both in size and flavour, according to
the nature of the coast, and the food with which
the locality is furnished. The oysters on the
south coast are generally very well flavoured ;

* Forbes and Hanley, ii. 298.
+t Juvenal, Sat. iv. 140.

232 MONOMYARIA.—OSTREAD &.

but it has been said that the best are found at
Purfleet, and the worst at Liverpool. The Tenby
oyster is large and rather coarse; but when fat is
well-flavoured, and excellent when well stewed or
pickled. Colchester, and other places in Essex,
are the great nurseries or feeding-grounds for sup-

ANIMAL OF THE OYSTER.

plying the metropolis, and indeed, in a great
measure, England generally, with this highly
flavoured species. Here the Oysters collected at
various places on the coast, even as far as Scot-
land, are brought, and laid on beds in creeks along

OYSTERS. 233

the shore, where their flavour and size are rapidly
improved. They have been known to augment
the circumference of their shell even to the extent
of an inch during the first two months, but in such
cases the concavity within the valves is shallow.”*

Almost all the information we yet possess on
the economy of the Oyster, is derived from Bishop
Sprat’s “ History of the Royal Society,” and is
contained in a paper entitled, “ The History of
the Generation and Ordering of Green Oysters,
commonly called Colchester Oysters.” It reads
as follows :—

‘Tn the month of May the oysters cast their
spawn (which the dredgers call their spat); it is
like to a drop of candle, and about the bigness of
an halfpenny. The spat cleaves to stones, old
oyster-shells, pieces of wood, and such like things
at the bottom of the sea, which they call cultch. It
is probably conjectured that the spat in twenty-
four hours begins to have a shell. In the month
of May, the dredgers (by the law of the Admiralty
Court) have liberty to catch all manner of oysters
of what size soever. When they have taken them,
with a knife they gently raise the small brood
from the cultch, and then they throw the cultch
in again, to preserve the ground for the future,
unless they be so newly spat that they cannot be
safely severed from the cultch; in that case they
are permitted to take the stone or shell, &c. that
the spat is upon, one shell having many times
twenty spats. After the month of May it is felony
to carry away the cultch, and punishable to take
any other oysters, unless it be those of size (that
is to say) aboutthe bigness of a half-crown piece,

* Penny Cyclop. xvii. 363.

254. MONOMYARIA.—OSTREAD&.

or when, the two shells being shut, a fair shilling
will rattle between them. The places where these
oysters are chiefly catched are called the Pont-
Burnham, Malden, and Colnewaters. * * * This
brood, and other oysters, they carry to creeks of
the sea at Brickel-sea, Mersey, Langro, Fringrego,
Wivenho, olesbury, and Saltcoase, and there
throw them into the channel, which they call their
beds or layers, where they grow and fatten, and
in two or three years the smallest brood will be
oysters of the size aforesaid. Those oysters which
they would have green, they put into pits about
three feet deep in the salt-marshes, which are
overflowed only at spring-tides, to which they
have sluices, and let out the sea-water until it is
about a foot and a half deep. These pits, from
some quality in the soil co-operating with the heat
of the sun,* will become green, and communicate
their colour to the oysters that are put into them
in four or five days, though they commonly let
them continue there six weeks or two months, in
which time they will be of a dark green. ...
“The oysters, when the tide comes in, lie with
their hollow shell downwards; and when it goes
out they turn on the other side. They remove not
from their places unless in cold weather, to cover
themselves in the ooze. The reason of the scarcity
of oysters, and, consequently, of the dearness, is
because they are of late years bought up by the
Dutch. There are great penalties by the Admi-
ralty Court laid upon those that fish out of those
grounds which the court appoints, or that destroy
the cultch, or that take any oysters that are not of

* Rather from the abundant increase in such pits of the
green Infusoria and Desmidec, on which the Oyster feeds.

OYSTERS. 23D

size, or that do not tread under their feet, or throw
upon the shore, a fish, which they call a five-finger,
resembling a spur-rowel, because that fish gets into
the oysters when they gape, and sucks them out....

‘The oysters are sick after they have their spat;

but in June and July they begin to mend, and in
August are perfectly well. The male oyster is
black sick, having a black substance in the fin.

They are salt in the pits, salter in the layers,
saltest at sea.”

For the most recent information respecting the
oyster-beds which supply the London market, the
extent of the supply, and the opinions of those
practically concerned in their management and in
the sale of their products, on points in the history
and value of what may be termed cultivated
oysters, we are indebted to Messrs. Forbes and
Hanley, who obtained it from gentlemen of prac-
tical experience in the trade. From their valuable
History of the British Mollusca the following par-
ticulars are extracted :—

“The oyster-beds from which the principal
supply for the London market is procured, are
those of Whitstable, Rochester, Milton, Colchester,
Burnham, Faversham, and Queenborough, all arti-
ficial beds, furnishing natives. Since the intro-
duction of steam-boats and railroads, considerable
quantities of sea-oysters are brought from Falmouth
and Helford, in Cornwall, from the coast of Wales,
the Isle of Wight and its neighbourhood i in Sussex,
and even from Ireland and Scotland, after the
winter sets in, as before they would not keep fresh
enough when brought from long distances. The
supply derived from natural beds varies much,
since on some of them the oysters are not sufti-

236 MONOMYARIA.—OSTREADA.

ciently abundant to pay for dredging. The sea-
oyster is often, before being brought to market,
kept for a time in artificial beds, in order to improve
its flavour.

‘“‘'The most esteemed oysters are those of the
small ovate, but deep-shelled variety, called Natives,
among which, those of the river Crouch, or Barn-
ham Oysters, are pre-eminent for the marine
flavour; probably on account of the facilities for
rapid importation of them in fine condition. Much
of the quality depends on the ground and condition
of the beds: the oysters of different years from the
same place often vary materially in this respect.
They are considered full-grown for the market
when from five to seven years old; sea-oysters
at four years. The age is shown by the annual
layers of growth, or ‘ shoots,’ on the convex valve.
Up to three or four years, each annual growth is
easily observed, but after their maturity it is not
so easy to count the layers. Aged oysters become
very thick in the shell. In the neighbourhood of
fresh water the oyster grows fast, and improves in
body and flavour. The flavour is said by some to
improve by shifting the oysters as they approach
their full growth. Frost kills numbers, and when
they are left dry at low ebps, the run of fresh
water from the land turns them, what is called,
‘foxy, of a brownish red colour. ‘They are some-
times seized with sickness during the spawning
season, and considerable numbers may die. Much
labour is required to keep the beds in good order,
cleansed from shells and rubbish, star-fishes, bar-
nacles, corallines, and sea-weed, which grow freely
in the spring of the year. On the cleanliness of
the ground the prolific character of the bed, if the

OYSTERS, 25%

oysters breed there, depends. If carefully attended
to, a bed may last any length of time; but if
neglected, it will become overgrown with weed
and buried in mud, so that it can only be reclaimed
by restocking at a great expense, or 1s altogether
destroyed. Artificial beds, for the purpose of
keeping a supply at hand for the London market,
are said to have been commenced about the year
1700, by the Kent and Kssex Companies of
Dredgers. The oyster does not breed freely, often
not at all, on artificial beds, so that they require to
be constantly restocked; and when they do spawn
under such circumstances, the fry are said seldom
to come to perfection. On their natural grounds
they spawn profusely during the season, ¢.e. during
the summer months.”

The nature of the “ spat”’ is thus explained by
Sir Anthony Carlisle: ‘‘ Oysters are viviparous, and
the young are found within the tracheal passages,
and between the folds of the coverlit (mantle),
during the months of June and July in this
climate. In its first state the oyster exhibits two
semi-orbicular films, of transparent shell, which
are continually opening and closing at regular
intervals. The whole brood are associated together
by being involved in a viscid slime, and in that
state called the spat; it being common among vivi-
parous animals of this kind to have their spawn
deposited in contact with the lungs; the involving
slime serves as the first nutriment, and we may
infer, that the foetal food so influenced by the gills
is, at the same time, a respiratory supply to the
imperfectly formed young.” *

** In London the chief consumption of common .

* Hunterian Oration, 1826.

238 MONOMYARIA.—OSTREAD &.

oysters is from the 4th of August to January, and
of natives from October to March. The consump-
tion is said to be greatest during the hottest
months after the commencement of the oyster
season; the warmer the weather, the more oysters
are consumed. They are brought to market in
craft of various sizes; they are packed in bulk
closely in the hold; in some cases a cask of salt-
water is kept, from which to sprinkle them super-
ficially. ‘Those that come by rail are packed with
the convex shells downwards, in bags or barrels.
From the boats they are transferred to the salesmen,
who keep them in a little salt and spring water,
and shift them every twelve hours. Some pretend
to improve them by ‘feeding’ them on oatmeal.
Oysters, like other bivalves, live chiefly on infu-
soria. The quantity consumed annually in Lon-
don varies in different seasons. One informant
states twenty thousand bushels of natives, one
hundred thousand bushels of common oysters, to
be about the mark : another estimates the quantity
sold in the season, from the 4th of August to the
12th of May, to be nearly one hundred thousand
London bushels; each bushel being three Man-
chester, or imperial, bushels; and that about
thirty thousand bushels of natives are sold during
the same period by various Companies. Durin
the season, commencing on August the 4th, 1848,
and ending May 12th, 1849, Mr. Wickenden
estimates about one hundred and thirty thousand
bushels of oysters to have been sold in London,
though of that quantity about one fourth was sent
away to various parts of the United Kingdom
and the Continent.” *
* Forbes and Hanley, ii. 315.

PEARL SHELLS. 239

FAMILY AVICULADZ.
(Pearl Shells.)

The members of this family effect a trans-
ition from those genera which have but a single
muscle, to those which have two; for though their
shells display two, or even more muscular impres-
sions, one is always found to predominate greatly
over the rest, which are but small.

The shell has its exterior portion commonly
black, or of the colour of horn, and composed of
prismatic cellular substance; the interior layers
are composed of nacre, and are therefore brilliantly
pearly. Their form is very irregular, the valves
being unequal, and always developed more towards
one side than the other. The hinge is without
teeth, the ligament thin, simple, or notched.

The animais have a mantle which does not
adhere to the shell, entirely open all round, pro-
longed into irregular lobes, without siphons; there
is a small foot which is grooved, and capable of
spinning a strong byssus.

The most important genus of the family con-
tains the Wing-shells, one species of which is the
Pearl-oyster, from the interior shell of which we
obtain the substance known as mother-of-pearl,
which is largely imported into this country, and
manufactured into shirt-buttons, knife-handles,
and various trinkets; it is also much used for
ornamental inlaying. But that which renders
this shell of much more value is the production of
pearls, the beauty of which has always rendered
them fit companions of the choicest precious stones,
for the purpose of personal adornment.

240 MONOMYARIA.—AVICULADZ,

Pearls are indeed produced by several genera of
shells both bivalve and univalve, but the most
precious are obtained from the species named
Avicula margaritifera, which is a native of the
Indian Ocean. On the coast of India and Persia
numerous fisheries are established, which supply
the markets of the world with precious pearls.
Some of these have been carried on from very

AVICULA.

ancient times; that for example at Catifa in Arabia,
which produced the celebrated pearl bought by
Tavernier for 110,000/., is mentioned by Pliny.
The most productive fisheries are prosecuted in
the Persian Gulf, and on the coast of Ceylon; that
of the Bahrein Islands, in the former locality, often
produces pearls to the value of 90,0002. sterling in
two months, the time in which it is prosecuted.
This is free to all adventurers on payment of the

PEARL SHELLS. 241

tax, but the fishery of Ceylon is a monopoly in the
hands of government.

A very interesting and graphic account of this
fishery is given by Captain Percival, from whose
‘History of Ceylon” the following particulars
are extracted.

“There is perhaps no spectacle,’ says the
author, ‘‘ which the island of Ceylon affords more
striking to a European than the Bay of Condatchy
during the season of the pearl fishery. This desert
and barren spot is at that time converted into a
scene which exceeds, in novelty and variety, almost
anything I ever witnessed: several thousands of
people of different colours, countries, castes and
occupations continually passing and repassing in a
busy erowd; the vast numbers of small tents and
huts erected on the shore, with the bazaar or market-
place before each; the multitude of boats returning
in the afternoon from the pearl banks, some of
them laden with riches; the anxious expecting
countenances of the boat owners, while the boats
are approaching the shore, and the eagerness and
avidity with which they run to them when arrived,
in hopes of a rich cargo; the vast numbers of
jewellers, brokers, merchants of all colours and all
descriptions, both natives and foreigners, who are
occupied in some way or other with the pearls,
some separating and assorting them, others weigh-
ing and ascertaining their number and value, while
others are hawking them about or drilling and
boring them for future use,—all these circumstances
tend to impress the mind with the value and im-
portance of that object which can of itself create
this scene.

“The Bay of Condatchy is the most central

R

BA? MONOMYARIA.—AVICULADZ.

rendezvous for the boats employed in the fishery.
The banks, where it is carried on, extend several
miles along the coast from Manaar southward off
Arippo, Condatchy and Pomparipoo. The princi-
pal bank is opposite to Condatchy, and hes out at
sea about twenty miles. After the survey of the
state of the beds, and the consequent report to
Government, the particular banks to be fished are
put up for sale to the highest bidder, and are
usually purchased by a black merchant. ‘The
Government, however, sometimes judges it more
advantageous to fish the banks on its own account,
and to dispose of the pearls to the merchants.

“The banks are divided into three or four dif-
ferent portions, which are fished annually in suc-
cession. These portions are distinct, and are set
up separately to sale, each in the year in which it is
to be fished. A sufficient interval is thus given to
the oysters to attain their proper growth; and as
the portion first used has generally recovered its
maturity by the time the last portion has been
fished, the fishery becomes almost regularly annual,
and may thus be considered as yielding a yearly
revenue. The oysters are supposed to attain their
complete state of maturity in seven years.

‘The fishing season commences in February,
and ends about the beginning of April. The
period allowed to the merchant to fish the banks
1s six weeks, or two months at the utmost; but
there are several interruptions which prevent the
fishing days from exceeding more than about
thirty. If it happen to be a very bad season, and
many stormy days intervene during the period
allotted, the purchaser of the fishery is often al-
lowed a few days more....

PEARL SHELLS. 243

“A signal gun is fired at Arippo about ten
o'clock at night, when the whole fleet sets sail
with the land-breeze. They reach the banks before
daybreak, and at sunrise commence fishing. In
this they continue busily occupied till the sea-
breeze, which arises about noon, warns them to
return to the bay. As soon as they appear within
sight, another gun is fired, and the colours hoisted,
to inform the anxious owners of their return.
When the boats come to land, their cargoes are
immediately taken out, as it 1s necessary to have
them completely unloaded before night. What-
ever may have been the success of their boats, the
owners seldom wear the looks of disappointment ;
for although they may have been unsuccessful one
day, they look with assurance of better fortune to
the next; as the Brahmins and conjurors, whom
they implicitly trust, in defiance of all experience,
understand too well the liberality of a man in
hopes of good fortune, not to promise them all
they can desire.

‘‘ Hach of the boats carries twenty men, with a
tindal, or chief boatman, who acts as pilot. Ten
of the men row and assist the divers in re-ascend-
ing. The other ten are divers; they go down
into the sea by five at a time; when the first five
come up, the other five go down, and by this
method of alternately diving, they give each other
time to recruit themselves for a fresh plunge.

“ In order to accelerate the descent of the divers,
large stones are employed: five of these are brought
in each boat for the purpose; they are of a reddish
granite, common in this country, and of a pyra-
midal shape, round at the top and bottom, with a
hole perforated through the smaller end sufficient

244 MONOMYARIA.—AVICULAD.

to admit a rope. Some of the divers use a stone
shaped like a half-moon, which they fasten round
the belly when they mean to descend, and thus
keep their feet free.

“These people are accustomed to dive from
their very infancy, and fearlessly descend to the
bottom in from four to ten fathoms water in search
of the oysters. The diver, when he is about to
plunge, seizes the rope to which one of the stones
we have described is attached, with the toes of
his right foot, while he takes hold of a bag of net-
work with those of his left, it being customary
among all the Indians to use their toes in working
or holding as well as their fingers; as, such is the
power of habit, they can pick up even the smallest
thing from the ground with their toes almost as
nimbly as a European could with his fingers. The
diver, thus prepared, seizes another rope with his
right hand, and holding his nostrils shut with the
left, plunges into the water, and by the assistance
of the stone speedily reaches the bottom. He then
hangs the net round his neck, and, with much
dexterity and all possible despatch, collects as
many oysters as he can while he is able to remain
under water, which is usually about two minutes ;
he then resumes his former position, makes a signal
to those above by pulling a rope in his night hand,
and is immediately by this means drawn up and
brought into the boat, leaving the stone to be
pulled up afterwards by a rope attached to it.”

The serious effects which so protracted a sub-
mersion must produce upon the human frame, are
manifested by a discharge of water from their
mouths, ears, and nostrils, and frequently of blood.
But this does not hinder them from gomg down

PEARL SHELLS. 245

in their turn. “ They will often,’ continues our
author, ‘‘ make from forty to fifty plunges in one
day, and at each plunge bring up about a hundred
oysters. Some rub their bodies over with oil,
and stuff their ears and noses to prevent the water
from entering, while others use no precautions
whatever. Although the usual time of remaining
under water does not much exceed two minutes,
yet there are instances known of divers who could
remain four or five minutes, which was the case
with a Caffre boy the last year I visited the
fishery. The longest ever known was that of a
diver who came from Anjango in 1797, and who
absolutely remained under water full six minutes.”

The last named period seems almost incredible,
but there is no reason to doubt Captain Percival’s
evidence. The chief horror and danger awaiting the
diver are concentrated in the ground-shark. This
animal isa common and fearful inhabitant of all the
seas in these latitudes; and its terrors are so con-
tinually before the eyes of the divers, that they
seek a vague safety in supernatural means. Betore
they begin diving, the priests or conjurors, who
are known in the Malabar language by the name
of Pillal Karras, or binders of sharks, are always
consulted, and whatever the conjuror says to them
is received with the most implicit confidence.

The divers are paid differently, according to
their private agreement with the boat-owners, either
in money, or with a proportion of the oysters
caught, which they take the chance of opening
on their own account; the latter is the method
most commonly adopted. The agreements with
the people who hire out the boats are conducted
much in the same manner. They contract either

246 MONOMYARIA.—AVICULADA.

to receive a certain sum, or permission to fish on
their own account. Some of those who pursue the
latter plan are very successful, and become rich,
while others are great losers by the speculation.
The spirit of gambling is more openly exhibited,
for oyster lotteries are carried on to a great extent,
and they consist of purchasing a quantity of the
oysters unopened, and running the chance of either
finding or not finding pearls in them. These
lotteries are great favourites with Huropean officers
and gentlemen. The boat-owners and the mer-
chants lose some of the best pearls while the
boats are on their return to the bay from the
banks, as the oysters when alive, and left for a
time undisturbed, frequently open their shells of
their own accord; a pearl may then be easily dis-
covered, and the oyster prevented, by means of a
bit of grass, or soft wood, from again closing its
shell, till an opportunity offers of picking out the
pearl.

Captain Percival thus concludes his interesting
account :—‘‘ As soon as the oysters are taken out
of the boats, they are carried by the different
people to whom they belong, and placed in holes
or pits, dug in the ground to the depth of about
two feet, or im small square places, cleared and
fenced round for the purpose, each person having
his own separate division. Mats are spread below
them to prevent the oysters from touching the
earth, and here they are left to die and rot. As
soon as they have passed through a state of putre-
faction, and have become dry, they are easily
opened, without any danger of injuring the pearls,
which might not be the case if they were opened
fresh, as at that time to do so requires great force.

PEARL SHELLS. 247

On the shell being opened the oyster is minutely
examined for the pearls; it is usual even to boil
the oyster, as the pearl, though commonly found
in the shell, is not unfrequently contained in the
body of .the fish itself.

“The stench occasioned by the oysters being left
to putrefy is intolerable, and remains for a long
while after the fishing is over. It corrupts the
atmosphere for several miles round Condatchy, and
renders the neighbourhood of that country ex-
tremely unpleasant till the monsoons and violent
south-west winds set in and purify the air. The
nauseous smell, however, is not able to overcome
the hope of gain; for months after the fishing
season, numbers of people are to be seen earnestly
searching and poring over the sands and_ places
where the oysters had been laid to putrefy; and
some are now and then fortunate enough to find a
pearl that amply compensates their trouble in
searching after them. In 1797, while Mr. Andrews
was collector, a coolie, or common fellow of the
lowest class, got by accident the most valuable
pearl seen that season, and sold it to Mr. Andrews
for a large sum.

“The pearls found at this fishery are of a whiter
colour than those got in the Gulf of Ormus, on
the Arabian coast, but in other respects are not
accounted so pure, or of so excellent a quality ;
for though the white pearls are more esteemed in
Europe, the natives prefer those of a yellowish or
golden cast. Off Tutucoreen, which is on the
Coromandel coast, nearly opposite to Condatchy,
there is another fishery ; but the pearls found there
are much inferior to those two species I have men-
tioned, being tinted with a blue or greyish tinge.

248 MONOMYARIA.—AVICULAD A.

“In preparing the pearls, particularly in drilling
and stringing them, the black people are wonder-
fully expert. I was very much struck with the
instrument they employ in drilling, as well as the
dexterity with which they use it. A machine made
of wood, of a shape resembling an obtuse inverted
cone, about six inches in length and four in breadth,
is supported upon three feet, each twelve inches
long. In the upper flat surface of this machine
holes or pits are formed to receive the larger pearls,
the smaller ones being beat in with a wooden
hammer. The drilling instruments are spindles of
various sizes, according to that of the pearls; they
are turned round in a wooden head by means of a
bow-handle to which they are attached. The
pearls being placed in the pits which we have
already mentioned, and the point of the spindle
adjusted to them, the workman presses on the
wooden head of the machine with his left hand,
while his right is employed in turning round the
bow-handle. During the process of drilling he
occasionally moistens the pearl, by dipping the
little finger of his right hand in a cocoa-nut filled
with water, which is placed by him for that pur-
pose; this he does with a dexterity and quickness
which scarcely impede the operation, and can only
be acquired by much practice.

‘They have also a variety of other instruments
both for cutting and drilling the pearls. To clean,
round, and polish them to that state in which we
see them, a powder made of the pearls themselves
is employed. These different operations in pre-
paring the pearls, occupy a great number of the
black men in various parts of the island. In the
black town or pettah of Columbo, in particular,

PEARL SHELLS. 249

many of them may every day be seen at this
work.”

GENUS PINNA.

The largest British bivalves belong to the genus
Pinna, in which the shell is fibrous, and horny in
texture, rather fragile and delicate ; the valves are
equal, triangular and exceedingly one-sided; the
hinge is straight, long and toothless, the ligament
marginal, and almost wholly internal.

The animal is triangular, with the mantle freely
open and having fringed edges ; the foot is small,
conical, or tongue-like, and grooved; there is a
small anterior muscle in the angle; the posterior
one is by far the larger.

The genus contains but few species, which are,
however, widely distributed, and most of them are
of large size; they range from deep water to near
the shore, living on sandy or muddy bottoms, with
their beaks plunged deep into the ground, and the
broad extremity gaping upwards.

In a cabinet of British shells the eye is sure
to be attracted by the great fan-like horny valves
of the Pinna (Pinna pectinata), which are not un-
commonly seen twelve inches long, and seven broad
at the gaping end. Young specimens are of a semi-
transparent horny texture, partially covered with
rows of hooked spinous scales; but these spines are
almost always worn away in old examples. The
interior is pearly in a slight degree, and loose pearls
of dull colour are sometimes found within the shells.
The silky byssus spun by these mollusks, which
is capable of being woven into small articles of
wearing apparel, has been already noticed.

The great Pinna is found all around the British

250 MONOMYARIA.—AVICULADZ.

coast, chiefly in deep water. Montagu found a bed
of them in Salcomb Bay, which was occasionally
accessible when the tide receded beyond its usual
limits. The valves stood upright, with the broader

PINNA.

end about an inch above the surface, and the lower
end fixed so firmly to the soil by a very large strong
byssus two or three inches in length, composed of
numerous fine silky fibres of a dark purplish brown
hue, as to demand the exercise of considerable force
for their removal.

PEARL SHELLS. 251

Mr. Couch, in his “ Fauna of Cornwall,” observes
that “this species is found in the greatest abun-
dance at the distance of from three to six leagues
south of the Deadman Point, where they stud the
bottom in multitudes, with only two or three inches
of the pointed end inserted into the soil. It is
common for the line or hook to become entangled
among these shells, and powerful effort is required
to drag them from their attachment, which is
only effected by breaking the byssus, or tearing
away the ground to which it 1s attached. In the
latter case a rich harvest of shells is often afforded,
but the pointed end of the Pinna is usually broken
off by the violence. It is perhaps owing to the
different degree of solidity of the ground, that
the shells living in the deeper water are so much
less buried than those of which Montagu speaks,
and one of the consequences may be a greater
degree of motion in the shell. Montagu observes
that the exposed end cannot be closed by art, but
the animal is capable of effecting it; and obser-
vation has taught me, that this is its method
of obtaining food. In its ordinary position this
opening is about two inches wide, exposing the
contained animal, which occupies but a small por-
tion of the cavity, and seems to offer itself a
prey to the first creature that may choose to devour
it. Some fish is thus tempted to enter, but the
first touch within is a signal for its destruction.
The shell closes not only at the side but at the top,
the latter action being effected by a separation of
the pointed ends, and the captive is either crushed
to death, or soon perishes from confinement.”

252 DIMYARIA.—ARCADA,.

ORDER II. DIMYARIA.

FamIty ARCADA.,
(Arks.)

A WELL marked character of this family, and one
that a glance is sufficient to recognise, is the pecu-
liarity of the hinge. This, whether straight or
bent, extends along a large portion of the margin
of each valve, and is formed of a great number of
minute comb-like teeth arranged in a row, nearly
parallel to each other, or slightly diverging. Those
of one valve correspond in shape and size to those
of the other, with which they accurately interlock.
The beaks (wmbones) are generally distant from
each other when the shell is closed. In form, size,
solidity, sculpture, and colour, there is much diver-
sity in the species; but all are covered with an
epidermis. ‘Two distinct muscular impressions
are strongly marked, which are remote from each
other, but are connected by a line running parallel
to the border of the valve, which is the pallial im-
pression.

The animal has the mantle freely open, without
siphonal tubes, except in a few species. It is
partially adherent to the shell; sometimes pro-
longed backwards. The foot is always considerably
developed, deeply grooved, and capable of expand-
ing into a disk, like that of a Gasteropod.

All the species are marine, and inhabit various

ARKS. 200

depths of water from tide-marks outwards. Some
of them affix themselves firmly to rocks, by means
of a stout byssus.

GENUS ARCA.

From the square boat-like form of the valves in
this genus, resembling that commonly attributed
in engravings to the Ark of Noah, these shells have
derived their name. The valves are generally
equal, much broader than long, and more developed
on one side than on the other; four-sided in out-
line, and usually solid in texture. Their surface
is covered with radiating close-set grooves, con-
cealed, however, by a rough, loose, horny epidermis.
The hinge is nearly or quite straight ; consisting
of numerous minute teeth, which are parallel in
the centre, but diverge at the sides.

The animal is oblong; the mantle, which, as
stated above, is open, is either fringed or simple
at its edges. The foot is large, oblong, bent,
grooved throughout, and capable of expanding
into a disk, with plain, or slightly plaited edges ;
it is furnished at its base with a gland from which
is spun a strong compact byssus. The mouth is
surrounded by lips, which are formed by the ex-
tremities of the gills.

These Mollusks inhabit all depths of water, but
are generally found near the shore; perhaps, how-
ever, this is because their peculiar habits render
them less accessible in other situations. They
chiefly live in holes and fissures of rocks, moored
by their powerful byssus. M. Rang remarks that
they sometimes adhere by their disk-like foot:
and Mr. Swainson states, that when young, they

254 DIMYARIA,—ARCADZ.

occasionally adhere by means of their fibrous
epidermis.

The species of this genus are chiefly distributed
through the seas of the tropics, where they are

NOAH’S ARK.

very numerous. We have three or four on our
own shores, the largest of which is commonly
known as the Ark of Noah, though the species
properly so named (A7ca Now) is a native of the
Mediterranean. Ours is the Arca tetragona of
conchologists. The valves are deep, four-sided,
and strongly angular, covered with fine radiating
lines, of a warm reddish-brown hue, becoming
paler and sometimes white on the front part. The
valves sometimes attain a breadth of two inches,
with a length of about three-fourths of an inch.
It is found commonly all round the British coasts,
most abundantly in the south-west, and in the ex-
treme north. ‘It is taken in crevices of rocks, in
chinks of old shells, in the interior of dead shells,
and sometimes quite free. When found in con-

MUSSELS. 255

fined localities it 1s often much distorted, but free
specimens are very regular.” * The epidermis in
this species often projects beyond the edges of the
valves, in the form of a ragged fibrous fringe.

FAMILY MytTILID&.
(Mussels.)

The members of this family are almost all
marine, though one genus (Dretssena) inhabits the
rivers of Eastern Europe, and is now found plenti-
fully in some of the navigable streams of this
country, having been introduced, as is supposed,
adhering to timber, or to the bottoms of ships.
The distinctive characters of the family, as enume-
rated by M. de Blainville, are as follows :—

The shell is regular, with the valves equal but
much lengthened, and produced on one side. The
hinge is destitute of teeth ; the ligament dorsal and
linear. ‘The texture of the shell is sometimes thin
and horny, and it is often covered with an epider-
mis. ‘There are two muscular impressions, the
hinder of which is considerably larger than the
other.

In the animal we find the mantle adhering to-
wards the borders, but open throughout its inferior
portion, with a distinct anal tube, but the branchial
one rudimentary, and indicated only by a thicken-
ing of the posterior borders of the mantle. The
foot is narrow and tongue-shaped, grooved down
its centre, and furnished with a byssus backwards
at its base. In some of the genera, as Lithodomus,
a foreign group which burrow in the hardest rocks,

* Forbes and Hanley.

256 DIMYARIA:—MYTILIDA.

the faculty of spinning is confined to the early life
of the animal, but in others a strong and copious
byssus is formed at pleasure through life.

GENUS MYTILUS.

The name of this familiar shell-fish is derived
from the obvious resemblance which its shell bears
to a mouse, the united beaks representing the nose.
The Greeks used the term Més for both the shell
and the quadruped, and both the Latin term Myti-
lus and our own Mussel are derived from that
appellation.

The genus is characterised by a shell very un-
equal-sided, but equal-valved, somewhat triangular,
running off into pointed terminal beaks, the valves
swelling, the surface covered with a horny skin ;
the hinge, though sometimes notched, has no true
teeth ; the narrow ligament is internal.

The animal is lengthened and oval, the lobes of
the mantle are simple or fringed, united behind in
a single point, so as to form an anal siphon. The
mouth is rather large, furnished with two pairs of
soft lips. The foot is slender, strap-shaped, grooved,
carrying at its base a silky byssus of considerable
strength.

The Edible Mussel (Mytilus edulis) is the only
British species, but is too abundant and too well
known to need description. Sold in every town
as an article of food, its three-sided shells, black
without and blue within, and the bearded animal,
both in its raw and cooked state, are familiar to
every one.

Dr. Knapp of Edinburgh has communicated to
Messrs. Forbes and Hanley a very interesting

MUSSELS. 20%

account of the quantities of this animal destroyed
annually in the neighbourhood of that city. “As
_an article of food,” he states, “‘ there cannot be used
fewer than ten bushels per week im Edinburgh and

MUSSEL.

Leith, say for forty weeks in the year; in all, 400
bushels annually. Each bushel of mussels, when
shelled and freed from all refuse, will probably con-
tain from three to four pints of the animals, or about
900 or 1,000, according to their size. Taking the
latter number, there will be consumed in Edin-
burgh and Leigh about 400,000 mussels. This is
a mere trifle compared to the enormous number
S

258 DIMYARIA.—MYTILIDA.

used as bait for all sorts of fish, especially had-
docks, cod, ling, halibut, plaice, skate, whiting, &c.
In Newhaven alone there are four large deep-sea.
fishing-boats, which generally go out three times
a-week, and fish for about thirty weeks in the year,
excluding Sundays and bad weather. Hach of
these large. boats carries eight men, with eight
lines of 800 yards in length, which, at a low calcu-
lation, take 1,200 mussels to bait each time they
are used; so that each large boat will use 28,800
mussels per week, equal to 864,000 per annum. But
there are about sixteen other smaller boats, which
go out daily, or rather at 12 o’clock every night, for
about the same number of weeks in the year.
Each carries four men, with four lines 800 yards
long. ‘Their consumption of mussels will come to
3,456,000. The total consumption of mussels for
bait annually in Newhaven alone may be reckoned
at 4,320,000. As there are nearly as many used
at Musselburgh, and Fisherrow, Buckhaven, Elie,
Anstruther, Pittenweem, Crail, and other places on
the Frith of Forth, we may calculate that thirty or
forty millions of mussels are used for bait alone by
the fishermen of this district each year. Numbers
come from the river Eden-on-Fife, and are sold at
25s. per cask. The best mussels at Newhaven are
got directly north of the Pier, in three fathoms
water, and are sold at 8d. per basket, each contain-
ing nearly a bushel. ‘The beds are private pro-
perty, and some of them having been injudiciously
or avariciously exhausted, the number of mussels
in the Forth has decreased, and the price increased,
within the last ten years.’

The eminent authors of the work just cited fur-
nish us with some other particulars of interest.

MUSSELS. 259

“Mussels are kept in many places in artificial
beds, to be used when required for bait. At
Anstruther, in Fifeshire, we have seen these ‘ mus-
sel gardens,’ as they are called—little plots of sea-
shore between tide-marks, edged in by stones, and
held as private property. In Northumberland,
Mr. Alder states, the fishermen build up piles of
stones among the rocks, to keep their mussels
sane.

The Freshwater Mussel (Unio) has long been
known as one of those shell-fish that produce
pearls ; but those procured trom the present species
are commonly small, ill-coloured, and of little value,
though they have been at various times much
sought for. The passage in Camden’s “ Britannia,”
about the pearls in Cumberland, evidently refers
to these. ‘ Higher up the little river that runs into
the sea,...the shell-fish, having by a kind of
irregular motion taken in the dew, which they
are extremely fond of, are impregnated and _ pro-
duce pearls, or to use the poet’s phrase, bacce
cochlew, shell-berries, which the inhabitants, when
the tide is out, search for, and our jewellers buy of
the poor for a trifle, and sell again at a very great
price.” The attempt to account for the origin of
pearls by the drinking in of dew-drops, my readers
may probably think more poetical than philosophi-
cal. A very curious account of a recent pearl-
fishery in North Wales is given by a correspondent
in “ Loudon’s Magazine of Natural History’”’ for
1830. The writer has confounded the Mytilus
edulis with the Unio. To the latter only his remark
on pearls “found up the river” applies. His ac-
count is as follows, with some slight omissions :—

* Brit. Mollusca, ii, 174, et seq.

260 DIMYARIA.—MYTILID A.

‘The pearl-mussel is found in abundance in the
river Conway, in North Wales, and is collected by
many of the natives, who obtain their livelihood
entirely by their industry in procuring the pearls.
When the tide is out, they go in several boats to
the bar at the mouth of the river, with their sacks,
and gather as many shells as they can before the
return of the tide. The mussels are then put into
a large kettle, over a fire, to be opened, and the
fish taken out singly from the shells with the fin-
gers and put into a tub, into which one of the
fishers goes barefoot and stamps upon them until
they are reduced to a sort of pulp. ‘They next
pour in water to separate the fishy substance, which
they call solach, from the more heavy parts, con-
sisting of sand, small pebbles, and the pearls,
which settle at the bottom. After numerous wash-
ings, until the fishy part is entirely removed, the
sediment, if I may so term it, is put out to dry,
and each pearl separated on a large wooden platter,
one at a time, with a feather; and when a sufficient
quantity is obtained, they are taken to the overseer,
who pays the fisher so much an ounce for them.
The price varies from eighteenpence to four shil-
lings: there are a number of persons who live by
this alone, and where there is a small family to
gather the shells and pick out the fish, it is prefer-
able to any other daily labour. The pearls are
generally a dirty white, sometimes blue, but never,
I believe, green or reddish. I cannot with accuracy
say how many ounces are taken to the overseer
each week, though I might say there are some
scores. But what makes this fishery more singular,
is the mystery which hangs over it. At present
it is a perfect monopoly, and there is but the one

MUSSELS. 261

who buys them up, that knows what becomes of
them afterwards. It has been carried on in this
manner for many years, and as such a thing, if
made public, might prove more beneficial to the
neighbouring poor, by causing a higher price to
be given for the pearls, it would be more so if any
of your numerous correspondents could throw some
light on this interesting subject. There have been
some curious and fanciful surmises, which may not
be thought worth mentioning. Some suppose that
the pearls are sent abroad to be manufactured into
seed pearls; others, more gravely, that they are
exported to India to be dissolved in the sherbet
of the nabobs! However, at present it is a mys-
tery; and, notwithstanding the pains taken and
the expense incurred by some liberal gentlemen in
endeavouring to find out the secret, it is as great a
mystery as ever. The huts which have been
erected for the convenience of boiling the fish, are
on the extremity of the marsh, about a mile north
of the town of Conway. ‘The pearls are seldom
found here much larger than the enclosed speci-
mens, though about twelve miles up the river
they have been found occasionally as large as a
moderate-sized pea, and have been sold for a
guinea the couple, but they are very rarely met
with. When I say that the. price varies from
eighteenpence to four shillings, I do not mean to
say that they are valued according to their size,
for the large and small pearls are all sold together:
but some years ago they were as high as four
shillings, now they are only two shillings per
ounce.

The ill effects produced by eating the mussel, at
least at certain times, and on certain constitutions,

262 DIMYARIA,—UNIONIDA.

have been before alluded to. (See ante, p. 43.)
Such cases, however, are rare, and, as Pennant
remarks, for one who is affected by eating mussels,
a hundred remain uninjured. In general, they are
simply boiled with us; but probably they might
be made much more savoury by a different mode
of cooking. Captain King, in speaking of a large
species (JZ. choros) found abundantly on some
islands on the Pacific coast of South America,
observes :—‘‘ The manner in which the natives of
these islands, both Indians and descendants of
foreigners, cook shell-fish is similar to that used
for baking in the South Sea Islands, and in some
parts of the coast of New Holland. A hole is
dug in the ground, in which large smooth stones
are laid, and upon them a fire is kindled. When
they are sufficiently heated, the ashes are cleared
away, the shell-fish heaped upon the stones, and
covered first with leaves or straw, and then with
earth. The fish thus baked are exceedingly tender
and good, and this mode of cooking them 1s supe-
rior to any other, as they retain within the shell
all their own juiciness.”

Famity UNIONIDZ.

(Freshwater Mussels.)

From the true Mussels the transition is easy to
those of this family. They are distinguished
chiefly by the structure of the foot of the animal,
which is greatly developed in dimensions, and, at
least in general, has not the power of spinning a
byssus. Mr. Anthony, however, a conchologist of
the United States, where the great abundance of

FRESHWATER MUSSELS. 263

these Mollusks in the large rivers affords peculiar
facilities for observation, has stated that under
peculiar circumstances certain species do spin a
byssus, both in the young and adult conditions. *

The shell is lengthened oblong, equal-valved,
unequal-sided, though in a much less degree than
the family last noticed. ‘The interior is pearly,
often very brillant; the exterior is invested by a
horny epidermis, which, though generally black or
olive, is sometimes richly coloured. The hinge
varies greatly, being sometimes destitute of teeth,
and sometimes furnished with long ones. The
muscular impressions are numerous, the ligament
and cartilages are external.

The animal has the mantle free all round, ex-
cept behind the hinder edges, forming, when in
conjunction, two tubes, the larger of which is
euarded by pointed and tooth-like tentacles. The
foot is large, compressed, somewhat four-sided.

These Mollusks live at the bottoms of rivers and
lakes, plunged perpendicularly into the mud, with
the terminations of the siphons just exposed. They
sink deeper when disturbed. Sometimes they are
found under the shelter of stones in rivers with
rocky bottoms.

The distribution of the family is peculiar. Very
few are found in the Eastern Hemisphere, but all
the rivers of America swarm with them. More
than two hundred species are enumerated as in-
habiting the United States.

The sexes of these animals are distinct, and may
be distinguished by the shell in the female being
more swollen than that of the male.

* Ann. Nat. Hist. vi.

264 DIMYARIA.—UNIONIDA.

GENUS UNIO.

The condition of the hinge affords the distine-
tive character in this family. The genus Unio has
it furnished with a short crested anterior tooth,
and a lengthened posterior lateral one in the right
valve, shutting between two similar teeth in the
opposite.

The shells of this genus, which are frequently
large and richly pearly in the interior, are fre-
quently used by artists for containing their colours.
One of our British species is hence named Unio
poctorum, or the Painter’s Unio. Many of them
yield pearls, which are generally superior to those of
the marine Mussels. Our finest native species, hence
named UW. margaritiferus, is one of these. It is
about five inches long, and half as broad, some-
what kidney-shaped, covered with a black epider-
mis, usually worn away at the beaks; the interior
1s pearly, but not brilliant. This species inhabits
the rapid streams of mountainous districts in vari-
ous parts of the British Islands.

“The Pearl Mussel, as this mollusk is familiarly
called, enjoys a distinguished reputation as one of
the few indigenous bivalves which yield the beau-
tiful productions whose name it bears. In ancient
times Britain enjoyed some celebrity for its pearls,
as they constituted one of its attractions for Julius
Cesar, who, however, does not seem to have reaped
a very rich harvest, so far as quality went, though
he obtained enough in quantity to cover with them
a buckler, which he dedicated to Venus Genetrix,
and suspended in her temple. ‘The pearls used for
the construction of his present were probably such
as Roman ladies would have scorned to wear,

FRESHWATER MUSSELS. 265

although they were ostentatiously offered to the
goddess of beauty; for Pliny, who narrates the
circumstance, states at the same time that the pearls
from Britain were small and lustreless, and not to
be compared with those from the East. Tacitus,
in his Life of Agricola, describes the pearls of Bri-
tain as ‘ subfusca ac liventia ;) and among ancient
Christian writers they are mentioned by Origen
and Bede. Pennant, and other writers, who have
treated of pearls, have all taken it for granted that
those mentioned by the ancient authors quoted
were derived from the Unio. This, however, is by
no means clear, and Cesar’s buckler was more pro-
bably covered with pearls from Mytilus edulis, very
much inferior in quality and size to those from the
fresh-water Pearl Mussel, and agreeing better with
the disparaging account of them in Pliny. Those
mentioned by Camden, as occurring at the mouth
of the Irt, in Cumberland, seem to have been of
the same nature. ‘he pearl-fishery at the mouth
of the Conway [to which I have already referred]
also concerns the Mytilus and not the Unio. Higher
up the latter river, however, and in many rivers of
all parts of the kingdom, especially in the neigh-
bourhood of mountainous districts, the Unio has
been at various times fished to a great extent for
pearls, and, in all probability, the fame of British
pearls that attracted the Roman conqueror was due
to the products of the shell before us. The best
account of these fisheries of the freshwater Pearl
Mussel is contained in a curious paper in the seven-
teenth volume of the ‘ Philosophical Transactions,’
(1693,) written by Sir Robert Redding, and com-
municated by Dr. Martin Lister. This paper has
been often referred to by subsequent writers, who,

266 DIMYARIA.—UNIONID.

however, seem to have made use of Pennant’s short
notice of it only, which itself was taken from the
abridgement, and not from the original. It is
a remarkable paper, on account of the correctness
of observation displayed in the personal statements
of the author, who seems to have been a person
with considerable natural-history powers. His de-
scription of both shell and animal is curiously cor-
rect as far it goes. He states that they were fished
in the rivers of Tyrone, Derry, Donegal, near Dun-
dalk, near Waterford, and in Kerry. The poor
people fished them in the warm months before
harvest time, when the rivers were low. They
took them with their hoes, or wooden tongs, or by
thrusting a stick into the shells which they caught
sight of among the stones as they lay in part
opened, with the white foot protruded, ‘like a
tongue out of the mouth.’ Sir Robert saw them
lying on their sides, and his informants described
them as ‘set up in the sand like eggs in salt, with the
sharp edge downwards, and the opening side turned
from the torrent.’ One in a hundred might con-
tain a pearl, and about one in a hundred of the
pearls was tolerably clear. There were no pearls
in the young mussels. ‘Some gentlemen of the
country made good advantage thereof, and I myself
whilst there saw one pearl bought for fifty shillings
that weighed thirty-six carats, and was valued at
forty pounds. Everybody abounds with stories of
the good pennyworths of the country, but I will
add one more. A miller took out a pearl which
he sold for four pounds ten shillings to a man who
sold it for ten pounds, who sold it to the late Lady
Glenealy for thirty pounds, with whom I saw it in
a necklace; she refused eighty pounds for it from

FRESHWATER MUSSELS. 267

the late Duchess of Ormond.’ ‘The pearl,’ Sir
Robert observes, ‘ lies in the toe,. or lesser end, at
the extremity of the gut, and out of the body of
the fish, between the two films or skins that line
the shell.’ He remarks that they correspond with
calculi in other animals.

“The pearls of the Conway had great fame.
According to Pennant a notion prevails in Wales,
‘that Sir Richard Wynne, of Gwydir, Chamber-
lain to Catherine, queen of Charles the Second,
presented her majesty with a pearl from the Con-
way, which is to this day honoured with a place in
the regal crown.’ He says the Pearl Mussels are
called by the Welsh Cregin Diluw, or Deluge
Shells, as if left there by the flood. Mr. Wilson,
of Warrington, in ‘ Loudon’s Magazine of Natural
History’ for June, 1830, says they are taken in the
upper part of the Conway, near Llanrwst, but the
search is very precarious. He mentions a Scotch
pearl half an inch in diameter. In Scotland, the
Tay was the seat of a pearl-fishery, extending from
Perth to Loch Tay. ‘It is said,’ writes Captain
Brown, ‘that the pearls sent from thence to Lon-
don, from the year 1761 to 1764, were worth ten
thousand pounds sterling; and it is not uncommon
at the present time to find pearls in the Teith and
Tay worth from one to two pounds each.’ The
variety Roissyz of this Unio was formerly much
sought for in the river near Braddan, in the Isle of
Man, on account of its pearls.” *

* Forbes and Hanley; Brit. Moll. ii. 149; et seq.

268 DIMYARIA.—CARDIADA,

FAMILY CARDIADZ.
(Cockles.)

This is a large, important, and, generally speak-
ing, well-defined group of bivalves, the characters
of which are thus given by Cuvier. In all the
mantle is open anteriorly, but posteriorly it pre-
sents two siphons or orifices, one for respiration,
the other for the egesta. ‘These form tubes some-
times distinct, sometimes united into a single mass.
There is always a transverse adductor muscle at
each extremity of the shell, and a foot which gene-
rally serves for the purpose of locomotion. It may
be laid down as a rule, that the species with elon-
gated siphons live buried in the mud, or sand.
This condition of organization may be recognised
on the shell, by the more or less developed contour
which the impression of attachment of the borders
of the mantle describes, before uniting with the
impression of the posterior transverse muscle; ”’
or, in other words, by the course of the pallial
impression.

These Mollusks are all marine, with one or two
doubtful exceptions; they frequently attain large
size, and are valued for the delicacy and wholesome-
ness of their flesh; their abundance often renders
them easy to be procured.

GENUS CARDIUM.

The shells of this well-known genus are globose
and heart-shaped: the valves are equal, with beaks
rolled in towards each other. The hinge is formed
by four teeth in each valve, of which the two pri-

COCKLES. 269

mary ones called cardinal are oblique, and one

lateral remote on
each side. The
valves are almost
always — covered
with well marked
ribs — alternating
with furrows,
which radiate from
the beaks to the
margins. ‘These
ribs are sometimes
studded with spin-
ous seales. The
ligament is exter-
nal and conspicu-
ous though short.
The animal is
shaped much like
the shell, being
round and swollen,
with the mantle
open in front, the
edges of which are
usually plain, but
strongly fringed in
the neighbourhood
of the two siphons;
the latter are short,
slightly separated
and fringed around
the edge. The foot
is very large, cy-
lindrical, with a

FOOT-MUSCLES OF COCKLE.

conical tip directed forwards. It is bent, with an

270 DIMYARIA,—CARDIADZA.

abrupt elbow near the middle. These animals in-
habit sandy or muddy shores, in which they live
immersed at a moderate depth, or covered only by
the tide at high-water. The powerful and versatile
organ known as the foot is admirably adapted for
the situations in which they reside. ‘This organ
in the present family is developed to a very great
size, and 1s moved by an immense number of
muscles of the most elaborate structure and arrange-
ment, as will be seen by the preceding engraving
of the dissected foot in a native species, Cardium
rusticum.

In order to enable the animal to burrow in the
sand, the foot, by means of its conical point, is
thrust beneath the surface. When stretched to
its utmost, it is bent into a hook, the whole organ
is then forcibly contracted, and the animal, shell
and all, is thus dragged a little way down into the
yielding sand. ‘This process is successively re-
peated, until the animal is sufficiently buried.
But the foot can be made an instrument of loco-
motion, of quite another kind. The Cockle is a
vigorous leaper, having been known to clear the
eunwale of a boat when laid on the bottom boards.
In order to effect this, the end of the foot bent
into a hook is pressed firmly against the plane on
which the animal is lying, in the position repre-
sented in the following engraving. ‘The foot is
then stiffened, when a sudden spring-like action
of the elongating muscles jerks the animal into
the air, with a force and agility that cannot fail
to surprise those who witness it for the first time.

The Cockles are widely distributed, being found
in nearly every sea, but their great metropolis is
in the Indian Ocean, whence, as from a centre,

COCKLES. Pel

the number of species diminishes in the ratio of
distance. About two hundred species exist in
collections, of which about ten are found on the
British coasts. The shells of this genus are gene-
rally remarkable for elegance of form, and often

COCKLE LEAPING.

for brilliancy of colouring. Our British species
are among the handsomest of our bivalves. “There
is-a pleasure,” observe the learned authors of the
British Mollusca, “ in investigating such a group
as this, wherein we find not only the greatest
variety, but also the greatest distinctness and con-
sequent certainty of specific determination.”

272 DIMYARIA.—CARDIADZ.

All the species are believed to be wholesome as
human food, and our own commonest species, Car-
dium edule, is very extensively sought after by
persons not always of the lowest class in this
country. It is said to be equally good raw or
cooked, and its attractions when pickled, to bipeds
of more than one class, are recorded in an amusing
story.

A certain Parrot’s loquacity had made her a
favourite with all the members of a family, except
the cook, whose resentment was incurred by Poll’s
thievish propensities. A jar of pickled cockles
was on a shelf in the cupboard, and whenever the
door was casually left open, the watchful bird
failed not to pay it a visit, though always scolded
when found out. One day Cook, coming suddenly
into the kitchen, caught Poll in the act of emerging
from the cupboard. Unable to restrain her wrath,
she cried, “ What! you’ve been at the pickled
cockles again, have you?” and at the same instant
dashed at the offending bird a tureen full of hot
soup which was in her,deind.

The poor bird was grievously scalded, and the
consequences were the loss of all the plumage of
her head, and of all her wonted garrulity. Nota
word was uttered for weeks, and it was feared she
had become hopelessly silent, when, one day, just
as the new feathers of her head were beginning to
sprout, a gentleman who was bald happened to
call. Struck with the similarity of condition dis-
played by the stranger’s smooth crown to her own,
Poll broke forth, vociferating with peculiar em-
phasis, “ What! you’ve been at the pickled cockles,
have you?”

HEART-SHELLS. | 2a

FAMILY CYPRINADA.

A group of fine shells, many of which are of
large size, is thus named after the principal genus,
Cyprina of Lamarck; though the appellation of
the genus and that of the family are alike objec-
tionable, as they have long been pre-occupied with
the slightest possible terminal difference by the
family and genus of the Carps among Fishes.
The Mollusks of this group are distinguished by
thick solid shells, often clothed with an epidermis,
but usually smooth on the surface, or if sculptured,
only with concentric lines running parallel to the
edges of the valves. They vary in colouring,
some being brilliant, others sombre. The hinge
has strongly developed teeth, and an external
ligament. The pallial impression is scarcely
sinuated in its course. ‘‘ This depends on a pecu-
har feature in the organization of the animal,
which has, instead of distinct and produced siphonal
tubes, only rudimentary ones in the shape of two
scarcely separated orifices.” The foot is thick and
tongue-like.

GENUS JSOCARDIA.

This genus presents many points of affinity with
the Cockles, and some with the great Clamps
(Chama) of tropical seas. The shells are large,
very convex, almost globose, heart-shaped, with
the beaks much inrolled, curving forwards and
outwards; the hinge is composed of two flattened
teeth. The animal will be described presently.

The form of the valves has given the name of
Heart-shell to the only British species, /socardia

if

274 DIMYARIA.—CYPRINADA,

cor; it ranks among the largest of our Mollusca,
being sometimes found nearly three inches in
length, and the same in breadth and thickness.
It is of an uniform dark brown or liver-colour.

The following interesting account of the animal
and its habits was communicated by the Rev. James
Bulwer to the second volume of the “ Zoological
Journal.”

HEART-SHELL.

“Mantle completely lining the shell, double at
the outer edge; exterior fold divided in_ front,
open at each end; at the posterior end forming two
short siphons or tubes, ciliated at the upper orifices ;
colour, yellowish white ; margin, orange. Foot very
muscular, broad, triangular, compressed, pointed,
orange. Branchiz external, concealed between the

HEART-SHELLS. 275

mantle and the body. Body soft, completely included
within the valves. On being placed in a vessel of
sea-water, the valves of the shell gradually opened
to the extent represented in the drawing [about
one-fourth of an inch]; the feelers or ciliated
fringe of the upper orifice of the mantle moved
slowly, as if in search of animalcule. . Having re-
mained in this situation about ten minutes, water
was ejected with considerable force from the lower
orifice, which till now had remained motionless.
The expulsion of the water appeared to be effected
by a sudden contraction of the muscles, because
this was never done without the valves nearly
closing at the same instant. After a few seconds
the valves gradually returned to their open position,
and remained quiescent as before, till the water
was again ejected with a jerk; this alternating
process was repeated at unequal intervals during
the whole time my specimens were under exami-
nation, but at shorter intervals on receiving fresh
supplies of sea-water, when I suppose food (its
quality I could not ascertain) was more abundant.
“The animal appears to be insensible both to
sound and light, as the presence and absence of
either did not at all interrupt its movements; but
its sense of feeling appeared to be. very delicate:
minute substances being dropped into the orifice of
the mantle instantly excited the animal, and a
column of water strongly directed expelled them
from the shell. With so much strength was the
water in some instances ejected, that it rose above
the surface of three inches of superincumbent fluid.
Animal small in proportion to its shell, occupying
when dead barely a third of the space enclosed in
the valves. Its mantle is slightly attached to the

276 DIMYARIA.—VENERIDZ.

shell, and to the epidermis at the margin, and
appears to be kept distended, and in contact with
the interior of the valves, by the included water.
The valves fit so closely that the animal can re-
main two days or more without permitting a single
drop of fluid to escape. Locomotion very con-
fined; it is capable, with the assistance of its foot,
which it used in the same manner (but in a much
more limited degree) as the Cardiacea, of fixing
itself firmly in the sand, generally choosing to
have the wmbones covered by it, and the orifices of
the tubes of the mantle nearly perpendicular.

‘‘ Resting in this position on the margin of a sand-
bank, of which the surrounding soil is mud, at too
great a depth to be disturbed by storms, the
Isocardia of our Irish sea patiently collects its food
from the surrounding element, assisted in its choice
by the current it is capable of creating by the
alternate opening and closing of its valves.” *

This fine species is nowhere very common; it
is, however, occasionally taken in deep water off
the extreme north of Scotland, and the extreme
south-west of England, but it appears to be most
abundant in the neighbourhood of Dublin. The
other species are but few, and are found in the
East Indian seas, and on the coasts of Australia.
They inhabit mud and sand, at a depth ranging
from ten to twenty fathoms.

FAMILY VENERIDZ.

(Venus Shells.)

The best character of this extensive family is, ac-
cording to Cuvier, that the teeth and lamin of the
* Zool. Journ. ii. 359.

VENUS SHELLS, 2h

hinge are approximated beneath the beak in a single
group. In general they are more flattened and
wider in proportion to their length than the Cockles,
from which they differ conspicuously also in having
the ribs never radiating towards the margin from
the beaks, but always, where present at all, in con-
centric lines parallel to the margin. The ligament
often leaves behind the beaks an oval depression,
commonly called the corslet. The muscular im-
pressions are strongly marked, and the pallial, or
that which indicates the adhesion of the mantle, is
much sinuated in its course.

The animal has two siphonal tubes, capable ot
being protruded in a greater or less degree, some-
times united to each other; their extremities are
fringed, though very slightly in some species. The
mantle is widely open in front, for the projection of
a large compressed foot, which serves for creeping.

This family is peculiarly rich in the number of
its species; the genera Venus and Cytherea alone
contain about a hundred each still existing, be-
sides half as many more which are fossil. They
are found in almost all seas, generally at a moderate
distance from the shore, but extending from tide-
marks to great depths. Our native species, Venus
striatula and ovata, for example, live indifferently
at low-water mark, and at the depth of a hundred
fathoms. ‘The tropical regions afford, as usual, the
greatest number of species, and those most remark-
able for beauty of form, sculpture, and colour, for
all which, however, the majority of the family
may be considered as preeminent among bivalves ;
whence the various appellations of the goddess of
beauty, and similar names have been selected for
the genera.

278 DIMYARIA.—VENERIDZ.

GENUS VENUS.

This extensive genus, including some of the
most highly prized ornaments of cabinets, is dis-
tinguished by a shell usually somewhat solid,
rounded in outline, or broader than long, equal-
valved, but somewhat unequal-sided. The surface
is generally adorned with many concentric ridges,
often rising into strong ribs, and sometimes divided
by radiating furrows. The margins are crenate, or
scalloped; the beaks prominent. The hinge is
formed of three diverging cardinal teeth in each
valve. The muscular impressions are round, and
well marked; the pallial sinus wide and pointed.

The animal is thick and globose, or oval; the
edges of the mantle, which 1s open, are fringed.
The siphons have fringed orifices, generally se-
parate. The foot 1s not grooved.

About half-a-dozen members of this beautiful
genus inhabit the British seas, which are considered
as nearly the northern limit of its geographical
range. Of these the finest is Venus casina, of
which the valves are about an inch and a half in
diameter. They are marked with strong concentric
ribs, white, or occasionally painted with two or
three crimson radiating bands.

Though this is a rare British shell, it has been
taken at various localities all round the coast.
I have obtained specimens from deep water off the
Isle of Portland.

FamMiLty MAcTRADA.

In some respects these shells present close re-
semblances to those of the last family; but their

MACTRADA. 279

outline is more triangular, and their surface is
smooth, or merely marked with fine concentric
lines. They are generally swollen; their sub-
stance varies much in texture; they are often in-
vested with a strong epidermis. ‘The valves are
connected together by a hinge, consisting of a
forked diverging tooth in one, raised on a liga-
mental fulcrum lodged in a cavity, which is margi-
nated in the other, a connecting cartilage and small
external ligament completing the union.” The
pallial impression closely resembles that of the
Veneride.

The animals of this family differ in the degree
in which the mantle is open or closed in front ; there
are two siphonal tubes, which are connected and
fringed at their orifices, and sometimes studded
with pointed warts.

GENUS MACTRA.

The shell is more or less triangular, slightly
gaping, with a smooth or concentrically striated
surface, covered with an epidermis. The hinge
is composed of a V-shaped cardinal tooth in one
valve, locking into a marginated pit in the other,
and of a long lateral tooth on each side of the same
valve, which also fits into a deep groove with tooth-
like margins. The sinus of the pallial impression
is shallow but wide.

The animal has the mantle open as far as the
siphons, its edges are fringed; the foot is strong,
tongue-shaped and bent, capable of protrusion to a
considerable extent. It is used, as in the Cockles,
for burrowing in sand, which these animals do
with great ease and rapidity. They are inhabi-

280 DIMYARIA.—DONACIDA.

tants of sandy shores in most seas, and the majority
of them are found in the vicinity of low-water mark.
Many of them are of a large size. We have a Bri-
tish species, Mactra helvacea, which attains the size
of three inches by two and a half in diameter.
This, however, is one of the rarest of our native
shells, as JZ. stultorum is one of the most abundant.
The latter is found on every sandy beach; it is
about half the size just mentioned, somewhat tri-
angular in outline, and varying much in colour,
from plain drab to fawn-colour, marked with pale
zones and white divergent rays.

FamiILty DoNACID.

The shell is more or less triangular and com-
pressed, broader than long, equal-valved, but un-
equal-sided, the hinder side being the shorter.
The texture is strong and compact, the hinge
variable, but always provided with conspicuous
primary teeth.

The animal is generally richly coloured, with
the mantle usually fringed; the siphonal tubes
are separate and much: developed, having their
orifices adorned with deeply-cut tentacles. The
foot is large, compressed, sharp-edged, and angular ;
the gills very unequal.

The species of this family, which are rather
numerous, occur in all parts of the world, but most
abundantly in the Southern Hemisphere. They
live buried in sand or sandy mud, with the short
side of the shell uppermost, the siphons being pro-
truded, and range from low-water mark to a depth
of ten fathoms.

DONAXES. 281

GENUS DONAX.

In addition to the family characters already
mentioned, the hinge in this the typical genus is
composed of two primary teeth in one valve, and
one in the other, with accessory lateral teeth. The
ligament is external, short, and swollen; the mus-
cular impressions are rounded, and the connecting
pallial impression is straight, with a wide and deep
sinus, hollowed out toward the hinder side. The
surface is covered with an epidermis.

Among the more beautiful of British shells must
be reckoned the Polished Donax (D. politus). It
is oblong in form, usually a little more than an
inch in breadth, and about half that length. It is
always vividly coloured, but varies much; the most
common condition is of a pale golden yellow, or faint
lilac hue, spotted and clouded with reddish brown;
a broad pale ray passes from the beak to the
margin. ‘The interior, which, like the exterior, is
highly polished, is generally of a rich purple, some-

POLISHED DONAX.

times varied near the beaks with golden yellow or
orange. ‘The animal is of a bright yellow colour,
with orange stripes and pink fringes; the foot is
large and white. This lovely species, nowhere
common, is found in many places on our southern
coasts.

282 DIMYARIA.—TELLINADZ.

FaMILyY TELLINADA.

(Tellens.)

This is a family very numerous in species, which
are generally remarkable for the elegance of their
form, the delicacy of their texture, and the bril-
liancy of their colour. The shell is generally much
compressed, greatly produced in breadth, regular,
and nearly equal-sided. ‘The hinder side, which is
often angular, has an irregular bend or fold at its
lower border, more or less conspicuous. The beaks
are very small, the hinge varies much, the ligament
is swollen and lengthened, the pallial impression
deeply hollowed. In general the valves are exceed-

TELLINA.

ingly thin and fragile, but painted with the most
beautiful colours, often arranged in elegant pat-
terns.

The animal has the mantle moderately open,

TELLENS. 283

bordered with fringes; the gills are unequal on
both sides. The siphons are very much lengthened,
separate, and diverging, returning into a fold of the
mantle; their orifices but slightly fringed. Not-
withstanding the gaiety of the shell, the animal in
this family is always arrayed in white, “ simplex
munditiis;” differing in this respect from Donaz,
the inhabitant of which usually rivals its shell in
gorgeousness of hues.

About seventy species are enumerated, which
live at various depths, chiefly in the warmer seas ;
their habits closely agree with those of the preced-
ing family. They are much preyed upon by the
carnivorous Gasteropoda, as Strombus, Buccinum,
&e., their thin shells exposing them with more
than ordinary ease to the depredations of those
boring Mollusks.

GENUS PSAMMOBLIA.

The shell in this lovely genus is more or less
oval, the breadth commonly being double the
length; the surface smooth, or delicately striated,
and clothed with a thin epidermis. The hinge is
composed of two cardinal teeth in one valve, re-
ceiving one from the other; the ligament is pro-
minent.

The animal is white, with the mantle open, and
slightly fringed; the very long siphons are marked
along their length with lines of cilia, and fringed
at their orifices. The foot is large and tongue-
shaped.

These Mollusks have the habits common to all
these allied families. They live, as their name

284 DIMYARIA.—SOLENID&.

indicates, in sand covered by the sea, from the water’s
edge to great depths. They are
said to be active in their motions,
burrowing with rapidity and ease
in the sandy bed of the sea.
We have several British species,
one of the most elegant of which
is sometimes called by collectors
the Setting Sun (Psammobia ves-
pertina), from its warm pink hue,
and the pale bands which radiate
from the beaks to all parts of the
margin, like the rays which fre-
quently stretch across the sky
from the evening horizon. This
Species is commonly about two
inches in breadth, and is not at
all uncommon, burrowing beneath
the surface near low-water mark
on most of our sandy beaches,
where the detached valves washed
on shore by the tides are often
picked up, and always admired.

FAMILY SOLENIDZ.
(Razor Shells.)

Every one who has_ paced
along the water's edge on a
sandy beach, is familiar with the
shells which form the type of this
family. ‘Their extreme narrow-
ness and length, (or, to speak
strictly, shortness and breadth,)

peammontA vEevbear we, Chel parallel sides and irmieste

RAZOR SHELLS. 285

extremities are so different from the forms of all
other shells, that even the unscientific observer
regards them with curiosity and interest. The
resemblance which the valves bear to the handle
(scales) of a razor 1s obvious, especially in such
species as are slightly curved. The valves are
thin and brittle, covered with an olive epidermis
which readily peels off. Beneath this the surface
is marked with strie recording the progress of
growth, which, following courses parallel to all of
the margins, impart a singular and peculiar aspect
to these shells.

The animals have the mantle united for a por-
tion of its edges, but allowing the protrusion of an
enormous foot, which is thick, long, and somewhat
club-shaped at the extremity. The siphons are
short, united more or less completely, and fringed
at the tips.

The species of this genus, which are not nume-
rous, live in sandy beaches near the verge of low-
water, or buried in the soil at greater depths.
They are most powerful and skilful burrowers,
often lying buried in a vertical position two feet
deep, though their ordinary habit is to go only so
low in the sand or mud, as to allow the extremities
of the siphons just to reach the top. “ They may
be said to have regular burrows. When the animal
is undisturbed, and the tide is in, it lies with the
tubes at the entrance of its perpendicular hole.
If it be disturbed, down it goes. In short, its life
is spent in descending to the depths of its burrow,
and ascending from it again, by means of the ex-
tension and contraction of its great muscular foot,
which is situated at that part of the shell which is
lowest.”

286 DIMYARIA.—SOLENID&.

GENUS SOLEN.

The characters already enumerated belong pre-
eminently to this, the principal genus; one or
two others which are associated with it presenting
them with less distinctness and with more approx1-

SOLEN.

mation to the neigbouring families. The hinge is
usually composed of a well-defined cardinal tooth
and a lateral fulcrum in each valve. It varies in
position. The hinder muscular impression is ob-

RAZOR SHELLS. 287

long, the anterior much lengthened. The pallial
impression is sinuated.,

Several species are common upon our sandy
shores, and as their flesh is highly esteemed, they
are taken in considerable quantities. When pro-
perly cooked, as by broiling, which is said to be
the most effective method, they are among the
most delicious of shell-fish.

The largest native species is Solen siliqua, which
is occasionally found eight inches in breadth, and
one in length. It may seem preposterous thus to
use the terms breadth and length, but the structure
of the shell as compared with other genera com-
pels such an application. The valves are nearly
straight, smooth, whitish, with purplish concentric
bands, covered with a yellowish epidermis. The
animal is large, and of a yellowish white hue.

“This shell is common on most of our sandy
shores, found buried to the depth of a foot or more,
near low-water mark; it frequently elevates one
end a little above the surface, and protrudes its
body in search of food: upon being disturbed, it
suddenly recedes. This place is known by a
small depression on the surface. In many places
it is sought after for food by the common people.”*
‘¢'The mode in which a dish full of these esculents
is rapidly collected by children, might successfully
be imitated by conchologists, for other than culi-
nary purposes; a long narrow wire, bent and
sharpened at one end, is suddenly thrust into the
hollows of the sands, indicative of the presence of
these animals, and passing between the valves,
the barbed portion fixes itself on retraction in the
animal, and forces it to the surface.” T

* Montagu, Test. Brit. 47. + Forbes and Hanley, i. 248.

288 DIMYARIA.—SOLENIDA.

The habits of a species closely allied to this
(S. marginatus) were made the subject of investi-
gation by the celebrated Reaumur, who published
an account of them, illustrated by figures, in the
‘ Mémoires de lAcadémie des Sciences,” for
1712. It burrows in sand near low-water mark,
spring-tides, to the depth of from a foot and a
half to two feet. The Solens he in their holes
nearly vertical, and their places are marked by
perforations shaped like keyholes, corresponding
to the form of the extremities of their united
siphons. They are nearly vertical, and do not
remain quiet, but rise up and down, now and then
shifting themselves partly above the sand, as if to
learn what is going on in the world above. When
the tide goes out they sink deeper. The fishermen
then endeavour to tempt them out as little boys
would catch birds if they could—by putting salt
on their tails. The salt penetrating the perfo-
ration, reaches and irritates the extremities of the
siphons, and the Solen, annoyed and pained, rises
suddenly to clear itself of the nuisance. His vigi-
lant human enemy watches the moment, and seizes
the opportunity—and the Solen, if he can catch
it; but unless very quick in his motions, those of
the Solen may be quicker, and once aware of the
danger impending, the sensible shell-fish will not
rise again, but submits patiently to the indignity
of being salted alive, rather than run the msk of
being caught and roasted, or else cut up for bait.
But if it be not touched, a second dose of salt will
cause it again to rise, which shows that knowledge
and recollection of the danger is the impediment
to its reappearance in the former case. Fishermen
in England have a queerly absurd fancy that when

GAPERS. 289

the razor-fish feels the salt, it thinks the tide is
coming in, and therefore rises in its hole.*

“Tf the Solen be taken out of its hole and placed
upon the sand, it immediately prepares to rebury
itself. It stretches out its foot to full length, and
then bends it so as to use the extremity as a sort
of auger. When the end has sunk into the sand,
it draws up its shell, which, first oblique, and after-
wards perpendicular, soon becomes immersed and
rapidly disappears. M. Deshayes, during his
Algerian researches, observed a remarkable in-
stinct of S. marginatus to swim when desirous of
changing its locality. When it finds itself on
ground too hard to be penetrated by its foot, it fills
the cavity of its mantle with water, and then con-
tracting and closing exactly at the same time its
siphonal orifices, elongates its foot ; then recontract-
ing that organ, it ejects the water with force from
the tubes, and thus propels itself after the manner
of a cuttle-fish for a foot or two forwards. Then if
it finds the surface favourable, it bores and buries
itself, but if not, it makes another leap to try its
chance anew.’ ’t

Famity MyYApa.
(Gapers.)

A large assemblage of genera of small importance,
presenting considerable variation in external form
and appearance, but having much more in common,
may, ina work such as the present, be conveniently
associated under the above title, the more especially
as they are united in one family by M. de Blain-

‘ville. He has named the group Pyloridea, includ-
* Forbes and Hanley, i. 244. + Ibid. i. 245.
U

290 DIMYARIA.—MYAD&.

ing in it the Solenide@ already described, as well as
the genera of which Messrs. Forbes & Hanley con-
stitute the three families Myade, Corbulide, and
Pandoride ; the British representatives of the last-
named two are few, and for the most part small,
though remarkable for the curious form of the shell,
which projects at one side as if distorted.

The shell in the MWyade is nearly regular and
equal-valved, oblong, and somewhat coarse in
appearance, gaping at the two extremities. The
hinge is incomplete, the teeth being gradually
effaced, but generally composed of one or two ob-
lique diverging folds. The ligament is sometimes
internal, sometimes external. There are two dis-
tinct muscular impressions connected by a pallial
impression, widely sinuated behind. The animal
is compressed, becoming in the different genera
more and more cylindrical, as well as more com-
pletely closed, and prolonged backwards into two
long siphons, which are ordinarily united, with
fringed extremities. In front, the mantle allows
the protrusion of a very small foot. The gills are
narrow, free, and prolonged into one of the siphons.

All the animals of this family live plunged in
the mud or sand, which is ordinarily covered by
the sea. They rarely change their place or their
position, invariably being vertically immersed, with
the siphons above and the foot beneath. Many of
the species grow to a large size, and as they are
both wholesome and palatable, they are on some
coasts much prized for the table.

GENUS MYA.

The hinge in this genus is composed of one or
two oblique folds, diverging backwards from a

GAPERS. 291

horizontal spoon-shaped process, belonging to the
left valve, and corresponding to a horizontal groove
or socket in the right. The ligament is internal,
inserted between the socket and the spoon-shaped
process. The shell is generally white, exhibiting
rude concentric lines of growth, and covered with
a wrinkled epidermis, which is continued over the
mantle and tubes of the animal.

The mollusk, thus encased in a thick and
leathery case, presents a close resemblance to one
of those Tunicated Ascidiw, which I shall pre-
sently notice, with the addition of a bivalve shell;
‘and no better mode could be devised of impress-
ing on the tyro in malacology the close affinity of
two great sections, so unlike in most of their
proper members, than the placing before him, side
by side, examples of the genera Mya and Cynthia.”

The species of this genus are eaten not only by
man; Otho Fabricius informs us, that on the in-
hospitable shores of Greenland, where they are
numerous, they are greedily devoured by the
walrus, the arctic fox, and by many predaceous
birds, as well as by large fishes,

We have two native species, both of consider-
able size, of which the larger is the Sand Gaper
(Mya arenaria), which attains a breadth of four
inches, and a length of nearly two and a half. It
is a coarse shell, of an earthy reddish or yellowish
hue, stained with dirty black, and marked by irre-
gular lines of growth. The animal, when its epi-
dermis is stripped off, is yellowish-white, the
orifices tinged with red; the investing coat is
brown, rough, and wrinkled.

This Gaper is common on many parts of our sea-
shore, in gravelly, clayey, or sandy ground, at low

292 DIMYARIA.—MYADA.

water, particularly near the mouths of rivers; and,
where it occurs, it is usually abundant. At South-
ampton they are dug up and sold for food, under
the name of “ Old Maids.” Their burrow, which

SAND GAPER.

descends to the depth of a foot or more, is indi-
cated by a slight depression on the wet surface,
from which, on the approach of a footfall, a jet of
water from the siphonal tube is spouted. A nar-
row spade or fork is instantly plunged down in an
oblique direction, with force sufficient to reach the
animal, which is then raised with a jerk, an evicted
tenant.

GAPERS. 293

One of the rarest of British bivalves (Panopea
Norvagica), allied to Mya, is an inhabitant of deep
water, and is interesting for its unusual square
form, and for its large size.

The following graphic account of Mr. Bean’s dis-
covery of this extremely scarce species is extracted
from the ‘‘ Magazine of Natural History,” wherein
the shell was first actually published as a native of
our seas: “ We have obtained at Scarborough three
specimens of this, in every sense of the word,
gigantic prize. To some of the fishermen of our
coast it appeared to be well known by the name of
the bacca-box, from a fancied resemblance to one of
their most useful household goods. They were all
caught by the hook, and rescued from destruction
ina singular manner. The first was destined for
a tobacco-box ; the second had the honour of hold-
ing the grease belonging to the boat-establishment ;
and the third, after amusing them (the members of
a philosophical society) by squirting water to the
ceiling, was at last seen by a learned friend, pur-
chased for a trifle, and generously placed in our
cabinet. The animal we have not seen, but its
colour is black.” Three additional individuals have
since then been obtained by Mr. Bean from the
same locality, and two single valves have been
dredged by Mr. M‘Andrew in ninety fathoms water,
twenty-five miles east of Zetland. It is likewise
captured, though very rarely, in deep water off the
Northumberland and Durham coasts (King and

Alder).*
* Cited in Br. Moll. i. 177.

294. . DIMYARIA.—GASTROCH ANID.

FAMILY GASTROCH ANID.
(Stone Borers.)

It is characteristic of all the families of Mollusca
lately noticed, that they live habitually concealed
in burrows of their own making. ‘These burrows
have, however, been commonly perforations in a
yielding medium, such as sand or mud, easily and
rapidly made by the animal, and obliterated as soon
as relinquished.

The species of the family last described occasion-
ally penetrate more resisting substances, such as
clay, and even chalk. But I have now to describe
genera which have the power of perforating the
hardest and most solid rocks. Some species, how-
ever, both of this and of the succeeding family,
though decided stone-borers, occasionally content
themselves with burrows in the softer materials.

In the family before us the shell is equal-valved,
but very unequal-sided, the valves usually gaping,
and connected by a hinge, which varies exceed-
ingly, sometimes being merely rudimentary, at
others having cardinal teeth. These latter, how-
ever, when present, are in some species lost under
certain conditions of growth.

The animal is oblong or club-shaped, with siphons
capable of great elongation, and united through
their whole length. The mantle is closed except
to give existence in front to a minute foot.

In the genus Gastrochena, represented by one
native species, the gallery perforated in the stone
is lined with a deposit of calcareous substance,
which forms a shelly tube frequently projecting
from the stone, and serving for the protection of

STONE BORERS. 295

the siphons when they are extended. Such an
one is now before me, which has been in my pos-

GASTROCHZENA.

session in a living state for several months, during
which time it has slightly increased the length of
its projecting tube by the addition of shelly
matter. Internally the tube gives indications of
a division into two, but the partition does not
extend to the middle from either side. The crim-
son tips of the siphons may often be seen when
the animal is undisturbed, just reaching to the tip
of the tube, or projecting in the smallest degree
beyond it. ‘The investing tube is found, on care-
fully breaking the stone, to enclose the animal
with its valves in a sort of flask or bottle. This
species (G. modiolina) is reckoned among our rarer
shells.

GENUS SAXICAVA.

No accessory tube is formed by the animals of
this genus, which live in the hardest rocks, espe-
cially those of calcareous formation. The shell is
oblong and gaping, with prominent beaks; the

2°6 DIMYARIA.—GASTROCH ENID

hinge furnished at one period of life with cardinal
teeth. The ligament is external and projecting.
The animal is oblong, with the mantle closed,
except in front, where exit is afforded for a minute
finger-like foot, furnished with a byssal groove
The siphons are united, and their orifices, which
are large, are margined with a fringe of simple
filaments.

SAXICAVA

“The Saxicave,’ observe the authors of the
British Mollusca, “ are borers, although the habit
of boring does not seem necessary to their exist-
ence, since we find them very commonly free. If
there be a crevice, however, in rock, shell, coral,
or sea-weed, into which they can thrust themselves,
they do so; and if near a limestone rock, perforate
it, and form crypts, in which they live. Mr. Osler
states that, when young, they are very active

STONE BORERS. 297

animals, and soon commence to perforate. Both
that gentleman and Mr. Garner have noticed that
their excavations are not round, nor the sides
smoothed off, like those of the holes made by
Pholas. As for us, we only know of their boring
into caleareous rocks, but Mr. Clarke has noticed
an instance of their perforating triassic sandstone
at Exmouth. Wherever we have a sea-coast of
mountain limestone, the surface of the rocks is
almost invariably found riddled by Saxicava. The
whole front of the Plymouth breakwater has been
attacked by it, and much alarm for its safety ex-
cited. Mr. Couch observes that the Sazxicava
never bores deeper than six inclies, and that, con-

sequently, unless a new surface be exposed by
the destruction of the perforated part, there 1s not
much danger. Owing, however, to the thinness
of the partitions, which often are the only separa-
tion between the crypts of these mollusks, there
is a great probability of the action of the sea
rapidly forming new surfaces in such cases. How
they bore has been as much discussed as the
question how Pholas bores. The general opinion
has been, that Sazicava bores by means of an
acid secretion ; an opinion held by many who will
not admit the probability of such an agent being
used by the Pholadide. My. Osler, though inclined
to such a view, could detect no acid, nor, for
reasons previously stated, is it likely. Mr. Han-
cock, as we have seen when treating of Pholas,
expressly asserts that the Saxicave bore by rasp-
ing, effected by means of siliceous particles con-
tained in the anterior part of the mantle. Mr.
Couch entertains a similar view. We have not
been able to satisfy ourselves of the presence of

.

298 DIMYARIA.—PHOLADIDZ.

such particles, though inclined to regard such a
view with favour, as in this case the surface of
the shell does not seem devised for rasping, as is
that of the shells of the Pholadide.” *

FamiILty PHOLADIDA.
(Borers.)

The members of this family have a very close
affinity with those of the last, both in structure
and habit, and have indeed been often united with
them by zoologists. They possess peculiarities,
however, which make their separation more natural.
The genera differ among themselves more in out-
ward appearance than in organization; they have
the body usually lengthened in various degrees,
and produced behind into very long siphons, which
are united through their length. The mantle is
closed except in front, where the foot protrudes ;
this organ is club-shaped, and has the extremity
obliquely flattened, so as to form a broad disk; it
is sometimes largely developed, at others minute.
The valves are equal, but very one-sided, always
gaping at both extremities; the hinge is without
teeth, and there is no proper hgament; each valve
is furnished with a curved calcareous process
beneath its summit, and at the back of the shell
there are generally two accessory plates resemb-
ling valves.

The mollusks of this group are as indomitable
borers as the Gastrochenade, but they less ex-
clusively confine themselves to hard substances.

* Brit. Moll. i. 138.

BORERS. Pied

Indurated mud, clay, and wood are perforated by
these animals as well as stone, and their boring
habits render them objects of painful anxiety to
those who are interested in submarine works.
The ship-worm (7Zeredo), whose terrible ravages
have been already alluded to (see ante, p: 41), is a
member of this family, though the great elonga-
tion of its body, the minuteness of its valves, and
the shelly tube with which it lines its burrow,
long caused it to be associated with the Worms
(Annelida), rather than with the Mollusca.

The fullest and most carefully prepared account
of the natural history of this animal was communi-
cated by Mr. W. Thompson to the Edinburgh
New Philosophical Journal, from which paper the
following interesting details of one of our British
species (of which we have unfortunately no fewer
than six) are extracted :-—

“ The greatest diameter of the testaceous tube
or case, at the larger end, is seven-eighths of an
inch ; at the smaller, it varies from one and a half
to two lines. All of the specimens have from one
and a half to two inches and upwards of the smaller
end of the tube greatly contracted within by
lamine, also the partition producing the double
aperture extending but a few lines from the very
extremity. ‘The greatest thickness of the shell 1s
at the smaller end, where, at the commencement
of the lamin, its consistence is from one-twentieth
to one-fortieth part of an inch: from this it becomes
gradually thinner towards the greater end, which
in the very largest specimens is found to be closed.
up, but in several others there is no deposition
whatever of testaceous matter for some distance
from the termination of the cell. In one perfora-

300 DIMYARIA.—PHOLADID&.

tion, about twenty inches long, the body of the
animal has had no testaceous covering for the last
three and a half inches; in two other. cells, of
about two feet, no deposition appears for four and
a half, and four inches and three quarters from
their termination. All the timber at Portpatrick
in which the Teredo had formed its habitation, is
pine, and perhaps to this circumstance the supe-
rior size of the animal may chiefly be attributed.
Though it is well known that the Teredo bores in the
direction of the grain, 1t may be observed that it
does so whether the position of the wood be per-
pendicular or otherwise. Captan Fayrer remarked,
that it has a decided disposition to work horizon-
tally. It is, however, often obliged to deviate
from a straightforward course, to avoid such
obstructions as nails, timber-knots, and tubes of
its fellows, and make a winding or angular habi-
tation according as such impediments occur ; but
these circumstances seem not eventually to impede
the progress of the animal, as some of the very
largest specimens I have examined are the most
tortuous. During the nine or ten years that the
Teredo has been established at Portpatrick, it has
not degenerated ; as specimens just received, which
were alive in their native element a few days ago,
are of equal size to those sent from the same place
five years since, showing that it has not been
affected by the cold of the winter season, as we
might reasonably expect were the animals truly
exotic. Ifthis animal had originally been intro-
duced, and has been preserved only by occasional
* importations, should we not rather look for it in
those parts of the United Kingdom where vessels
from every quarter of the globe are congregated,

BORERS. 301

than in the obscure harbour of Portpatrick, which
has never been visited by a foreign craft?” *

GENUS PHOLAS.

The shells of this genus are of delicate and
fragile texture, and of a pure white hue, when un-
defiled by extraneous substances. The valves are
much developed behind, gaping at both ends, but
especially in front. Their exterior surface is
rough, with transverse scaly ridges and furrows.
A spoon-shaped process springs from beneath the
beaks in each valve, directed forwards. The beaks
are covered by a callosity, and there are accessory
plates or valves at the back of the shell.

The animal is thick and club-shaped, with long
siphonal tubes united externally into one. The
foot generally is large, thick, oblique, and flat at
its extremity. The burrows in this genus are
never lined with a shelly coat.

Frequent mention has been made in the pre-
ceding pages of the siphonal tubes, with which
many genera of Conchifera are furnished; and it
has been explained that, whether apparently united
in one or obviously distinct, these tubes are the
external organs accessory to respiration. Even
when apparently united, as in the present genus,
a glance at the very tip shows that there are two
openings, one of which is a little smaller than the
other, and commonly this subordinate orifice di-
verges at a slight angle from the principai one.

The latter is the entrance, the former the exit
for the water, a perpetual change of which is abso-
lutely indispensable to the life of the animal. The

* Edin. New Phil. Journ. 1835.

302 DIMYARIA.—PHOLADIDA.

interior of these tubes is said to be lined with
innumerable delicate cilia; by the action of which
the surrounding water is drawn towards the enter-
ing orifice, and conveyed in a strong current
through the tube over the surface of the gills.
Then, having been deprived of its oxygen, it is
poured through the other tube and expelled in a
jet at its extremity, by a similar machinery.

This apparatus of double siphonal tubes is prin-
cipally developed in those species which burrow,
whether in sand, mud, wood or stone. As the
burrowing bivalve usually, if not always, dwells
in the interior of the passage it has excavated, it
is needful that there should be a communication
with the external water, and hence a hole is always
found extending to the surface of the material
bored. ‘The entering and departing currents keep
this passage clear, a process which in mud or sand
might seem at first not very easy of accomplish-
ment. It is facilitated, however, by the faculty
which the boring bivalves have of lengthening the
siphonal tubes at will; and the degree to which
this may be accomplished depends on the depth of
the cavity which the species is accustomed to
make.

If we take one of the stone-boring Mollusca, a
Pholas or a Saxicava for example, from its excava-
tion, without injuring the animal, and place it in
a glass vessel of sea-water, it will not be difficult
to detect the currents in question, even with the
naked eye; though a lens of moderate power will
render them more distinctly appreciable. The
vessel should be so placed as that the light may
be nearly, but not exactly, opposite to the eye.
By this arrangement the minute atoms of floating

BORERS. 303

matter are illuminated while the back-ground is
dark, and these by their motion clearly reveal the
currents of the fluid in which they are suspended.
A few moments’ practice will enable even an un-
accustomed eye to perceive the atoms converging
from all points around, with an even but increasing
velocity, towards the principal tube, down which
they disappear like the streams of passengers and
traffic in the neighbourhood of a great city, con-
verging towards it as to a common centre of
attraction by a hundred different routes. The
current of the expelling tube is even still more
marked in its character; a forcible jet of water is
periodically ejected from this orifice, which draws
the surrounding particles into its vortex, and
shoots them forward to a distance of many inches.
It is by the expulsive force of this anal current,
chiefly, that the passage is kept free from the
deposit of mud and other substances, which would
otherwise soon choke it up.

A fresh supply of water for respiration, and its
dismissal when no longer fit for use, are efficiently
provided for by this contrivance. But since many
particles of matter float in the water, which from
their form or other qualities might be hurtful to
the delicate tissues of the viscera to be traversed,
how is the entrance of these to be guarded against
in an indiscriminating current? A beautiful con-
trivance is provided for this necessity. The mar-
gin of the entering siphon, and sometimes, though
more rarely, of the ejecting one, is set round with
a number of short tentacular processes, varying
indeed in their length, but the longest scarcely
more than equalling half the diameter of the mouth
of the tube. In Sazicava rugosa, which bores

304 DIMYARIA.—PHOLADIDA.

through and through, with small holes, the hard-
est limestone of our coast, these tentacular append-
ages are found fringing both the tubes. The
tentacles in this species are simple, and appear as
if cut off transversely; and some are not more
than half as long as the others, with which they
irregularly alternate. The object of this diversity
in length will be manifested presently. In Pholas
parva, the processes are few and short, and are
confined to the receiving tube, from the interior
margin of which they project, towards the centre.
But it is in Pholas dactylus, a noble species of
large size, that excavates the softer rocks on our
shores, that this apparatus is developed with pecu-
liar beauty, and its use is made most clearly
manifest. The tentacular filaments are in this
case also confined to the oral tube. They are
numerous, each forming a little tree, with pinnate
branches, bearing no small resemblance to the
flower of feathery branchie, that expands around
the mouth of a Holothuria. ‘These branched ten-
tacula are ordinarily bent down across the mouth
of the tube, the longest of them just meeting in
the centre; alternating with these are placed
others of similar structure, but inferior size: and
the interspaces are occupied by others smaller
still, and simply pinnate ; so that when the whole
occupy their ordinary transverse position, the
small ones fill up the angles of the larger, and the
branches of all form a net-work of exquisite
tracery, spread across the orifice, through the in-
terstices or meshes of which the current of enter-
ing water freely percolates, while they exclude all
except the most minute floating atoms of extraneous
matter.

BORERS.

305

The mode in which the boring Mollusca execute

their perforations is yet a
matter of uncertainty. ‘The
principal hypotheses that
have been put forth on the
subject have been already
briefly enumerated, but it
may not be amiss to add an
expression of opinion on
their value, and a careful
summing upof the evidence,
by zoologists eminently
worthy of deference, theable
authors of the “‘ British Mol-
lusea.”

‘¢ Of all these theories,”
observe Messrs. Forbes and
Hanley, “the chemical one,
so far as a secreted solvent
is concerned, bears least ex-
amination in the case of
the Pholadide. 'The sub-
stances perforated are wood,
limestones, hard and soft,
argillaceous shales, clays,
sandstone, and (in the case
of a Pholas, in the mag-
nificent collection of Mr.
Cuming) wax. The notion
of a secreted solvent, that
would act indifferently on
all these substances is, at
present at least, purely hy-
pothetical ; and, since all

attempted tests have failed

x

PHOLAS.

to detect an acid,

' 306 DIMYARIA.—PHOLADID.

gratuitously so; for we can hardly suppose that
any of those who have taken this view of the
cause would maintain, that the animals have the
power of secreting different acids at will, according
to the substance they have ‘to attack. Yet this
notion has been most favoured by naturalists, who,
sceptical as to the perforating power of such fragile
instruments as are the shells of many of these crea-
tures, endowed the animals with supernatural che-
mical qualifications. Even good experimental
observers—Mr. Osler for one—whilst they proved.
that the Pholas could bore mechanically by the
rotation of its valves, could not free their minds
from the prejudice in favour of a solvent. The
important statement put forward by Mr. Albany
Hancock, respecting the instruments by which
Mollusca bore, and which, so far as Gasteropoda
are concerned, appear to furnish us with a true
explanation,—namely, that it was effected by
means of silicious particles, variously arranged in
certain portions of the animal’s body,—led us to
hope that a better cause than any yet alleged had
been discovered. But we cannot bear it out with
respect to the Pholadide. We can find no such
particles in the mantle of the Teredo, nor have any
been noticed by Home or Deshayes, or by the most
recent observers, Fray and Leuckart, who paid
especial attention to the structure of the tissues in
this genus. Nor could we, although aided by the
anatomical and microscopical skill of Mr. Busk,
detect any silicious particles in either the mantle,
foot, or siphon tube of Pholas candida. If present
in any species, therefore, they are exceptional, so
far as the genus Pholas and its allies are concerned.
The shells of several British species of Pholas, and

BORERS. 307

that of Pholadidea, have been chemically examined
by our friend, Mr. Trenham Reeks, with a nega-
tive result as regards the presence of particles of
silex in their substance, where, after the statement
of Mr. Hancock respecting the structure of the
mantle, we thought they might possibly be found.
On the other hand, taking into consideration its
mineralogical nature, as stated by M. Necker, there
is no reason for supposing that the shell of the Pho-
ladide is so weak a perforating instrument as some
have fancied. With its peculiar form, and the
saw-like asperities of its surface, especially of its
anteal extremity, it is well adapted for an auger,
when wielded fresh and elastic by its well-muscled
animal inhabitant, whose foot, in all the members
of this tribe, even in Zeredo, where it is least de-
veloped, seems specially organized to serve as a
fulcrum. We have no evidence that they perforate
any substances essentially harder than their shells,
or so hard. ‘The sandstones in which they occa-
sionally occur are either friable or marly, when
fresh, though cabinet specimens seem so solid.
The explanation of Necker accounts for their per-
forations in the hardest limestones. Wood, wax,
and other substances in which they occur, offer no
difficulty. The statements put forward respecting
their boring in lava and granite, have long ago
been shown to be mistakes. That they exhibit a
rotatory motion, during the action of boring, has
been proved by competent observers; and the
cavities they excavate, if examined when fresh,
invariably show transverse groovings, which could
have been caused only by such motions. Currents
of water, set in motion by cilia, doubtless aid mate-
rially the animal’s operations, and possibly may

308 DIMYARIA.—PHOLADIDA.

be the means by which the larvee effect their first
lodgment; but, considermg the arrangement of
the parts of the body in the adult animal, it seems
to us that Mr. Garner’s view of their being the
primary cause of the perforation, whilst the rasping
of the valves is secondary, should be reversed.
Such currents must be most effective in clearing
away loosened and loosening particles. If there
be any chemical action aiding, it must be due to
the carbonic acid set free during the respiratory
process. Evidence of a secreted solvent there is
none.

To the same authority I am indebted for another
interesting fact in the history of this genus.

“A remarkable property of the animals of this
genus, and one which has long attracted notice, is
their phosphorescence when placed in the dark.
This phenomenon is exhibited by some other
acephalous mollusks, and by the compound tuni-
eated genus Pyrosoma. The light is of a bluish-
white hue, and is regarded by Mayer to proceed
from a luminous mucus, like that given off by the
Meduse. ‘This mucus is thrown off into the sur-
rounding water, so that the currents proceeding
from the animal are luminous. Dr. Coldstream
states, that the light is given out most strongly by
the internal surfaces of the respiratory tubes, and
that it is strongest in summer. Professor John
Miiller has observed, that when Pholades are placed
in a vacuum, the light disappears, but reappears on
the admission of air; also that, when dried, they
recover their luminous property on being rubbed
or moistened.” *

* Brit. Moll. i. 104, e¢ seq.

ARM-FOOTED MOLLUSKS. 309

CLASS V. BRACHIOPODA.

(Arm-footed Mollusks.)

THE animals bearing the above title are inhabit-
ants of bivalve shells, one valve of which is fre-
quently perforated, to give exit to a fleshy peduncle
or stem, by which the animal is affixed to the rocks.
When we open the two valves of the shell, we tind
each of them lined with a broad membrane, very
thin, delicate, and semi-transparent, which together
constitute the mantle. The edges of these mem-
branes are thickened, and fringed with organs,
already several times mentioned in these pages, and
which we shall see assuming great importance as
we investigate the economy of the lower tribes of
animals. ‘hese organs are called cilia, and consist
of very subtile and microscopically minute hairs,
arranged in close series, and capable of moving in
unison, with vibratile waves, and of thus producing
rapid currents in the water.

At the bottom of the cleft formed by the two
leaves of the mantle, the mouth is placed, on each
side of which is a long fleshy process, fringed all
along one side with delicate hairs. In some species,
these arms (which give name to the Class) are enor-
mously developed ; they are free for their whole
length, and are capable, at the will of the animal,
of being coiled up in many spiral folds, or of being
protruded from the shell to a distance equal to
thrice its length. The mechanism by which they

310 BRACHIOPODA.

are unfolded is simple and beautiful. ‘The stem of
the process is hollow, and partially filled with a
fluid, which being forcibly injected towards the
extremity, by the contraction of a double series of
muscles behind, the whole of the lengthened organ
is straightened and projected.

Most of the species have a shelly frame-work
within one of the valves, consisting of slender
loops and arches, variously arranged, and more or
less complex. This is intended to support the
fringed arms, and to keep the valves open, or even
to assist in opening them; for there is in this
class nothing corresponding to the hinge-cartilage,
which performs the latter function in the Con-
chifera.

Respiration in these animals seems to be per-
formed by the mantle itself; the long fringed arms
having apparently nothing to do with this office,
notwithstanding their gill-like structure.

Some of the species are found in the shallows of
sandy shores; but others inhabit the darkness and
solitude of the deep sea; some of the Terebratule
dwelling in water from sixty to ninety fathoms
deep; while Crania personata has been dredged
up from a depth of 255 fathoms. The respiration
and nutrition of animals that can subsist beneath a
pressure so enormous, are subjects, as Professor
Owen remarks, “ suggestive of interesting reflec-
tions, and lead one to contemplate with less sur-
prise the great strength and complexity of some of
the minutest parts of the frame of these diminutive
creatures. In the unbroken stillness which must
pervade those abysses, their existence must depend
upon their power of exciting a perpetual current
around them, in order to dissipate the water already

ARM-FOOTED MOLLUSKS. Sit

jaden with their effete particles, and to bring within
the reach of their prehensile organs the animalcules
adapted for their sustenance.”*

Genus TEREBRATULA.

In this genus, which I select to represent the
Class, the valves are unequal; and the lower one,
more prominent than the other, is perforated to
admit the passage of a short fleshy stem, by which
the animal is firmly attached to rocks, and other
foreign bodies. The shell is delicate in texture,
more or less triangular, and symmetrical. The
shelly frame-work of the arms, sometimes called
by collectors the carriage-spring, is attached to the
inner surface of the upper valve, or that which is
not perforated.

Most of the species of this genus, as of the whole
Class, are known only in a fossil state ; those which
are recent are widely diffused, and flourish in ex-
tremely warm and extremely cold climates, as well
as those which are intermediate. ‘Thus some are
found in the Indian ocean, beneath the equator ;
while the 7. psittacea, brought home from the late
Arctic expedition, was dredged at Boothia in the

Polar sea.
* Comp. Anat. i, 279.

312 TUNICATA.

CLASS VI. TUNICATA.
(Ascidian Mollusks.)

THE calcareous shell entirely disappears in the
animals of this Class, their organs being enclosed
in a case of leathery substance, more or less thick
and tough, usually called the tunic or test. In
general, they bear a close resemblance to the
Conchifera, if the latter be deprived of their pro-
tecting valves, as has already been noticed in
speaking of the Myade. The ordinary form which
they assume is that of a leathery, usually semi-
pellucid sac, with two openings, the one for the
entrance, the other for the exit, of the nourishing
water. The gills never appear in the form of free
leaves, but constitute a kind of bag, the surface of
which is covered witlr oblong cells or depressions,
lined with cilia. Their circulatory system has this
remarkable peculiarity, that it ebbs and flows: the
blood, being driven from the heart through the
vessels in one direction for a certain time, suddenly
stops, and after a few moments pursues a retrograde
course for a like period.

All the Tunicate Mollusca are marine; many of
them are permanently fixed to other substances, -
others are permanently free; all, however, have
the power of locomotion during the infancy of their
existence. Some of the genera are single and
isolated ; others are social, always living aggre-
gated in groups; and others are united into masses,

ASCIDIAN MOLLUSKS. S13

organically possessing a compound life. Through
these last-named the transition is easy and natural
to the lowest forms of animal life, the Polypes ; for
the Class of animals denominated Lryozoa or
Polyzoa, which form the exquisite aggregations of
calcareous cells known as Sea-mats (/lustra), and
their allies, are truly Ascidians in their structure,
with their entering orifice surrounded by a radiated
circle of ciliated tentacles.

FAMILY ASCIDIADA.

Whoever has turned over stones at the extreme
verge of low-water (and there is no student of
marine natural history who has not) is familiar
with uncouth pellucid bodies adhering to their
under surfaces, that resemble bags, of a substance
somewhat between leather and jelly. The dredger,
however, is far more familiar with them, for
scarcely can any part of the bottom of the sea be
raked without an abundance of these curious crea-
tures being brought up, varying much in size and
colour. Some are sufficiently rude and uncouth,
coarse and rough in texture, and dingy in hue;
others are attractive, often of brilliant colours, of a
semi-transparent clearness, resembling strange pel-
lucid fruits, or masses of ice. They are always
found adherent, either by the base of the sac or by
its side, to foreign bodies, as stones, shells, and
sea-weeds, and thus not only are they deprived of
locomotion, but almost of all appearance of vitality,
for no movement is perceptible in them externally,
except the periodical opening and closing of the
two orifices which give admission and exit to the
currents of water for respiration and food.

314 TUNICATA.— ASCIDIAD A.

The branchial sac occupies the upper part of the
animal ; its interior surface is divided into cells by
plaits or ridges, which are clothed with cilia; its
orifice is surrounded by a cirele of tentacles, and
its inferior extremity merges into the digestive
tube. For as the food of these animals consists of
microscopic organisms, which are drawn in by the
entering currents, the same influx of water brings
oxygen for the respiration, and food for the nutri-
ment of the system.

The water, in yielding its vital properties, passes
towards the bottom of the body, and then returning
by an upward course is discharged through an
orifice closely resembling the other in appearance,
and situated near to it on one side. Both orifices
can be completely closed at will, by being drawn
together in wrinkles, and each is commonly sur-

ASCIDIA VIRGINEA.

rounded with minute coloured specks, that are con-
sidered to represent eyes. These specks are usually
eight around the receiving orifice, and six around
the discharging one.

SOCIAL ASCIDIANS. 315

The species of this family are very numerous:
nearly fifty are enumerated as British; and pro-
bably not half of the whole number have yet been
described. One of the most common is Ascidia
virginea, Which grows to an inch and a half in
length, and about three quarters in breadth. It is
pellucid and crystalline, of a pale yellowish tinge,
revealing through the test the branchial sac, spot-
ted with crimson, and crossed with lines of white.
It adheres to stones, dead shells, and living sea-
weeds in deep water.

FAMILY CLAVELINADZ.

(Social Ascidians.)

In essential points these resemble the preceding
family, but the individuals are not distinct, but
united by a common root-thread, from which they
spring, like buds from a creeping root-stock. The
thread creeps over the surfaces of stones, the stems
of sea-plants, &c., continually growing by a length-
ening of its extremity, and increasing by throwing
out, either in groups or at regular intervals, a kind
of buds, that develop into Ascidian mollusks,
which commonly stand on more or less distinct
foot-stalks.

The family may be illustrated by the accom-
panying figure, greatly magnified, of a tiny species
(Perophora Listert), found occasionally on our own
coasts. I obtained the individual from which the
figure was taken at Ilfracombe, attached to a frag-
ment of sea-weed. It is, to the naked eye, a
globule of clear jelly, not larger than a pin’s head,
yet disclosing, under the microscope, an elaborate

316 TUNICATA.—CLAVELINADA.

system of organs for respiration, circulation, and
digestion.
The rows of oval rings are the cells of the

e
en, ”*
ao 2?

oO 7h Re

9
.
>
°

. ° eo” x
moan

PEROPHORA.

branchial sac, and the arrows show the course of
the blood as it circulates from the oblong heart at
the bottom of the body all around the system.

STARRY ASCIDIANS. S14

FAMILY BOTRYLLIDA.
(Starry Ascidians.)

The stones that are ordinarily covered by the
tide, and the coarser sea-weeds, such as the Fucz
and Laminarie, that grow at low-water, are very
frequently studded with irregular patches of dark-
coloured substance, gelatinous to the feel, and often
somewhat brightly coloured, the more common
hues being blue, purple, green, grey, and white.
On closer examination, we find embedded in this
mass, circles of stars, each consisting of a definite
number of bright-hued, minute, oblong bodies,
radiating from a common centre.

These masses belong to the genus Botryllus, the
representative of the family before us; and each
radiating point is an individual animal. From ten
to twenty of such animals are ordinarily grouped
together to form one of the wheel-like systems ;
and there are often as many systems in one en-
crusting mass.

The organization of these little animals is in
general conformable to what has been already
described; but the discharging orifice of each
individual is placed at the opposite end from the
mouth, and opens into the common centre, which,
rising with a circular rim, expands and contracts
as a discharging orifice for the whole of that
system.

Several species of this genus are common with
us, one of the most abundant of which is the
Botryllus polycyclus, which is found encrusting
the broad leaves of the common Tangle (Laminaria
digitata). Itis of a bluish purple hue, with the
individuals marked by white rays.

318 TUNICATA.—SALPADA.

Other genera in this family form similar encrust-
ing masses, but the animals are placed in irregular
tortuous lines instead of stars, and the two orifices
are near together. Others do not encrust foreign
substances, but are grouped in variously shaped

knots, or fruit-like bodies, adhering to stones and
shells.

FAMILY SALPADA.
(Swimming Ascidians.)

The body in this group is free, or not adherent ;
more or less cylindrical; with a thick external
envelope, which is somewhat cartilaginous; trans-
parent; having the two orifices, which are ordina-
rily very large and distant, nearly terminal, one at
each extremity. The branchie, in the form of a
narrow band, traverse obliquely the respiratory
cavity of the receiving orifice to the aperture of
the mouth.

M. de Blainville remarks, that one may easily
perceive the relationship of this family to the other
Tunicata, by supposing an Ascidia slit between the
two tubes which terminate it, and then extended
lengthwise. It is then, he observes, easy to
determine the analogy of the apertures, of which
neither the one nor the other is properly any more
the mouth or the anus than in the Ascidie ; but
one (the widest, the greatest, and the most distant
from the mouth), is the entrance of the incretory
or respiratory tube, and the other is that of the
excretory tube. He adds, that the species of
this family are, like those of the preceding, suscep-
tible of living solitary, or aggregated in a fixed

SWIMMING ASCIDIANS. 319

manner, which would seem to make them compo-
site animals, though they are not such; and he
divides it into two tribes:—1. The simple Sal-
paceans (Salpa); 2. The aggregate Salpaceans
(Pyrosoma). .

‘A great interest,’ observe Messrs. Forbes and
Hanley, “is attached to the natural history of the
Salpe, on account of their singular mode of repro-
duction, discovered by the German naturalist
Chamisso, and the extraordinary generalization to
which that discovery in a great measure gave rise.
Previous observers had noticed that these animals
were sometimes found solitary, at others united
together in long chains, composed of numerous
individuals of similar form, each an independent
being, though constantly associated, and linearly
ageregated with its companions. These long
chains swim through the tranquil water with
regular serpentine movements; for the creatures
of which they are composed contratt and expand
simultaneously, keeping time, as it were, like a
regiment of soldiers upon parade. Each chain
seems, consequently, to be a single being, acting
through the influence of an unique will; and hence
sailors often look upon it as a reptile; and in many
seas the Salpa-chains are called sea-serpents. But
when taken out of the water, the links of the chain
fall asunder, the several distinct animals of which
it is composed suddenly losing their power of ad-
hesion. In consequence of accidents, broken-up
chains and separated members of such communities
are not unfrequently met with, in seas where Salpe
are numerous. But other Salpe are also met with,
very dissimilar in form, and never united together
in chains. Now, the discovery of Chamisso was,

oA 0) TUNICATA.—SALPADA.

that such constantly solitary Salpe did not belong
to species distinct from those united in chains,
however dissimilar (and they are so dissimilar
usually, as to appear even generically distinct),
but were either the parents or the progeny, as the
case might be, of the aggregate forms; that chained
Salpe did not produce chained Salpe, but solitary
Salpe, which, in their turn, did not produce solitary
beings, but chained. Cansequently, as Chamisso
graphically observes, ‘a Salpa mother is not like
its daughter or its own mother, but resembles its
sister, its grandaughter, and its grandmother.’” *

More recent researches have fully confirmed the
correctness of these observations, strange as they
at first appeared. Nor are the facts so singular as
they were then believed to be; for the same law
(now known as that of the Alternation of Genera-
tions), has been found to prevail extensively in the
Meduse and Hydroid Polypes.

One or more species of this genus have been at
various times observed in the seas which wash the
British coasts; and the first detection of the genus
we owe to the eminent geologist, Dr. McCulloch.
His graphic description of the discovery is so in-
teresting, that I shall give it with a slight abridge-
ment, though it repeats some details already
mentioned. The. species was probably Salpa
runcinata. }

“Some marine animals occur in these seas
which remain still unrecorded in the catalogue of
British zoology. Among these, indeed, it is pro-
bable that a few will be found still undescribed by
naturalists, since fresh additions are even yet
occasionally made to our catalogue of these ob-

* Brit. Moll. i. 47.

SWIMMING ASCIDIANS. PAL!

scurer parts of the creation. Many of these animals
have occasionally fallen under my notice; but amid
pursuits which rendered it impossible to attend
either to their examination or preservation. I have,
however, preserved a memorial of one, as it appears
to form a new species, in a tribe of which no indi-
vidual has yet been observed within the limits of
the British seas. It belongs, apparently, to the
genus Salpa. .. .

“The mode in which the republic is linked
together, is observed to be constant in each species;
and it is sufficiently remarkable in this one, to
distinguish it from the rest of the genus, as far as
it is yet described. Hach individual adheres to the
preceding, by a regular sequence of superposition,
lengthwise ; so that the whole forms a long, simple
chain, the adhesion continuing as in the ovarium,
for some time after hatching. They were found
from the middle to the latter end of August, and
always linked together. Itis probable that their
separation takes place at a later season of the year,
but I did not observe them in that state. The
individual is amongst the most simple in shape of
those yet described, presenting an oval-lanceolate
and slightly rhomboidal flattened figure, without
appendages. ‘The anal opening is of a bright
brown hue, and circular, being placed at some
distance from the extremity; and when the chain
is linked together, all these apertures are directed
the same way. ‘The animal is perfectly hyaline,
and tender, and the adhesion of the chain so slight,
that the individuals are easily separated. The act
of swimming is known to result from the introduc-
tion and emission of water by each animal: and as
the republic swims together by an undulating

x

322 TUNICATA.—SALPADZ.

motion resembling that of a serpent—the chain
often extending to many feet in length —it 1s
evident that this motion must arise from the un-
equal manner in which the different individuals
act throughout the whole line... .

‘“‘T had occasion to remark of this animal, that,
like the MWeduse and analogous tribes, 1t cannot
bear to be confined in a limited portion of water,
as it died, even in the ship’s bucket, in less than
half an hour—a very remarkable circumstance in
the economy of these imperfect animals.

“Hitherto, this genus is only known as the
inhabitant of hot climates, and of the Mediterra-
nean Sea. I found it in great abundance in the |
harbours of Canna and Campbelltown, rising to the
surface in calm weather, and crowding the water
as the Meduse often do at the same time of the
fremr ss, Se:

“JT was desirous of observing whether this
animal, like many other of the marine worms,
emitted light, but had no opportunity of ascertain-
ing the fact, as they seemed always to retire to the
bottom at sunset, and those which were taken on
board died (as I have already observed), in a very
short time.” *

The Pyrosomata are aggregated in another man-
ner. ‘They consist of lengthened individual Asci-
dians, united to each other at their basal part, and
free at the opposite extremity, with their connexion
so arranged as to compose numerous and regular
rings, which concur to form a long, free cylinder,
or tube, open at one extremity and closed at the
other.

Cuvier states, that this great cylinder swims

* Western Isles, ii. 187.

SWIMMING ASCIDIANS. 323

in the sea by means of the combined contractions
and dilatations of all the individual animals which
compose it. The branchial orifices are pierced
near the points, and the anus opens into the inte-
rior cavity of the tube. Thus, says Cuvier,
one may compare a Pyrosoma to a great number
of stars of Botrylli, strung one after the other, but
the whole of which would be moveable.

Mr. George Bennett, in his interesting ““ Wan-
derings in New South Wales,” after some valuable
remarks on the luminosity of the ocean, proceeds
as follows :—

“On the 8th of June, being then in latitude 30’
south, and longitude 27° 5’ west, having fine wea-
ther and a fresh south-easterly trade-wind, and the
range of the thermometer being from 78° to 84°, late
at night, the mate of the watch came and called
me to witness a very unusual appearance in the
water, which he, on first seeing it, considered to
be breakers. On arriving upon the deck, this was
found to be a very broad and extensive sheet of
phosphorescence, extending in a direction from
east to west, as far as the eye could reach. The
luminosity was confined to the range of animals in
this shoal, for there was no similar light in any
other direction. I immediately cast the towing-
net over the stern of the ship, as we approached
nearer the luminous streak, to ascertain the cause
of this extraordinary and so limited phenomenon.
The ship soon cleaved through the brilliant mass,
from which, by the disturbance, strong flashes of
light were emitted ; and the shoal, judging from
the time the vessel took in passing through the
mass, may have been a mile in breadth. The
passage of the vessel through them increased the

324 TUNICATA.—SALPADA.

light around to a far stronger degree, illuminating
the ship. On taking in the towing-net, it was
found half filled with Pyrosoma (Atlanticum?),
which shone with a beautiful pale-greenish light ;
and there were also a few shell-fish in the net at
the same time. After the mass had been passed
through, the light was still seen astern, until it
became invisible in the distance; and the whole of
the ocean then became hidden in darkness as be-
fore this took place. The scene was as novel as
beautiful and interesting ; more so from my having
ascertained, by capturing luminous animals, the
cause of the phenomenon.

‘The second occasion of my meeting these crea-
tures was not exactly similar to the preceding;
but though also limited, was curious, as occurring
in a high latitude, during the winter season. It
was on the 19th of August, the weather dark and
gloomy, with light breezes from north-north-east,
in latitude 40° 30° south, and longitude 138° 3’
east, being then distant about 868 miles from
King’s Island (at the western entrance of Bass’s
Straits). It was about eight o'clock p.M. when the
ship’s wake was perceived to be luminous; and
scintillations of the same light were also abundant
around. As this was unusual, and had not been
seen before, and it occasionally, also, appeared in
larger and smaller detached masses, giving out a
high degree of brilliancy,—to ascertain the cause,
so unusual in high latitudes during the winter
season, I threw the towing-net overboard, and in
twenty minutes succeeded in capturing several
Pyrosomata, giving out their usual pale-green
light ; and it was, no doubt, detached groups of
these animals that were the occasion of the light

SWIMMING ASCIDIANS. 325

in question. The beautiful light given out by
these molluscous animals soon ceased to be seen
emitted from every part of their bodies; but by
moving them about, it could be reproduced for
some length of time after. As long as the lumi-
nosity of the ocean was visible (which continued
most part of the night), a number of Pyrosoma
Atlanticum, two species of Phyllosoma, an animal
apparently allied to Leptocephalus, as well as
several crustaceous animals (all of which I had
before considered as intertropical species), were
caught and preserved. At half-past ten p.m. the
temperature of the atmosphere on deck was 52°,
and that of the water 514°. The luminosity of
the water gradually decreased during the night,
and towards morning was no longer seen, nor on
any subsequent night.” *

* Wanderings, vol. i.

PAGE
Crowned Eolis 125
Cuttles . 3,18, 23, 31, 33, 38, 58,

60, 66, 68
D:
| Dog-winkle 181, 184
Donax J ney eee sil
Doris 106, 107, 108, 124
E.
Ear-shells . 37
Edible Mussel 256
Edible Snail 92, 94
Eolis . . 122,123, 124
F,
Fin-footed Mollusks rel
Flying Squid . 67
Fools-cap Limpet 212
Freshwater Mussel . 259
Frill . 230
G.
| Gaper oe eee
Gaping Bulla . 147, 148.

A.
PAGE
Argonaut . ih) Be
Ark of Noah . 253, 254
SAGA, ge efi eels 252
Arm-footed Mollusk 309
Ascidian ditto 312
B:
Bivalves . 18,18, 24, 30, 50,223 |
Borers 298 |
CG:
Cap of Liberty . sas
Cephalopods . 61, 63, 70
Chitons 76, 160, 161
Clamps . 273 |
Clams : ay 20
Clon 5 ee ees
Cockle . 24, 26, 33, 219, 222, 270
Comb-gilled Mollusks . 163
Conchifera . > 48
Conchs . Jk, to
Covered-gilled Mollusks 127
Cowry 37, 76, 136,171
Crawling Mollusks . 127 |

INDEX. 327
PAGE | PAGE
Garden Snail. . 11, 26, 27,90 | Many-ribbed Harp . 57, 178
Gasteropods . 136, 151,217,252 | Marsh Snails . 202
Giant Strombus . 12°} Mussel . 33, 43, 48, 50, 183
Glass Shells FL. |) “Mya. 292
Glaucus . IVT, 14, 1h5, 116
Granulated Top . 207 N.
Grey Slug . 98
Grey Top . 909 ako eed Mollusks . 99
Great Scallop . 6, 230 ES Poa age 186
Names ss acc at 6 5
H. Nerits haa RE
Head-footed Mollusks . 58 Nudibranch Mollusea 103, 136,
Heart-shell 273 uae
Helmets Sere ae ey O.
Hungarian Bonnet . . . 212
Old Maids . 292
I. Orange Cowry Biel
Illyrian Snail . 35 Oyster 35, 37, 219, 222, 233
Imperial Sun . 206
Isocardia 275 Pp.
Paper Nautilus 22, 64
K. Pearl Mussel 259, 264
Keyhole Limpets 210 | Pearl Oyster . 240
Pearly Nautilus . 22, 64
Ls Pearly Top 206
Lake Mud-shell . 86 | Pecten 226, 228
Lima Gs ee) Pelicairstogt ) 196
Limpet 18,26,32, 52,128, 150, 154 Perspective Staircase . 206

Lung-breathing Mollusks . 80
M.

Mactra . 280

Many-feet . 34

Periwinkle 26,32,33,199,202,219
Pholas . . 388, 305
Pinna . 249, 251
Polished Donax . oo 281
Pond-Snails . 18, 82, 84, 87, 141

528

INDEX.
PAGE PAGE
Porpita,:. 2 ot Aaltth ALLS | Stome-borers .. . Rage eee
Poulpe . . 17,31, 34, 58,60 | Swimming Ascidians . . 318
Precious Wentletrap 193,194
PUCOPOUEE Reset os. pedal T.
Tectibranch Mollusca . . 136
Q. Mellens: <3. 2776." fe eee
Quins ee tt. =) 226 |) Tentacled Bithinia <7 ssaeels
Teredo . 41, 42, 43
R. Top-shells . . 37, 206
Torbay Bonnet+;. ... . 212
Razor-shells . . . . . 284 Tefientia. tee
Ropicslels ye) i+ <> 44) eateed Ohiton.. + ee aereee
Royal Staircase . . . - 195 | muskshells . . . . . Q14
Two-gilled Cuttles . . . 65
8.
Sand Gaper 2° au) geceel U.
Saxicava . . . . . + 296 | Univalves . 24, 30, 37, 82
Scallop . 5, 25, 219, 226
Sea-hares . 187, 142,144 vy.
saat yal 49, a Venus-shells. . . . . 276
Slug . o5 bgt Slo
Smooth Tusk 0.) .0's) -) ete W.
Snail . 7,9, 18, 20, 27, 31; 84,90; |: Water-snails 220). - 72 ypiee
97, 219 | Wentletraps =. >a. sales
Social Ascidians . . ..)... 3815.) Whalefood. ...-. -aamuege
Solen 286,288 | Whelk 33, 38, 174, 179, 183
Squids . . 3,31, 34,66 (| Whirl-shells ;° <° .) -.ihummee
Starry Ascidians . . . 817 | Woodcock’s-head . . . 175

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