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THE

CAMBRIDGE NATURAL HISTORY

ees

EDITED BY

S. F. HARMER, M.A., Fellow of King’s College, Cambridge ; Super-
intendent of the University Museum of Zoology

AND

ma HE SEIPLEY, M.A, Fellow of Christ’s College, (Cambridge;
University Lecturer on the Morphology of Invertebrates

VOLUME III

O

AUSTRALASIAN

Map to illustrate

THE GEOGRAPHICAL DISTRIBUTION

of the
LAND OPERCULATE MOLLUSCA
The figures trdicate the raunber of known species

ue
, MOLLUSCS
ay By the Rev. A. H. CooKkE, M.A., Fellow and Tutor of

King’s College, Cambridge

PreaGEiOPODs (RECENT)

By A. E. SHIPLEY, M.A., Fellow of Christ’s College,

Cambridge

PReacniOPODS (FOSsir

By F. R. C. REED, M.A., Trinity College, Cambridge

London
MACMIELAN AND: CO.

AND NEW YORK

1895

Allrights reserved

06

AUSTRALASIA

180

eewe enn need

ane

THE GEOGRAPHICAL DISTRIBUTION
of the

LAND OPERCULATE MOLLUSCA
The figures indicate the raunber of known species

165 10135 120 105

ae

75

=—— a o
15 W.Long: 0.E.Lons: 16

105

London: Maemillan &L°

——
150 165 180

TondonStanfords Ge09'Estab®

“Why, you might take to some light study ; conchology now ;

I always think that must be a light study.”

trorGr Exot, Middlemarch.

PREFACE TO THE MOLLUSCA

THE general plan of classification adopted in this work is not
that of any single authority. It has been thought better to
adopt the views of recognised leading specialists in the various
groups, and thus place before the reader the combined results of
recent investigation. This method may, perhaps, occasion a
certain number of small discrepancies, but it is believed that the
ultimate effect will be to the advantage of the student.

The classification adopted for the recent Cephalopoda is that
of Hoyle (‘Challenger’ Reports, Zoology, vol. xvi.), for the fossil
Cephalopoda (Nautiloidea) that of Foord (Catalogue of the Fossil
Cephalopoda in the British Museum, 1888-91), and (Ammonoidea )
P. Fischer (Manuel de Conchyliologie, 1887). In the Gasteropoda
the outlines are those adopted by Pelseneer (J/ém. Soc. Malacol.
Belg. xxvii. 1894), while the details are derived, in the main,
from P. Fischer. The Amphineura, however, have not been
regarded as a separate class. The grouping of the Nudi-
branchiata is that of Bergh (Semper, Reisen im Archipel der
Philippinen, ii. 3). The Pelecypoda are classified according to
Pelseneer’s most recent grouping.

Acknowledgment of the principal sources of information has
been made in footnotes, and a short list of leading authorities has
been appended to the chapters on anatomy, for the use of

students desirous to pursue the subject further. In the case of

1asqot

Vi PREFACE

geographical distribution the authorities are too numerous and
scattered to admit of a lst being given.

A special word of thanks is due to Mr, Edwin Wilson for
his patient care in preparing the illustrations, the majority of
which are taken from specimens in the University Museum of
Zoology. Mr. Edgar Smith, besides affording the kind help
which visitors to the British Museum always experience at
his hands, has permitted me to use many specimens for the

purposes of illustration,

A. H. COOKE.

Kine@’s COLLEGE, CAMBRIDGE.
20th December 1894.

CONTENTS

SCHEME OF THE CLASSIFICATION ADOPTED IN THIS Book

MOLLUSCA

CHAPTER I

INTRODUCTION—PosITION OF MoLLUSCA .IN THE ANIMAL KINGDOM—CLASSI-
FICATION—ORIGIN OF LAND AND FRESH-WATER MOLLUSCA

CHAPTER. If

LAND AND FRESH-WATER MOoLuiuscA, THEIR Hapirs AND GENERAL

EcoNoMY
CEIANE PER mul
ENEMIES OF THE MoLtuscA—MEANS OF DEFENCE—MIMICRY AND PROTEC-

TIVE COLORATION—PARASITIC MoLLUuscA—COMMENSALISM— VARIATION

CHAPTER IV

Uses oF SHELLS FOR MoNEY, ORNAMENT, AND FooOD—CULTIVATION OF
THE OysTER, MUSSEL, AND SNAIL—SNAILS AS MEDICINE— PRICES
GIVEN FOR SHELLS .

CHAPTER V

REPRODUCTION — DEposITION OF EGGS—DrvELOPMENT OF THE FERTILISED
OvuM — DIFFERENCES OF Sex — Diorclous AND HERMAPHRODITE
Mo.uiuscA—DrvELOPMENT OF FRESH-WATER BIVALVES

bo
co

Vill CONTENTS

CHAPTER VI

RESPIRATION AND CIRCULATION—THE MANTLE . : : z : 5 105x0)

CHAPTER VII

ORGANS oF SENSE: TovucH, SicuT, SMELL, Hearinc —TuE Foot—TuHrE
Nervous SYSTEM . ‘ . 4 ? : F : ’ 3 on lie

“I

CHAPTER VIII

THE DIcEsTIVE ORGANS, JAW, AND RapuLA: ExcRETORY ORGANS . » 209

CEA Phin

THE SHELL, Irs Form, CoMPposITION AND GROWTH — DESIGNATION OF ITS
VARIOUS PARTS i ; : , ; F ; ; : ‘ . 244

CHAPTER X

GEOGRAPHICAL DISTRIBUTION OF LAND AND FRESH-WATER MoLLUSCA—THE

PALAEARCTIC, ORIENTAL, AND AUSTRALASIAN REGIONS Dilip
(CHEAPER sel:
GEOGRAPHICAL DISTRIBUTION OF LAND Mo3uusca (continwed)—Tar Erut-
OPIAN, NEARCTIC, AND NEOTROPICAL REGIONS . F ; : 5. BPs)
CHEAP AER, Xe
DISTRIBUTION OF MARINE MoLiuscA— Drrp-szrA MOoLLUsScA AND THEIR
CHARACTERISTICS . 5 : ; ; : : ; : : . 360

CHAPTER XIII

CLASS CEPHALOPODA ; : ; ; ; ; : : P j % Byits

CONDENS 1X

CHAPTER XIV

CrLass GASTEROPODA—AMPHINEURA AND PROSOBRANCHIATA ; : . 400

CHAPTER XV

=I,

Ciass GAsTEROPODA (continued): OPISTHOBRANCHIATA AND PULMONATA . 42

CHAPTER XVI

CLASSES SCAPHOPODA AND PELECYPODA 2 : : : c . 444

BRACHIOPODA (RECENT)

CHAPTER XVII

INTRODUCTION —SHELL—BopyY—DIGESTIVE SysTEM—Bopy Caviry—Crrcv-
LATORY Syst—EM — ExcreTrory ORGANS — MuscLes — NERvous SYSTEM
— REPRODUCTIVE SysTeM — EmpryoLocy — Hanrrs — DistrRInbuTION—
CLASSIFICATION , : , ; ; ; ; ; P 2 5 alo}

BRACHIOPODA (FOSSIL)

CHAPTER, SoviuiT

InrRopUCTION—DtIvision I. EcarpINES—EXTERNAL CHARACTERS—INTER-
NAL CHARACTERS —Irvision II. TrsTicARDINES— EXTERNAL CHAR-
ACTERS — INTERNAL CHARACTERS—SYNOPSIS OF FAMILIES — STRATI-
GRAPHICAL DISTRIBUTION—PHYLOGENY AND ONTOGENY : ; . 491

SCHEME OF THE CLASSIFICATION ADOPTED IN
THIS BOOK

MOLLUSCA
Class. Order. Sub-order. Section.
f OCTOPODA (p. 382).
Dibranchi- | | Phi: agmophora (p. 386).
ata 5 at Bel: Sepiophora (p. 388).
| Distel zone { Myopsidae (p. 389).
; | Chondrophora a heh hgeecse oar
CEPHALO- | Oigopsidae (p. 390).
SUMS Sy. { Retrosiphonata (p. 393).
AUTILOIDEA > tect shonata (0. 20%
Tetra- { Prosiphonata (p. 395).
branchiata
aa fe { Retrosiphonata (p. 397).
| Prosiphonata (p. 397).
( : { PoLyPLACOPHORA (p. 400).
Aanphinewra | ApLacopHora (p. 404).
Docoglossa (p, 405).
‘Zygobranchiata (p.
DIoOTOCARDIA - Rhinidocless: | 406).
| Cae ee een Azygobranchiata (p.
| “0.
Proso- J
branchiata | ( Ptenoglossa (p. 411).
p Bikce Wea ts { Platypoda (p. 411).
MoNOTOCARDIA - ce | Heteropoda (p. 420).
“=== - | -Gymmoglossa) (p. 422):
GASTERO- Rachiglossa (p. 422).
PODA L Toxoglossa (p. 426).
Bulloidea (p. 429).
TECTI- | Aplysioidea (p. 430).
BRANCHIATA | Pleurobranchoidea (p. 431).
Siphonarioidea (p. 431).
Opistho- | ASCOGLOSSA (p. 431).
branchiata | Nupt- { Cladohepatica (p. 432).
BRANCHIATA | Holohepatica (p. 433).
| PrEROPODA { Thecosomata (p. 435).
\ Gymnosomata (p. 437).

{ BASOMMATOPHORA (p. 438).

ulmona
IO) | SryLoMMATOPHORA (p. 439).

SCHEME OF MOLLUSCA

AND BRACHIOPODA

Class. Order.
SCAPHOPODA
(p. 444).
Protobranchiata (p. 447).
Filibranchiata
Pseudolamellibranchiata ().
PELECYPODA

Eulamellibranchiata

Septibranchiata (p. 459).

Sub-order.

ANOMIACEA (p. 448).
ARCACEA (p. 448).
MyTILACcEA (p. 448).

f
|
449),
, SUBMYTILACEA (p. 451).
TELLINACEA (p. 453).
| VENERACEA (p. 454).
CARDIACEA (p. 454).
MYACEA (p. 456).
PHOLADACEA (p. 457).
»« ANATINACEA (p. 458).

BRACHIOPODA

Order.

ECARDINES |

Family.
Lingulidae (pp. 487 and 503).
Obolidae (p. 504).
Discinidae (pp. 487 and 504).
Craniidae (pp. 487 and 504).
Trimerellidae (p. 504).

’ Productidae (p. 504).

Brachiopoda ~

TESTICARDINES 4

Strophomenidae (p. 505).
Koninckinidae (p. 505).
Spiriferidae (p. 505).

Atrypidae (p. 505).
Rhynchonellidae (pp. 487 and 505).
Terebratulidae (pp. 487 and 506).
Argiopidae (p. 506).
Stringocephalidae (p. 506).
Thecidiidae (pp. 487 and 506).

LIST OF MAPS

THE GEOGRAPHICAL DISTRIBUTION OF THE LAND OPERCULATE MOLLUSCA
Frontispiece

THE GEOGRAPHICAL DISTRIBUTION OF THE LAND MoLiusca oF THE EAST
INDIAN ARCHIPELAGO . ; : : . Letween pp. 308 and 309

THE RELATIONS OF THE LAND MouLiusca OF NEW GUINEA WITH THOSE OF
NorrtH AUSTRALIA : : 5 ; ; : : . To face p. 322

THE GEOGRAPHICAL DISTRIBUTION OF THE LAND MOLLUSCA OF THE
West INDIEs . ; : : . Between pp. 344 and 345

MOLLUSCS

BY

2EV, A. H. COOKE, M.A.

Fellow and Tutor of King’s College, Cambridge.

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CAMBRIDGE NATURAL HISTORY

MOL Tit

ERRATA

13th line from bottom: for ‘‘ JZ.” read ‘‘NV.”

4th line from bottom: for ‘‘neap: tides” read ‘‘ weak spring-tides.”
9th line from bottom: for ‘185” read ‘*155.”

9th line from bottom : for ‘‘ Aeolidiidae”’ read ‘‘ Aeolididae.”

4th line from top: for ‘“‘near” read ‘‘ nearly.”

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7

co

CHAPTER I

INTRODUCTION —— POSITION OF MOLLUSCA IN THE ANIMAL KING-
DOM——CLASSIFICATION——ORIGIN OF LAND AND FRESH-WATER
MOLLUSCA

It is the generally accepted opinion among men of science that
all life originated in the sea. Not that all parts of the sea are
equally favourable to the development of forms of hfe. The
ocean surface, with its entire absence of shelter or resting-place,
and the deep sea, whose abysses are always dark and cold and
changeless, offer little encouragement to plant or animal life, as
an original starting-point. True, both the surface and the depths
of the sea have become colonised by myriads of forms, Mollusca
amongst them, but these quarters are in the truest sense colonised,
for the ancestors of those who inhabit them in all probability
migrated from elsewhere.

It was no doubt the littoral region and the shallow waters
immediately below it, a region of changeable currents, of light
and shade, of variation, within definite limits, of temperature
and tide effects, which became the scene of the original develop-
ment of plant life, in other words, of the food-supply which
rendered possible its colonisation by higher animals. But the
littoral region, besides the advantages of tenancy which it offers
to animal life, has also its drawbacks. The violence of the surf
may beat its inhabitants in pieces, the retreat of the tide exposes
them, not merely to innumerable enemies in the shape of pre-
datory birds and beasts, but also to a change in the atmospheric
medium by which they are surrounded. Hence, in all proba-
bility, have arisen the various forms of adaptation which are
calculated to bring about the ‘survival of the fittest’; hence, to

~

VOL. Ill > B

bo

VARIETIES OF STATION CHAP.

narrow our point of view to the Mo.Liusca, the development of
hard shells, or exoskeletons, hence the sand-burrowing, rock-boring,
rock-clinging instincts of various genera and species.!

What was the primitive form of molluscan life is little lkely
to be ever positively known, although, on grounds of comparative
anatomy, something approaching to the archi-molluse is often
constructed, with more or less probability, by careful observers.
From one of the oldest known geological strata, the Cambrian,
nearly four hundred species of Mollusca are known, which include
representatives of nearly all the great Orders as they exist at the
present day, and without the slightest sign of approximation to
one another. With regard to the origin of the land and fresh-
water Mollusca some definite conclusions can be arrived at, which
will be given in their proper place.

Scarcely any portion of the coast-line of the world is desti-
tute of molluscan hfe, except in regions where extreme cold
forbids its existence. Thus along the shores of Northern Asia
there is no proper littoral fauna, the constant influence of travel-
ling ice sweeping it all away; animal life begins at about
three fathoms. But in every coast region not positively hostile
to existence Mollusca make their home. Each description of
habitat has its own peculiar species, which there flourish best,
and exist precariously, if at all, elsewhere. Thus the sandy
waste of estuaries, the loose and shingly beaches, the slimy mud-
flats beset with mangroves, the low stretches of jagged rock,
and even the precipitous cliffs, from whose base the sea never
recedes, have all their own special inhabitants. The same is
true of the deep sea, and of the ocean surface. And when we
come to examine the land and fresh-water Mollusea, it is found
not merely that some Mollusca are terrestrial and others fluvia-
tile, but that certain species haunt the hills and others the
valleys, some the recesses of woods and others the open meadow
sides, some prefer the limestone rocks, others the sandy or clayey
districts, some live only in still or gently moving waters, while
others are never found except where the current is rapid and
powerful.

It is within the tropics that the Mollusca become most num-
erous, and assume their finest and quaintest forms. <A tropical
beach, especially where there is a good tide-fall and considerable

1 See especially Moseley, Nature, 1885, p. 417.

I A TROPICAL BEACH

WwW

variety of station, abounds in mollusean life to an extent which
must literally be seen to be believed. The beach at Panama, to
select an instance familar to the present writer, is astonishingly
rich in species, which probably amount in all to several hundreds.
This is due to the immense variety of habitat. On the rocks
at high-water mark, and even above them, oceur 7vruncatella,
Melampus, Littorina, and Siphonaria ; where a mangrove-swamp
replaces the rock, on the branches overhead are huge Littorina,
while three species of Cerithidea crawl on the mud, and Cyrena
and Arca burrow into it. Lower down, in the rock pools at
half-tide mark are Cerithium, Purpura, Omphalius, Anachis
(2 sp.), Massa, and several Crepidula. At low-water mark of
ordinary tides, under stones half buried in clean sand, are Coecwm
and Vitrinella ; under the blocks which rest on solid rock are
Cypraea (4 or 5 sp.), Cantharus, more Anachis, Columbella (3
sp. including the graceful C. harpiformis), and Nitidella. Where
the blocks of rock are rather muddy, Conus lurks, and with it
Turritella and Latirus. Where the rocks form a flat-topped
platform 2 or 3 feet high, with here and there a deep crack,
huge Chitons 3 inches long conceal themselves, with two species
of Turbo, Purpura and Clavella. At extreme low-water mark
of spring tides, on the isolated rocks are Monoceros, Leucozonia,
and Vermetus, in them are Pholas and a burrowing Mytilus,
under them are more Conus, Doliwm, and huge frilled Murices.
Patches of clean gravelly sand here produce Strombus; on
the operculum of the great Str. galea is sure to be a Crepidula,
exactly fitting its breadth. On the liquid mud-flats to the
north glide about Marginella, Nassa and Truncaria, in the clean
sand-stretch to the west Olivella ploughs about by hundreds
with several species of Natica, and Tellina and Donax bury
themselves deep, while farther down are Artemis, Chione, and,
where mud begins to mix with the sand, JJytilus and more
Arca. Each of these species has its own habitat, often cireum-
scribed to a few square feet at the most, and it would be
utterly useless to seek for it anywhere except in its own special
domain.

Equally abundant are the land Mollusca of the tropics. Prof.
C. B. Adams relates that within the limits of a single parish
in Jamaica, named Manchester, which measures no more than
four miles long and one mile broad, he obtained no fewer than

So

4 LAND MOLLUSCA IN THE TROPICS CHAP.

one hundred species. Mr. J. S. Gibbons, in a description of
the Mollusca he obtained near St. Ann’s, Curacao, gives a
lively picture of their abundance in an exceptionally favoured
locality :—*

“Near the outskirts of the town a waste piece of ground
supplied me with occupation for all the time I had to spare.
Neither grass nor water was to be seen, the only vegetation
consisting of a few stunted cacti and still fewer acacia bushes.
This, however, was so rich in shells that of several species enough
specimens could have been collected in a few yards to supply,
I should suppose, all the shell cabinets in the world.

The stones, plants, and ground were covered with Strophia uva
L., Ludora megacheila, P. and M., was in equal abundance,
suspended by its silk-like thread from acacia boughs, or strewed
thickly on the ground underneath. <A Bulimulus (B. multi-
lineatus var. sisalensis) abounded on the smaller boughs, while
under masses of coral Macroceramus inermis Gundl., Pupa par-
raianda VOrb, and P. pellucida Pfr., were abundant. In the loose
soil Cylindrella Ravent Bland, Cistula Raveni Bland, and a curious
Cionella were so numerous that a spade would have been the
best instrument with which to collect them. I wasted a good
deal of valuable time in separating them from the soil, when by
simply taking away a few handfuls of mould, I might have
obtained a larger number of specimens. A species of Stenogyra
and a Succinea complete a list, all of which might have been
gathered from almost any square yard of ground on the hillside.”

Position of Mollusca in the Animal Kingdom.— Up to
very recent times it was usual to regard the Mollusca as one
of the four subdivisions of a great family known as Malacozoa,
the subdivisions being (1) Mollusca, (2) Tunicata, (3) Brachio-
poda, (4) Polyzoa or Bryozoa. This classification is still retained
in the leading modern manual on the subject.2 The progress,
however, of investigation leads to the belief that the Mollusca
are not so closely related to these other groups as such a classi-
fication would seem to imply. The Tunicata, for instance,
appear, from the whole course of their development, to occupy.

1 Quart. Journ. Conch. i. p. 871.
2 Manuel de Conchyliologie et de Paléontologie Conchyliologique. Dr. P. Fischer,
Paris, 1887.

I POSITION IN ANIMAL KINGDOM 5

a position near to the Vertebrata. The relations of the Brachio-
poda and Polyzoa will be more particularly referred to in that
part of this History which deals especially with those groups.
The position of the Mollusca is, in many respects, one of con-
siderable isolation. Any attempt, therefore, definitely to relate
them to one group or another, is, in all probability, to go further
than the present state of our knowledge warrants. Especially
to be deprecated are systems of classification which confidently
derive the Mollusca in general from this or that group. The
first undisputed traces of animal life, which appear in the
“Cambrian: epoch, exhibit the. same phyletic distinctions as now
exist. Sponges, Echinoderms, Mollusca, and Worms, formed
already, in those immeasurably remote ages, groups apparently
as generally distinct from one another as they are at the present
time. It would seem that any theory of development, which
confidently teaches the derivation of any one of these groups
from any other, is, in the present state of the evidence before us,
hazardous in the extreme.

Some indications of relationship, which must not be pushed
too far, may be drawn from a consideration of embryonic re-
semblance. An especial characteristic of the Mollusca is the
possession of a particular form of larva, which occurs in one of
the stages of development, known as the trochosphere (see p. 130).
This form of larva is shared with two orders of Annelida, the
Chaetopoda and the Gephyrea armata, and, in all probability,
with the Polyzoa as well. It may also be significant that the
adult form in Rotifera bears a close resemblance to the trocho-
sphere larva in those groups.

Basis of Classification.—The Mollusca are divided into
four great Orders—Cephalopoda, Gasteropoda, Scaphopoda,
and Pelecypoda.t Each name, it will be noticed, bears reference
to the ‘foot, ze. to the organ of motion which corresponds in
function to the foot in the Vertcbrata.

In the Cephalopoda the feet, or, as they are more frequently
termed, the ‘arms, are arranged symmetrically round the head
or mouth. The common forms of ‘ cuttle-fish’ (Octopus, Loligo)
are familiar examples of Cephalopods.

The Gasteropoda crawl on the flat. under-surface or ‘sole’

1 xepady, head; yaorjp, stomach; oxdmrew, to dig; mé\exus, an axe; rovs,
modés, a foot.

6 CLASSIFICATION CHAP.

of the foot. Snails, slugs, sea-hares, whelks, periwinkles, and
coats-of-mail or chitons are examples of this Order.

The Scaphopoda possess a long tubular shell open at both
ends: with their small and elongated foot they are supposed to
dig into the mud in which they live. The common Dentalium
or tusk-shell of our coasts is a representative of this Order.

Fic. 1.—Examples of the four
Orders: A, Cephalopoda ;
B, Gasteropoda; C, Scapho-
poda, and D, Pelecypoda:

A, Ommastrephes sagittatus
Lam., Naples: a, a, arms
surrounding the mouth; /,
funnel; ¢, ¢, the two ‘ tentacu-
lar’ arms. x2. B, Buccinwm
undatum L., Britain: f, foot ;
pr, proboscis. x4. C, Den-
talium entalis L., Norway: 7,
foot. D, Cardium oblonguin
Chem., Naples: jf, foot; s,
efferent or anal siphon; s’,
afferent or branchial siphon.

x}

The Pelecypoda' are enclosed in a bivalve shell fastened by a
muscular hinge, the adjacent part of the valves being generally
more or less toothed; the foot is as a rule roughly comparable
to the shape of an axe-head.

To these four Orders is frequently added a fifth, the Pteropoda,
whose exact position is at present not absolutely settled. The
Pteropoda ? are ‘ pelagic, ¢.e. they live in the open waters of the
ocean, rising to the surface at night, and sinking into cooler water
by day. They are provided with a pair of wing-hke appendages

1 Also known as Lamedlibranchiata, Conchifera and Acephala.
2 mrepov, wing.

I CLASSIFICATION hl

or ‘feet,’ on each side of the head, by means of which they are
enabled to swim. Some authorities regard the Pteropoda as a
subdivision of Gasteropoda, others as forming a separate Order,
of equivalent value to the other four. The question will be
further discussed below (see chap. xv.), but for the present it will
be sufficient to state that the weight of evidence appears to
show that the Pteropoda are modified Gasteropoda, with special
adaptations to pelagic life, and are therefore not entitled to rank
as a separate Order.

Some writers conveniently group together the first three of
these Orders, the Cephalopoda, Gasteropoda, and Scaphopoda,
under the title Glossophora,) or Mollusca furnished with a
radula or ribbon-shaped ‘tongue, set with rows of teeth and
situated in something of the nature of a head, as distinguished
from the Aglossa (or Lipocephala),? i.e. those Mollusca which
have no radula and no head. To the latter belong only the
fourth Order, the Pelecypoda. This view postulates, for the
primitive ancestral Mollusc, a body with a more or less developed
head, and possibly the rudiments of an apparatus for grinding
or triturating food. This form, it is held, either developed or
degenerated. In the former case, in consequence of the more
active mode of life upon which it may be supposed to have
entered, it gave rise to all the more highly organised forms
which are grouped under the three great Orders. When, on the
other hand, the ancestral form associated itself with an inactive
or sedentary life, it was, we may believe, modified accordingly,
and either lost by atrophy or failed to acquire those special
points of organisation which characterise the highly-developed
form. Hence the Pelecypoda, or bivalves, whose characteristic
is the absence of any definite cephalic region or masticatory
apparatus. It is a remarkable fact in support of this theory
of the origin of the Aglossa that certain of their larvae are
known to possess traces of higher organisation, eg. an external
mouth and eyes, the former of which becomes covered by the
mantle lobes, while the latter disappear long before the adult
stage is reached.

1 yiGooa, tongue ; pépew, to carry. > Nelrew, to be wanting.

8 CLASSIFICATION OF GASTEROPODA CHAP.

Thus we have
MOLLUSCA
|
|
Glossophora Aglossa

Cephalopoda Gasteropoda Scaphopoda Pelecypoda

Classification of Gasteropoda.—The (Gasteropoda are nu-
merically very largely in excess of the two other Orders of the
Glossophora, far more complicated as regards classification, and
contain a large proportion of those examples of the Mollusca
which are most familiar to the ordinary observer. It will there-
fore be convenient to postpone for the present a fuller discussion
of the subdivisions of the Cephalopoda and Scaphopoda, as well
as of the Aglossa, returning to them again in special chapters
(chaps. xiii. and xvi.), and to devote a few introductory words to
the classification and relations of the Gasteropoda.

The Gasteropoda are divided into four Classes, Amphineura
Prosobranchiata, Opisthobranchiata, and Pulmonata.

(1) The Amphineura? are bilaterally symmetrical Mollusca,

2

Fic. 3.—An example of the
Aplacophora, Neomenia ca-
rinata Tullb. : a, anus; g7,
ventral groove ; m, mouth.

Fic. 2.—An example of the
Polyplacophora: Chiton spin-
osus Brug.

“Ze. with organs either single and central, or paired and disposed
on either side of the longer axis of the animal. The shell, when

‘ dui, on both sides; vefpov, nerve, vessel. Some authorities regard the
Amphineura as a distinct Order.

I CLASSIFICATION OF GASTEROPODA 9

present, is never spiral, but consists of eight overlapping plates,
kept together by an elliptical girdle. The Amphineura are
divided into (@) Polyplacophora,’ or Chitons, and (b) Aplacophora
(Chaetoderma and Neomenia).

(2) The Prosobranchiata? are so named from the fact that
the breathing organ (branchia or ctenidium *) is as a rule situated
in front of the heart, the auricle at the same time being in front
of the ventricle. They are asymmetrical, almost always furnished
with a shell, which is at some time spiral, and with an operculum.
The sexes are separate. They are either marine animals, or
can be shown to be more or less directly derived from genera
which are marine. They are divided into (a) Diotocardia*
(Haliotis, Fissurella, Trochus, Nerita, Patella), which have, or
whose immediate ancestors are believed to have had, two
auricles to the heart, two sets of breathing organs, two kidneys,
but no proboscis, penis, or
siphon, and (0) JIMonoto-
cardia, in which the heart
has only one auricle, the
true breathing organ is
single, and there is a single
kidney. To this division
belong the great majority
of marine univalve Mol-
lusca, e.g. Cypraea, Bucei-
num, Murex, Littorina,

Fia. 4.—Example of a Heteropod, Carinaria
mediterranea Lam., Naples: a, anus; br,

Ianthina, all the land and branchia ; 7, foot; 7, intestine; m, mouth ;
: p, penis; s, sucker; sh, shell; ¢, tentacles.
fresh - water operculates x4. The animal swims foot uppermost.

(Cyclostoma, Melania, Pa-
ludina, ete.), as well as the Heteropoda, which are a group of
Prosobranchiata which have betaken themselves to a pelagic life.
(5) In the Opisthobranchiata® the breathing organs (when
present) are behind the heart, and the auricle of the heart is
consequently behind the ventricle. They are asymmetrical
marine animals; usually, but by no means always, without a
shell, scarcely ever with an operculum in the adult state. The

moNvs, many ; mAdé, plate.

° rpdow, in front. Often alluded to in the sequel as ‘ operculate Gasteropoda.’
xrevid.ov, a little comb. + dw, two; uovos, single; Ora, auricles; capéla, heart.
> Omicbev, behind.

IO CLASSIFICATION OF GASTEROPODA CHAP,

sexes are united in the same individual. The Opisthobranchiata
fall into two divisions: (#) Tectibranchiata, in which the breathing
organ is more or less covered by the mantle, and a shell is
usually present, which is sometimes rudimentary, eg. Bulla,

Fic. 5.—A, A Tectibran-
chiate Opisthobranch,
Umbrella mediterra-
nea Lam., Naples: a,
anus; br, branchia ; /,
foot; m, mouth; rh,
rhinophores ; si, shell.

B, A Pteropod, Hya-
laea tridentata Forsk.,
Naples: sh, shell ; 7, 7,
swimming lobes of foot.

C, A Nudibranchi-
ate Opisthobranch, Ae-
olis peregrina, Naples:
J, foot ; c, cerata.

Aplysia, Umbrella, and the whole group of Pteropoda; (b) Nudi-
branchiata, or sea slugs, which have no shell and no true
ctenidia, but breathe either by the skin, or by ‘cerata’ or
papilliform organs prominently developed on the back: eg.
Doris, Aeolis, Dendronotus.

(4) The Pulmonata’ are asymmetrical air-breathing non-

Fria. 6.—Examples of —A, Pulmonata Basommatophora, the common Limnaea
peregra Miill.: e, e, eyes; ¢, ¢, tentacles. 3B, Pulmonata Stylommatophora,
Helix hortensis Miill.: e, e, eyes; ¢, ¢t, tentacles; py. 0, pulmonary orifice (the
position of the pulmonary orifice in ZLimnaea will be seen by reference to
Fig. 101).

marine Mollusca, generally, but not always, furnished with a
shell. The sexes are always united in the same individual, and
the operculum is always wanting, except in Amphibola. They

1 Pulmo, a lung.

1 ORIGIN OF THE LAND AND FRESH-WATER MOLLUSCA 1}

are conveniently divided into Stylommatophora,’ in which the
eyes are at the tip of the upper tentacles, which are retractile
(Helix, Limax, Bulimus, and all true land slugs and snails), and
Basommatophora, 11 which the eyes are at the base of the
tentacles, which are not retractile (Limnaea, Planorbis, Physa,
and all the Awriculidae).

Thus we have

SIRs a { Polyplacophora
Amphineura \Apidcophess
Prosobranchiata { Diotocardia

\ Monotocardia (incl. Heteropoda)
Tectibranchiata (incl. Pteropoda)
Nudibranchiata ”
Stylommatophora
Basommatophora

Gasteropoda
Opisthobranchiata

Pulmonata
\

The relation of the four great Orders to one another will be
better discussed when we come to deal with each Order
separately. The problem of the origin and mutual relationship
of the various forms of molluscan life is of extreme subtlety, and
its solution can only be approached after a comprehensive
survey of many complicated anatomical details. But there is
one branch of the Mollusca—the land and fresh-water genera
whose origin is, comparatively speaking, of recent date, and
whose relationships are therefore less likely to have suffered
complete obliteration.

Origin of the Land and Fresh-water Mollusca.—The
ultimate derivation of the whole of the land and fresh-water
molluscan fauna must, as has already been remarked, be looked
for in the sea. In certain cases the process of conversion,
if it may be so termed, from a marine to a non-marine genus,
is still in progress, and can be definitely observed; in others
the conversion is complete, but the modification of form has
been so slight, or the date of its occurrence so recent, that
the connexion is unmistakable, or at least highly probable ;
in others again, the modification has been so great, or the
date of its occurrence so remote, that the actual line of deriva-
tion is obscured or at best only conjectural.

This passage from a marine to a non-marine life—in other

1 crodXos, pillar ; dupara, eyes.
2 The Ascoglossa ave dealt with below (chap. xv.).

12. ORIGIN OF THE LAND AND FRESH-WATER MOLLUSCA cu.

words, this direct derivation of non-marine from marine genera
—is illustrated by the faunal phenomena of an inland brackish-
water sea lke the Caspian, which is known to have been
originally in connexion with the Mediterranean, and therefore
originally supported a marine fauna. The Mollusca of the
Caspian, although without exception brackish- or fresh-water
species, are In their general facies distinctly marine. Of the 26
univalve species which inhabit it 19 belong to 4 peculiar genera
(Micromelania, Caspia, Clessinia, Nematurella), all of which are
modified forms of the marine
Rissoidae. The character-
istic bivalves belong to the
genera Adacna, Didacna,
and Monodacna, all of
which can be shown to be
derived from the common
Cardium edule. We have
here a case where complete
isolation from the — sea,
combined no doubt with
a gradual freshening of the
water, has resulted in the

Fic. 7.—A, the common cockle (Cardium development of a number
edule L.). B, Adacna plicata EHichw., of new genera. The sincu-
Caspian Sea. ©, Didacna_ trigonoides oie ae: 7
Pall., Caspian Sea. larly marine facies of several

of the fresh-water genera
now inhabiting Lake Tanganyika, has given rise to the belief,
among some authorities, that that lake was at one time an
inlet of the Indian Ocean. In the upper waters of the Baltic,
marine and fresh-water Mollusca flourish side by side. So
complete is the intermixture, that an observer who had lived
on no other shores would probably be unable to separate the
one set of species from the other.' Thus between Drago and

Papenwick”? Mytilus edulis, Cardium edule, Tellina balthica,

Mya arenaria, Inttorina rudis, and Hydrobia balthica are the

only true marine species; with these live Unio, Cyclas, Neritina,

Limnaea, and Bithynia. The marine species and Weritina live
1 Beudant, by very gradually changing the water, accustomed marine species to

live in fresh, and fresh-water species to live in salt water.
2 Braun, Arch. f. Natwrk. Liv. (2), x. p. 102 f.

1 EMIGRATION TO LAND AND FRESH WATER 13

down to 15-20 fath., the rest only down to 3 fath. Under stones
close to the shore of the Skiirgard at Stockholm * are found young
Cardium and Tellina, and at 3 to 6 fath. Limnaea peregra, and
Physa fontinalis. Near Gothland Limnaea is found in the open
sea at 8-12 fath., and with it occur Cardiwm and Tellina. At
the Frisches Haff* Mya arenaria is the only marine species,
and lives in company with 6 sp. Limnaea, 1 Physa, 9 Planorbis,
1 Ancylus, 4 Valvata, 2 Sphaerium. Were the Sound to become
closed, and the waters of the Baltic perfectly fresh, it would
be inevitable that Mya arenaria, and such other marine species
as continued to live under their changed conditions, should in
course of time submit to modifications similar in kind to those
experienced by the quondam marine species of the Caspian.

It seems probable, however, that the origin, at least in
a great part, of the land and fresh-water Mollusca need not
be accounted for by such involuntary changes of environment
as the enclosure of arms of the sea, or the possible drying
up of inland lakes. These cases may be taken as illustrations
of the much more gradual processes of nature by which the
land and fresh-water fauna must have been developed. The
ancestry of that fauna must be looked for, as far as the
Gasteropoda are concerned, in the littoral and estuarine spectes ;
for the Pelecypoda, in the estuarine alone. The effect of the
recess of the tide, in the one case, and the effect of the reduced
percentage of salt, in the other, has tended to produce a gradual
adaptation to new surroundings, an adaptation which becomes
more and more perfect. It may be safely asserted that no
marine species could pass into a land or fresh-water species
except after a period, more or less prolonged, of littoral ‘or
estuarine existence. Thus we find no land or fresh-water
species exhibiting relationships with such deep-sea genera
as the Volutidae, Cancellarwidae, Terebridae, or even with genera
trenching on the lowest part of the littoral zone, such as the
Haliotidae, Conidae; Olividae, Capulidae. The signs of connexion
are rather with the Neritidae, Cerithiidae, and above all the
Littorinidae, which are accustomed to live for hours, and in the
case of Littorina for days or even weeks, without being moistened
by the tide. Similarly the fresh-water Pelecypoda exhibit re-

1 Lindstrom, Oef. A. Vet. Foérh. Stockh., 1855, p. 49.
* Mendthal, Schr. Ges. Konigsb., xxx. p. 27.

14 ORIGIN OF FRESH-WATER BIVALVES CHAP.

lationships, not with genera exclusively marine, but with genera
known to inhabit estuaries, such as the Mytilidae, Corbulidae,
Cardiidae.

It would be natural to expect that we should find this
process of conversion still going on, and that we should be
able to detect particular species or groups of species in process
of emigration from sea to land, or from sea to fresh water.
Such species will be intermediate between a marine and a
land or fresh-water species, and difficult to classify distinctly
as one or the other. Cases of Mollusca occupying this interme-
diate position occur all over the world. They inhabit brackish
swamps, damp places at high-water mark, and rocks only at
intervals visited by the tide. Such are Potamides, Assiminea,
Siphonaria, Melampus, Hydrobia, Truncatella, among the uni-
valves, and many species of Cyrena and Arca among the
bivalves.

Origin of the Fresh-water Fauna

(a) Pelecypoda, — Estuarine species, which have become
accustomed to a certain admixture of fresh water, have gradually
ascended the streams or been cut off from the sea, and have at
last become habituated to water which is perfectly fresh.

Fic. 9.—A, <Arca navicella Reeve,

Philippines, a marine species. B,

Fra. 8.—A, The common Mytilus edulis Arca (Scaphula) pinna Bens., R.

I., a marine genus and species. B, Tenasserim, a fresh-water species

Dreissensia, a fresh-water genus, closely which lives many miles above the
allied to Mytilus. tide-way.

Thus Dreissensia (rivers and canals throughout N. Europe
and N. America) and JMytilopsis (rivers of America) are
scarcely modified IMytili (Fig. 8); Seaphula is a modified Areca,

I ORIGIN OF FRESH-WATER BIVALVES 15

and lives in the Ganges, the Jumna, and the Tenasserim at
a distance of 1600 miles from the sea (Fig. 9). Pholas rivicola
is found imbedded in floating wood on the R. Pantai many
mules from its mouth. Cyrena, Corbicula, and probably Sphaerium
and Pisidiwm are derived, in different degrees of removal, from
the exclusively marine Veneridae ; Potamomya (rivers of S.
America), and Himella (R. Amazon) are forms of Corbula.
The Caspian genera derived from Cardium (Adacna, Didacna,
JMonodacna), have already been referred to. Nausitora is a
form of Zeredo, which lives in fresh water in Bengal. Rangia,
Fischeria, and Galatea probably share the derivation of the
Cyrenidae, while in /phigenia we have one of the Donacidae
which has not yet mounted rivers, but is confined to a strictly
estuarine life. The familar Scrobicularia piperata of our own
estuaries 1s a Zellina, which lives by preference in brackish
water.

The great family of the Unionidae is regarded by Neumayr !
as derived from Trigonia, the poimts of
sunilarity being the development of a
nacreous shell, the presence of a strong
epidermis, and the arrangement of the
muscular sears. It is remarkable, too,
that on many Uniones of Phocene times
there is found shell ornamentation of such
«a type as occurs elsewhere among the
Pelecypoda only on Zrigonia.

The genera of fresh-water Pelecypoda
are comparatively few in number, and Fic. 10.—Trigonia _pec-
their origin is far more clearly discernible aha Sa wb tak
than that of any other group. This is
perhaps due to the fact that the essential changes of structure
required to convert a marine into a fresh-water bivalve are but
sheht. Both animals “breathe water,’ and both obtain: their
nutriment from matter contamed in water. Similar remarks

apply to fresh-water operculate Gasteropoda. But the passage
from a marine to an aerial lite involves much profounder changes
of environment, which have to be met by correspondingly im-
portant changes in the organism, This may be in part the

1 SB. K. Akad. Wiss. Wien, 1889, p. 4, but the view is not universally
accepted.

16 ORIGIN OF FRESH-WATER UNIVALVES CHAP.

reason why the ancestry of all Pulmonata, whether land or fresh-
water, is so difficult to trace.

(b) Gasteropoda.—(1) Operculate. Canidia and Clea are
closely allied, with but little modification, to
the marine Cominella’ (Fig. 11), as is also
Nassodonta to Nassa. They occur (in fresh
water) in the rivers of India, Indo-China, Java,
and Borneo, associated with essentially fresh-
water species. Potamides, with its various

subgenera (Telescopium, Pyrazus, Pirenella,

Fig. 11.—A, Cominedla, Ce oe iicatere wallatatiehennalnt ; oka
amarinegenus,which Ceretne ea,ete.),all of which inhabit swamps anc
lives between tide a udflats just above high-water markin allwarm

marks, and from ee : ua Sage =f 9

which’ is probably Countries, are derived from Cerithium (Fig. 12);

derived B, Clea, © Assiminea, Hydrobia, and perhaps Truncatella,

genus occurring only a ; ‘
in fresh water. from Rissoa. It is a remarkable fact that in
Geomelania (with its subgenera Chittya and
Blandiella) we have a form of Zruncatella which has entirely ”

Fie. 12.—A, Cerithium columna Sowb. (marine). B, Potamides microptera Kien.
(brackish water). ©, Zo spinosa Lea, one of the Plewroceridae (fresh water).

deserted the neighbourhood of the sea, and lives in woody
mountainous localities in certain of the West Indies. Cremno-
conchus, a remarkable shell occurring only on wet cliffs in the
ghats of southern India, is a modified Littorina. Neritina and
Nerita form a very interesting case in illustration of the whole
process. Nerita is a purely marine genus, occurring on rocks in
the littoral zone; one species however (WV. lineata, Chem.) ascends

1 Not to Vassa, as has been generally held. The shape of the operculum, and
particularly the teeth of the radula, show a much closer connexion with Comine//a.

I ORIGIN OF FRESH-WATER UNIVALVES 17

rivers as far as 25 miles from their mouth, and others haunt
marshes of brackish water. Neritina is the fresh-water form,
some species of which are found in brackish swamps or even
creeping on wet mud between tide marks, while the great
majority are fluviatile, one group (Neritodryas) actually occurring
in the Philippines on trees of some height, at a distance of a
quarter of a mile from any water. Navicella is a still further
modified form of WVeritina, occurring only on wet rocks, branches,
etc., in non-tidal streams (Fig. 15).

Fic. 13.—Illustrating the development of the fresh-water genus Navicella, through the
brackish-water Neritiaa, from the marine Nerita, with corresponding changes in the
operculum. 1. Nerita; 2, 3. Neritina; 4. Neritina, intermediate form; 5, 6.
Navicella.

The great family of the Melaniidae, which occurs in the
rivers of warm countries all over the world, and that of the
Pleuroceridae, which is confined to North America, are, in all
probability, derived from some form or forms of Cerithiwm. The
origin of the Paludinidae, Valvatidae, and Ampullariidae is more
doubtful. Their migration from the sea was probably of an
early date, since the first traces of all three appear in the lower
Cretaceous, while Melaniidae are not known until Tertiary times.
Ampullaria, however, shows: distinct signs of relationship to
Natica, while the affinities of Paludina and Valvata cannot as
yet be approximately affirmed.

(2) Pulmonata.—Intermediate between the essentially fresh-
water and the essentially marine species come the group some-
times known as Gehydrophila, consisting of the two families
Auriculidae and Otinidae. These may be regarded as Mollusca
which, though definitely removed from all marine species by the
development of a true lung or lung cavity in place of a gill,

VOL. III C

18 INTERMEDIATE FORMS CHAP.

have yet never become, in respect of habitat, genuine fresh-
water species. Like Potamides, they haunt salt marshes, man-
grove swamps, and the region
about high-water mark. In some
cases (Otina, Melampus, Pedipes)
they live on rocks which are
moistened, or even bathed by the
spray, in others (Cassidula, Auri-
cula) they are immersed in some
depth of brackish water at high
tide, in others again (Scarabus)
they are more definitely terres-
trial, and live under dead leaves
in woods at some little distance
Fic. 14.—Examples of the Awriculidae : from water. Indeed one genus of

A, Auricula Judae Lam., Borneo; diminutive size (Carychium) has

B, Scarabus Lessoni Blainv., E. eae / 5 ; is

Indies; C, Cassidula mustelinad Completely abandoned the neigh-

Desh., N. Zealand ; D, Melumpus |yourhood of the sea, and inhabits

castaneus Mihlf., S. Pacific ; E,

Pedipes quadridens Pfr., Jamaica. SWalmpy ground almost all over

the world.

To this same section Gehydrophila have been assigned two
remarkable forms of air-breathing “limpet,” Siphonaria and
Gadinia (see page 151), and the aberrant Amphibola, a unique
instance of a true operculated pulmonate. Sipho-
naria possesses a pulmonary cavity as well as
a gill, while Gadinia and Amphibola are ex-
clusively air-breathing. Siphonaria lives on
rocks at or above high-water mark, Gadinia
between tide marks, Amphibola (Fig. 15) in
brackish water at the estuaries of rivers, half NR Re eA
buried in the sand. There can be little doubt CoE is Sat
that all these are marine forms which are “axa Chem.), the

d : only true Pulmo-
gradually becoming accustomed to a terrestrial nate which _ pos-
existence. In Gadinia and Amphibola the pro- To
cess is so far complete that they have ex-
changed gills for a pulmonary cavity, while in Siphonaria
we have an intermediate stage in which both organs exist
together. A curious parallel to this is found in the case of
Ampullaria, which is furnished with two gills and a pulmonary
chamber, and breathes indifferently air and water. It is a little

I AFFINITIES OF THE LIMNAEIDAE Ze)

remarkable that Siphonaria, which lives at a higher tide level
than Gadinia, should retain the gill, while Gadinia has lost it.

The ultimate affinities of the essentially fresh-water groups,
Limnaea, Physa, Chilina, cannot be precisely affirmed. The form
of shell in Latia, Gundlachia, and perhaps Ancylus, may suggest
to some a connexion with the Otinidae, and in Chilina, a similar
connexion with the Auriculidae. But, in a question of deriva-
tion, similarities of shell alone are of little value. It is not a
httle remarkable, for instance, that we should find a simple patelli-
form shell in genera so completely distinct from one another in all
anatomical essentials as Ancylus, Patella, Siphonaria, Propilidium,
Hipponyx, Cocculina, and Umbrella.

Some recent authors, on grounds of general organisation,
regard the Limnaeidae and their allies as Opisthobranchs
adapted to an aerial life. It is held! that the Nudibranchiate
Opisthobranchs have given birth to the Pulmonata Stylommato-
phora or land snails, and the Tectibranchiate Opisthobranchs to
the Pulmonata Basommatophora or fresh-water snails. Such a
view seems at first sight open to some objection from other views
than those which deal simply with anatomy. The Opistho-
branchiata are not, to any marked extent, littoral genera, nor do
they specially haunt the mouths of rivers. On the contrary,
they inhabit, as a rule, only the very lowest part of the littoral
zone, and are seldom found, except where the water is purely
salt. In other cases, when the derivation of land or fresh-water
genera is fairly well established, intermediate forms persist,
which indicate, with more or less clearness, the lines along which
modification has proceeded. It has, however, recently been
shown that Stphonaria? and Gadinia,? which have, as has been
already mentioned, hitherto been classified as Pulmonata, are in
reality modified forms of Opisthobranchiata, which are in process
of adaptation to a life partly marine, partly on land. They may
therefore be regarded as supplying the lnk, hitherto missing,
between the land Pulmonata and the marine groups from one or
other of which the latter must have been derived. The general
consensus of recent opinion inclines towards accepting these
views, some writers * being content to regard the Pulmonata, as

1 #.g. Bouvier, Le Natural. 1889, p. 242.
* Kohler, Zool. Jahrb. vii. 1893, p. 1 f; Haller, Arb. Zool. Ist. Wien, x. p. 71.
3 Plate, SB. kin. Preuss. Ak. Wiss. Berl. 1893, p. 959.
4 Eig. Pelseneer, Bull. Sc. France Belg. xxiv. p. 347 f.

20 ORIGIN OF LAND OPERCULATES CHAP.

a Whole, as derived from the Tectibranchiate Opisthobranchs,
while others' go further and regard the Stylommatophora as
derived directly from the Basommatophora.

Origin of the Land Fauna

Gasteropoda.—(1) Operculate. On a priori grounds, one
might predict a double origin for land operculates. Marine
species might be imagined to accustom themselves to a terres-
trial existence, after a period, more or less prolonged, of littoral
probation. Or again, fresh-water species, themselves ultimately
derived from the sea, night submit to a similar transformation,
after a preliminary or intermediate stage of life on mudbanks,
wet swamps, branches overhanging the water, etc. Two great
families in this group, and two only, seem to have undergone
these transformations, the Littorinidae and the Neritidae. The
derivation of almost all existing land operculates may be referred
to one or other of these groups.

Fic. 16.—Two rows of the radula of Littorina littorea L., x 72.

The power of the Littorinidae to live for days or even weeks
without bemeg moistened by the sea may be verified by the most
casual observer. In the tropics this power seems even greater
than on our own shores. I have seen, in various parts of
Jamaica, Littorina muricata living at the top of low cliffs among
grass and herbage. At Panama I have taken three large species
of Littorina (varia, fausciata, pulchra), on trees at and above
high-water mark. Cases have been recorded in which a number
of L. muricata, collected and put aside, have lived for three
months, and ZL. irrorata for four months. These facts are
significant, when we know that the land operculates almost
certainly originated in a tropical climate.

! E.g. Bergh, Zoole Jahrb. v. p. 1 f.
2 Calkins, Amer. Nat. xi. p. 687.

I ORIGIN OF LAND OPERCULATES Z1

The Cyclophoridae, Cyclostomatidae, and Aciculidae, which,
as contrasted with the other land operculates, form one group,
have very close relations, particularly in the length and formation
of the radula, or lingual ribbon, with the Littorinidae.

Fra. 17.—Two rows of the radula of Cyclophorus sp., India, x 40.

On the other hand, the Helicinidae, Hydrocenidae, and
Proserpinidae are equally closely related to Neritina. The
Proserpinidae (restricted to the Greater Antilles, Central America
and Venezuela) may perhaps be regarded as the ultimate term
of the series. They have lost the characteristic operculum,
which in their case is replaced by a number of folds or lamellae
in the interior of the shell. It has already been noticed how
one group of Neritina (Neritodryas) occurs normally out of the
water. This group furnishes a link between the fresh-water and
land forms. It is interesting to notice that here we have the
most perfect sequence of derivatives; Nerita in the main a

Fic. 18.—A, WNeritina reticularis Sowb., Calcutta (brackish water); B, Helicina
neritella Lam., Jamaica (land) ; C, Proserpina (Ceres) eolina Ducl., Central America
(land).

purely marine form, with certain species occurring also in
brackish water; Weritina in the main fresh-water, but some
species occurring on the muddy shore, others on dry land:
Helicina the developed land form; and finally Proserpina, an
aberrant derivative which has lost the operculum.!

' One step even further (or perhaps it should be termed a branch derivative) is

seen in the genus Smaragdia, which is probably a Nevritina which has resumed a
purely marine habit of life.

22 ORIGIN OF LAND PULMONATA CHAP. 1!

Gasteropoda.—(2) Pulmonata. The origin of these, the
bulk of the land fauna, must at present be regarded as a problem
not yet finally solved. Some authorities, as we have seen, regard
them as derived from the Nudibranchiate, others, probably more
correctly, from the Tectibranchiate Opisthobranchs.

The first known members of the land Pulmonata (Pupa [?],
Hyalinia) ave from the Carboniferous of North America. Similar
but new forms appear in the Cretaceous, from which time to the
present we have an unbroken series. The characteristically
modern forms, according to Simroth,' are Helices with thick
shells. According to the same author, Vitrina and Hyalinia
are ancestral types, which give origin not only to many modern
genera with shells, but to many shell-less genera also, e.g. Testa-
cella is probably derived through Daudebardia from Hyalinia,
while from Vitrina came Limax and Amalia. A consideration
of the radulae of the genera concerned certainly tends in favour
of these views.

Godwin- Austen, speaking generally, considers” genera of
land Pulmonata with strongly developed mantle-lobes and rudi-
mentary shell as more advanced in development than genera
in which the shell is large and covers all or nearly all the
animal.

1 SB. Naturf. Gesell. Leipz. 1886-87, pp. 40-48.
2 L. and F. W. Moll. of India, iv. p. 167.

CHAPTER II

LAND AND FRESH-WATER MOLLUSCA, THEIR HABITS
AND GENERAL ECONOMY

THE majority of the Land Mollusca are probably more sensitive
than is usually believed. The humidity of the air must affect
the surface of their skin to a considerable extent. Every one
has noticed how the snails ‘come out’ on a damp evening,
especially after rain. As a rule, they wait till rain is over,
probably objecting to the patter of the drops upon their delicate
tentacles. Snails kept in captivity under a bell-glass are acutely
sensitive of a damp atmosphere, and will bestir themselves after
rain just as if they were in the open air. Certain Helices which
are accustomed to live in moist places, will find their way to
water, 1f removed from their usual haunts. A case is recorded !
of a specimen of HZ. arbustorwm, kept in a kitchen, which used
to find its way directly under the cold water tap, and appeared
to enjoy the luxury of a douche. How delicately the conditions
of life are balanced in some of these creatures is seen in the case
of Omalonyx, a genus akin to Succinea, which is found in Brazil
and the northern parts of South America. It lives creeping on
plants which overhang the margin of water, but perishes equally,
if placed in the water itself, or removed to a distance from it for
any leneth of time.

Endurance of Heat and Cold.—The Mollusca are capable,
at least as far as some species are concerned, of enduring severe
extremes both of cold and heat. The most northern pulmonate
yet observed is a fresh-water species, Physa (Aplecta) hypnorum L.
This hardy mollusc, whose shell is so fragile as to need most
careful handling, has been noticed on the peninsula of Taimyr,

1 T. Scott, Journ. of Conch. v. p. 230. 2 J. S. Gibbons, ibid. ii. p, 129.

24 HABITS OF LAND MOLLUSCA CHAP.

North Siberia, in 73° 30’ N. lat., a region whose mean annual
temperature is below 10° F. with a range of from 40° F. in July
to — 30° F. in January. ,

It is well known that the Limnaeidae, and probably most
fresh-water Mollusca of sub-temperate regions, can continue to
live not merely under, but enveloped in ice, and themselves
frozen hard. Garnier relates! that, during the winter of 1829-
30, some large Limnaea auricularia, which had been placed in a
small basin, were frozen into a solid mass, experiencing. a cold
of — 2° F. He supposed they were dead, but, to his surprise,
when the basin thawed, the Limnaea gradually revived. Paludina
vivipara and Anodonta anatina have been known to resist a
temperature of 23° F., and the former has produced young shortly
after being thawed out of the ice.” As far north as Bodo in
Norway (67° 37’ N. lat., well within the Arctic circle) there
are found no less than fourteen species of terrestrial Mollusca,
among them being Balea perversa and Clausilia rugosa.°

Vitrina is one of our most hardy molluscs, and may be
observed crawling on bright mornings over the frost-covered
leaves of a wood or copse. V. glacialis is said by Charpentier
to live in the Alps at a height where the stones are covered with
snow from nine to ten months of the year. Many of the Hyaliniae
are very hardy. Arion, in spite of having no external shell to
protect it, is apparently less affected by the cold than He/iz, and
does not commence hibernation till a later period in the autumn.
The operculate land Mollusca, in spite of the protection which
their operculum may be supposed to afford, are exceedingly
sensitive to cold, and the whole group is without doubt a product
of tropical or semi-tropical regions (see map at frontispiece). A
species of Helicina which inhabits the southern States of North
America has been known to be almost exterminated from certain
districts by the occurrence of an unusually severe winter.

One of the highest altitudes at which a land shell is known
to live appears to be the Liti Pass (Himalayas, 14,000 ft.). At
this enormous altitude, two species of Buliminus (arcuatus Hutt.
‘and nivicola Bens.) live on juniper bushes among patches of
snow. An Anadenus is said to have been found in a similar

1 Buil. Soc. Linn. Nord, Abbeville, 1840, p. 150.
° Joly, Comptes Rendus, 1842, p. 460; compare W. A. Gain, Science Gossip,
XXVll. p. 118. 3 Von Martens, SB. Nat. Fr. Berl. 1881, p. 34.

ll ENDURANCE OF HEAT AND COLD 25

locality at 15,000 ft., while Limnaea Hookeri has been taken
from over 16,400 ft. in Landour. In the Andes of Peru and
Bolivia, five species of Bulimulus, one of Pupa, and one of Limax
occur at an elevation of 10,500 to 15,000 ft. Several fresh-
water Mollusca inhabit Lake Titicaca, which stands at a height
of 12,550 ft. in the Bolivian table-land.

In certain parts of the desert of Algeria, where there is not
a trace of vegetation to be seen, and the temperature at mid-day
is 110° F., the ground is sometimes so covered with Helix lactea
as to appear perfectly white. Dr. F. H. H. Guillemard has told
me that he noticed, in somewhat similar surroundings between
Fez and Tangier, H. pisana in such extraordinary abundance
that they hung from the low scrub in bunches the size of a man’s
two fists. It is singular that Mollusca should live, and not
only live, but flourish, in localities apparently so unpromising.
Shells which occur in the Algerian Sahara are actually larger
and altogether finer than the ordinary European form of the same
species. In order to protect themselves to some extent against
the scorching heat and consequent evaporation, desert species
are frequently modified in one of two ways; the shell becomes
either white or a light dusky brown, as in the familiar Helix
desertorum, or else it gains immensely in thickness. Specimens
of H. pomatia, recently procured from Fez, are of extraordinary
thickness as compared with forms from our own chalk downs of
Kent and Surrey.

Fresh-water Mollusca are frequently found inhabiting hot
springs. Thus Neritina fluviatilis lives at Bagneres de Bigorre
in water at about 68° F. In another hot spring in the eastern
Pyrenees a Lithynia lives at a temperature of over 73° F.; while
Blainville mentions another case of a ithynia living in water
at 122° F.

Hibernation and Aestivation——As autumn begins to draw
on, and the first frosts to nip vegetation, terrestrial species retire
beneath stones, into cracks in old walls, holes in tree trunks,
deep fissures in rocks, and nooks and crannies of every kind,
or else bury themselves deeply in the earth or in moss and
heaps of leaves. They thus commence their period of hiberna-
tion, which varies in length according to the duration of winter.
Frequently masses of Helices may be found attached to one
another, probably not so much for the sake of warmth, for their

26 HIBERNATION AND AESTIVATION CHAP.

temperature is but low, as to share the comforts of a cosy
retreat In common. Slugs generally hibernate alone, excavating
a sort of nest in the earth, in which they encyst themselves,
contracting their bodies until they are almost round, and secret-
ing a covering of their own slime. The Helices usually close
up the mouth of their shell by the formation of a membranous
or chalky epiphragm, which will be further described below.
Both snails and sluys take care to be in good condition at the
time their winter sleep begins, and for this reason the former
are said to be most esteemed by foreign epicures if captured just
at this period.t

During hibernation, the action of the heart in land Pulmonata
ceases almost entirely. This appears to be directly due to the
effect of cold. Mr. C. Ashford has related? some interesting
experiments made upon HZ. hortensis and Hyal. cellaria, with the
view of ascertaining the effect of cold upon their pulsations.
His observations may be tabulated as follows :—

Number of pulsations per minute.

Helix hortensis. Hyal. cellaria. At degrees Fahr.
22 21 aos
14 12 44°
10 1a 38°
4 9 30°

At low temperatures the character, as well as the number of
the pulsations changed; they became imperfect and intermittent,
although exceptionally at 31° F. a H. rufescens gave five or six
pulsations a minute, very full and deliberate. The result of
taking the Hyalinia suddenly into the heat of a greenhouse
was to bring on palpitations. Further experiments resulted in
evidence of a similar kind. Hyal. radiatula, placed upon a deal
table in a room, showed 52 pulsations per minute at 62° F.
Placed upon the palm of the hand, the action soon rose to 108.
Hyal. alliaria, similarly treated, rose from 72 pulsations to 110.
Floated upon water, the action of the heart of the latter suddenly
fell to 29.

Fresh-water Pulmonata do not appear to hibernate. Unio
and Anodonta, however, bury themselves more deeply in the
mud, and Dreissensia casts off its byssus and retires under the

1 Moquin-Tandon, doll. de France, i. p. 116.
2 Journ. of Conch. iii. p. 321 f.; iv. p. 18; Science Gloss. 1866, p. 158.

II EFFECTS OF COLD AND HEAT 27,

mud in deeper water. Limnaea and Planorbis have often been
noticed to crawl about under the lower surface of a thick coating
of ice. In periods of prolonged drought, when the water in
the ponds dries up, the majority of genera bury themselves in
the mud. I have known Limnaea peregra bury itself three
inches deep, when surprised by a sudden fall of the water in
the ditch on Coe Fen, behind Peterhouse, Cambridge. Physa
hypnorum frequents by preference ditches which dry up in
summer, as does also Panorbis spirorbis, the latter often form-
ing a sort of epiphragm against evaporation. Ancylus has been
observed to spend the whole winter out of water, and P. spirorbis
has been noticed alive after four months’ desiccation.?

True aestivation, however, occurs mainly in the tropics,
where there is no winter, but only a period when it is not quite
so hot as the rest of the year, or on a coast like the Mediter-
ranean, Which is subject to sudden and severe heat. This period
is usually rainless, and the heat is therefore a dry heat. At
this season, which may last for three or four months, most of the
Jand Mollusca enter upon a period of inaction, either burying
themselves deeply in the ground, or else permanently attaching
themselves to the stalks of grass and other herbage, or the under
sides of rocks. For instance, the large and beautifully painted
Orthalicus, Corona, and Porphyrobaphe, which inhabit Brazil,
Ecuador, and eastern Peru, bury themselves deeply in the
ground during the dry season, while in the rains they climb to
the topmost branches of the great forest trees Thus it may
well happen that a visitor to a tropical island, Ceylon for
instance, or one of the Greater Antilles, if he time his visit to
coincide with the rainless season, may be grievously disappointed
at what seems its unaccountable poverty in land Mollusca. But
as soon as the weather breaks, and the moisture penetrates their
retreats, every bush and every stone, in favoured localities, will
be alive with interesting species.

The Epiphragm.—A considerable number of the land Pul-
monata (and a very few of the fresh-water) possess the power
of closing the aperture of their shell by means of what is known
as an epiphragm or covering ot hardened mucus. This epi-
phragm is habitually formed by certain species during hibernation
1 Reichel, Zool. Anz. x. p. 488. * Schumann, Schr. Ges. Danz. (2) vi. p. 159.

3 Tischer and Crosse, Mexico, p. 437.

28 THE EPIPHRAGM CHAP.

or aestivation, or even during shorter periods of inactivity
and retirement, the object being, either to check evaporation of
the moisture of the body, or to secure the animal against the cold
by retaining a thin layer of shghtly warm air immediately
within the aperture of the shell.

The epiphragm differs widely in character in different species,
sometimes (Clausilia, Pupa, Planorbis) consisting of the merest
pellicle of transparent membrane, while at others (Helia aperta,
Hf. yomatia) it is a thick chalky substance, with a considerable
admixture of carbonate of lime, with the consistency of a hard-
ened layer of plaster of Paris. Within these extremes every
variety of thickness, solidity, and transparency occurs. During
long hibernation several epiphragms are not unfrequently formed
by the same individual snail, one within the other, at gradually
lessening distances. The epiphragm thus performs, to a certain
extent, the part of an operculum, but it must be remembered
that it differs radically from an operculum physiologically, in
beine only a temporary secretion, while the operculum is actually
a living part of the animal.

The actual mode of formation of the epiphragm would seem
to differ in different species. According to Fischer,' the mollusc
withdraws into its shell, completely blocking all passage of air
into the interior, and closing the pulmonary orifice. Then, from
the middle part of the foot, which is held exactly at the same
plane as the aperture, is slowly secreted a transparent pellicle,
which gradually thickens, and in certain species becomes cal-
careous. Dr. Binney, who kept a large number of Helia hortensis
in confinement, had frequently an opportunity of noticing the
manner in which the epiphragm was formed” The aperture of
the shell being upward, and the collar of the animal having
been brought to a level with it, a quantity of gelatinous matter
is thrown out [? where from]. The pulmonary orifice is then
opened, and a portion of the air within suddenly ejected, with
such force as to separate the viscid matter from the collar, and
to project it, hke a bubble of air, from the aperture. The animal
then quickly withdraws farther into the shell, and the pressure
of the external air forces back the vesicle to a level with the
aperture, when it hardens and forms the epiphragm. In some

1 Journ. de Conch. iv. p. 397, but the species observed is not mentioned.
2 Bull. Mus. C. Z. Harv. iv. p. 378.

II SPINNING OF THREADS 29

of the European species in which the gelatinous secretion con-
tains more carbonate of lime, solidification seems to take place
at the moment when the air is expelled, and the epiphragm in
these is in consequence strongly convex.

Thread-spinning.—A considerable number of fresh-water
Mollusca possess the power of stretching a thread, which is no
more than an exceedingly elongated piece of mucus, to the
surface of the water, and of using it as a means of locomotion.
This thread bears no analogy whatever to the fibrous byssus of
certain bivalves, being formed in an entirely different manner,
_ without the need of a special gland.

The threads are ‘spun’ by several species of Limnaea, Physa,
and Planorbis, by Bithynia tentaculata, and several of the
Cycladidae. They are anchored to the surface by a minute
concavity at the upper end, which appears to act like a small
boat in keeping the thread steady. The longest threads are
those of the Physae, which have been noticed to attain a length,
in confinement, of 14 inches. They are always spun in the
ascent, and as a rule, when the animal descends, it rolls the
thread up and carries it down as it goes. A single thread is
never spun on the descent, but occasionally, when a thread has
become more or less of a permanence, it becomes stronger by
the addition of more mucus each time it is used, whether for
ascending or descending purposes. Cyclas cornea appears to be
an exception to the rule that threads are only spun on the
ascent. This species, which is particularly fond of crawling
along the under surface of the water, has been noticed to spin
a thread half an inch in length while on the surface, and to hang
suspended from it for a considerable time.

What the exact use of the thread may be, must to a certain
extent be matter of conjecture. The Limnaeidae are, in the
great majority of cases, compelled to make periodic visits to the
surface in order to inspire oxygen. It is also a favourite habit
with them to float just under the surface, or crawl about on its
under side, perhaps in pursuit of tiny vegetable organisms.
Whatever may be the object of an excursion to the surface, a
taut thread will obviously be a nearer way up than any other
which is likely to present itself; indeed, without this thread-
spinning power, which ensures a tolerably rapid arrival at the
surface, the animai might find itself asphyxiated, or at least

30 USE OF THREADS CHAP.

seriously inconvenienced, before it could succeed in taking in
the desired supply of oxygen. With the Cycladidae, which do
not breathe air, such an explanation is out of place; in their
case the thread seems to be a convenient means of resting in
one position in the intervals of the periods of active exercise to
which several of the species are so much addicted.

The power of suspension by a thread is also possessed by
certain of the Cyclostomatidae, by some Cerithidea, several Rissoa
and other marine genera, prominent among which is Zitiopa
bombyx, whose name expresses its power of anchoring itself to
the Sargasso weed by a silken thread of mucus. Several
species of slugs are known to be able to let themselves down by
threads from the branches of trees. Limax arborum is especially
noted for this property, and has been observed suspended in
pairs during the breeding time. According to Binney, all the
American species of Limax, besides those of Tebennophorus,
possess this singular property. Limax arborum appears to be
the only slug which has been noticed to ascend, as well as
descend, its thread. It has also been observed! that when this
species 1s gorged with food, its slime is thin and watery, and
unable to sustain its weight, but that after the process
of digestion has been performed, the mucus again becomes
thick and tenacious. It appears therefore that when the
animal is hungry and most in need of the power of making
distant excursions in search of food, its condition enables
it to do so, but that when no such necessity is pressing, the
thread-forming mucus is not secreted, or is perhaps held in
suspense while the glands assist in lubricating the food before
digestion.”

Food of Land and Fresh-water Mollusca.—drion ater, the
great black slug, although normally frugivorous, is unquestion-
ably carnivorous as well, feeding on all sorts of animal matter,
whether decaying, freshly killed, or even in a living state. It is
frequently noticed feeding on earthworms; kept in captivity, it
will eat raw beef; it does not disdain the carcases of its own
dead brethren. An old man near Berwick-on-Tweed, going out
one morning to mow grass, found a black slug devouring, as he
supposed, a dead mouse. Being of an inquisitive turn, and

1 W. Harte, Proc. Dubl. N. H. Soc. iv. p. 182.
* See on the whole subject of threads G. S. 'l'ye, Jowrn. of Conch. i. p. 401.

ll FOOD OF SLUGS 31

wishing to ascertain if it were really thus engaged, he drew the
mouse a little back. When he returned in the evening, the
mouse was reduced almost to a skeleton, and the slug was still
there. Indeed it would seem almost difficult to name anything
which Arion ater will not eat. Dr. Gray mentions? a case
of a specimen which devoured sand recently taken from the
beach, which contained just enough animal matter to render it
luminous when trodden on in the dark; after a little time the
faeces of the slug were composed of pure sand, united together
by a little mucus. A specimen kept two days in captivity
was turned out on a newspaper, and commenced at once to
devour it. The same specimen ate dead bodies of five other
species of slugs, a dead Unio, pupae of Adimonia tanaceti,
part of the abdomen of a dragon-fly, and Pears’ soap, the latter
reluctantly.

According to Simroth ¢ and Scharff’ the food of several of our
British slugs, eg. Limax maximus, L. flavus, Arion subfuscus,
A. intermedius, consists of non-chlorophyllaceous substances
only, while anything containing chlorophyll is as a rule refused.
On the other hand ZL. agrestis and Amalia carinata feed almost
entirely on green food, and are most destructive in gardens.
The latter species lives several inches under ground during the
day, and comes to the surface only at night. It is largely
responsible for the disappearance of bulbs, to which it is ex-
tremely partial. LZ. marginatus (=arborum Bouch.) feeds ex-
clusively on lichens, and in captivity absolutely refuses green
leaves and a flesh diet. It follows therefore, if these observa-
tions are correct, that the popular notions about slugs must be
revised, and that while we continue to exterminate from our
gardens those species which have a taste for chlorophyll, we
ought to spare, if not encourage those whose tastes le in the
opposite direction.

Limax agrestis has been seen devouring the crushed remains
of Arion ater. Five specimens of the same species were once
noticed busily devouring a May-fly each, and this in the middle
of a large meadow, where it may be presumed there was no lack

1 Zoologist, il. p. 296; ili. p. 833; iv. p. 12165 iii. p. 1036; iv. p. 1216; iii.
p- 1037.

2 Ann. Nat. Hist. ii. 1838, p. 310. % H. W. Kew, Naturalist, 1889, p. 103.

* Zeit. wiss. Zool. xiii. p. 203 f. ° Sci. Trans. R. Dubl. Soc. (2) iv. p. 520f.

FOOD OF SLUGS CHAP.

Go
1)

of green food. The capture and eating of insects by Mollusca
seems very remarkable, but this story does not stand alone.
Mr. T. Vernon Wollaston once enclosed in a bottle at least three
dozen specimens of Coleoptera together with 4 Helia cantiana,
5 H. hispida, and .1 H. virgata, together with an abundant
supply of fresh leaves and grass. About a fortnight afterwards,
on the bottle being opened, it was found that every single
specimen of the Coleoptera had been devoured by the snails.’
Amalia marginata in captivity has been fed upon the larvae of
Huchelia jacobaeae, eating three in two hours.”

Limax maximus (Fig. 19) has been seen frequently to make
its way into a dairy and feed on raw beef? Individuals kept in
confinement are guilty of
eannibalism. Mr. W. A.
Gain kept three specimens
in a box together, and found
one of them two - thirds
eaten, “the tail left clean
cut off, reminding one of
that portion of a fish on a
fishmonger’s stall.” —- That
starvation did not prompt
Fic. 19.—Limax maximus L. PO, pulmonary the crime was proved by

orifice : x 3. the fact that during the
preceding night the slug had been supplied with, and had eaten,
a considerable quantity of its favourite food. On two other
occasions the same observer found one of his slugs deprived of

its slime and a portion of its skin, and in a dying condition.
An adult ZL. maximus, kept for thirty-three days in captivity with
a young Arion ater, attacked it frequently, denuded it of its slime,
and gnawed numerous small pieces of skin off the body and
mantle.° The present writer has found no better bait for this
species on a warm summer night than the bodies of its brethren
which were slain on the night preceding; it will also devour
dead Helix aspersa. Mr. Gain considers it a very dainty feeder,
preferring fungi to all other foods, and apparently doing no harm
in the garden.
1 Zoologist, iv. p. 1504 ; iii. p. 1038 ; iii. p. 948.
Ze Wie Kew, dane 3 Zoologist, xix. p. 7819.
+ Naturalist, 1889, p. 55. ® H. W. Kew, 7. c.

II FOOD OF SLUGS AND SNAILS 33

Limax flavus, which is fond of inhabiting the vicinity of
cellars, makes its presence most disagreeable by attacking articles
of food, and especially by insinuating itself into vessels containing
meal and flour.’ It is particularly partial to cream.

Slugs will sometimes bite their captor’s hands. Mr. Kew
relates that a Lomax agrestis, on being stopped with the finger,
while endeavouring to escape from the attack of a large Arion,
attempted to bite fiercely, the rasping action of its radula being
plainly felt. According to the same authority, probably all the
slugs will rasp the skin of the finger, if it is held out to them,
and continue to do so for a considerable time, without however
actually drawing blood.? While Mr. Gain was handling a large
Arion ater, it at once seized one of the folds of skin between the
fingers of the hand on which it was placed; after the action of
the radula had been allowed to continue for about a minute, the
skin was seen to be abraded.* Another specimen of Arion ater,
carried in the hand for a long time enclosed in a dock leaf,
began to rasp the skin. ‘The operation was permitted until it
became too painful to bear. Examination with a lens showed
the skin almost rasped away, and the place remained tender and
sore, like a slight burn, for several days.*

feliz pisana, if freshly caught, and placed in a box with
other species, will set to work and devour them within twenty-
four hours. The present writer has noticed it, in this position,
attack and kill large specimens of H. ericetorum, cleaning them
completely out, and inserting its elongated body into the top
whorls of its unfortunate victims in a most remarkable manner.
Amongst a large number of species bred in captivity by Miss
F. M. Hele was Hyalinia Draparnaldi. In the first summer
the young offspring were fed on cabbage, coltsfoot, and broad-
leafed docks. They would not hibernate even in the severest
frosts, and, no outdoor food being available, were fed on chopped
beef. This, Miss Hele thinks, must have degenerated their
appetites, for in the following spring and summer they constantly
devoured each other.

Zonites algirus feeds on decayed fruit and vegetables, and
on stinking flesh.6 Achatina panthera has been known to eat

1 W. G. Binney, Bull. Mus. C. 2. Harv. iv. p. 144. 2 Naturalist, 1. c.
3 Sctence Gossip, 1885, p. 154. + RK, Standen, Journ. of Conch. vii. p. 197.
5 Journ. of Conch. v. p. 43. 6 A. Paladilhe in MS. letter.

VOL. III Dd

34 FOOD OF SLUGS AND SNAILS CHAP.

meat, other snails (when dead), vegetables, and paper.' The
common Stenogyra decollata of the South of Europe has a very
bad character for flesh-eating habits, when kept in captivity.
Mr. Binney? kept a number for a long time as scavengers, to
clean the shells of other snails. As soon as a Lving Helix was
placed in a box with them, one would attack it, introduce itself
into the upper whorls, and completely remove the animal. One
day a number of Succinea ovalis were left with them for a short
time, and disappeared entirely! The Stenogyra had eaten shell
as well as animal. This view of Stenogyra is quite confirmed
by Miss Hele, who has bred them in thousands. “TI can keep,”
she writes? “no small Heliz or Bulimus with them, for they at
once kill them and eat them. They will also eat raw meat.”
Even the common Limnaea stagnalis, which is usually re-
garded as strictly herbivorous, will sometimes betake itself,
apparently by preference, to a diet of flesh. Karl Semper
frequently observed the Limnaeae in his aquarium suddenly
attack healthy living specimens of the common large water newt
(Triton taeniatus), overcome them, and devour them, although
there was plenty of their favourite vegetable food growing
within easy reach. The same species has also been noticed to
devour its own ova, and the larvae of Dytiscus. Limnaea peregra
has been detected capturing and partially devouring minnows in
an aquarium, when deprived of other food, and Dr. Jeffreys has
seen the same species attack its own relatives under similar
circumstances, piercing the spire at its thinnest point near to the
apex. JL. stagnalis, kept in an aquarium, has succeeded in
overpowering and partially devouring healthy specimens of the
common stickleback.®
Powers of Intelligence, Homing, and finding Food.—lt is

not easy to discover whether land Mollusca possess any faculties
which correspond to what we call intelligence, as distinct from
their capacities for smell, sight, taste, and hearing. Darwin
mentions’ a remarkable case, communicated to him by Mr.
Lonsdale. A couple of Helix pomatia, one of which was sickly,

1 J. 8. Gibbons, Quart. Jowrn. Conch. ii. p. 143.

2 Bull. Mus. C. Z. Harv. iv. p. 193.

21 @y 105 koe 4 Animal Life, p. 59.

5 Zoologist, 1861, p. 7400; Brit. Conch. i. p. 108.

6 H. Ullyett, Science Gossip, xxii. (1886) p. 214.
7 Descent of Man, i. p. 325, ed. 1.

II HOMING AND FINDING FOOD

Oo
Sal

were placed in a small and ill-provided garden. The stronger of
the two soon disappeared over the wall into the next garden,
which was well furnished with food. It was concluded that the
snail had deserted its weakly mate, but after twenty-four hours
it returned, and apparently communicated the results of its
expedition, for after a short time both started off along the same
track, and disappeared over the wall. According to Dr. W. H.
Dall} a young girl who possessed a remarkable power over
animals succeeded in training a snail (47. albolabris) to come out
of its lurking-place at her call. If placed in a room, it would
shrink into its shell at the sound of any other voice, but it would
always start off in the direction of hers.

Snails and slugs possess to a considerable extent the faculty
of ‘homing,’ or returning to the same hiding-place day after day,
after their night excursions in search of food. Mr. C. Ashford
once marked with a dab of white paint seven Helix aspersa found
lurking under a broken flagstone; at 10 p.m. the same evening
three had disappeared on the forage; the next morning all were
‘at home.’ The following night at 10 P.M. five were gone out,
two being discovered with some difficulty ‘in a small jungle’
six feet away; the next morning six out of the seven were safely
beneath the flagstone. According to the same authority, Helix
aspersa will find its way across a cinder-path (which it specially
detests) to get to its favourite food, and will return by the same
way to its old quarters, although it could easily have found new
lodgings nearer the food-supply. A snail has been observed to
occupy a hole in the brick wall of a kitchen-garden about four
feet from the ground. Leaning against the wall, and immediately
under the hole, was a piece of wood, the lower end of which rested
in a bed of herbs. For months the snail employed this ladder
between its food and its home, coming down as soon as it was
dark, and retiring to rest during the day.

In greenhouses a slug will forage night after night—as
gardeners know to their cost—over the same beat, and will
always return to the same hiding-place. Limax flavus has been
noticed crawling with great regularity to a sink from a hole near
the water-pipe, and keeping to a well-marked circular track. In
all probability the scent, either of the desired object of food, or of
the creature’s own trail, plays a considerable part in keeping it

1 Amer. Nat. xv. 1881, p. 976.

36 HOMING AND FINDING FOOD CHAP.

to the same outward and homeward track, or at least in guiding
it back to its hiding-place. Yet even scent is occasionally at
fault, for on one occasion a Limax flavus was accustomed to make
nightly excursions to some basins of cream, which were kept in
a cool cellar. When the basins were removed to a distant shelf,
the creature was found the next morning ‘wandering dis-
consolately’ about in the place where the basins had formerly
stood.!

A remarkable case of the power of smell, combined with great
perseverance on the part of a Helix, is recorded by Furtado.?
He noticed a Helix aspersa lodged between a column on a
verandah and a flower-pot containing a young banana plant, and
threw it away into a little court below, and six or seven yards
distant. Next morning the snail was in precisely the same place
on the flower-pot. Again he threw it away, to the same distance,
and determined to notice what happened. Next morning at nine
o'clock, the snail was resting on the rail of a staircase leading up
to the verandah from the court; in the evening it started again,
quickening its pace as it advanced, eventually attacking the
banana in precisely the same place where it had been gnawed
before.

For further instances of the power of smell in snails, see
chap. vil.

Slugs have been known to make their way into bee-hives,
presumably for the sake of the honey.? ‘Sugaring’ the trees at
night for moths will often attract a surprising concourse of slugs.
Sometimes a particular plant in a greenhouse will become the
object of the slugs’ persistent attacks, and they will neglect every
other food in order to obtain it. arfugiwm grande is one of
these favourite foods, “the young leaves and shoots being always
eaten in preference to all other plants growing in the houses;
where no Farfugiwms were kept the slugs nibbled indis-
criminately at many kinds.”* The flowers of orchidaceous plants
exercise a special attraction over slugs, which appear to have
some means of discovering when the plants are in bloom. “I
have often observed,” says Mr. T. Baines, “that a slug will travel

1 W. A. Gain, quoted by H. W. Kew in Naturalist, 1890, p. 307, an article to
which I am much indebted. 2 Ann. Mag. Nat. Hist. (5) xvi. p. 519.

3 Science Gossip, 1882, pp. 237, 262.

4H. W. Kew, Natwradist, 1893, p. 149, another most valuable article.

II SLUGS IN GREENHOUSES ay

over the surface of a pot in which is growing a Dendrobium
nobile, a Cattleya, Vanda, or similar upright plant for a score
of times without ever attempting to ascend into the head of the
plant unless it is in bloom, in which case they are certain to find
their way straight to the flowers; after which they will descend,
and return to some favourite hiding-place, often at the opposite
end of the house.’* Mr. R. Warner has “actually seen many
little slugs suspending themselves by slime-threads from the
rafters and descending on the spikes of the beautiful Odonto-
glossum alexandrae ; and thus many spikes, thickly wadded round
with cotton wool (which the slugs could not travel over), and
growing in pots surrounded by water, had been lost.”* Perhaps
the most singular instance of a liking for a particular food is
that related by Mr. E. Step.? In a London publishing house,
slugs were observed, during a period of nearly twelve months, to
have fed almost nightly on the colouring matter in certain book-
covers, and though the trails were often seen over the shelves,
and cabbage and lettuce leaves laid down to tempt the creatures,
they continued their depredations with impunity for the time
above mentioned.

Limnaea peregra las been observed feeding on old fish-heads
thrown into a dirty stream, and a large gathering of Limnaca
stagnalis has been noticed feeding upon an old newspaper in a
pond on Chislehurst Common, ‘so that for the space of about a
square foot nothing else could be seen.’ +

Tenacity of Life—Land Mollusca have been known to exhibit,
under unusual conditions, remarkable tenacity of life. Some of
the most noteworthy and best authenticated instances of this
faculty may be here mentioned.

The well-known story of the British Museum snail is thus
related by Mr. Baird. On the 25th March 1846 two specimens
of Helix desertoruwm, collected by Charles Lamb, Esq., in Egypt
some time previously, were fixed upon tablets and placed in the
collection among the other Mollusca of the Museum. There they
remained fast gummed to the tablet. About the 15th March
1850, having occasion to examine some shells in the same case,

1 Garden, v. p. 201, quoted by Kew, wt sup.

2 Kew, wt sup. 3 Science Gossip, 1883, p. 163.
4 T. D. A. Cockerell, Science Gossip, 1885, p. 211.

> Ann. May. Nat. Hist. (2) vi. (1850) p. 68,

38 TENACITY OF LIFE CHAD.

Mr. Baird noticed a recently formed epiphragm over the mouth
of one of these snails. On removing the snails from the tablet
and placing them in tepid water, one of them came out of its
shell, and the next day ate some cabbage leaf. A month or two
afterwards it began repairing the lip of its shell, which was broken
when it was first affixed to the tablet.

While resident in Porto Santo, from 27th April to 4th May
1848, Mr. 8. P. Woodward?! collected a number of Helices and
sorted them out into separate pill-boxes. On returning home,
these boxes were placed in empty drawers in an insect cabinet,
and on 19th October 1850, nearly two and a half years after-
wards, many of them were found to be still alive. A whole bagful
of H. turricula, collected on the Ilheo de Cima on 24th April
1849, were all alive at the above-mentioned date.

In September 1858 Mr. Bryce Wright sent”? to the British
Museum two specimens of H. desertorwm which had been dormant
for four years. They were originally collected in Egypt by a Mr.
Vernedi, who, in May 1854, while stopping at one of the stations
in the desert, found a heap of thorn-bushes lying in a corner of
the building, rather thickly studded with the snails. He picked
off fifteen or twenty specimens, which he carried home and locked
up in a drawer, where they remained undisturbed until he gave
two to Mr. Wright in September 1858.

In June 1855 Dr. Woodward placed specimens of H. candidis-
sima and H. aperta in a glass box, to test thei tenacity of life ;
he writes of their being still alive in April 1859.

Mr. R. E. C. Stearns records * a case of Buliminus pallidior and
HT. Veatchwi trom Cerros I. living without food from 1859 to March
1865.

H. Aucapitaine mentions * a case of H. lactea found in calcin-
ated ground in a part of the Sahara heated to 122° F., where
no rain was said to have fallen for five years. The specimen
revived after being enclosed in a bottle for three and a half years.

In August 1863, Mr. W. J. Sterland® put specimens of #.
nemoralis in a box and afterwards placed the box in his cabinet ;
in November 1866 one specimen was discovered to be alive.

Gaskoin relates ® a case in which specimens of Hf. lactew were

1 Ann. Mag. Nat. Hist. (2) vi. p. 489. 2 Ibid. (8) iii. p. 448.
SeAnen. Nat. xi. (874) ps LOOK Proc. (Cali. Aco ii pa 329:
4 Gaz. Med. Alger. 1865, 5th Jan. p. 9. ° Science Gossip, 1867, p. 40.

6 Ann. Mag. Nat. Hist. (2) ix. p. 498.

Ul AGE OF SNAILS 39

purchased from a dealer in whose drawer they had been for two
years. This dealer had them from a merchant at Mogador, who
had kept them for more than that time under similar conditions.
One of these shells on being immersed in water revived, and in
April 1849 was placed quite alone under a bell jar with earth
and food. In the end of the following October about thirty young
HT, lactea were found crawling on the glass.

Mr. R. D. Darbishire bought! some HZ. aperta in the market
at Nice on 18th February 1885. Two specimens of these, placed
with wool in a paper box, were alive in December 1888. This
is a very remarkable case, H. aperta not being, like H. desertorum,
H. lactea, H. Veatchii and Bul. pallidior, a desert snail, and there-
fore not accustomed to fasting at all.

Age of Snails.—It would appear, from the existing evidence,
which is not too plentiful, that five years is about the average
age of the common garden snail. Mr. Gain has published ? some
interesting observations on the life of a specimen from the cradle
to the grave, which may be exhibited in a tabular form.

Aug. 1882. Eggs hatched; one attained diameter of 2 in.

before winter; fed on coltsfoot and cabbage.
dth Oct. 1885. Shell L in. in diameter, no lp formed.

July 1884. Shell finished; diameter 12 in., including

perfect lip.

rd May 1885. Left winter quarters; companion introduced,

with which it was seen in company on
oth August.

9th Aug. ,, Laid eggs in soil, which were hatched on

10th September, and feeding on 17th
September; in May 1886 the largest of
these was +} in. diameter.

15th Oct. 1887. Old snail died, aged 5 years 2 months.

According to Clessin, the duration of life in Vitrina is one
year, Cyclas 2 years; Hyalinia, Succinea, Limnaea, Planorbis, and
Ancylus are full grown in 2 to 5 years, Helix and Paludina in 2
to 4,and Anodonta in 12 to 14. Hazay finds ® that the duration
of lite in Hyalinia is 2 years, in Helix pomatia 6 to 8, in Helix
candicans 2 to 3, in Paludina 8 to 10,in Limnaea and Planorbis
3 to 4.

1 Journ. of Conch. vi. p. 101. * Naturalist, 1889, p. 55.
® Malak. Blatt. (2) iv. pp. 48 and 221.

40 GROWTH OF THE SHELL CHAP.

Growth of the Shell—Mr. EK. J. Lowe, many years ago, con-
ducted? some interesting experiments on the growth of snails.
The facts arrived at were—

(1) The shells of Helicidae increase but little for a consider-
able period, never arriving at maturity before the animal has once
become dormant.

(2) Shells do not grow whilst the animal itself remains
dormant.

(3) The growth of shells is very rapid when it does take
place.

(4) Most species bury themselves in the ground to increase
the dimensions of their shells.

Six recently hatched H. pomatia were placed in a box and
regularly fed on lettuce and cabbage leaves from August until
December, when they buried themselves in the soil for winter ;
at this period they had gradually increased in dimensions to the
size of H. hispida. On the 1st April following, the box was
placed in the garden, and on the 3rd the Helices reappeared on
the surface, being no larger in size than they were in December.
Although regularly fed up to 20th June, they were not per-
ceptibly larger, but on that day five of them disappeared, having
buried themselves, with the mouth of the shell downwards, in the
soil. After ten days they reappeared, having in that short time
grown so rapidly as to be equal in size to H. pisana. On the
15th July they again buried themselves, and reappeared on 1st
August, having again increased in size. For three months from
this date they did not become perceptibly larger; on 2nd
November food was withheld for the winter and they became
dormant.

A similar experiment, with similar results, was carried on
with a number of H. aspersa, hatched on 20th June. During
the summer they grew but little, buried themselves on 10th
October with the head wpwards, and rose to the surface again on
oth April, not having grown during the winter. In May they
buried themselves with the head downwards, and appeared again
in a week double the size; this went on at about fortnightly
intervals until 18th July, when they were almost fully
grown.

Hehz nemoralis, H. virgata, H. caperata, and H. hispida bury

1 Phil. Trans. 1854 (1856), p. 8.

-

Il SELF-BURIAL OF SNAILS 41

themselves to grow; H. rotundata burrows into decayed wood ;
Hyalinia radiatula appears to remain on decaying blades of
erass ; Pupa umbilicata, Clausilia rugosa, and Buliminus obscurus
bury their heads only.

The observations of Mr. W. E. Collinge’ do not at all agree
with those of Mr. Lowe, with regard to the mode in which land
Mollusca enlarge their shells. He bred and reared most of the
commoner forms of Heliz and also Clausilia rugosa, but never
saw them bury any part of their shell when enlarging it. While
admitting that they may increase their shells when in holes or
burrows of earthworms, he thinks that the process of burying
would seriously interfere with the action of the mantle during
deposition, and in many cases damage the membranaceous film
before the calcareous portion was deposited. Mr. Collinge
has found the following species under the surface in winter:
Arion ater (3-4 in.), Agriolimax agrestis (6—8 in.), Hyalinia
cellaria and H. alliaria (6—8 in.), Hyalinia glabra (5 in.), Helia
aspersa (5—6 in.), H. rufescens (4—6 in.), H. rotundata (4—5 in.),
Hf, hispida (7 in.), Buliminus obscurus (4—6 in.), B. montanus?
(24 in.), and the following in summer, Hyalinia cellaria and
alliaria (6-8 in.), Helix rotundata (4-5 in.), Balea perversa
(6—8 in.), Cyclostoma elegans (3-4 in.). The same author has
found the following species of fresh-water mollusca living in
hard dry mud: Sphaerium corneum (3-14 in.), S. rivicola (5-6
in.), S. lacustre (10-14 in.), all the British species of Pisidiwm
(4-12 in.), Limnaea truncatula (18 in., a single specimen). All
our species of Unio, Anodonta, Bithynia, and Paludina bury
themselves habitually in fine or thick wet mud, to a depth of
from 4 to 14 inches.

This burying propensity on the part of Mollusca has been
known to play its part in detecting fraud. When my friend
Mr. E. L. Layard was administering justice in Ceylon, a native
landowner on a small scale complained to him of the conduct of
his neighbour, who had, during his absence from home, diverted
a small watercourse, which ran between their holdings, in such
a way as to filch a certain portion of the land. The offender
had filled up and obliterated the ancient course of the stream,
and protested that it had never run but in its present. bed.

1 Naturalist, 1891, p. 75 f. ; Conchologist, ii. 1892, p. 29.
2 Taylor, Journ. of Conch. 1888, p: 299:

42 DEPOSITION OF EGGS CHAP.

Mr. Layard promptly had a trench sunk across what was said to
be the old course, and the discovery of numerous living Ampul-
laria, buried in the mud, confirmed the story of one of the
litigants and confounded the other.’

Depositing and Hatching of Eggs: Self-fertilisation.—
There appears to be no doubt that Helices, when once im-
pregnated, can lay successive batches of eges, and possibly can
continue laying for several years, without a further act of union.
A specimen of Helia aspersa was noticed in company with
another on 5th August; on 9th August it laid eggs in the soil,
and early in the following summer it laid a second batch of eggs,
although its companion had been removed directly after its first
introduction. An Arion received from a distance laid 30 eggs
on 5th September, and 70 more on the 23rd of the same month,
although quite isolated during the whole time.” By far the
most remarkable case of the kind is related by Gaskoin.? <A
specimen of Helix lactea was kept in a drawer for about
two years, and then in another drawer for about two years
more. It was then taken out, and placed in water, when it
revived, and was placed alone under a bell jar with earth
and food. Six months after, about 30 youne H. lactea were
found crawling on the glass, the act of oviposition not having
been observed.

The observations of Mr. F. W. Wotton,* with regard to the
fertilisation and egg-laying of Arion ater, are of extreme
interest and value. A pair of this species, kept in captivity,
united on 10th September 1889, the act lasting about 25
minutes. From that date until the eggs were laid, the animals
looked sickly, dull of colour, with a somewhat dry skin. Eggs
were deposited in batches, one, which we will call A, beginning
three days before £ On 10th October A laid 80 eggs; on the
16th, 110; on the 25th, 77; on 8th November, 82; and on
17th November, 47; making a total of 396. Specimen B, which
began on 13th October, three days after A, made up for the delay
by laying 246 eggs in 40 hours; on 26th October it laid 9, on
10th November, 121; and on 30th November, 101; a total of 477.

1 See Tennent’s Ceylon, i. p. 221, ed. 5.

2 W. A. Gain, Vaturalist, 1889, p. 55; Brockmeier, Nachr. Deutsch. Maluk.
Gesell. xx. p. 118.

> Ann. Mag. Nat. Hist. (2) ix. p. 498. 4 Journ. Conch. vii. 1893, p. 158 f.

1 HATCHING OF EGGS 43

These eggs weighed 624 to the ounce, and, in excluding the
batch of 246, B parted with ~ of its own weight in 40 hours,
while the whole number laid were rather over } of its own
weight !

While depositing the eggs, the slug remained throughout in
the same position on the surface of the ground, with the head
drawn up underneath the mantle, which was lifted just above
the reproductive orifice. When taken into the hand, it went on
laying eggs without interruption or agitation of any kind. After
it had finished laying it ate half a raw potato and then took a
bath, remaining submerged for more than an hour. Bathing is
a favourite pastime at all periods. Specimens, says Mr. Wotton,
have survived a compulsory bath, with total submersion, of
nearly three days’ duration.

Mr. Wotton’s account of the hatching of the eggs is equally
interesting. It is noticeable that the eggs of one batch do not
hatch by any means simultaneously; several days frequently
intervene. The average period is about 60 days, a damp and
warm situation bringing out the young in 40 days, while cold
and dryness extended the time to 74 days, extremes of any
kind proving fatal. Of the batch of eggs laid by B on
30th November, the tirst 2 were hatched on the following
16th January, and 2 more on the 17th; others, from 10 to 20,
followed suit on the succeeding 5 days, until 82 in all were
hatched, the remaining 19 being unproductive.!

sy placing the egg on a looking-glass the act of exclusion
can be pertectly observed. For several days the inmate can be
seen in motion, until at last a small crack appears in the surface
of the shell: this gradually enlarges, until the baby slug is able
to crawl out, although it not unfrequently packs into the shell
again, as if unwilling to risk itself in the world. When it once
begins to crawl freely, it buries itself in the ground for 4 or 5
days without food, after which time it emerges, nearly double
its original size. At exclusion, the average length is 9 mm.,
increasing to 56 mm. after the end of 5 months. Full growth
is attained about the middle of the second year, and nearly all
die at the end of this year or the beginning of the next. Death
from exhaustion frequently occurs after parturition. Death

* I succeeded in hatching out eggs of Helix aspersa, during the very warm
summer of 1893, in 17 days.

44 REPRODUCTION OF LOST PARTS CHAP.

from suffocation is sometimes the result of the formation of
small blisters on the margin of the respiratory aperture. The
attacks of an internal parasite cause death in a singular way.
The upper tentacles swell at the base in such a way as to
prevent their extrusion; digestive troubles follow, with rigidity
and loss of moisture, and death ensues in 2 or 5 days.

Mr. Wotton isolated newly-hatched specimens, with the view
of experimenting on their power of self-fertilisation, if the
opportunity of fertilising and being fertilised by others was
denied them. One of these, after remaining in absolute solitude
for 104 months, began to lay, scantily at first (11th January, 2;
25th January, 2; 11th February, 2), but more abundantly after-
wards (8rd April, 60; 15th and 16th, 70; 29th, 53, etc.), the
egos being hatched out in 42-48 days. The precautions taken
seem to have been absolutely satisfactory, and the fact of the
power of self-fertilisation appears established as far as Arion ater
is concerned.

Braun took young individuals of Limnaea auricularia on the
day they were hatched out, and placed them singly in separate
vessels with differing amounts of water. This was on 15th June,
1887. In August 1888 specimen A had only produced a little
spawn, out of which three young were hatched; specimen B
had produced four pieces of spawn of different sizes, all of which
were hatched; specimen C, which happened to be living with
three Planorbis, produced five pieces of spawn distinctly Lim-
naeidan, but nothing is recorded of their hatching. Self-
impregnation, therefore, with a fruitful result, appears estab-
lished for this species of Limnaea.'

Reproduction of Lost Parts—When deprived of their
tentacles, eyes, or portions of the foot, Mollusca do not seem to
‘suffer severely, and generally reproduce the lost parts in a short
time. If, however, one of the ganglia is injured, they perish.
Certain of the Mollusca possess the curious property of being
able to amputate certain parts at will When Prophysaon, a
species of Californian slug, is annoyed by being handled, an
indented line appears at a point about two-thirds of the length
from the head, the line deepens, and eventually the tail is
shaken completely off. Sometimes the Prophysaon only threatens
this spontaneous dismemberment; this line appears (always

1 Nachr. Deutsch. Malak. Gesell. xx. p. 146.

II STRENGTH OF SNAILS 45

exactly in the same place), but it thinks better of it, and the
indentation proceeds no further.’ According to Gundlach,
Helix imperator and H. crenilabris, two large species from Cuba,
possess the same property, which is said to be also character-
istic of the subgenus Stenopus (W. Indies). Amongst marine
species, Harpa ventricosa and Solen siliqua have been observed
to act in a similar way, Harpa apparently cutting off the end of
the foot by pressure of the shell. Karl Semper, in commenting
on the same property in species of Helicarion from the Philp-
pines (which whisk their tail up and down with almost convul-
sive rapidity, until it drops off), considers’ it greatly to the
advantage of the mollusc, since any predacious bird which
attempted to seize it, but only secured a fragment of tail, would
probably be discouraged from a second attack, especially as the
FHelicarion would meanwhile have had time to conceal itself
among the foliage.

Strength and Muscular Force.—The muscular strength of
snails is surprisingly great. Sandford relates * an experiment on
a Helix aspersa, weighing + oz. He found it could drag verti-
cally a weight of 24 oz., or nine times its own weight. Another
snail, weighing 4 oz., was able to drag in a horizontal direction
along a smooth table twelve reels of cotton, a pair of scissors, a
screwdriver, a key, and a knife, weighing in all no less than 17 oz.,
or more than fifty times its own weight. This latter experiment
was much the same as asking a man of 12 stone to pull a load
of over 3:3 tons.

If a snail be placed on a piece of glass and made to crawl, it
will be seen that a series of waves appear to pursue one another
along the under surface of the foot, travelling from back to
front in the direction in which the animal is moving. Simroth
has shown that the sole of the foot is covered with a dense net-
work of ‘muscular fibres, those which run longitudinally being
chiefly instrumental in producing the undulatory motion. By
means of these muscles the sole is first elongated in front, and
then shortened behind to an equal extent. Thus a snail slides,
not on the ground, but on its own mucus, which it deposits
mechanically, and which serves the purpose of lubricating the

1 Raymond, Nautilus, iv. p. 6.
2 Quoted by Oehlert, Rév. Sc. xxxviii. p. 701.
3 Animal Life, Intern. Scientif. Serv, ed. 1, p. 395. 4 Zoologist, 1886, p. 491.

46 SUDDEN APPEARANCE AND DISAPPEARANCE CHAP.

ground on which it travels. It has been calculated that an
average sized snail of moderate pace progresses at the rate of
about a mile in 16 days 14 hours!

Sudden Appearance of Mollusca.—lIt is very remarkable
to notice how suddenly Pulmonata seem to appear in certain
districts where they have not been noticed before. This sudden
appearance 1s more common in the case of fresh-water than of land
Mollusca, and there can be little doubt that, wherever a new pond
happens to be formed, unless there is something in its situation
or nature which is absolutely hostile to molluscan hfe, Mollusca
are certain to be found in it sooner or later. “Some 23 years
ago,” writes Mr. W. Nelson,” “I was in the habit of collecting
shells in a small pond near to the Black Hills, Leeds. At that
time the only molluscan forms found there were a dwarf form of
Sphaerium lacustre, Pisidium pusillum, Planorbis nautileus, and
Iimnaea peregra. About 10 years ago I resumed my visits to
the locality, and found, in addition to the species already
enumerated, Planorbis corneus. These were the only species found
there until this spring [1885], when, during one of my frequent
visits, I was surprised to find Physa fontinalis and Planorbis
vortex were added to the growing list of species. Later on PI.
carinatus, Limnaea stagnalis, and Ancylus lacustris turned up;
and during June, P/. contortus was found in this small but prolific
pond.” Limnaea glutinosa is prominent for these remarkable
appearances and disappearances. In 1822 this species suddenly
appeared in some small gravel pits at Bottisham, Cambs., in
such numbers that they might have been scooped out by hand-
fuls. After that year they did not appear numerous, and after
three or four seasons they gradually disappeared.” Physa
(Aplecta) hypnorum is noted in a similar way. In February 1852,
for instance, after a wet month, the water stood in small puddles
about 3 feet by 2 in a particular part of Bottisham Park
which was sometimes a little swampy, though usually quite dry.
One of these puddles was found to contain immense numbers of
the Aplecta, which up to that time had not been noted as occur-
ring in Cambridgeshire at all.* In a few days the species entirely
disappeared and was never again noticed in the locality.®
1 Thomas, quoted by Jeffreys, Brit. Conch. i. p. 30. * Journ. of Conch. iv. p. 117.

3 Rey. L. Jenyns, Observations in Nat. Hist., p. 318. 4 Id. ib. p. 319.
* Further detailed examples will be found in Kew, The Dispersal of Shells, pp. 5-26.

IL SHOWERS OF SHELLS 47

Writing to the Zoological Society of London from New
Caledonia, Mr. E. L. Layard remarks:* “The West Indian
species Stenogyra octona has suddenly turned up here in
thousands; how introduced, none can tell. They are on a
coffee estate at Kanala on the east coast. I have made in-
quiries, and cannot find that the planter ever had seed coffee
from the West Indies. All he planted came from Bombay, and
it would be interesting to find out whether the species has
appeared there also.”

Sometimes a very small event is sufficient to disturb the
natural equilibrium of a locality, and to become the cause either
of the introduction or of the destruction of a species. In 1883
a colony of Helia sericea occupied a portion of a hedge bottom
twenty yards long near Newark. It scarcely occurred outside
this limit, but within it was very plentiful, living in company
with H. nemoralis, H. hortensis, H. hispida, H. rotundata, Hyalinia
cellaria and Hy. nitidula, and Cochlicopa lubrica. In 1888 the
hedge was well trimmed, but the bottom was not touched, and
the next year a long and careful search was required to find
even six specimens of the sericea.”

Showers of Shells.— Helix virgata, H. caperata, and Cochli-
cella acuta sometimes occur on downs near our sea-coasts in such
extraordinary profusion, that their sudden appearance out of
their hiding-places at the roots of the herbage after a shower of
rain has led to the belief, amongst credulous people, that they
have actually descended with the rain. There seems, however, no
reason to doubt that Mollusca may be caught up by whirlwinds
into the air and subsequently deposited at some considerable
distance from their original habitat, in the same way as frogs
and fishes. A very recent instance of such a phenomenon
occurred * at Paderborn, in Westphalia, where, on 9th August
1892, a yellowish cloud suddenly attracted attention from its
colour and the rapidity of its motion. In a few moments it
burst, with thunder and a torrential rain, and immediately after-
wards the pavements were found to be covered with numbers of
Anodonta anatina, all of which had the shell broken by the
violence of the fall. It was clearly established that the shells

1 P. Z. S. 1888, p. 358. * W. A. Gain, Naturalist, 1889, p. 58.
* Das Wetter, Dec. 1892. Another case is recorded in Amer. Nat. iii. p.
556.

48 SINGULAR HABITAT—-UNDERGROUND SNAILS CHAP.

could not have been washed into the streets from any adjacent
river or pond, and their true origin was probably indicated
when it was found that the funnel-shaped cloud which burst
over the town had passed across the one piece of water near
Paderborn, which was known to contain the Anodonta in
abundance.

Cases of Singular Habitat.—Mollusca sometimes accustom
themselves to living in very strange localities, besides the
extremes of heat and cold mentioned above (pp. 23-24). In the
year 1852, when some large waterpipes in the City Road, near
St. Luke’s Hospital, were being taken up for repairs, they were
found to be inhabited in considerable numbers by WNeritina
fluviatilis and a species of Limnaea.' Dreissensia polymorpha
has been found in a similar situation in Oxford Street, and also
in Hamburg, and has even been known to block the pipes and
cisterns of private houses. In an engine cistern at Burnley,
60 feet above the canal from which the water was pumped
into the cistern, were found the following species: Sphaervum
corneum, S. lacustre; Valvata piscinalis, Bithynia tentaculata ;
Limnaea peregra, very like Succinea in form and texture;
Planorbis albus, P. corneus, P. nitidus, P. glaber, and thousands
of P. dilatatus, much larger than the forms in the canal below,
a fact probably due to the equable temperature of the water in
the cistern all the year round. In certain parts of southern
Algeria the fresh-water genera Melania and Melanopsis inhabit
abundantly waters so surcharged with salt that the marine
Cardium edule has actually become extinct from excess of brine.
The common Mytilus edulis is sometimes found within the
branchial chamber and attached to the abdomen of crabs
(Carcinus maenas), which are obliged to carry about a burden
of which they are powerless to rid themselves (see p. 78). <A
variety of the common Limnaca peregra lives in the hot water
of some of the geysers of Iceland, and has accordingly been
named geisericola.

Underground Snails.— Not only do many of the land Mollusca
aestivate, or hibernate, as the case may be, beneath the surface of
the soil, but a certain number of species live permanently under-
ground, like the mole, and scarcely ever appear in the light of
day. Our own little Caecilianella acicula lives habitually from

1 Zooloyist, x. p. 3430. 2 Science Gossip, 1888, p. 281.

ul UNDERGROUND AND ROCK-BORING SNAILS 49

1 to 3 feet below ground, appearing to prefer the vicinity of
graveyards. Testacella, the carnivorous slug, scarcely ever appears
on the surface during the day, except when driven by excessive
rain, and even then it lurks awhile under some protecting cover
of leafage. There is a curious little Helix (tristis Pfr.), peculiar
to Corsica, which is of distinctly subterranean habits. It lives
in drifted sand above high-water mark, always at the roots of
Genista Saltzmanni, at a depth which varies with the tempera-
ture and dryness of the air. In hot and very dry weather it
buries itself nearly 2 feet below the surface, only coming up
during rain, and burying itself again immediately the rain is
over. Like a Solen, it often has a hole above its burrow, by
which it communicates with the air above, so as to avoid being
stifled in the sand. The animal, in spite of its dry habitat, is
singularly soft and succulent, and exudes a very glutinous
mucus. It probably descends in its burrow until it arrives at
the humid stratum, the persistence of which is due to the capil-
larity of the sand." T am assured by Mr. E. L. Layard that
precisely similar underground habits are characteristic of Coeli-
axis Layardi, which lives exclusively in sand at the roots of
scrub and coarse grass at East London.

Rock-boring Snails.—Cases have sometimes been recorded,
from which it would appear that certain species of snails possess
the power of excavating holes in rocks to serve as hiding-places.
At Les Bois des Roches, ten miles from Boulogne, occur a
number of solid calcareous rocks scattered about in the wood.
The sides of the rocks which face N.E. and E. are covered
with multitudes of funnel-shaped holes, 14 inch in diameter at
the opening and contracting suddenly within to 4 inch. Some-
times the holes are 6 inches deep, and terminate, after considerable
windings, in a cup-shaped cavity. Helix hortensis inhabits these
holes, and has been observed to excavate them at the rate of
x inch each hibernation, choosing always the side of the rock
which is sheltered from the prevailing rains. It does not form
an epiphragm, but protrudes part of its body against the rock.
That the snails secrete an acid which acts as a solvent seems
probable from the fact that red litmus paper, on being applied to
the place where the foot has been, becomes stained with violet.

1 Lecoq, Journ. de Conch. ii. p. 146.
* Bouchard-Chantereaux, Ann. Sei. Nut. Zool. (4) xvi. (1861) p. 197.
VOL. III E

50 PRODUCTION OF MUSICAL SOUNDS CHAP.

Helix aspersa is said to excavate holes 10 to 12 cm. deep
at Constantine, and H. Mazzullii is recorded as_ perforating
limestone at Palermo.?

Snails as Barometers.—An American writer of more than
thirty years ago® gave his experience of Helices as weather-
prophets. According to him, H. alternata is never seen abroad
except shortly before rain; it then climbs on the bark of trees,
and stations itself on leaves. Helix clausa, H. ligera, H. penn-
sylvanica, and H. elevata climb trees two days before rain, if it
is to be abundant and continuous. Succinea does the same, and
its body is yellow before rain and bluish after it. Several of the
Helices assume a sombre colour after rain, when their bodies
are exceedingly humid; after the humidity has passed off they
resume a clearer and lighter tint.

Production of Musical and other Sounds.—Certain molluscs
are said to be capable of producing musical sounds. Sir J. E.
Tennent describes his visit to a brackish-water lake at Batticaloa,
in Ceylon, where the fishermen give the name of the ‘crying
shell’ to the animal supposed to produce the sounds. “The
sounds,” he says,t “came up from the water like the gentle
thrills of a musical chord, or the faint vibrations of a wine-glass
when its rim is rubbed by a moistened finger. It was not one
sustained note, but a multitude of tiny sounds, each clear and
distinct in itself; the sweetest treble mingling with the lowest
bass. On applying the ear to the woodwork of the boat, the
vibration was greatly increased in volume. The sounds varied
considerably at different points as we moved across the lake,
and occasionally we rowed out of hearing of them altogether.”
According to the fishermen, the shells were Pyrazus palustris
and Littorina laevis. It appears uncertain whether the sounds
are really due to Mollusca. Fishermen in other parts of India
assert that the sounds are made by fish, and, lke those in
Ceylon, produce the fish which they say ‘sings.’ The same, or a
similar sound, has also been noticed to issue from the water in
certain parts of Chili, and on the northern shores of the Gulf of

1 Forel, Ann. Sci. Nat. (3) xx. p. 576; Bretonniere, Comptes Rendus, cvii.
p. 566.

? Brit. Mus. Collection.

3 Thomas, quoted by Récluz in Journ. de Conch. vii. 1858, p. 178.

4 Nat. Hist. of Ceylon, p. 882. See also T. L. Taylor, Rep. Brit. Ass. for 1848,
p. 82.

II HABITS OF CARNIVOROUS SNAILS AND SLUGS Sl

Mexico. Dendronotus arborescens, when confined in a glass jar
of sea water, has been noticed! to emit a sound like the clink of
a steel wire. According to Lieut.-Col. Portlock,? F.R.S., Helix
aperta, ® very common species in South Europe, has the propert y
of emitting sounds when irritated. When at Corfu, he noticed
that if the animal is irritated by a touch with a piece of straw
or other light material, it emits a noise, as if grumbling at
being disturbed. He kept a Specimen in his house for a con-
siderable time, which would make this noise whenever it was
touched.

The Rev. H. G. Barnacle describes the musica] properties of
Achatinella in the following terms :3 “When up the mountains
of Oahu I heard the grandest but wildest music, as from
hundreds of Aeolian harps, wafted to me on the breezes, and
my companion (a native) told me it came from, as he called
them, the singing shells. It was sublime. TI could not believe
it, but a tree close at hand proved it. On it were many of the
Achatinella, the animals drawing after them their shells, which
grated against the wood and so caused a sound; the multitude
of sounds produced the fanciful music. On this one tree I took
70 shells of all varieties.” :

Habits of the Agnatha.—Not much is known of the habits
and mode of life of the Agnatha, or carnivorous Land Mollusca.
In this country we have only two, or at most three, of this
group, belonging to the genus 7vstacella, and, in all probability,
not indigenous to our shores. There seems little doubt, when
all the circumstances of their discovery are taken into account,
that both Testacella haliotidea and 7 Maugei have been
imported, perhaps from Spain or Portugal in the first instance,
along with roots imbedded in foreign earth, for their earliest
appearances can almost invariably be traced back to the neigh-
bourhood of large nursery grounds, or else to gardens supplied
directly from such establishments.

The underground life of Zestacella makes observation of its
habits difficult. It is believed to feed exclusively on earth-
worms, which it pursues in their burrows. Continued wet
weather drives it to the surface, for though loving damp soil it

Dr. R. E. Grant, Edinb. Phil. Journ. xiv. p- 188.
* Rep. Brit. Ass. for 1848, p. 80. The statement is confirmed by Rossmissler,
* Journ. of Conch. iv. p. 118.

52 HABITS OF CARNIVOROUS SNAILS AND SLUGS CHAP.

is decidedly averse to too much moisture, and under such cir-
cumstances it has even been noticed’ in considerable numbers
crawling over a low wall. In the spring and autumn months,
according to Lacaze-Duthiers, it comes to the surface at night,
hiding itself under stones and débris during the day. Earth-
worms are, at these periods, nearer the surface, and the Vestacella
has been seen creeping down into their burrows. The author
has taken 7. Maugei abundantly under clumps of the common
white pink in very wet weather, lying in a sort of open nest in
the moist earth. On the other hand, when the earth is baked
dry by continued drought, they either bury themselves deeper,
sometimes at a depth of 3 feet, in the eround, or else become
encysted in a capsule of hardened mucus to prevent evaporation
from the skin. When first taken from the earth and placed in
a box, the Testacella invariably resents its capture by spitting up
the contents of its stomach in the shape of long fragments of
half-digested worms.

It appears not to bite the worm up betore swallowing it, but
contrives, in the most remarkable manner, to take down whole

Fic. 20.—Testacella haliotidea Drap., protruding its pharynx (ph) and radula (7) ;
oe, oesophagus ; p.o, pulmonary orifice ; sh, shell; ¢, tentacles (after Lacaze-
Duthiers).

worms apparently much too large for its stomach. Mr. Butterell
relates ® that, after teasing a specimen of 7. Maugei, and making
it emit a quantity of frothy mucus from the respiratory aperture,
he procured a worm of about three inches long, and rubbed the
worm gently across the head of the Yestacella. The tongue was
rapidly extended, and the victim seized. The odontophore was
then withdrawn, carrying with it the struggling worm, which
made every effort to escape, but in vain; in about five minutes all
had disappeared except the head, which was rejected. This
protrusion of the tongue (radula) and indeed of the whole

1 Zoologist, 1887, p. 29. 2 Arch. Zool. Exp. Gén. (2) Vv. p. 459 f.
3 Journ. of Conch. iii. p. 277 ; compare W. M. Webb, Zoologist, 1893, p. 281.

II HABITS OF CARNIVOROUS SNAILS AND SLUGS 53

pharynx, is a very remarkable feature in the habits of the
animal. It appears, as it were, to harpoon its prey by a rapid
thrust, and when the victim is once pierced by a few of the
powerful sickle-shaped teeth (compare chap. viii.) 1t is slowly but
surely drawn into the oesophagus (Fig. 20).

Most gardeners are entirely ignorant of the character of
Testacella, and confuse it, if they happen to notice it at all, with
the common enemies of their tender nurslings. Cases have been
known, however, when an intelligent gardener has kept specimens
on purpose to kill worms in ferneries or conservatories. In some
districts these slugs are very numerous ; Lacaze-Duthiers once dug
182 specimens from a good well-manured piece of ground whose
surface measured only ten square yards.

Towards the end of September or beginning of October the
period of hibernation begins. I infer this from the behaviour of
specimens kept in captivity, which, for about a fortnight before
this time, gorged themselves inordinately on as many worms as I
chose to put into their box, and then suddenly refused food, buried
themselves deeply in the earth, and appeared no more during the
winter. The eggs are apparently much less numerous than is the
case with imax or Helix, and very large, measuring about 4 inch
in diameter. They are enveloped in a remarkably tough and
elastic membrane, and, if dropped upon any hard surface, rebound
several inches, just like an india-rubber ball.

The animal creeps rather rapidly, and has the power of
elongating its body to a remarkable extent. When placed on the
surface of the ground, in the full light of day, it soon betrays
uneasiness, and endeavours to creep into concealment. Its method
of burying itself is very interesting to watch. It first elongates
its neck and inserts its head into the soil; gradually the body
begins to follow, while the tail tilts upwards into the air. No
surface motion of the skin, no writhing or wriggling motion of
any kind occurs; the creature simply works its way down in a
stealthy and mysterious way, until at last it is lost to view.

The great Glandina, which attain their maximum develop-
ment in Mexico and the southern United States, are a very
noticeable family in this group. According to Mr. Binney,'
Glandina truncata Gmel., one of the commonest species of the .
genus, 1s somewhat aquatic in its habits. It is found in the sea

1 Bull. Mus. Comp. Zool. Harv. iv. p. 85.

54 HABITS OF CARNIVOROUS SNAILS AND SLUGS CHAP.

islands of Georgia and around the keys and everglades of Florida,
where it attains a maximum length of 4 inches, while in less
humid situations it scarcely measures more than 1 inch. — It
occurs most abundantly in the centre of clumps and tussocks of
coarse grass in marshes close to the sea-coast. By the action of
the sharp, sickle-shaped teeth of its radula the soft parts of its
prey (which consists chiefly of living Helices) are rapidly rasped
away ; sometimes they are swallowed whole. It has been known
to attack Limaxz when confined in the same box, rasping off large
pieces of the integument. In one case an individual was noticed
to devour one of its own species, thrusting its long neck into the
interior of the shell, and removing all the viscera.

Fic. 21.—Glandinu sowerbyana Pfr. (Strebel).

The Glandinae of southern Europe, although scarcely rivalling
those of Central America in size or beauty, possess similar
carnivorous propensities. Glandina Poireti has been observed,!
on Veglia Island, attacking a living Cyclostoma elegans. By its
powerful teeth it filed through two or three whorls of the shell
of its victim, and then proceeded to devour it, exactly in the
same manner as a Natica or Buccinum perforates the shell of a
Tellina or Mactra in order to get at its contents.

Few observations appear to have been made on the habits
or food of Streptaxis, Rhytida, Ennea, Daudebardia, Paryphanta,
and other carnivorous Mollusca. A specimen of Hnnea sulcata,
enclosed in the same box as a Madagascar Helia (sepulchralis
Fér.) many times its own size, completely emptied the shell of
its inhabitant.” Mr. E. L. Layard informs me that certain Cape
Rhytida, eg. R. capsula Bens., R. dumeticola Bens., and R. verni-
cosa Kr., eat Cyclostoma affine, Helix capensis, H. cotyledonis, etc.
To Mr. Layard Tam also indebted for the—perhaps apocryphal
tradition that the best time to capture the great <Aerope caffra

1 Erjavec, Nachr. Deutsch. Malak, Gescil. 1885, p. 88.
* Crosse, Journ. de Conch. (3) xiv. (1874) p. 228.

II HABITS OF CARNIVOROUS SNAILS AND SLUGS 55

Fer. in numbers was after an engagement between the Kaffirs
and Zulus, when they might be observed streaming from all points
of the compass towards the field of slaughter. The Cuban
Oleacina are known to secrete a very bitter fluid which they
emit; this perhaps produces a poisoning or benumbing effect
upon their victims when seized. They devour operculates, e.g.
FHelicina regina and sagraiana.'

1 C. Wright, Zoologist, 1869, p. 1700.

CHAPTER: Wt

ENEMIES OF THE MOLLUSCA—-MEANS OF DEFENCE—MIMICRY AND
PROTECTIVE COLORATION—-PARASITIC MOLLUSCA——COMMEN-
SALISM—VARIATION.

Enemies of the Mollusca

THE juicy flesh and defenceless condition of many of the Mollusca
make them the favourite food and often the easy prey of a host of
enemies besidesman. Gulls are especially partial to bivalves, and
may be noticed, in our large sandy bays at the recess of the tide,
busily devouring Zellina, Mactra, Mya, Syndosmya, and Solen. On
the Irish coast near Drogheda a herring gull has been observed ?
to take a large mussel, fly up with it in the air over some shingly
ground and let it fall. On alighting and finding that the shell
was unbroken it again took it up and repeated the process a
number of times, flying higher and higher with it until the shell
was broken. Hooded crows, after many unavailing attempts to
break open mussels with their beak, have been seen to behave
in a similar way.? Crows, vultures, and aquatic birds carry
thousands of mussels, ete., up to the top of the mountains above
Cape Town, where their empty shells lie in enormous heaps
about the cliffs.®

The common limpet is the favourite food of the oyster-
catcher, whose strong bill, with its flattened end, is admirably
calculated to dislodge the limpet from its seat on the rock.
When the limpet is young, the bird swallows shell and all, and
it has been calculated that a single flock of oyster-catchers,
frequenting a small Scotch loch, must consume hundreds of

1 W. V. Legge, Zoologist, 1866, p. 190. * Blackwall, Researches, p. 139
3 Barrow, Travels in South Africa, i. p. 67.

CHAP. III BIRDS, RATS, AND LIMPETS SH

thousands of limpets in the course of a single year. Rats are
exceedingly fond of limpets, whose shells are frequently found in
heaps at the mouth of rat holes, especially where a cliff shelves
gradually towards a rocky shore. A rat jerks the limpet off with
a sudden movement of his powerful jaw, and, judging from the
size of the empty shells about the holes, has no difficulty in
dislodging the largest specimens. ‘I once landed, relates a
shepherd to Mr. W. Anderson Smith ‘on the I. of Dun-
staffnage to cut grass, and it was so full of rats that I was afraid
to go on; and the grass was so full of limpets that I could
scarcely use the scythe, and had to keep sharpening it all the
time.’ Sometimes, however, the limpet gets the better both of
bird and beast. The same writer mentions the case of a rat
being caught by the lip by a limpet shell, which it was trying
to dislodge. A workman once observed? a bird on Plymouth
breakwater fluttering in rather an extraordinary manner, and, on
going to the spot, found that a ring dotterel had somehow got
its toe under a limpet, which, in closing instantly to the rock,
held it fast. Similar cases of the capture of ducks by powerful
bivalves are not uncommon, and it is said that on some parts of
the American coasts, where clams abound, it is impossible to keep
ducks at all, for they are sure to be caught by the molluscs and
drowned by the rising tide.

The Weekly Bulletin of San Francisco, 17th May 1893, con-
tains an account of the trapping of a coyote, or prairie wolf,
at Punta Banda, San Diego Co., by a Haliotis Cracherodii. The
coyote had evidently been hunting for a fish breakfast, and
finding the Haliotis partially clinging to the rock, had inserted
his muzzle underneath to detach it, when the Haliotis instantly
closed down upon him and kept him fast prisoner.

Rats devour the ponderous Uniones of North America. When
Unio moves, the foot projects half an inch or more beyond the
valves. If, when in this condition, the valves are tightly pinched,
the foot is caught, and if the pinching is continued the animal
becomes paralysed and unable to make use of the adductor
muscles, and consequently flies open even if the pressure is
relaxed. The musk-rat (Miber zibethicus) seizes the Unio in his
jaws, and by the time he reaches his hole, the Unio is ready to

1 Loch Creran, p. 102. * Cordeaux, Zoologist, 1873, p. 3396.
% Amer. Nat. xii. p. 695 ; Science Gossip, 1865, p. 79.

58 ENEMIES OF SLUGS AND SNAILS CHAP.

gape! Rats also eat Vivipara, and even Limnaea, in every part
of the world.

Every kind of slug and snail is eaten greedily by blackbirds,
thrushes, chaffinches, and in fact by many species of birds. <A
thrush will very often have a special sacrificial stone, on which
he dashes the shells of Helix aspersa and nemoralis, holding
them by the lip with his beak, until the upper whorls are broken ;
heaps of empty shells will be found lying about the place of
slaughter. The bearded Titmouse (Parus biarmicus) consumes
quantities of Succinea putris and small Pupa, which are swallowed
whole and become triturated in the bird’s stomach by the aid of
numerous angular fragments of quartz.”

Frogs and toads are very partial to land Mollusca. A garden
attached to the Laboratory of Agricultural Chemistry at Rouen
had been abandoned for three years to weeds and slugs. The
director introduced 100 toads and 90 frogs, and in less than a
month all the slugs were destroyed, and all kinds of vegetables
and flowers, whose cultivation had until then been impossible,
were enabled to flourish.’

Certain Coleoptera are known to prey upon Helices and
other land Mollusca. Récluz noticed, near Agde, a beetle (Staphy-
linus olens) attack Helix ericetorum when crawhng among herb-
age, sticking its sharp mandibles into its head. Every time
the snail retreated into its shell the beetle waited patiently
for its reappearance, until at last the snail succumbed to the
repeated assaults. M. Lucas noticed, at Oran, the larva of a
Drilus attacking a Cyclostoma. The Drilus stood sentinel at the
mouth of the shell, which was closed by the operculum, until the
animal began to issue forth. The Drilus then with its mandibles
cut the muscle which attaches the operculum to the foot, dis-
abling it sufficiently to prevent its being securely closed, upon
which it entered and took possession of the body of its defence-
less host, completing its metamorphosis inside the shell, after a
period of six weeks. The female glow-worm (Lampyris noctiluca)
attacks and kills Helix nemoralis.

Among the Clavicornia, some species of Si/pha carry on a
determined warfare against small Helices. They seize the shell

1 Journ. Trent. N. H. Soc. 1887, p. 58. 7? Ann. Nat. Hist. iii. 1893, pp. 238, 239.
3 Rev. Nat. Sc. Ouest, 1891, p. 261.
4 Petit de la Saussaye, Journ. de Conch. iui. p. 97 f.

Ill ENEMIES OF SLUGS AND SNAILS 59

in their mandibles, and then, throwing their head backwards,
break the shell by striking it against their prothorax.

The common water beetle, Dytiscus marginalis, from its
strength and savage disposition, is a dangerous enemy to fresh-
water Mollusca. One Dytiscus, kept in an aquarium, has been
noticed to kill and devour seven Limnaea stagnalis in the course
of one afternoon. The beetles also eat L. peregra, but apparently
prefer stagnalis, for when equal quantities of both species were
placed within their reach, they fixed on the latter species first.1

In East Africa a species of Ichneumon (Herpestes fasciatus)
devours snails, lifting them up in its forepaws and dashing them
down upon some hard substance.?. In certain islands off the south
coasts of Burmah, flat rocks covered with oysters are laid bare at
low tide. <A species of Monkey (Jacacus cynomolgus) has been
noticed to furnish himself with a stone, and knock the oysters
open, always breaking the hinge-end first, and then pulling out
the mollusc with his fingers.®

The walrus is said to support himself almost entirely on two
species of Mya (truncata and arenaria), digging them out of the
sand, in which they live buried at a depth of about 14 feet, with
his powerful tusks. Whales swallow enormous numbers of pelagic
molluses (Clio, Limacina), which are at times so abundant in the
Arctic seas, as to colour the surface for miles. Many of the
larger Cetacea subsist in great part on Cephalopoda; as many as
18 lbs. of beaks of Teuthidae have been taken from the stomach
of a single Hyperoodon.

Fish are remarkably partial to Mollusca of various kinds.
The cat-fish (Chimaera) devours Pectunculus and Cyprina, crush-
ing the stout shells with its powerful jaws, while flounders and
soles content themselves with the smaller Ze/lina and Syndosmya
which they swallow whole. As many as from 30 to 40 speci-
mens of buccinum undatum have been taken from the stomach
of a single cod, and the same ‘habitat’ has been recorded for
some of the rarer whelks, eg. Buce. humphreysianum, Fusus
fenestratus, the latter also occurring as the food of the haddock
and the red gurnard. No less than 35,000 Zurtonia minuta
have been found in the stomach of a single mullet. Nudibranchs
are no doubt dainty morsels for fish, and hence have developed,

1 J.W. Williams, Science Gossip, 1889, p. 280. 2 Noack, Zool. JB. ii. p. 254.

3 La Nature, xv. (2) p. 46.

60 MOLLUSCA AS FOOD FOR FISH AND FOR ONE ANOTHER cu.

in many cases, special faculties for concealment, or, if distasteful,
special means of remaining conspicuous (see pp. 71-74).

Besides the dangers to which they are exposed from other
enemies, many of the weaker
forms of Mollusca fall a prey to
their own brethren. Vassa and
Murex on this side of the At-
lantic, and Urosalpina on the
other, are the determined foes
of the oyster. Purpura lapillus
prefers Mytilus edulis to any
other food, piercing the shell in
about two days time by its
powerful radula, which it ap-
Fig. 22,.—Two seas of Bel an a pears to employ somewhat m

Dee cuca gf tue holes Gemlet: fashion.” = Tt A/a.

bored by Purpura in about 100 speci- cannot be procured, it will eat

mens of Mytilus, gathered at New- ; ; .

quay, Cornwall. Littorina or Trochus, but 1ts

attempts on the hard shell of
Patella ave generally failures. The statement which is some-
times made, that the Purpura makes its hole over the vital parts
of the Mytilus, appears, according to the evidence embodied in
the annexed figure, to be without foundation. The fact is that
a hole in any part of its shell is fatal to the Mytilus, since the
long proboscis of the Purpura, having once made an entrance,
can reach from one end of the shell to the other. The branchiae
are first attacked, the adductor muscles and edges of the mantle
last. Natica and Nassa pierce in a similar way the shells of
Mactra, Tellina, Donax, and Venus. Murex fortispina 1s furnished
with a powerful tooth at the lower part of its outer lip. At
Nouméa, in New Caledonia, its favourite food is Arca pilosa,
which lives half buried in coral refuse. The Murex has been
seen to drag the Arca from its place of concealment, and insert

the tooth between the valves, so as to prevent their closing, upon
which it was enabled to devour its prey at leisure.’
The carnivorous land Mollusca, with the exception of Testa-
cella, appear to feed by preference upon other snails (pp. 54, 55).
Parasitic Worms, Mites, etc. — A considerable number of
the Trematode worms pass one or more of the stages in the

1 Francois, Arch. Zool. Exp. (én. (2) ix. p. 240.

III WORMS PARASITIC IN MOLLUSCA 61

cycle of their development within the bodies of Mollusca, attain-
ing to the more perfect or sexual form on reaching the interior
of some vertebrate. Thus Distoma endolabum Duj. finds its
first intermediate host in Limnaea stagnalis and L. ovata, its
second in JL. stagnalis, or in one of the fresh-water shrimps
(Gammarus pulex), or in the larvae of one of the Phryganeidae
(Limnophilus rhombicus), attaining to the sexual form in the
common frog. Distoma ascidia v. Ben. passes firstly through
Limnaea stagnalis or Planorbis corneus, secondly through certain
flies and gnats (Hphemera, Perla, Chironomus), and finally arrives
within certain species of bats. Distoma noduloswm Zed. inhabits
firstly Paludina impura, secondly certain
fishes (Cyprinus, Acerina), and lastly the
conmon perch. The sporocyst of Distoma
macrostomum imbhabits NSuccinea putris,
pushing itself up into the tentacles, which
become unnaturally distended (Fig. 23).
While in this situation it is swallowed by

. = 0 ho Gk -
various birds, such as the thrush, wagtail, !!¢ 28.—A Trematode
‘S worm (Leucochloridium

and blackbird, which are partial to Succinea, paradoxum Car.) para-
and thus obtains lodgment in their bodies. pitig tm ihe tenbeele et

: Succinea putris L. x 20
Amphistoma subclavatum spends an early (after Baudon).

stage in Planorbis contortus, after which it
becomes encysted on the skin of a frog. When the frog sheds
its skin, it swallows it, and with it the Amphistoma, which
thus becomes established in the frog’s stomach.t

The common liver-fluke, which in the winter of 1879-1880
cost this country the lives of no less than three million sheep, is
perhaps the best known of these remarkable parasitic forms of
lite. Its history shows us, in one important particular, how
essential it is for the creature to meet, at certain stages of its
existence, with the exact host to which it is accustomed. Unless
the newly-hatched embryo finds a Limnaea truncatula within
about eight hours it becomes exhausted, sinks, and dies. It has
been tried with all the other common pond and river Mollusca, with
Limnaea peregra, palustris, auricularia, stagnalis, with Planorbis
marginatus, carinatus, vortex, aud spirorbis, with Physa fontinalis,
Lithynia tentaculata, Paludina vivipara, as well as with Succinea
putris, Limax agrestis and maximus, Arion ater and hortensis.

1 A. Lang, Ber. Naturf. Ges. Freib. vi. 1892, p. 81.

62 WORMS PARASITIC IN MOLLUSCA CHAP.

Not one of them would it touch, except occasionally very young
specimens of L. peregra, and in these its development was arrested
at an early stage. But on touching a L. truncatula the embryo
seems to know at once that it has got what it wants, and sets
to work immediately to bore its way into the tissues of its
involuntary host, making by preference for the branchial chamber;
those which enter the foot or other outlying parts of the Limnaca
proceed no farther.t

Many similar cases occur, in which littoral Mollusca, such as
Littorina and Buccinum, form the intermediate host to a worm
which eventually arrives within some sea-bird.

Certain Nematode worms (Rhabditis) are known to inhabit
the intestine of Arion, and the salivary glands of Limax agrestis.
Diptera habitually lay their eggs within the eggs of Helix and
Limax. Many species of mite (Acarina) infest land Pulmonata.
No adult Limax maximus is without at least one specimen of
Philodromus (?) limacum, and the same, or an allied species, appears
to occur on the larger of our Helices, retiring upon occasion into
the pulmonary chamber.

Several of the Crustacea live associated with certain molluscs.
Pinnotheres lives within the shell of Pinna, Ostrea, Astarte,
Pectunculus, and others. Apparently the females alone reside
within the shell of their host, while the males seize favourable
opportunities to visit them there. A specimen of the great
pearl-oyster (Meleagrina margaritifera) was recently observed
which contained a male Pinnotheres encysted in nacre. It was
suggested that he had intruded at an unfortunate time, when no
female of his kind happened to be in, and that, having penetrated
too far beneath the mantle in the ardour of his search, was made
prisoner before he could escape.? Ostracotheres Tridacnae lives
in the branchiae of the great Zridacna. <A little brachyurous
crustacean inhabits the raft of Janthina, and assumes the brilliant
blue colour of the mollusc.

Means of Defence
As a rule, among the Mollusca, the shell forms a passive
mode of resistance to the attacks of enemies. 3ivalves are

1 A, P. Thomas, Q. J. Micr. Sc., N. S., xxiii. (1883) p. 99.
2 H. Woodward, P. 7. S. 1886, p. 176.

Ill TEETH IN APERTURE OF SNAILS 63

enabled, by closing their valves, to baffle the assault of their
smaller foes, and the operculum of univalves, both marine and
land, serves a similar purpose. Many land Mollusca, especially
Helix and Pupa, as well as a number of Awriculidae, have the
inside of the aperture beset with teeth, which are sometimes so
numerous and so large that it is puzzling to understand how the
animal can ever come out of its shell, or, having come out, can
ever draw itself back again. Several striking cases of these
toothed apertures are given in Fig. 24. Whatever may be the

oy

Fic. 24.—Tllustrating the elaborate arrangement of teeth in the aperture of some land
Pulmonata. A. Helix (Labyrinthus) bifurcata Desh., Equador. B. H. (Pleuro-
donta) picturata Ad., Jamaica. C. AH. (Dentellaria) .nux denticulata Chem.,
Demerara. D. Anostoma carinatum Pfr., Brazil; a, tube communicating with
interior of shell. E. H. (Stenotrema) stenotrema Feér., Tennessee, x 3. F. H.

(Polygyra) auriculata Say, Florida, x3. G. H. (Plectopylis) refuga Gld., Tenas-

serim (a and b x 2),
origin of these teeth, there can be little doubt that their extreme
development must have a protective result in opposing a barrier
to the entrance, predatory or simply inquisitive, of beetles and
other insects. Sometimes, it will be noticed (4), the aperture
itself is fairly simple, but a formidable array of obstacles is
encountered a little way in. It is possible that the froth emitted
by many land snails has a similar effect in involving an irritating
intruder in a mass of sticky slime. The mucus of slugs and
snails, on the other hand, is more probably, besides its use in
facilitating locomotion, a contrivance for checking evaporation,
by surrounding the exposed parts of their bodies with a viscid
medium.

Some species of Zima shelter themselves in a nest constructed
of all kinds of marine refuse, held together by byssiferous threads.

64 MEANS OF CONCEALMENT CHAP.
ee ee a eS
Modiola adriatica, M. barbata, and sometimes I. modiolus, con-
ceal themselves in a similar way. Gastrochaena frequently
encloses itself in a sort of half cocoon of cement-like material.
The singular genus Xenophora protects itself from observation by
gluing stones, shells, and various débris to the upper side of its
whorls (Fig. 25). Sometimes the selection is made with remark-
able care; the Challenger, for instance, obtained a specimen
which had decorated its body whorl exclusively with long and
pointed shells (Fig. 26).

Fic. 25.—Xenophora (Phorus)

conchyliophora Born., con- Fic. 26.— Xenophora(Phorus) pall idula Reeve.
cealed by the stones which A mollusc which escapes detection by
it glues to the upper surface covering itself with dead shells of other
of its shell. (From a British species. (From a Challenger specimen in
Museum specimen. ) the British Museum, x 4-)

The formidable spines with which the shells, eg. of the
Murex family, are furnished must contribute greatly to their
protection against fishes, and other predatory animals. Murex
tenuispina, for instance (see chap. ix.), would prove as dangerous
a morsel in the mouth of a fish as a hedgehog in that of a dog.
Whether the singular tooth in the outer lip of Leucozonia (see
chap. xiv.), a feature which is repeated, to a less marked extent, in
Monoceros and several of the West Coast muricoids, is developed
for defensive purposes, cannot at present be decided.

The Strombidae possess the power of executing long leaps,
which they doubtless employ to escape from their foes. In their
case alone this power is combined with singular quickness of
vision. On one occasion Mr. Cuming, the celebrated collector,
lost a beautiful specimen of . Terebellum, by the animal suddenly

III MEANS OF DEFENCE 65

leaping into the water, as he was holding and admiring it in his
hand. Miss Saul has informed me that the first living specimen
of Zrigonia that was ever obtained was lost in a similar way. It
was dredged by Mr. Stutchbury in Sydney Harbour, and placed
on the thwart of a small boat. He had just remarked to a
companion that it must be a Zrigonia, and his companion had
laughed at the idea, reminding him that all known 77igonia were
fossil, when the shell in question baffled their efforts to discover
its generic position by suddenly leaping into the sea, and it was
three months before Mr. Stutchbury succeeded in obtaining
another.

Some genera possess more than merely passive means of
defence. Many Cephalopoda emit a cloud of inky fluid, which
is of a somewhat viscous nature, and perhaps, besides being a
means of covering retreat, serves to entangle or impede the
pursuer. The formidable suckers and hooks possessed by many
genera in this Order are most dangerous weapons, both for
offence and defence. Aplysia, when irritated, ejects a purple
fluid which used to be considered dangerously venomous. Many
of the Aeolididae, including our own common 4eolis papillosa,
possess stinging cells at the end of their dorsal papillae, the effect
of which is probably to render them exceedingly distasteful to
fish.

The common Vitrina pellucida has a curious habit which in
all probability serves for a defence against birds in the winter.
When crawling on the edge of a stone or twig it has the power
of suddenly jerking its ‘ tail,’ so as to throw itself on the ground,
where it is probably lost to sight among decaying leaves. At
other times it rolls away a few inches and repeats the jump. It
also possesses the power of attaching to itself bits of leaves or
soil, which entirely cover and conceal both shell and animal.
The property of parting with the tail altogether, a remarkable
form of self-defence, has already been noticed on p. 44.

The poisonous nature of the bite of certain species of Conus is
well authenticated. Surgeon Hinde, R.N., saw” a native on the
I. of Matupi, New Britain, who had been bitten by a Conus
geographus, and who had at once cut small incisions with a sharp
stone all over his arm and shoulder. The blood flowed freely,

1 W. E. Collinge, Zoologist, 1890, p. 467.
* Proc. Linn. Soc. N. S. Wales, ix. p. 944.
VOL. Il F

66 POISONOUS BITE OF CONUS CHAP.

and the native explained that had he not taken these precautions
he would have died. Instances have been
recorded of poisonous wounds being inflicted
by the bite of Conus aulicus, C. textile, and C.
tulipa. According to Mr. J. Maegillivray* C.
teatile at Aneiteum (S. Pacific) is called intrag,
and the natives say it spits the poison upon
them from several inches off! Two cases of
bites from ©. textile occurred to this gentle-
man’s notice, one of which terminated fatally
by gangrene. = Sir Edward Belcher, when in
command of the Samarang, was bitten? by
a Conus aulicus at a little island off Ternate in
the Moluccas. As he took the creature out of
the water, it suddenly exserted its proboscis
and inflicted a wound, causing a sensation
similar to that produced by the burning of
Rae oy nth ae phosphorus under the skin. The wound was
the radula of Conus a Small, deep, triangular mark, succeeded by a
imperialis L., x 50, watery vesicle. The natives of New Guinea
showing barb and :
poison duct. have a wholesome dread of the bite of Cones.
Mr. C. Hedley relates * that while collecting on
a coral reef he once rolled over a boulder and exposed a living
C. textile. Before he could pick it up, one of the natives hastily
snatched it away, and explained, with vivid gesticulations, its
hurtful qualities. On no account would he permit Mr. Hedley
to touch it, but insisted on himself placing it in the bottle of
spirits.

Mimicry and Protective Coloration

Cases of Mimicry, or protective resemblance, when a species
otherwise defenceless adopts the outward appearance of a better
protected species, are rare among the Mollusca. Karl Semper +
mentions an interesting case of the mimicry of Helicarion tigrinus
by Xesta Cumingii, in the Philippines. It appears that all
Zoologist, xviii. (1860) p. 7136.

A. Adams, Samarang, vol. ii. Zoology, p. 357.
In Thomson’s British New Guinea, p. 283.

4 Animal Life, p. 395. Itshould be mentioned that Von Méllendorff (Ber. Senck.
Ges. 1890, p. 198) ridicules the whole theory.

1
2
3

Il MIMICRY 67

species of Helicarion possess the singular property of shaking off
the ‘tail’ or hinder part of the foot, when seized or irritated.
Specimens captured by collectors, Hel. tigrinus amongst them,
have succeeded in escaping from the hand, and concealing them-
selves, by a sort of convulsive leap, among the dry leaves on the
ground. This power of self-amputation must be of great value
to Helicarion, not only as enabling it to escape from the clutch
of its enemies, but also as tending to discourage them from
attempting to capture it at all. Now the genus Yesta is, in
anatomy, very far removed from Helicarion, and the majority of
the species are also, as far as the shell is concerned, equally
distinct. esta Cumingit, however, has, according to Semper,
assumed the appearance of a Helicarion, the thin shell, the long
tail, and the mantle lobes reflected over the shell; but it has not
the power of parting with its tail at short notice. It lives
associated with Helicarion, and so close is the resemblance between
them that, until Semper pointed out its true position, it had
always been classified as a member of that group.

In the same passage Semper draws attention to two other
cases of apparent mimicry. ‘The first is another species of Yesta
(mindanaensis) which closely resembles a species of Rhysota
(Antonii), a genus not indeed so far removed from ‘esta as
Felicarion, but, as far as the shell is concerned, well distinguished
from it. In this case, however, there is no obvious advantage
gained by the resemblance, since Rhysota as compared with
Aestu is not known to possess any definite point of superiority
which it would be worth while to counterfeit. A second case of
resemblance between certain species of the genus Chloraea and
the characteristic Philippine group Cochlostyla will not hold good
as affording evidence of mimicry, for Chloraea is now recognised
as a subgenus of Cochlostyla.

The Mollusca are not much mimicked by creatures of different
organisation. This appears at first sight strange, since it might
have been thought that the strong defensive house of a snail was
worth imitating. Still it is probably not easy for creatures
bilaterally symmetrical to curl themselves up into an elevated
spiral for any length of time. One or two instances, however,
may be mentioned. The larva of a moth belonging to the
Psychidae, and occurring in France, Germany, the Tyrol, and
Syria, coils itself up into a sinistral spiral of three whorls, and is

68 MIMICRY CHAP.

aptly named Psyche helix, a kindred species from Italy being
known as Ps. planorbis.

An insect larva (Cochlophora valvata) from E. Africa is said
to resemble a Valvata or young Cyclostoma. In this case the
spiral is indifferently dextral or sinistral, the ‘shell’ being formed
of masticated vegetable matter, united together by threads spun by
the larva. Certain larvae of the Phryganeidae (“ Caddis-worms ”)
enclose themselves in houses which more or less resemble a
spiral shell, and have in some cases actually been described as
molluscan. Such species, some of which belong to Helicopsyche,
have been noticed in S. Europe, Ceylon, Further India, China,
Tasmania, New Zealand, Tennessee, Mexico, Central America,
Venezuela, Brazil, and Argentina, and all’ possess a dextral
‘shell’ In all these cases ‘mimicry’ is probably not so much to
be thought of as the practical advantages which accrue to the
animal in question from the spiral form, which gives it greater
strength to resist external blows, and enables it to occupy, during
a very defenceless portion of its existence, a very small amount
of space.

The larva of some species of the Syrphidae (Diptera) fixes itself
on the under side of stones in the Tyrol, and closely resembles a
small slug. The naturalist Von Spix, in 1825, described to the
Bavarian Academy as a new genus of land Mollusca a somewhat
similar larval form found in decaying wood on the banks of a
German lake.2 Simroth mentions® a curious case as occurring
near Grimma. The caterpillars of certain Microlepidoptera occur
on slabs of porphyry, associated with a species of Clausilia.
Besides being of the same colour as the Clausiliae, the caterpillars
have actually developed cross lines on the back, 7.e. on the side
turned away from the rock, in imitation of the suture of the
mollusc.

It has been suggested+ that there is mimicry between Aeolis
papillosa (a common British nudibranch) and Sagartia troglodytes
(an Actinian), and also between another species of Sagartia and
Aeolidiella Aldert. The facts observed are not sufficient to
warrant a decided opinion, but it seems more probable that the

1 Von Martens, SB. Nat. Fr. Berl, 1891, p. 83.

2 ‘Von Martens, zbid. 1887, p. 183. 3 SB. Nat. Gesell. Leipz. xiii.-xiv. p. 45.

4 Garstang, Journ. Mar. Biol. Ass. N. 8. i. p. 482; Giard, Dull. Sci. Fr. Belg.
1888, p. 502 f.

it

Ill MIMICRY 69

Actinian mimics the nudibranch than vice versd, since Aeolis is
known to be unpalatable to fishes.

Certain species of Strombus (mauritianus 1., luhuanus 1.)
show a remarkable similarity in the
shape of the shell to that of Conus,
so much so, that a tiro would be
sure to mistake them, at first sight,
for Cones. In the case of S. luh-
uanus at least, this similarity is
increased by the possession of a
remarkably stout brown epidermis.
Now Conus is a flesh-eating genus,
armed with very powerful teeth
which are capable of inflicting even Tine 18 =e, Gepoiia bine onUReonAIS
on man a poisonous and sometimes Lam., which mimics Conus in
fatal wound (see p. 66). Strombus, eee Consents ENiese:
on the other hand, is probably frugi-
vorous, and is furnished with weak and inoffensive teeth. It is
possible that this resemblance is a case of ‘mimicry. It is quite
conceivable that powerful fishes which would swallow a Strombus
whole and not suffer for it, might acquire a distaste for a Cone,
which was capable of lacerating their insides after being swal-
lowed. And therefore the more lke a Cone the Strombus became,
the better chance it would have of being passed over as an
ineligible article of food.

Protective coloration is not wncommon among the Mollusca.
Littorina obtusata is habitually found, on our own coasts, on
Fucus vesiculosus, the air-bladders of which it closely resembles
in colour and shape. Littorina pagodus, a large and showy

species, resembles so closely the spongy crumbling rocks of
Timor, on which it lives, that it can hardly be discerned a pace
off. Helcion pellucidum, the common British ‘ blue limpet,’ lives,
when young, almost exclusively on the iridescent leaves of
the great Laminariae, with the hues of which its own con-
spicuous blue lines harmonise exactly. In mature life, when
the Helcion invariably transfers its place of abode to the lower
parts of the stall and finally to the root of the Laminaria, which
are quite destitute of iridescence, these blue lines disappear or
become much less marked.

The specimens of Purpura lapillus which oceur at Newquay

7O PROTECTIVE COLORATION CHAP.

in Cornwall are banded with rings of colour, especially with
black and white, in a more varied and striking way than any
other specimens that have ever occurred to my notice. I am
inclined to refer this peculiarity to a tendency towards protective
coloration, since the rocks on which the Purpura occurs are
often banded with veins of white and colour, and variegated to a
very marked extent.

Ovula varies the colour of its shell from yellow to red, to
match the colour of the Gorgonia on which it lives. The same is
the case with Pedicularia, which occurs on red and yellow coral.

Helix desertorum, by its gray-brown colour, harmonises
well with the prevailing tint of the desert sands, among which
it finds a home. Benson observes that the gaudy A. haemastoma,
which lives on the trunks of palm-trees in Ceylon, daubs its shell
with its excrement. Our own Buliminus obscurus, which lives
principally on the trunks of smooth-barked trees, daubs its
shell with mud, and must often escape the observation of
its enemies by its striking resemblance to the little knots on
the bark, especially of beech trees, its favourite haunt. Some
species of Microphysa, from the West Indies, habitually encrust
their shells with dirt, and the same pecuharity in Vitrina
has already been mentioned. <Ariophanta Dohertyi Aldr., a
recent discovery from Sumatra, is of a green colour, with
a singularly delicate epidermis; it is arboreal in its habits,
and is almost invisible amongst the foliage.’ Many of our
own slugs, according to Scharff, are coloured protectively
according to their surroundings. A claret-coloured variety
of Arion ater occurred to this observer only in pine woods,
where it harmonised with the general colouring of the ground
and the pine-needles, while young winter forms of the same
species choose for hiding-places the yellow fallen leaves,
whose colour they closely resemble. Limax marginatus ( = arbo-
rum Bouch.) haunts tree trunks, and may easily be mistaken
for a piece of bark; Amalia carinata lives on and under the
ground, and in colour resembles the mould; Arion intermedius
feeds almost exclusively on fungi, to which its colour, which
is white, gray, or light yellow, tends to approximate it closely ;
Geomalacus maculosus conceals itself by its striking resemblance
to the lichens which grow on the surface of rocks, and actually

1 Nautilus, vi. 1892. p. 90.

II PROTECTIVE COLORATION IN NUDIBRANCHS LMS

presumes on this resemblance so much as to expose itself,
contrary to the usual custom of its congeners, to the full light
of the afternoon sun.!

Several views have been advanced with regard to the dorsal
papillae, or cerata, in the Nudibranchs. Professor W. A.
Herdman, who has examined a considerable number of our
own British species, in which these processes occur, is of
opinion” that they are of two quite distinct kinds. In the
first place, they may contain large offshoots, or diverticula,
of the liver, and thus be directly concerned in the work of
digestion. This is the case with Aeolis and Doto. In the
second place, they may be simply lobes on the skin, with no
connection with the liver, and no special function to perform.
This is the case with 7ritonia, Ancula, and Dendronotus.

Professor Herdman is of opinion that although the cerata
may in all cases aid in respiration to a certain extent, yet
that extent is so small as to be left out of consideration
altogether. He regards the cerata in both the two classes
mentioned above as “of primary importance in giving to the
animals, by their varied shapes and colours, appearances which
are in some cases protective, and in others conspicuous and
warning.”

Thus, for instance, 7ritonia plebeia, which is fairly abundant
at Puflin and Hilbre Is., appears always to be found creeping
on the colonies of a particular polyp, <Alcyoniwm digitatum,
and nowhere else. The specimens in each colony of the polyp
differ noticeably both in the matter of colour, and of size,
and of varied degrees of expansion. The TZritonia differs
also, being marked in varied tints of yellow, brown, blue,
gray, black, and opaque white, in such a way as to harmonise
with the varied colours of the Alecyoniwm upon which it
lives. The cerata on the. back of the Zritonia contribute
to this general resemblance. They are placed just at the
right distance apart, and are just the right size and colour,
to resemble the crown of tentacles on the half-expanded
polyp.

Similarly, Doto coronata, which, when examined by itself,
is a very conspicuous animal, with showy, bright-coloured cerata,
1 R, F. Scharff, Sei. Trans. R. Dubl. Soc. (2) iv. p. 553 f.

2 Q. Journ. Micr. Sci. N. 8. xxxi. (1890) p. 41 f.

72 PROTECTIVE COLORATION IN NUDIBRANCHS CHAP.

is found by Professor Herdman to haunt no other situations
but the under-side of stones and overhanging ledges of rock
which are colonised by a hydroid, known as Clava multicornis.
The Doto is masked by the tentacles and clusters of sporosacs
on the zoophyte, with whose colouring and size its own cerata
singularly correspond. A similar and even more deceptive
correspondence with environment was noticed in the case of
the very conspicuous Dendronotus arborescens.

In these cases, the colouring and general shape of the cerata
are protective, ze. they match their surroundings in such a
way as to enable the animal, in all probability, to escape the
observation of its enemies. According to Professor Herdman,
however, the brilliant and showy coloration of the cerata of
Aeolis.is not protective but ‘warning. Aeolis does not hide
itself away as if shunning observation, like Doto, Tritonia, and
Dendronotus ; on the contrary, it seems perfectly fearless and
indifferent to being noticed. Its cerata are provided with
sting-cells, like those of Coelenterata, at their tips, and its very
conspicuousness 1s a warning to its enemies that they had
better not try to attack it, just as the showy white tail of
the skunk acts as a sort of danger-signal to its own particular
foes. It is important for the -deolis, not merely to be an
unpalatable nettle in animal shape, but also to be conspicuous
enough to prevent its being experimented upon as an article of
food, in mistake for something less nasty.

Professor Herdman subsequently conducted some experi-
ments * with fishes, with the view of testing his theory that the
shapes and colours of Nudibranchs serve the purpose either of
protection or warning, and bear direct relation to the creature’s
edibility. These experiments, on the whole, distinctly tended
to confirm the theory. Aeolis was evidently very nasty, and
probably stung the mouths of the fishes who tried it. For the
complete success of the theory, they ought to have let it severely
alone, but the fish were evidently accustomed to make a dash
at anything that was dropped into their tank. Another con-
spicuous mollusc, Ancula cristata, was introduced, Professor
Herdman and his collaborator each commencing operations by
eating a live specimen themselves. They found the taste
pleasant, distinctly like that of an oyster. The fish, however,

1 A detailed account is given in Proc. Liverp. Biol. Soc. iv. (1890) pp. 150-163.

111 PROTECLIVE COLORATION We

when the experiments were conducted under conditions which
made the scene as much lke ‘real life’ as possible, did not
agree with Professor Herdman. The Ancula crawled over
various parts of the tank for several days untouched by the
fish, who sometimes went close to them and looked at them,
but never attempted to taste them. Experiments with species
whose colours were protective, such as Dendronotus, were also
conducted, and the decided edibility of these species was
established, the fish competing eagerly for them, and tearing
them rapidly to pieces.

Mr. W. Garstang, of the Plymouth Laboratory of the Marine
Biological Association, confirms’ Professor Herdman’s views as
to the shape and colour of Opisthobranchs. Plewrobranchus
membranaceus is known to secrete, on the surface of the body,
an acid which reddens blue litmus paper. It is, therefore, no
doubt distasteful to fish, which all abominate the taste of acids,
and is conspicuously marked with red-brown and yellowish
‘warning’ colours. Haminea and Philine, on the other hand,
are good to eat, and consequently possess ‘protective’ colora-
tion. Runeina Hancocki, which is of a brown colour, crawls
over brown mud and weeds, but avoids green weeds, on
whose surface it would appear conspicuous. Hlysia viridis
varies its colour according to its habitat, being green when
on green weeds, and dark olive, brown, or reddish brown, on
pools among tufts of littoral algae. Green specimens of
Hermaea dendritica were kept in captivity, and placed in a dish
with green and red sea-weeds. They were never observed
crawling upon the red weed, upon which they would have
been very conspicuous. Archidoris flammea occurred on bright
red sponges, to which its colour was so closely assimilated
that Mr. Garstang at first quite overlooked it. Goniodoris
castanea was found under stones, feeding on compound Ascidians
(Botryllus), which it sufficiently resembled to be very in-
conspicuous in that position.

Again, Jorunna Johnstoni lives” upon stones on our southern
coast, associated with a certain sponge (Halichondria sp.), which
it resembles so closely in outline, in colour, in character of
surface, and in its projecting plumes, as to make it very

» Journ. Mar. Biol. Ass. N. 8. i. p. 418 f.
2 Garstang, Conchologist, ii. p. 49.

74 PROTECTIVE COLORATION—PARASITIC MOLLUSCA cnap.

difficult even for the careful observer to distinguish the one
from the other. “And, since fishes are known to be distinctly
averse to sponges of any kind as an article of food, this re-
semblance must be decidedly to the advantage of the Jorwnna.
Another Nudibranch (Calma glaucoides A. and H.) imitates
the ova of certain fishes, on which it feeds. Its elongated
and depressed form of body, transparent imnteguments, and
silvery gray papillae combine to give it a strong resemblance
to the spawn of the fish, which is deposited on stones, the
roots of Laminaria, ete.

The common Lamellaria perspicua appears to possess the
power of protectively assimilating its colour, markings, ete., .
to the Ascidians on which it lives. A recent case, occurring
off the Isle of Man, is thus described by Professor Herdman.?
“The mollusc was on a colony of Leptoclinum maculatum, in
which it had eaten a large hole. It lay in this cavity so as
to be flush with the general surface; and its dorsal integument
was not only whitish with small darker marks which exactly
reproduced the appearance of the Leptoclinum surface with
the ascidiozooids scattered over it, but there were also two
larger elliptical clear marks which looked hke the large common
cloacal apertures of the Ascidian colony. . . . Presumably the
Lamellaria escapes the observation of its enemies through
being mistaken for part of the Leptoclinwm colony; and the
Leptoclinum, being crowded like a sponge with minute sharp-
pointed spicules, is, I suppose, avoided as inedible (if not
actually noxious through some peculiar smell or taste) by
carnivorous animals which might devour such things as the
soft unprotected mollusc.”

Parasitic Mollusca

Various grades of parasitism occur among the Mollusca,
from the true parasite, living and nourishing itself on the tissues
and secretions of its host, to simple cases of commensalism.
Some authors have divided these forms into endo- and ecto-
parasites, according as they live inside or outside of their host.

1 Hecht, Comptes Rendus, exv. p. 746.
2 Conchologist, ii. p. 130.

IIL MOLLUSCA PARASITIC ON CORALS 75

Such a division, however, cannot be rigidly carried out, for certain
forms are indifferently endo- and ecto-parasitical, while others
are ecto-parasitic in the young form, and become endo-parasitic
in the adult. It will be convenient, therefore, simply to group
the different forms according to the home on which they find a
lodgment.

On Sponges. —Vulsella and Crenatula almost invariably
occur in large masses of irregu-
lar shape, boring into sponges.
They are especially abundant on
Porifera from the Red _ Sea.
Corals form a favourite home
of many species, amongst which

ibe,

f

: any

are several forms of Corallio- et
: . ‘ y |!
phila, Rhizochilus, Leptoconchus, si

and Sistrum. LRhizochilus is a
very singular creature, inhabiting
branching corals. When adult, it
forms irregular shelly extensions

Fic. 29.— Magilus antiquus L.:

of both the inner and outer lips, A, the adult, imbedded in coral,
which adhere to the shafts of the which has been broken away to

: show the tube; B, the young
coral, or to the surface of neigh- (free) form.

bouring shells; at length the aper-

ture becomes completely closed with the exception of the
siphonal tube, which becomes long, and consists of the same
shelly material The common MMagilus (Fig. 29), from the
Red Sea and Indian Ocean, in the young form is shaped lke
a small Buccinum. As the coral (Meandrina) to which it
attaches itself grows, the Magilus develops at the mouth a
long calcareous tube, the aperture of which keeps pace with
the growth of the coral, and prevents the mollusc from being
entombed. The animal lives at the free, or outer, end of the
tube, and is thus continually shifting its position, while the
space it abandons becomes completely closed by a mass of solid
calcareous matter. Certain species of Ovula inhabit Gorgonia,
assuming the colour, yellow or red, of their host, and, in
certain cases, developing, probably for prehensile purposes, a
pointed extension of the two extremities of the shell. Pedic-
ularia, «a form akin to Cypraea, but with a more patulous
mouth, inhabits the common Corallium rubrum of the Mediter-

76 MOLLUSCA PARASITIC ON ECHINODERMS CHAP.

ranean, and another species has been noticed by Graeffe’ on
Melithaea ochracea in Fiji.

On Echinodermata.—(a) Crinoidea. Stilina comatulicola lives
on Comatula mediterranea, fixed to the outer skin, which it pene-
trates by a very long proboscis; the shell is quite transparent.?
A curious case of a fossil parasite has been noticed by Roberts.?
A Calyptraea-shaped shell named Platyceras always occurred on
the ventral side of a crinoid, encompassed by the arms. For
some time this was thought to afford conclusive proof of the
rapacity and carnivorous habits of the echinoderm, which had
died in the act of seizing its prey. Subsequent investigations,
however, showed that in all the cases noticed (about 150) the
Platyceras covered the anal opening of the crinoid in such a way
that the mouth of the mollusc must have been directly over the
orifice of the anus. (0b) <Asteroidea. The comparatively soft
texture of the skin of the starfishes renders them a favourite
home of various parasites. The brothers Sarasin noticed* a
species of Stilifer encysted on the rays of Linchkia multiformis.
Each shell was enveloped up to the apex, which just projected
from a hole at the top of the cyst. The proboscis was long, and
at its base was a kind of false mantle, which appeared to possess
a pumping action. On the under side of the rays of the same
starfish occurred a capuliform molluse (Zhyca ectoconcha), fur-
nished with a muscular plate, whose cuticular surface was in-
dented in such a way as to grip the skin of the Linckia. This
plate was furnished with a hole, through which the pharynx
projected into the texture of the starfish, acting as a proboscis
and apparently furnished with a kind of pumping or sucking
action. Adams and Reeve® describe Pileopsis astericola as living
‘on the tubercle of a starfish, and Stilifer astericola, from the
coast of Borneo, as ‘living in the body of a starfish.’ In the
British Museum there is a specimen of Pileopsis crystallina ‘in
situ’ on the ray of a starfish. (¢) On the brittle starfishes (Ophiu-
roidea) occur several species of Stiliferina. (d) Echinoidea. Vari-
ous species of Stilifer occur on the ventral spines of echinoids,

1 Described as a Cypraca, but no doubt an Ovula or Pedicularia: CB. Bakt.
Par. v. p. 548.
Von Grafl, 7. wiss. Zool. xxv. p. 124.
Proc. Amer. Phil. Soc. xxv. p. 231.
Ergeb. naturw. Forsch. Ceylon, abstr. in Journ. Roy. Micr. Soc. (2) vi. p. 412.
Voyage of the Samarang, Moll. p. 69, Pl. xi. f. 1; p. 47, Pl. xvii. fi 5.

to

a i]

III MOLLUSCA PARASITIC ON ECHINODERMS Wi

where they probably subsist on the excreta, and are sometimes
found imbedded in the spines themselves. St. Zurtoni occurs on
the British coasts on several species of Hehinus, and Montacuta
substriata frequents Spatangus purpureus aud certain species of
Lchinocardium, Cidaris, and Brissus. Lepton parasiticum has
been described from Kerguelen I. on a Hemiaster, and a new
genus, Robillardia, has recently been established + for a Hyalinia-
shaped shell, parasitic on an Hehinus from Mauritius. (e) Holo-
thurioidea. The ‘sea-cucumbers’ afford lodgment to a variety
of curious forms, some of which have experienced such modi-
fications that their generic position is by no means established.
Entoconcha occurs fixed by its buccal end to the blood-vessels
of certain Synapta in the Mediterranean and the Philippines.
Lntocolax has been dredged from 180 fath. in Behring’s Straits,
attached by its head to certain anterior muscles of a Myriotro-
chus” A curious case of parasitism is described by Voeltzkow 3
as occurring on a Synapta found between tide-marks on the I. of
Zanzibar. In the oesophagus of the Synapta was found a small
bivalve (Entovalva), the animal of which was very large for its
shell, and almost entirely enveloped the valves by its mantle.
As many as five specimens occurred on a single Synapta. In
the gut of the same Holothurian lived a small univalve, not
creeping freely, but fixed to a portion of the stomach wall by a
very long proboscis which pierced through it into the body
cavity. This proboscis was nearly three times as long as the
animal, and the forward portion of it was set with sharp thorns,
no doubt in order to enable it to retain its hold and resist
evacuation. Various species of Hulima have been noticed in
every part of the world, from Norway to the Philippines, both
inside and outside Holothurians.4 Stilifer also occurs on this
section of Echinoderms.®

On Annelida.—Cochliolepas parasiticus has been noticed under
the scales of Acoetes lupina (a kind of ‘ sea-mouse’) in Charleston
Harbour.®

On Crustacea.—A mussel, 3 in. long, has been found’? living

1 E. A. Smith, dan. Mag. Nat. Hist. (6) iii. p. 270.

* Journ. de Conch. (3) xxix. p. 101. 3 Zool. Jahrb. Abth. f. Syst. v. p. 619.

* See especially Semper, Animal Life, Ed. 1, p. 351.

° Gould, Moll. of U.S. expl. exped. 1852, p. 207 (St. acicula, from Fiji).

° Stimpson, Proc. Bost. Soc. N. H. vi. 1858, p. 308.

7 Pidgeon, Nature, xxxix. p. 127.

78 MOLLUSCA PARASITIC ON MOLLUSCA CUAP.

under the carapace of the common shore-crab (Carcinus maenas),
and one case has been noticed! where two mussels, one of several
months growth, the other smaller, well secured
by their byssi, were found under the abdomen
of the same species, in such a position as to
force the appendages apart and askew. — These,
however, are not so much cases of parasitism
as of involuntary habitat, the mussel no doubt
having become involved in the branchiae and
the abdomen of the crab in the larval form.

On Mollusca.—A species of Odostomia
(pallida Mont.) is found on our own coasts on
the ‘ears’ of Pecten maximus, and also? on the
operculum of TZurritella communis. Another
Fic. 30. —Crepidula Species (0. rissoides) frequently occurs in hiding

onyx Sowb., para- under beds of mussels, but it is not clear
SACL on: whether the habitat is due to parasitism, or
gueatus Swains., simply to the fact that the mass of mussels,

Panama. - :

knitted together and to the rock by the byssi,
affords the Odostomia a safe lurking-place. At Panama the
present writer found Crepidula (2 sp.) plentiful on the opercula
of the great Strombus galea and of Cerithium irroratum. In
each case the parasite exactly fitted the size of the operculum, and
had assumed its colour, dark brown or chestnut. Amalthea is
very commonly found on Conus, Turbo, and other large shells

from the South Pacific, but this 1s probably not a case of

parasitism, but simply of convenience of habitat, just as young
oysters are frequently seen on the carapace and even on the
legs of large crabs.

On Tunicata—Lamellaria deposits its eggs and lives on an
Ascidian (Leptoclinum), and the common Modiolaria marmorata
lives in colonies imbedded in the test of Ascidia mentula and
other simple Ascidians.

Special points of interest with regard to parasitic Mollusca
relate to (1) Colour. This is in most cases absent, the shell
being of a uniform hyaline or milky white. This may be due,
in the case of the endo-parasitic forms, to absence of light, and
possibly, in those living outside their host, to some deficiency

1 W. Anderson Smith, Loch Creran, p. 46.
2 Smart, Jowrnal of Conch. v. p. 152.

III COLOUR OF PARASITIC MOLLUSCA 79

in the nutritive material. A colourless shell is not necessarily
protective, for though a transparent shell might evade detection,
a milk-white hue would probably be conspicuous. (2) Modifica-
tions of structure. ‘These are in many cases considerable. Hnto-
concha and Entocolax have no respiratory or circulatory organs,
and no known nervous system; Zhyca
and certain Stilifer possess a curious
suctorial apparatus; the foot im many
eases has aborted, since the necessity
for locomotion is reduced to a minimum,
and its place is supplied by an enormous
development of the proboscis, which en-
ables the creature to provide itself with
nutriment without shifting its position.
K. Semper notices a case where a Lulima,
whose habitat is the stomach of a Holo- F!¢. 31.—Two species of Eu-

4 A es ; lima: A is sessile on the
thurian, retains the foot unmodified, while skin of a Holothurian,
a species occurring on the outer skin, Heian a ae
but provided with a long proboscis, has B creeps freely in the
losis ats: fact altogether’ Special pro- “temech ofa Holothunan:

* : : : ; (After K. Semper. )
vision for holding on is noticed in cer-

tain cases, reminding us of similar provision in human_ para-
sites. Eyes are frequently, but not always wanting, even in
endo-parasitic forms. A specially interesting modification of
structure occurs in (3) the Radula or ribbon-shaped arrangement
of the teeth. In most cases of parasitism (Hulima, Stilifer,
Odostomia, Entoconcha, Entocolax, Magilus, Coralliophila, Lepto-
concha) it 1s absent altogether. In Ovula and Pedicularia, genera
which are in all other respects closely allied to Cypraea, the
radula exhibits marked differences from the typical radula of
the Cypraeidae. The formula (3:13) remains the same, but the
laterals are greatly produced and become fimbriated, sometimes
at the extremity only, sometimes along the whole length. <A
very similar modification occurs in the radula of Sistrum spectrum
Reeve, a species which is known to live parasitically on one of
the branching corals. Here the laterals differ from those of
the typical Purpuridae in being very long and curved at the
extremity. The general effect of these modifications appears to
be the production of a radula rather of the type of the vegetable-
1 Animal Life, p. 351.

80 CASES OF COMMENSALISM CHAP.

feeding Zrochidae, which may perhaps be regarded as a lnk in
the chain of gradually degraded forms which eventually termi-
nate in the absence of the organ altogether. The softer the
food, the less necessity there is for strong teeth to tear it; the
teeth either become smaller and more numerous, or else longer
and more slender, and eventually pass away altogether. It is
curious, however, that the same modified form of radula should
appear in species of Ovula (e.g. ovum) and that the same absence
of radula should occur in species of Hulima (e.g. polita) known
to be not parasitic. This fact perhaps points back to a time
when the ancestral forms of each group are parasitic and whose
radulae were modified or wanting, the modification or absence
of that organ being continued in some of their non-parasitical
descendants.

Commensalism

Mollusca are concerned in several interesting cases of com-
mensalism, or the habitual association of two organisms, as dis-
tinguished from parasitism, where one form preys more or less
upon the other.

Mr. J. T. Marshall has given! an interesting account of the
association of Montacuta ferruginosa with Echinocardium cor-
datum. The Echinoderm lives in muddy sand in Torbay, at a
depth of about 6 inches, and the MJontacuta lives in a burrow
leading from its ventral end and running irregularly in a sloping
direction for 3 or 4 inches, the burrow, which is made by a
current from the Echinoderm, being almost exactly the width of
the Montacuta. The Montacuta were always arranged in the
burrows in order of size, the largest being close to the Echinoderm,
and the smallest of a string of about six at the other end of the
burrow. In another part of 8. Devon, where the sand was soft
and sloppy, the Echinocardia rise to the surface and travel
along the sand; in this case the Montacuta were attached to
their host by means of a byssus, and were dragged along as it
travelled. :

The Rev. Dr. Norman has noted? a somewhat similar habitat
for Lepton squamosum. This rare little British species was found
at Salcombe, living in the burrows of Grebia stellata, in all prob-
ability feeding upon the secretions from the body of the crustacean.

1 Journ. of Conch. vi. 1891, p. 399. 2 Ann. Mag. N. H. (6) vii. p. 276.

III CASES OF COMMENSALISM 8I

ee

Dr. Norman suggests that the extreme flatness of the shell of the
Lepton is of great advantage in enabling it not to get in the way
of the Gebia as he scuttles up and down his burrow. Another
species of Lepton is found on the coast of Florida in a precisely
sunilar locality,! while a third species, occurring on the Oregon
and California coasts, actually attaches itself to the inner surface
of the abdomen of a Gebia.2

A very singular case of commensalism has been recently dis-
covered with regard to a genus of Australian bivalve shells,
Ephippodonta. This genus is never found except in the burrow
of a species of prawn (Axius plectorhynehus Str.). For some
reason at present unexplained, the burrow of this particular
prawn appears to be exceedingly popular as a habitat for certain
bivalves, for, besides two species of Eph ippodonta, a Kellia and

Fic. 32.—Ephippodonta Mac-
dougalli Tate, S. Australia,
A, burrow of prawn, the x
indicating the position of the
mollusc ; sp, sponge. B,
Ventral view of Lphippo-
donta ; by, byssus; f, foot ;
m, mantle ; mm, fused mantle
borders. ©, View of interior
of shells ; h, hinge ; m’m’,
adductor muscles. (A x 3;
B and C x2.)

three Mylitta are found there, and there alone. Sometimes the
prawn, when the rock is hard, builds a tunnel of mud upon it,
at other times it excavates the soft calciferous sandstone. “This
burrow is lined with a tenacious brown mud, composed of excre-
mentitious matter; and, in addition to the mud lining, there is
always more or less present an orange-coloured sponge which I
have never found elsewhere. Upon the mud or sponge, and
adhering very closely, are found the Ephippodonta. They quickly
form a pit-like depression by means of their foot, and appear
almost covered by the mud.” During the winter months (March—
1 Stimpson, quoted by Jeffreys, Brit. Conch. ii. 194.
* Stimpson, Journ. Bost. Soc. N. H. vi. 1857, p. 48.
VOL. III a

82 VARIATION CHAP.

July) the prawn appears to fill his burrow, possibly as a
provision against stormy weather, with large quantities of minced
seaweed, underneath which immense numbers of very young
Ephippodonta are found living.t The extreme flatness of the
Ephippodonta must be due to the same cause as the flatness of
the Lepton noticed above, namely, the necessity of not impeding
or interfering with the lively motions of the prawn. In the case
of Lepton the two valves close completely and the shell is still
very flat, in Lphippodonta, on the other hand, the same result
is produced by the valves being opened to their widest possible
extent. As in Hntovalva, a continuation of the mantle covers
the outer surface of the shell.

Variation

It is a familiar experience to the student, not only of the
Mollusea, but of every branch of animal or vegetable life, to
come across examples which exhibit certain slight deviations
from the type form as usually understood. These deviations
may be more or less pronounced, but, as a rule, a series of forms
ean be discovered, gradually leading up to or down from the
type. The definition of what constitutes a species,—and, still
more, the rigid application of such definition—will always
remain a difficult task, so long as the personal element persists
in him who defines.2. What seems to one authority ample
ground for distinction of species, another may regard as of
comparatively trivial importance. The practical outcome of
these divergent views is sufficiently illustrated by the attitude
of Mr. F. P. Marrat on the one hand, and of what may be called
the modern French school of conchologists on the other. Mr.
Marrat holds, or held, that the great genus WVassa, of which more
than 150 species are generally recognised, is one shell (species)
in an endless variety of forms. The modern French school go to
the other extreme, and apparently proceed upon the view that
almost any difference in form, however slight, is sufficient to con-
stitute a separate species.

It will be generally admitted, however, that some structural

1 EK. H. Matthews, Conchologist, ii. p. 144.
2 Thus Limnaea involuta, which is almost universally regarded asa good and
distinct species, has been held to be no more than a variety of L. peregra produced

by locality ; see Zoologist, 1889, p. 154.

III EFFECTS OF CHANGES IN THE ENVIRONMENT 83

difference in the organisation of the animal (as distinct from that
of the shell alone) is necessary for the permanent constitution of
specific rank! What amount of structural difference is required.
what particular organ or organs must exhibit this difference, will
depend largely upon the idiosyncrasy of the observer. But if
this, or something like this definition of a species be accepted,
it will follow that a so-called ‘variety’ will be a form which
exhibits differences from the type which do not amount to per-
manent structural differences in the organisation of the animal.
The final court of appeal as to what affords sufficient evidence for
‘permanent structural differences’ will have to be, as with
Aristotle of old, the judgment of the educated man.

It is, however, more to our present purpose to discuss the
causes of variation than to lay down definitions of what variation
is. One of the most obvious causes of variation lies in a change
or changes in the environment. If we may assume, for the
moment, that the type form of a species is the form which is the
mean of all the extremes, and that this form is the resultant of
all the varied forces brought to bear upon it, whether of food,
climate, temperature, competition of numbers, soil, h¢ht, amount
of water, etc., it will follow that any change in one or more of
these forces, if continuous and considerable, any change, in other
words, of the environment, will produce its effect upon the
organism in question. And this effect will be for the better or
for the worse, according to the particular nature of the change
itself as tending towards, or away from, the optimum of environ-
ment for the species concerned. Hence may be produced varieties,
more or less marked according to the gravity of the change,
although it must be noted that at times a change apparently
unimportant from our point of view, will produce very marked
results upon the species. It is indeed scarcely possible to predict
with any certainty, in the present state of our knowledge (beyond
certain broad results) what will be the particular effect upon a
species of any given change in its surroundings.

Effects of Change in the Environment as tending to
produce Variation.

(a) Changes in Climate, Temperature, Elevation, ete—In the
eastern basin of the Baltic the marine Mollusca are much more

1 J. W. Taylor, Journ. of Conch. v. p. 289, an interesting article, with many
useful references.

84 EFFECTS OF CHANGES IN THE ENVIRONMENT CHAP.

stunted than in the western For instance, Mytilus edulis near
Kiel is 8—9 em. long, while near Gothland it only attains a
length of 3-4 cm. Mollusca living at only a shallow depth (e.g.
Tellina balthica, Mya arenaria, Cardium edule) do not differ
much in size in different parts of the Baltic, but in the far
eastern basin the calcareous layers of the shells of Mya arenaria
and Tellina balthica are extraordinarily thin, and disappear very
rapidly after death, leaving only the cuticular membrane, still
united by the ligament, in a perfect state of preservation. These
remarkable variations are no doubt to a large extent due to the
violent changes of temperature which are experienced in the
Baltic, and by which the steady development of the animals in
question is interrupted and thrown out of gear. The same species
occur on the coasts of Greenland and Iceland, where they attain
a considerably larger size than in the Baltic, in spite of the lower
mean temperature, probably because their development is not
interrupted by any sudden change from cold to heat or vice
versa.
Karl Semper has shown that Zimnaca stagnalis is developed,
lives and feeds best in a mean temperature of about 20° C.
= 68° F.). This mean, however, must not be the mean of two
distant extremes, for the Limnaea cannot digest its food and
grow in a temperature which is less than 14° or 15° C. (= 57° or
59° F.),-or more than 30° to 32° C.( = 86° to 90° F.). In certain
localities, therefore, the interruption to the growth of this species
must be serious and prolonged, and may tend towards the pro-
duction of more or less dwarfed varieties. Thus specimens from
Malham Tarn, a lake in Yorkshire 1250 feet above the sea, are
permanently dwarfed, and have a very thin and fragile shell.
Limnaea peregra in the Pyrenees, Alps, and Himalayas is
generally of a very delicate form and dwarfed habit, while the
small variety known as lacustris occurs, according to Jeffreys,
only in mountain lakes in Zetland, Scotland, Ireland, and N.
England. Specimens brought by Mr. Bateson from lakes near
the Sea of Aral, which are salt for some months and comparatively
fresh for others, exhibit clearly the effect of changes in the
environment (Figs. 33 and 34). Excess of heat produces similar
results to excess of cold. LZ. peregra var. thermalis, found in the
warm springs of the Pyrenees and the Vosges, and the var.

1 Mobius, Report on ‘Pommerania’ Exped. pp. 138-141.

ie ce

|
|
|
|

III VARIATION DUE TO HEAT AND COLD 85

geisericola, from the hot water of the Iceland geysers. are alike
thin and dwarfed forms.

Many instances may be given of ‘varieties due to locality.’
In some of these, the cause which predisposes towards variation
can be inferred with some approach to certainty, in others we
must be content to note the fact, without at present beimg able
to perceive its explanation.

Desert specimens of widely distributed species, e.g. Helix
pomatia, H. niciensis, H. pisana, Leucochroa candidissima are
much thicker than the type, and tend to lose all trace of
coloured bands. These modifications are clearly the means of
preventing evaporation of moisture, the dull white or grayish

Fic. 33.—Four examples of Lim-
naea peregra Miill., from salt
marshes near the Sea of Aral,
showing different effects produced
by abnormal conditions of life.

Fic. 34.—-Four examples of Lim-
naea stagnalis L., from marshes
in the Aral district which are salt
for several months in the year,
illustrating variation produced by
changes in the environment. x 3.

brown colour being calculated to absorb the smallest possible
amount of heat. Desert shells in all parts of the world (e.g. N.
Africa, Arabia, Central Asia, S. Africa, W. America) have been
noticed to exhibit these peculiarities.

A very singular case of the reverse process, 7.c. the production
of darkened forms of shell through cold, has been noticed by
Fischer as characteristic of the marine shells of the west coast
of South America This melanism is especially noticeable
in Trochus, Turbo, Chiton, Mitra, and Pleurotoma, and is attested
by the specific names, not merely expressive of actual blackness
(eg. nigerrimus, ater, atramentarius, maurus), but also of a
generally lugubrious tone (e.g. moestus, funebralis, tristis, lugubris,
luctuosus). It is highly probable that this concurrence of
specific melanism (which stands quite alone in the world) is

1 Journ. de Conchyl. xxiii. 1875, p. 105.

86 VARIATION IN SLUGS CHAP.

due to the cold polar current which impinges on the Chilian
coasts, for the same genera occur on the opposite shores of the
continent without exhibiting any trace whatever of this mournful
characteristic.

It is a well-known fact, attested by many observers, that our
common Limax agrestis as well as the young of Arion ater
become decidedly darker in summer than in winter. If these
slugs were accustomed to disport themselves in the sun, it might
have been suggested that this increased darkness of colour
tended to absorb more of the heat rays. But since this is not
the case, the result is probably due to some unexplained effect of
higher temperature. According to Lessona and Pollonera, the
length of the keel in Limawx arborum varies greatly in different
parts of Italy, being shorter in specimens from low ground, but
much longer in those inhabiting more elevated regions. The
longer the keel, the more obscure the colouring becomes, so that
in the Upper Alps of Piedmont individuals are practically black.
Roebuck has observed that Scottish specimens of this same
slug are much darker and less translucent than English forms.
According to Simroth, our common black slug, Arion ater, is a
northern type, which in more southern latitudes assumes the
form known as 4. rufus. Similarly Limax maximus “in its
northern form cinereo-niger is almost wholly black, but in
the more genial climate of Italy develops a series of brilliantly
coloured and strikingly marked variations which have received
numerous distinctive names from Italian limacologists.”! Ac-
cording to Scharff, however? (who regards the colours of slugs
as in the main protective), these dark forms are by no means
exclusively northern, being found equally on the parched plains
of Spain and Portugal, and in the bleak climate of Norway. The
same authority observes that similar forms occur both in the dry
regions of E. Germany, and in the very humid district of western
Treland.

It appears unquestionable that marine genera from high
northern latitudes are provided with shells of uniform colour, or
whitish with a pale brown epidermis; spots, bands, or stripes
seldom occur. The arctic forms of Buccinwm, Trophon, Chryso-
domus, Margarita, Crenella, Leda, Yoldia, Astarte illustrate this
fact. In the more temperate seas of Europe, colours tend on the

1 J. W. Taylor, wt sup. p. 200. 2 Sci. Trans. R. Dubl. Soc. (2) iv. p. 555.

M1 VARIATION IN SNAILS 87

whole to increase, although there are certain genera (e.g. Pecten)
which are not more brightly coloured in Mediterranean than in
Icelandic waters.

Land Mollusca inhabiting the mainland of a continent not
unfrequently become smaller when they have spread to adjacent
islands where perhaps the rainfall is less abundant or the soil
and food-supply less nicely adjusted to their wants. Orthalicus
undatus is decidedly larger on the mainland of S$. America than
on the adjacent islands of Trinidad and Grenada. Specimens
of Bulimulus exilis from Barbados are invariably broader and
more obese than those from §$. Thomas, while those from the
voleanic island of S. Lucia, where lime is deficient, are small and
very slender. Streptaxis deformis, as occurring at Trinidad, is
only half the size of specimens from Georgetown, Demerara.!

Certain localities appear, for some unexplained reason, to be
particularly favourable to the production of albino varieties. The
neighbourhood of Lewes, in Sussex, has produced no fewer than
fourteen of these forms of land Mollusca and five of fresh water.?

Our common feliz aspersa, as found near Bristol, is said to
be ‘dark coloured’; about Weston-super-mare brown, with black
markings’; near Bath ‘ very pale and much mottled’; at Cheddar
‘very solid and large.’? Sometimes the same kind of variation
is exhibited by different species in the same locality. Thus
specimens of HZ. aspersa, H. nemoralis, and H. hortensis, taken
from the same bank at Torquay, presented a straw-coloured tinge
of ground colour, with red-brown bands or markings. Trochi-
form H. nemoralis and H. arbustorum, sinistral H. hortensis and
Hf, aspersa, sinistral H. aspersa and H. virgata, and similarly
banded forms of AH. caperata and H. virgata, have been taken
together.*

The immediate neighbourhood of the sea appears frequently
to have the effect of dwarfing land Mollusca. Thus the var.
conoidea of Helix aspersa, which is small, conical, with a com-
pressed mouth, occurs ‘on sandhills and cliffs at the seaside.’
The varieties conica and nana of Helix hispida are found ‘ near
the sea.” Helix virgata is exceedingly small in similar localities,
and tends to become unicoloured. HH. caperata var. Gigaxit, a

1 J. S. Gibbons, Journ. of Conch. ii. p. 129.

2 C. H. Morris, zbid. vii. p. 191. 3 ¥. M. Hele, zbid. iv. p. 93.
4T, D. A. Cockerell, Science Gossip, 1887, p. 67.

88 VARIATION IN SNAILS CHAP.

small depressed form, occurs at ‘Sandwich and Falmouth.’
Sometimes, however, the exact opposite is the case, for H.
nemoralis var. major, which is ‘much larger’ than the type,
occurs on ‘sandhills and downs’ and is ‘remarkably large in the
I. of Arran, Co. Galway.’ The dwarf form of Limnaea peregra
known as maritima appears to be confined to the neighbourhood
of the sea.

Dwarfing of the shell seems frequently to be the result of an
elevated locality, not perhaps so much as the direct consequence
of purer air and less barometric pressure, as of changes in the
character of the food supply and in the humidity of the air.
Several species of Helia have a variety minor which is charac-
teristic of an Alpine habitat. Helix arbustorum var. alpestris,
which is scarcely two-thirds the size of the type, occurs on the
Swiss Alps in the region of perpetual snow. Sometimes a very
slight elevation is sufficient to produce the dwarfed form. At
Tenby the type form of Helix pisana is scattered in countless
numbers over the sandhills just above high-water mark. At the
extreme western end of these sandhills rises abruptly to a
height of over 100 feet the promontory known as Giltar Head,
the vegetation of which is entirely distinct from that of the
burrows below. There is a colony of Hf. pisana at the end of
Giltar, all of which are devoid of the characteristic markings of
the typical form, and most are dwarfed and stunted in growth.

Occasionally the same variety will be found to be produced
by surroundings of very different nature. Thus the var. alpestris
of H. arbustorum mentioned above, besides being characteristic
of high Alpine localities, also occurs abundantly in low marshes
at Hoddesdon on the River Lea. Helix pulchella var. costata, ac-
cording to Jeffreys, is found in dry and sandy places, often under
loose stones and bricks on walls, while other authorities have
noticed it in wet and dry localities quite indifferently.

Sometimes the production of a variety may be traced to the
intrusion of some other organism. According to Brot, nine-
tenths of the Zimnaea peregra inhabiting a certain pond near
Geneva, were, during one season, afflicted with a malformation
of the base of the columella. This deformity coincided with the
appearance, in the same waters, of extraordinary numbers of
Hydra viridis. The next season, when the Hydra disappeared,

1 J. G. Jeffreys, British Conchology, vol. i. p. 214.

III VARIATION IN SNAILS 89

the next generation of Limnaea was found to have resumed its
normal form.

It has been noticed that a form of Helix caperata with a
flattened spire and wide umbilicus is restricted to tilled fields,
especially the borders of clover fields, while a form with a more
elevated spire and more compact whorls occurs exclusively in
open downs and uncultivated places. The Rev. S. 8. Pearce
accounts + for this divergence by the explanation that the flatter
spire enables the shell of the fields to creep about more easily
under the leaves or matted weeds, seldom requiring to crawl up
a stalk or stem, while on the short turf of the downs and
pastures the smaller and more rounded shell enables the animal
to manoeuvre in and out of the blades of grass, and even to
crawl up them with considerable activity. The same writer
endeavours to explain the causes which regulate the distribution
of H. caperata var. ornata. Ue found that this variety (dark
bands on a white ground) occurred almost exclusively on downs
which were fed upon by sheep, associated with the common or
mottled form, while the latter form alone occurred in localities
where sheep were not accustomed to feed. Assuming then, as
is probably the case, that sheep, in the course of their close
pasturing, devour many small snails, he believes that individuals
of the more conspicuous form ornata were more likely to be
noticed, and therefore avoided, by the sheep, than the mottled
form, which would more easily escape their observation. Hence
the var. ornata is due to the advantage which strikingly coloured
individuals obtained owing to their conspicuous habit, as com-
pared with the typical form, which would be less readily
detected.

(b) Changes in Soil, Station, Character of Water, ete—A de-
ficiency of lime in the composition of the soil of any particular
locality produces very marked effects upon the shells of the
Mollusca which inhabit it; they become small and very thin,
occasionally almost transparent. The well-known var. tenuis of
Helix aspersa occurs on downs in the Channel Islands where
calcareous material is scarce. For similar reasons, H. arbustoruwm
develops a var. fusca, which is depressed, very thin, and trans-
parent, at Scilly, and also at Lunna I., E. Zetland.

The common dog-whelk (Purpura lapillus) of our own coasts

1 Journ. of Conch. vi. p. 128.

=X

i

(i

EY

Fic. 35.—19 specimens of Purpura lapillus L., Great Britain, illustrating variation.

(1) Felixstowe, sheltered coast; (2), (83) Newquay, on veined and coloured rock; (4), Herm,
rather exposed ; (5), Solent, very sheltered ; (6), Land’s End, exposed rocks, small food supply ;
(7) Scilly, exposed rocks, fair food supply; (8) St. Leonards, flat mussel beds at extreme low water ;
(9) Robin Hood's Bay, sheltered under boulders, good food supply; (10) Rhoscollyn, on oyster bed,
4-7 fath. (Macandrew); (11) Guernsey, rather exposed rocks ; (12) Estuary of Conway, very shel-
tered, abundant food supply ; (13), (14) Robin Hood’s Bay, very exposed rocks, poor food supply,
(14) slightly monstrous ; (15), (16), (17), Morthoe, rather exposed rocks, but abundant food supply ;
(8) St. Bride’s Bay; (19) L. Swilly, sheltered, but small food supply. All from the author's collec-

tion, except (10).

III VARIATION OF PURPURA LAPILLUS gI

is an exceedingly variable species, and in many cases. the
variations may be shown to bear a direct relation to the manner
of life (Fig. 35). Forms occurring in very exposed situations,
eg. Land’s End, outer rocks of the Scilly Is., coasts of N. Devon
and Yorkshire, are stunted, with a short spire and _ relatively
large mouth, the latter being developed in order to increase the
power of adherence to the rock and consequently of resistance
to wave force. On the other hand, shells occurring in sheltered
situations, estuaries, narrow straits, or even on open coasts where
there is plenty of shelter from the waves, are comparatively of
ereat size, with a well-developed, sometimes produced spire, and
a mouth small in proportion to the area of shell surface. In the
accompanying figure, the specimens from the Conway estuary and
the Solent (12, 5) well illustrate this latter form of shell, while that
from exposed rocks is illustrated by the specimens from Robin
Hood’s Bay (15, 14). Had these specimens occurred alone, or had
they been brought from some distant and unexplored region,
they must inevitably have been described as two distinct species.

Mr. W. Bateson has made! some observations on the shells
of Cardium edule taken from a series of terraces on the border

Fic. 36.—Valves of Cardium edule from the four upper terraces of Shumish Kul, a dry
salt lake adjacent to the Aral Sea. (After Bateson.)

of certain salt lakes which once formed a portion of the Sea of
Aral. As these lakes gradually became dry, the water they
contained became salter, and thus the successive layers of dead
shells deposited on their borders form an interesting record of
the progressive variation of this species under conditions which,
in one respect at least, can be clearly appreciated. At the same
time the diminishing volume of water, and the increasing average
temperature, would not be without their effect. It was found

1 Phil. Trans. 1889, vol. 180 B, p. 297. A somewhat similar case (the celebrated

teinheim series of Planorbis) is dealt with by Hilgendorf, IB. Akad. Berl. 1866,
p. 4743 and Hyatt, Proc. Amer. Ass. Sc. xxix. p. 527.

92 VARIATION IN UNIO AND ANODONTA CHAP.

that the principal changes were as follows: the thickness, and
consequently the weight, of the shells became diminished, the
size of the beaks was reduced, the shell became highly coloured,
and diminished considerably in size, and the breadth of the shells
increased in proportion to their length (Fig. 36). Shells of
the same species of Cardium, occurring in Lake Mareotis, were
found to exhibit very similar variations as regards colour, size,
shape, and thickness.

Unio pictorum var. compressa occurs near Norwich at two
similar localities six or seven miles distant from one another,
under circumstances which tend to show that similar conditions
have produced similar results. The form occurs where the river,
by bending sharply in horse-shoe shape, causes the current to
rush across to the opposite side and form an eddy near the bank
on the outside of the bend. Just at the edge of the sharp
current next the eddy the shells are found, the peculiar form
being probably due to the current continually washing away the
soft particles of mud and compelling the shell to elongate itself
in order to keep partly buried at the bottom.!

The rivers Ouse and Foss, which unite just below York, are
rivers of strikingly different character, the Ouse being deep,
rapid, with a bare, stony bottom, and little vegetable growth,
and receiving a good deal of drainage, while the Foss is shallow,
slow, muddy, full of weeds and with very little drainage. In
the Foss, fine specimens of Anodonta anatina occur, lustrous,
with beautifully rayed shells. A few yards off, in the Ouse, the
same species of Anodonta is dull brown in colour, its interior
clouded, the beaks and epidermis often deeply eroded. Precisely
the same contrast is shown in specimens of Unio tumidus, taken
from the same rivers, Ouse specimens being also slightly curved
in form. Just above Yearsley Lock in the Foss, Unio tumidus
occurs, but always dwarfed and malformed, a result probably due
to the effect of rapidly running water upon a species accustomed
to live in still water.2 Simroth records the occurrence of remark-
ably distorted varieties in two species of Aetheria which lived in
swift falls of the River Congo.®

A variety of Limnaea peregra with a short spire and rather
strong, stoutly built shell occurs in Lakes Windermere, Derwent-

1 J. B. Bridgman, Quart. Jowrn. Conch. i. p. 70.
2 W. C. Hey, Journ. of Conch. iii. p. 268. 3 Zool. Anz. xiii. p. 662.

Ill VARIATION IN LITTORINA 93

water, and Llyn-y-van-fach. It lives adhering to stones in places
where there are very few weeds, its shape enabling it to with-
stand the surf of these large lakes, to which the ordinary form
would probably succumb.1

Scalariform specimens of Planorbis are said to occur most
commonly in waters which are choked by vegetation, and it has
been shown that this form of shell is able to make its way
through masses of dense weed much more readily than specimens
of normal shape.

Continental authorities have long considered Limnaea peregra
and J. ovata as two distinct species. Hazay, however, has
succeeded in rearing specimens of so-called peregra from the ova
of ovata, and so-called ovata from the ova of peregra, simply by
placing one species in running water, and the other in still
water.

According to Mr. J. 8. Gibbons? certain species of Littorina,
in tropical and subtropical regions, are confined to water more
or less brackish, being incapable of living in pure salt water.
“JT have met,” says Mr. Gibbons, “with three of these species,
and in each case they have been distinguished from the truly
marine species by the extreme (comparative) thinness of their
shells, and by their colouring being richer and more varied ;
they are also usually more elaborately marked. They are to be
met with under three different conditions—(1) in harbours and
bays where the water is salt with but a shght admixture of fresh
water; (2) in mangrove swamps where salt and fresh water mix
in pretty equal volume; (3) on dry land, but near a marsh or
the dry bed of one.

“LI. intermedia Reeve, a widely diffused E. African shell,
attaches itself by a thin pellicle of dried mucus to grass growing
by the margin of slightly brackish marshes near the coast, re-
sembling in its mode of suspension the Old World Cyclostoma.
I have found it in vast numbers in situations where, during the
greater part of the year, it is exposed to the full glare of an
almost vertical sun, its only source of moisture being a slight
dew at night-time. The W. Indian ZL. angulifera Lam., and a
beautifully coloured E. African species (? LZ. carinifera), are found
in mangrove swamps; they are, however, less independent of salt
water than the last.”

1 J. Madison, Jowrn. of Conch. v. p. 260. 2 Quart. Journ. Conch. i. 339.

94 EFFECT OF VOLUME OF WATER CHAP,

Mr. Gibbons goes on to note that brackish water species
(although not so solid as truly marine species) tend to become
more solid as the water they inhabit becomes less salt. This
is a curious fact, and the reverse of what one would expect.
Specimens of ZL. intermedia on stakes at the mouth of the
Lorenco Marques River, Delagoa Bay, are much smaller, darker,
and more fragile, than those living on grass a few hundred
yards away. JL. angulifera is unusually solid and heavy at
Puerto Plata (S. Domingo) among mangroves, where the water
is in a great measure fresh; at Havana and at Colon, where it
lives on stakes in water but slightly brackish, it is thinner and
smaller and also darker coloured.

(c) Changes in the Volume of Water.—It has long been known
that the largest specimens, e.g. of Limnaea stagnalis and Anodonta
anatina, only occurred in pieces of water of considerable size.
Recent observation, however, has shown conclusively that the
volume of water in which certain species live has a very close
relation to the actual size of their shells, besides producing other
effects. Limnaea megasoma, when kept in an aquarium of
limited size, deposited eggs which hatched out; this process was
continued in the same aquarium for four generations in all, the
form of the shell of the last generation having become such
that an experienced conchologist gave it as his opinion that the
first and last terms of the series could have no possible specific
relation to one another. The size of the shell became greatly
diminished, and in particular the spire became very slender.

The same species being again kept in an aquarium under
similar conditions, it was found that the third generation had a
shell only four-sevenths the length of their great grandparents.
It was noticed also that the sexual capacities of the animals
changed as well. The liver was greatly reduced, and the male
organs were entirely lost.”

K. Semper conducted some well-known experiments bearing
on this point. He separated® specimens of Limnaea stagnalis
from the same mass of eggs as soon as they were hatched, and
placed them simultaneously in bodies of water varying in volume
from 100 to 2000 cubic centimetres. All the other conditions
of life, and especially the food supply, were kept at the known

1 Whitfield, Bull. Amer. Mus. N. H. 1. p. 29.
2 Amer. Nat. xiv. p. 51. 3 Animal Life, Ed. 1, p. 160 f.
I p

III EFFECT OF VOLUME OF WATER 95

optimum. He found, in the result, that the size of the shell
varied directly in proportion to the volume of the water in which
it lived, and that this was the case, whether an individual speci-
men was kept alone in a given quantity of water, or shared it
with several others. At the close of 65 days the specimens

raised in 100 cubic cm. of water were only
6 mm. long, those in 250 cubic cm. were
9mm. long, those in 600 cubic cm. were (3
12 mm. long, while those kept in 2000
A B c D

cubic cm. attained a length of 18 mm.
Bie, Si():
( ‘Si ) ; Fic. 87.—Four equally old
An interesting effect of a sudden fall © shells of Limnaea stagna-
of temperature was noticed by Semper in “> hatched from the same
- ‘ : mass of ova, but reared
connection with the above experiments. in different volumes of
Ti 3 : Soa ar avaya water: A in 100, B in
SSels S c s1zZe 2ON tal & specl- y= 5 2 =
Vessels ot unequal size, containing speCl- 959 "q in 600, and D in
mens of the Limnaea, happened to stand 2000 cubic centimetres.
before a window at a time when the tem- ‘Aer . Semper.)
perature suddenly fell to about 55° F. The sun, which shone
through the window, warmed the water in the smaller vessels,
but had no effect upon the temperature of the larger. The
result was, that the Zimnaea in 2000 cubic cm., which ought
to have been 10 mm. long when 25 days old, were scarcely
longer, at the end of that period, than those which had lived in
the smaller vessels, but whose water had been sufficiently warm.

CHAPTER: IV

USES OF SHELLS FOR MONEY, ORNAMENT, AND FOOD——CULTIVATION
OF THE OYSTER, MUSSEL, AND SNAIL——-SNAILS AS MEDICINE
—PRICES GIVEN FOR SHELLS

THE employment of shells as a medium of exchange was
exceedingly common amongst uncivilised tribes in all parts of
the world, and has by no means yet become obsolete. One of
the commonest species thus employed is the ‘money cowry’
(Cypraea moneta, L.), which stands almost alone in being used
entire, while nearly all the other forms of shell money are made
out of portions of shells, thus requiring a certain amount of
labour in the process of formation.

One of the earliest mentions of the cowry as money occurs
in an ancient Hindoo treatise on mathematics, written in the
seventh century A.D. A question is propounded thus: ‘the + of +4,
of 4 of # of 2 of $a dramma was given to a beggar by one from
whom he asked an alms; tell me how many cowry shells the miser
gave. In British India about 4000 are said to have passed
for a shilling, but the value appears to differ according to their
condition, poor specimens being comparatively worthless. Accord-
ing to Reeve! a gentleman residing at Cuttack is said to have paid
for the erection of his bungalow entirely in cowries. The building
cost him 4000 Rs. sicca (about £400), and as 64 cowries = 1 pice,
and 64 pice = 1 rupee sicea, he paid over 16,000,000 cowries in all.

Cowries are imported to England from India and other places
for the purposes of exportation to West Africa, to be exchanged
for native products. The trade, however, appears to be greatly
on the decrease. At the port of Lagos, in 1870, 50,000 cwts.
of cowries were imported.”

1 Conch. Syst. il. p. 262 n.
2 P. L. Simmonds, Commercial Products of the Sea, p. 278.

CHAP. 1V SHELLS AS MONEY—WAMPUM 97

A banded form of Nerita polita was used as money in certain
parts of the South Pacific. The sandal-wood imported into the
China market is largely obtained from the New Hebrides, being
purchased of the natives in exchange for Ovulum angulosum,
which they especially esteem as an ornament. Sometimes, as
in the Duke cf York group, the use of shell money is specially
restricted to certain kinds of purchase, being employed there
only in the buying of swine.

Among the tribes of the North-West coasts of America the
common Dentalium indianorum used to form the standard of
value, until it was superseded, under the auspices of the Hudson’s
Bay Company, by blankets. A slave was valued at a fathom of
from 25 to 40 of these shells, strung lengthwise. Inferior or
broken specimens were strung together in a similar way, but
were less highly esteemed; they corresponded more to our
silver and copper coins, while the strings of the best shells
represented gold. .

The wampum of the eastern coast of North America differed
from all these forms of shell money, in that it required a laborious
process for its manufacture. Wampum consisted of strings of
cylindrical beads, each about a quarter of an inch in length and
half that breadth. The beads were of two colours, white and
purple, the latter being the more valuable. Both were formed
from the common clam, Venus mercenaria, the valves of which
are often stained with purple at the lower margins, while the
rest of the shell is white. Cut small, ground down, and pierced,
these shells were converted into money, which appears to have
been current along the whole seaboard of North America from
Maine to Florida, and on the Gulf Coast as far as Central
America, as well as among the inland tribes east of the
Mississippi. Another kind of wampum was made from the
shells of Busycon carica and B. perversum. By staining the
Wampum with various colours, and disposing these colours in
belts im various forms of arrangement, the Indians were able to
preserve records, send messages, and keep account of any kind of
event, treaty, or transaction.

Another common form of money in California was Olivella
biplicata, strung together by rubbing down the apex. Button-
shaped disks cut from Sawzidomus arata and Pachydesma
crassatelloides, as well as oblong pieces of Haliotis, were em-

VOL. III . H

98 SHELLS AS ORNAMENTS CHAP.

ployed for the same purpose, when strung together in lengths of
several yards.

“There is a curious old custom,’ writes Mr. W. Anderson
Smith, “that used formerly to be in use in this locality [the
western coast of Scotland], and no doubt was generally em-
ployed along the seaboard, as the most simple and ready means
of arrangement of bargains by a non-writing population. That
was, when a bargain was made, each party to the transaction
got one half of a bivalve shell—such as mussel, cockle, or oyster—
and when the bargain was implemented, the half that fitted
exactly was delivered up as a receipt! Thus a man who had a
box full of unfitted shells might be either a creditor or a debtor ;
but the box filled with fitted shells represented receipted accounts.
Those who know the difficulty of fitting the valves of some classes
of bivalves will readily acknowledge the value of this arrangement.”

Shells are employed for use and for ornament by savage—
and even by civilised—tribes in all parts of the world. The
natives of Fiji thread the large Turbo argyrostoma and crenulatus
as weights at the edge of their nets, and also employ them as
sinkers. <A Cypraea tigris cut into two halves and placed round
a stone, with two or three showy Oliva at the sides, is used as a
bait for cuttles. Avicula margaritifera is cut into scrapers and
knives by this and several other tribes. Breast ornaments of
Chama, grouped with Solarium perspectivum and Terebra dupli-
cata are common among the Fijians, who also mount the Avicula
on a backing of whales’ teeth sawn in two, for the same purpose.
The great Orange Cowry (Cypraca aurantiaca) 1s used as a
badge of high rank among the chieftains. One of the most
remarkable Fijian industries is the working of whales’ teeth to
represent this cowry, as well as the commoner C. talpa, which is
more easily imitated.

Among the Solomon islanders, cowries are used to ornament
their shields on great field days, and split cowries are worn as
a necklace, to represent human teeth. Small bunches of Zere-
bellum subulatum are worn as earrings, and a large valve of
Avicula is employed as a head ornament in the centre of a
fillet. The same islanders ornament the raised prows of their
canoes, as well as the inside of the stern-post, with a long row of
single Natiea.

1 Benderloch, p. 118.

IV SHELLS AS ORNAMENTS 99

The native Papuans employ shells for an immense variety of
purposes. Circlets for the head are formed of rows of Nassa
gibbosula, rubbed down till little but the mouth remains.
Necklaces are worn which consist of strings of Oliva, young
Avicula, Natica melanostoma, opercula of Zurbo, and valves of
a rich brown species of Cardiwm, pendent at the end of strings
of the seeds known as Job’s tears. Struthiolaria is rubbed
down until nothing but the mouth is left, and worn in strings
round the neck. ‘This is remarkable, since Struthiolaria is not
a native Papuan shell, and indeed occurs no nearer than New
Zealand. Sections of JZelo are also worn as a breast ornament,
dependent from a necklace of cornelian stones. Cypraea erosa
is used to ornament drinking bowls, and Ovulum ovum is
attached to the native drums, at the base of a bunch of casso-
wary feathers, as well as being fastened to the handle of a
sago-beater.

In the same island, the great Zurbo and Conus millepunctatus
are ground down to form bracelets, which are worn on the
biceps. The crimson lip of Strombus luhuanus is cut into beads
and perforated for necklaces. Village elders are distinguished
by a single Ovulum verrucosum, worn in the centre of the fore-
head. The thick lip of Cassis cornuta is ground down to form
nose pieces, 44 inches long. Fragments of a shell called Kaima
(probably valves of a large Spondylus) are worn suspended from
the ears, with little wisps of hair twisted up and thrust through
a hole in the centre. For trumpets, Cassis cornuta, Triton
tritonis, and Ranella lampas are used, with a hole drilled as a
mouthpiece in one of the upper whorls. Valves of SBatissa,
Unio, and Mytilus are used as knives for peeling yams. Spoons
for scooping the white from the cocoa-nut are made from
Avicula margaritifera. Melo diadema is used as a baler in the
canoes.!

In the Sandwich Islands Melampus luteus is worn as a
necklace, as well as in the Navigator Islands. A very striking
necklace, in the latter group, is formed of the apices of a
Nautilus, rubbed down to show the nacre. The New Zealanders
use the green opercula of a Turbo, a small species of Venus, and
Cypraea asellus to form the eyes of their idols. Fish-hooks are
made throughout the Pacific of the shells of Avieula and

1 C. Hedley in J. P. Thomson, Brit. New Guinea, p. 283.

100 SHELLS AS ORNAMENTS—AS SYMBOLS OF WORSHIP cn.

Haliotis, and are sometimes strengthened by a backing made of
the columella of Cypraea arabica. Small axe-heads are made
from Zerebra crenulata ground down (Woodlark I.), and larger
forms are fashioned from the giant Zridacna (Fiji).

Shells are used to ornament the elaborate cloaks worn by the
women of rank in the Indian tribes of South America. Speci-
mens of Ampullaria, Orthalicus, Labyrinthus, and Bulimulus
depend from the bottom and back of these garments, while great
Bulimi, 6 inches long, are worn as a breast ornament, and at the
end of a string of beads and teeth.!

The chank-shell (Zurbinella rapa) is of especial interest from
its connexion with the religion of the Hindoos. The god
Vishnu is represented as holding this shell in his hand, and the
sinistral form of it, which is excessively rare, is regarded with
extraordinary veneration. The chank appears as a symbol on
the coins of some of the ancient Indian Empires, and is still
retained on the coinage of the Rajah of Travancore.

The chief fishery of the chank-shell is at Tuticorin, on the
Gulf of Manaar, and is conducted during the N.E. monsoon,
October-—May. In 1885-86 as many as 332,000 specimens
were obtained, the net amount realised being nearly Rs.24,000.
In former days the trade was much more lucrative, 4 or 5
millions of specimens being frequently shipped. The govern-
ment of Ceylon used to receive £4000 a year for licenses to
fish, but now the trade is free. The shells are brought up by
divers from 2 or 3 fathoms of water. In 1887 a sinistral
specimen was found at Jaffna, which sold for Rs.700.2 Nearly
all the shells are sent to Dacca, where they are sliced into
bangles and anklets to be worn by the Hindoo women.

Perhaps the most important industry which deals only with
the shells of Mollusca is that connected with the ‘ pearl-oyster.’
The history of the trade forms a small literature in itself. It
must be suflicient here to note that the species in question is
not an ‘oyster, properly so called, but an Avicula (margaritifera
Lam.). The ‘mother-of-pearl? which is extensively employed
for the manufacture of buttons, studs, knife-handles, fans, card-
cases, brooches, boxes, and every kind of inlaid work, is the

1 Most of the above facts are derived from a study of a collection of native
implements, weapons, ornaments, ete., in the Antiquarian Museum at Cambridge.
2 Thurston, Votes on the Pearl and Chank Fisheries, Madras, 1890.

IV PEARL FISHERIES IOI

internal nacreous laminae of the shell of this species. The most
important fisheries are those of the Aru Islands, the Soo-loo
Archipelago, the Persian Gulf, the Red Sea, Queensland, and the
Pearl Islands in the Bay of Panama. The shell also occurs in
several of the groups of the South Pacific—the Paumotu,
Gambier and Navigator Islands, Tahiti being the centre of the
trade—and also on the coasts of Lower California.

Pearls are the result of a disease in the animal of this species
of Avicuwla and probably in all other species within which they
occur. When the Avicula is large, well formed, and with
ample space for individual development, pearls scarcely occur
at all, but when the shells are crowded together, and become
humped and distorted, as well as affording cover for all kinds of
marine worms and parasitic creatures, then pearls are sure to be
found. Pearls of inferior value and size are also produced by
Placuna placenta, many species of Pinna, the great Tridacna,
the common Ostrea edulis, and several other marine bivalves.
They are not uncommon in Unio and Anodonta, and the common
Margaritana margaritifera of our rapid streams is still said to
be collected, in some parts of Wales, for the purpose of ex-
tracting its small ‘seed-pearls.’ Pink pearls are obtained from
the giant conch-shell of the West Indies (Strombus gigas), as
well as from certain Zurbinella.

In Canton, many houses are illuminated almost entirely by
skylights and windows made of shells, probably the semi-
transparent valves of Placuna placenta. In China lime is
commonly made of ground cockle-shells, and, when mixed with
oil, forms an excellent putty, used for cementing coffins, and in
forming a surface for the frescoes with which the gables of
temples and private houses are adorned. Those who suffer from
cutaneous diseases, and convalescents from small-pox, are washed
in Canton with the water in which cockles have been boiled.?

A recent issue of the Peking Gazette contains a report from
the outgoing Viceroy of Fukhien, stating that he had handed over
the insignia of office to his successor, including inter alia the
conch-shell bestowed by the Throne. A conch-shell with a
whorl turning to the right, i.e. a sinistral specimen, is supposed
when blown to have the effect of stilling the waves, and hence is

1 See in particular, P. L. Simmonds, Zhe Commercial Products of the Sea.
2-H. Friend, Field Club, iv. 1893, p. 100.

102 VARIOUS USES OF SHELLS CHAP.

bestowed by the Emperor upon high officers whose duties oblige
them to take voyages by sea. The Viceroy of Fukhien probably
possesses one of these shells in virtue of his jurisdiction over
Formosa, to which island periodical visits are supposed to be
made.?

Shells appear to be used occasionally by other species besides
man. Oyster-catchers at breeding time prepare a number of
imitation nests in the gravel on the spit of land where they
build, putting bits of white shell in them to represent eggs.’
This looks like a trick in order to conceal the position of the
true nest. According to Nordenskjold, when the eider duck of
Spitzbergen has only one or two eggs in its nest, it places a shell
of Buccinum glaciale beside them. The appropriation of old
shells by hermit-crabs is a familiar sight all over the world.
Perhaps it is most striking in the tropics, where it is really
startling, at first experience, to meet—as I have done—a_ large
Cassis or Turbo, walking about in a wood or on a hill side at
considerable distances from the sea. A Gephyrean (Phascolion
strombi) habitually establishes itself in the discarded shells of
marine Mollusca. Certain Hymenoptera make use of dead shells
of Helix hortensis in which they build their cells*® Magnus
believes that in times when heavy rains prevail, and the usual
insects do not venture out, certain flowers are fertilised by snails
and slugs crawling over them, eg. Leucanthemum vulgare by
Limaz laevis.*

Mollusca as Food for Man.—Probably there are few countries
in the world in which less use is made of the Mollusca as a form
of food than in our own. There are scarcely ten native species
which can be said to be at all commonly employed for this
purpose. Neighbouring countries show us an example in this
respect. The French, Italians, and Spanish eat Natica, Turbo,
Triton, and Murex, and, among bivalves, Donax, Venus, Lithodomus,
Pholas, Tapes, and Cardita, as well as the smaller Cephalopoda.
Under the general designation of clam the Americans eat Venus
mercenaria, Mya arenaria, and Mactra solidissima. In the Suez
markets are exposed for sale Strombus and Melongena, Avicula
and Cytherea. At Panama Donax and Solen are delicacies, while ©

1 Nature, xxxi. 1885, p. 492.
2 W. Anderson Smith, Benderloch, p. 173.
3 Dominique, Feuill. Nat. xviil.p. 22. 4 SB. Nat. Fr. Berl. 1889, p. 197.

IV MOLLUSCA AS FOOD FOR MAN 103.

the natives also eat the great Murex and Pyrula, and even the
huge Area grandis, which lives embedded in the liquid river mud.

The common littoral bivalves seem to be eaten in nearly all
countries except our own, and it is therefore needless to enume-
rate them. The Gasteropoda, whose habits are scarcely so:
cleanly, seem to require a bolder spirit and less delicate palate to
venture on their consumption.

The Malays of the East Indian islands eat Telescopiwm
fuscum and Pyrazus palustris, which abound in the mangrove
swamps. They throw them on their wood fires, and when they
are sufficiently cooked, break off the top of the spire and suck
the animal out through the opening. Haliotis they take out of
the shell, string together, and dry in the sun. The lower classes
in the Philippines eat Arca inaequivalvis, boiling them as
we do mussels.t In the Corean islands a species of Monodonta
and another of Mytilus are quite peppery, and bite the tongue ;
our own Helix revelata, as I can vouch from personal experience,
has a similar flavour. usus colosseus, Rapana bezoar, and
Purpura luteostoma are eaten on the southern coasts of China;
Strombus luhuanus, Turbo chrysostomus, Trochus niloticus, and
Patella testudinaria, by the natives of New Caledonia; Strombus
gigas and Livona pica in the West Indies; Zurbo niger and
Concholepas peruvianus on the Chilian coasts; four species of
Strombus and Nerita, one each of Purpura and Turbo, besides
two Zridacna and one Hippopus, by the natives of British New
Guinea. West Indian negroes eat the large Chitons which are
abundant on their rocky coasts, cutting off and swallowing raw
the fleshy foot, which they call ‘beef, and rejecting the viscera.
Dried cephalopods are a favourite Chinese dish, and are regu-
larly exported to San Francisco, where the Chinamen make them
into soup. The ‘Challenger’ obtained two species of Sepia and
two of Loligo from the market at Yokohama.

The insipidity of fresh-water Mollusca renders them much
less desirable as a form of food. Some species of Unionidae,
however, are said to be eaten in France. Anodonta edulis is
specially cultivated for food in certain districts of China, and
the African Aetheriae are eaten by negroes. Navicella and
Neritina are eaten in Mauritius, Ampullaria and Neritina in
Guadeloupe, and Paludina in Cambodia.

1 A, Adams, Voyage of the ‘ Samarang,’ ii. p. 308.

104 OYSTERS UNDER THE ROMANS CHAP.

The vast heaps of empty shells known as ‘kitchen-middens,’
occur in almost every part of the world. They are found in
Scotland, Denmark, the east and west coasts of North America,
Brazil, Tierra del Fuego, Australia and New Zealand, and are
sometimes several hundred yards in length. They are invariably
composed of the edible shells of the adjacent coast, mixed with
bones of Mammals, birds, and fish. From their great size, it
is believed that many of them must have taken centuries to
form. :

Pre-eminent among existing shell-fish industries stands the
cultivation of the oyster and the mussel, a more detailed account
of which may prove interesting.

The cultivation of the oyster! as a luxury of food dates at
least from the gastronomic age of Rome. Every one has heard.
of the epicure whose taste was so educated that

“he could tell
At the first mouthful, if his oysters fed
On the Rutupian or the Lucrine bed
Or at Circeii.”?

The first artificial oyster-cultivator on a large scale appears
to have been a certain Roman named Sergius Orata, who lived
about a century B.c. His object, according to Pliny the elder,’
was not to please his own appetite so much as to make money
by ministering to the appetites of others. His vivaria were
situated on the Lucrine Lake, near Baiae, and the Lucrine
oysters obtained under his cultivation a notoriety which they
never entirely lost, although British oysters eventually came to
be more highly esteemed. He must have been a great enthusiast
in his trade, for on one occasion when he became involved in a
law-suit with one of the riparian proprietors, his counsel declared
that Orata’s opponent made a great mistake if he expected to
damp his ardour by expelling him from the lake, for, sooner
than not grow oysters at all, he would grow them upon the roof
of his house. Orata’s successors in the business seem to have
understood the secret of planting young oysters in new beds, for

1 Much information has been derived, on this subject, from Bertram’s Harvest
of the Sea, Simmonds’ Commercial Products of the Sea, the publications of the
Fisheries Exhibition, especially vol. xi. (Anson and Willett) ; see also Philpots,
Oysters and all about them.

2 Juvenal, Sat. iv. 140-142. 2) Hist, WNataixs (9. 1th AGHA, ie, 3

IV OYSTERS UNDER THE ROMANS 105

we are told that specimens brought from Brundisium and even
from Britain were placed for a while in the Lucrine lake, to
fatten after their long journey, and also to acquire the esteemed
“ Lucrine flavour.”

Oysters are ‘in season’ whenever there is an ‘r’ in the
month, in other words, from September to April. ‘ Mensibus
erratis, as the poet has it, ‘vos ostrea manducatis!’ It has
been computed that the quantity annually produced in Great
Britain amounts to no less than sixteen hundred million, while
in America the number is estimated at five thousand five
hundred million, the value being over thirteen million dollars,
and the number of persons employed fifty thousand. Arcachon,
one of the principal French oyster-parks, has nearly 10,000 acres
of oyster beds, the annual value being from eight to ten million
franes; in 1884—85, 178,359,000 oysters were exported from this
place alone. In the season 1889-90, 50,000 tons of oysters
were consumed in London.

Few will now be found to echo the poet Gay’s opinion:

“That man had sure a palate covered o’er
With brass or steel, that on the rocky shore

First broke the oozy oyster’s pearly coat,
And risq’d the living morsel down his throat.”

There were haleyon days in England once, when oysters
were to be procured at 8d. the bushel. Now it costs exactly
that amount before a bushel, brought up the Thames, can even
be exposed for sale at Billingsgate (4d. porterage, 4d. market
toll), and prime Whitstable natives average from 33d. to 4d.
each. The principal causes of this rise in prices, apart from the
increased demand, are (1) over-dredging, (2) ignorant cultiva-
tion, and to these may be added (3) the effect of bad seasons in
destroying young oysters, or preventing the spat from maturing.
Our own principal beds are those at Whitstable, Rochester,
Colchester, Milton (famous for its ‘melting’ natives), Faversham,
Queenborough, Burnham, Poole, and Carlingford in Co. Down,
and Newhaven, near Edinburgh.

The oyster-farms at Whitstable, public and private, extend
over an area of more than 27 square miles. The principal of
these is a kind of joint-stock company, with no other privilege of
entrance except birth as a free dredgeman of the town. When
a holder dies, his interest dies with him. Twelve directors,

106 CULTIVATION OF THE OYSTER IN BRITISH ISLANDS cu.

known as “the Jury,” manage the affairs of the company, which
finds employment for several thousand people, and sometimes
turns over as much as £200,000 a year. The term ‘ Natives, as
applied to these Whitstable or to other English oysters, requires
a word of explanation. A ‘Native’ oyster is simply an oyster
which has been bred on or near the Thames estuary, but very
probably it may be developed from a brood which came from
Scotland or some other place at a distance. For some unexplained
reason, oysters bred on the London clay acquire a greater delicacy
of flavour than elsewhere. The company pay large sums for
brood to stock their own grounds, since there can be no certainty
that the spat from their own oysters will fall favourably, or even
within their own domains at all. Besides purchases from other
beds, the parks are largely stocked with small oysters picked up.
along the coast or dredged from grounds public to all, some-
times as much as 50s. a bushel being paid for the best brood.
It is probably this system of transplanting, combined with
systematic working of the beds, which has made the Whitstable
oyster so excellent both as to quality and quantity of flesh.
The whole surface of the ‘layings’ is explored every year by the
dredge, successive portions of the ground being gone over in
regular rotation, and every provision being made for the well-
being of the crop, and the destruction of their enemies. For
three days of every week the men dredge for ‘ planting, ¢.e. for
the transference of suitable specimens from one place to another,
the separation of adhering shells, the removal of odd valves and
of every kind of refuse, and the killing off of dangerous foes.
On the other three days they dredge for the market, taking care
only to lift such a number as will match the demand.

The Colne beds are natural beds, as opposed to the majority
of the great working beds, which are artificial They are the
property of the town of Colchester, which appoints a water-
bailiff to manage the concern. Under his direction is a jury of
twelve, who regulate the times of dredging, the price at which
sales are to be made, and are generally responsible for the
practical working of the trade. Here, and at Faversham, Queen-
borough, Rochester, and other places, ‘natives’ are grown which
rival those of Whitstable.

There can be no question, however, that the cultivation of
oysters by the French is far more complete and efficient than

IV CULTIVATION OF THE OYSTER IN FRANCE 107

our own, and has reached a higher degree of scientific perfection
combined with economy and solid profits. And yet, between
40 and 50 years ago, the French beds were utterly exhausted
and unproductive, and showed every sign of failure and decay.
It was in 1858 that the celebrated beds on the Ile de Ré, near
Rochelle, were first started. Their originator was a certain
shrewd stone-mason, by name Boeuf. He determined to try,
entirely on his own account, whether oysters could not be made
to grow on the long muddy fore-shore which is left by the ebb
of the tide. Accordingly, he constructed with his own hands a
small basin enclosed by a low wall, and placed at the bottom a
number of stones picked out of the surrounding mud, stocking
his ‘pare’ with a few bushels of healthy young brood. The
experiment was entirely successful, in spite of the jeers of his
neighbours, and Boeut’s profits, which soon began to mount up
at an astonishing rate, induced others to start similar or more
extensive farms for themselves. The movement spread rapidly,
and in a few years a stretch of miles of unproductive mud banks
was converted into the seat of a most prosperous industry. The
general interests of the trade appear to be regulated in a similar
manner to that at Whitstable; delegates are appointed by the
various communities to watch over the business as a whole,
while questions affecting the well-being of oyster-culture are
discussed in a sort of representative assembly.

At the same time as Boeuf was planting his first oysters on
the shores of the Ile de Ré, M. Coste had been reporting to the
French government in favour of such a system of ostreiculture
as was then practised by the Italians in the old classic Lakes
Avernus and Lucrinus. The principle there adopted was to
prevent, as far as possible, the escape of the spat from the
ground at the time when it is first emitted by the breeding
oyster. Stakes and fascines of wood were placed in such a
position as to catch the spat and give it a chance of obtaining a
hold before it perished or was carried away into the open sea.
The old oyster beds in the Bay of St. Brieue were renewed on
this principle, banks being constructed and overlaid with bundles
of wood to prevent the escape of the new spat. The attempt
was entirely successful, and led to the establishment or re-
establishment of those numerous pares, with which the French
coast is studded from Brest to the Gironde. The principal

108 GREEN OYSTERS CHAP.

centres of the industry are Arcachon, Auray, Cancale, and la
Teste.

It is at Marennes, in Normandy, that the production of the
celebrated ‘green oyster’ is carried out, that especial luxury of
the French epicure. Green. oysters are a peculiarly French
taste, and, though they sometimes occur on the Essex marshes,
there is no market for them in England. The preference for
them, on the continent, may be traced back as early as 1713,
when we find a record of their having been served up at a
supper given by an ambassador at the Hague. Green oysters
are not always green, it is only after they are placed in the
‘claires, or fattening ponds, that they acquire the hue; they
never occur in the open sea. The green colour does not extend
over the whole animal, but is found only in the branchiae and
labial tentacles, which are of a deep blue-green. Various theories
have been started to explain the ‘ greening’ of the mollusc; the
presence of copper in the tanks, the chlorophyll of marine algae,
an overgrowth of some parasite, a disease akin to liver complaint,
have all found their advocates. Prof. Lankester seems to have
established? the fact,—which indeed had been observed 70 years
before by a M. Gaillon—that the greening is due to the growth
of a certain diatom (Navicula ostrearia) in the water of the tanks.
This diatom, which is of a deep blue-green colour, appears from
April to June, and in September. The oyster swallows quantities
of the Navicula ; the pigment enters the blood in a condition of
chemical modification, which makes it colourless in all the other
parts of the body, but when the blood reaches the gills the
action of the secretion cells causes the blue tint to be restored.
The fact that the colour is rather green than blue in the gills,
which are yellowish brown, is due to certain optical conditions.

Not till the young white oyster has been steeped for several
years in the muddy waters of the ‘claires’ does it acquire the
proper tint to qualify it for the Parisian restaurant. The ‘claires’
are each about 100 feet square, surrounded by low broad banks
of earth, about 3 feet high and 6 feet thick at the base. Before
the oysters are laid down, the gates which admit the tide are
carefully opened and shut a great many times, in order to
collect a sufficient amount of the Navicula. When this is done,
the beds are formed, and are not again overflowed by the sea,

1 Quart. Journ. Micr. Sc. xxvi. p. 71.

IV OYSTERS IN AMERICA 109

except at very high tides. The oysters are shifted from one
‘claire’ to another, in order to perfect the ‘greening’ process.
About fifty million of these ‘huitres de Marennes’ are produced
annually, yielding a revenue of 2,500,000 francs.

It appears, from the experience of one of the most enthusiastic
of French oyster-growers (Dr. Kemmerer), that oysters grow best
in muddy water, and breed best in clear water. Thus the open
sea is the place where the spat should fall and be secured, and,
as soon as it is of a suitable size, it should be transferred to the
closed tank or reservoir, where it will find the quiet and the
food (confervae, infusoria, minute algae) which are so requisite
for its proper growth. In muddy ground the animal and
phosphorous matter increases, and the flesh becomes fatter and
more oily. A sudden change from the clear sea-water to the
muddy tank is inadvisable, and thus a series of shiftings through
tanks with water of graduated degrees of nourishment is the
secret of proper oyster cultivation.

The American oyster trade is larger even than the French.
The Baltimore oyster beds in the Chesapeake river and_ its
tributaries cover 53000 acres, and produce an annual crop of
25 million bushels, as many as 100,000 bushels being sometimes
taken from Chesapeake Bay in a single day. Baltimore is the
centre of the tinned oyster trade, while that in raw oysters
centres in New York. Most of the beds whose produce is
carried to New York are situated in New Jersey, Connecticut,
Delaware, or Virginia. The laws of these states do not allow
the beds to be owned by any but resident owners, and the
New York dealers have consequently to form fictitious part-
nerships with residents near the various oyster beds, supply
them with money to buy the beds and plant the oysters, and
then give them a share in the profits. It has been estimated
that from the Virginia beds 4,000,000 bushels of oysters are
carried every year to Fair Haven in New England, 4,000,000
to New York, 3,000,000 to Providence, and 2,000,000 each to
Boston, Philadelphia, and Baltimore. The American ‘native’
(O. virginica) is a distinct species from our own, being much
larger and longer in proportion to its breadth; it is said to be
also much more prolific.

According to Milne-Edwards,! in the great oyster parks on

1 See G, H. Lewes, Sea-side Studies, p. 339.

Ilo OYSTERS IN AMERICA CHAP.

the coasts of Calvados, the oysters are educated to keep their
shells closed when out of water, and so retain water enough
inside to keep their gills moist, and arrive at their destination
in good condition. As soon as an oyster is taken out of the
sea, 1t closes its shells, and keeps them closed until the shock of
removal has passed away, or perhaps until the desirability of a
fresh supply of water suggests itself. The men take advantage
of this to exercise the oysters, removing them from the sea for
longer and longer periods. In time this has the desired effect ;
the well-educated mollusc learns that it is hopeless to ‘open’
when out of the water, and so keeps his shell closed and his gills
moist, and his general economy in good condition.

Oysters have been known to live entirely out of water for a
considerable time. Prof. Verrill once noticed? a large cluster of
oysters attached to an old boot, hanging outside a fish-shop in
Washington. They had been taken out of the water on about
10th December, and on 25th February following some of the
largest were still alive. It was noticed that all those which sur-
vived had the hinge upward and the ventral edge downward, this
being the most favourable position possible for the retention of
water within the gill-cavity, since the edge of the mantle would
pack against the margins of the shell, and prevent the water
from leaking away.

Such a succulent creature as the oyster has naturally many
enemies. One of the worst of these is the ravenous Starfish, or
Five-finger. His omnivorous capacities are well described by a
clever writer and shrewd observer of nature: “Here is one
doubled up like a sea-urchin, brilliant of hue, and when spread
out quite 16 inches in diameter; where, and oh where, can you
obtain a prey? The hoe we carry is thrust out and the mass
dragged shorewards, when the rascal disgorges two large dog-
whelks he has been in the process of devouring. We feel a
comfortable glow of satisfaction to think that this enemy of our
oyster-beds is also the enemy of our other enemy, this carnivor-
ous borer. Here, quite close alongside, is another, only inferior
in size, and we drag him ashore lkewise, to find that the fellow
has actually had the courage and audacity to suck the contents
out of a large horse-mussel (Modiola), the strong muscle alone
remaining undevoured. We proceed along but a short way

1 Bull. U. §. Fish. Comm. v. p. 161.

Iv ENEMIES OF THE OYSTER Teter

when we meet with still another in the curled-up condition in
which they gorge themselves, and as we drag it shorewards the
shell of a Yapes pullastra drops from the relaxing grasp of the
ogre. Slowly the extended stomach returns to its place, and
the monster settles back to an uncomfortable after-dinner siesta
on an exposed boulder; for the starfish wraps its turned-out
stomach around the prey it has secured, in place of attempting
to devour the limey covering in which most of its game is
protected. Once the mouth of the shell is enclosed in the
stomach of the starfish, the creature soon sickens, the hinge-
spring relaxes its hold, and the shell opening permits the star-
fish to suck out the gelatinous contents, and cast free the
calcareous skeleton.” 4

According to other observers the starfish seizes the oyster
with two of his fingers, while with the other three he files away
the edge of the flat or upper valve until the points of contact
with the round valve are reduced almost to nothing; then he can
introduce an arm, and the rest is easy work. Others suggest
that the starfish suffocates the oyster by applying two of its
fingers so closely to the edge of the valves that the oyster is
unable to open them; after a while the vital powers relax and
the shell gapes. The Rev. J. G. Wood holds” that the starfish
pours a secretion from its mouth which “paralyses the hinge
muscle and causes the shell to open.” Sometimes in a single
night a whole bed of oysters will be totally destroyed by an
invasion of starfish. Another dreaded enemy is the ‘ whelk, a
term which includes Purpura lapillus, Murex erinaceus, Buccinum
undatum, and probably also Nassa reticulata. All these species
perforate the shell with the end of their radula, and then suck
out the contents through the neatly drilled hole. Skate fish
are the cause of terrible destruction in the open beds, and a
scarcely less dangerous visitant is the octopus. Crabs crush the
young shells with their claws, and are said to gather in bands
and scratch sand or mud over the larger specimens, which makes
them open their shells. Yet another, and perhaps unconscious,
foe is found in the common mussel, which takes up room meant
for the young oysters, grows over the larger individuals, and
harbours all sorts of refuse between and under its closely packed

1 W. Anderson Smith, Loch Creran, p. 228.
2 Longmans Magazinc, June 1889.

112 BREEDING OF THE OYSTER CHAP.

ranks. Cliona, a parasitic sponge, bores in between the layers
of the oyster’s shell, pitting them with tiny holes (corresponding
to its oscula), and disturbing the inmate, who has constantly to
construct new layers of shell from the inside. Weed, annelids,
‘blubber, shifting sand or mud, sewage or any poisoning of the
water, are seriously harmful to the oyster’s best interests. <A
very severe winter is often the cause of wholesale destruction in
the beds. According to the Daily News of 26th March 1891,
the Whitstable oyster companies lost property to the value of
£30,000 in the exceptionally cold winter of 1890-91, when, on
the coast of Kent, the surface temperature of the sea sank below
32°, and the advancing tide pushed a small ice-floe before it.
Two million oysters were laid down in one week of the following
spring, to make up for the loss. During the severe winter of
1892-93 extraordinary efforts were made at Hayling I. to protect
the oysters from the frost. Twenty million oysters were placed
in ponds for the winter, and a steam-engine was for days
employed to keep the ponds thawed and supplied with water,
while large coal and coke fires were kept burning at the edge of
the ponds.' On the other hand, the unusually warm and sunny
summer of 1893 is said to have resulted in the finest fall of spat
known in Whitstable for fifty years.’

The reproductive activity of the oyster is supposed to com-
mence about the third year. Careful research has shown ® that
the sexes in the English oyster are not separate, but that each
individual is male as well as female, producing spermatozoa as
well as ova in the same gland. Here, however, two divergent
views appear. Some authorities hold that the oyster does not
fecundate its own eggs, but that this operation is performed by
spermatozoa emitted by other specimens. It is believed that,
in each individual, the spermatozoa arrive at maturity first, and
that the ova are not produced until after: the spermatozoa have

een emitted; thus the oyster is first male and then female,
morphologically hermaphrodite, but physiologically unisexual.
Others are of opinion that the oyster does fecundate its own
egos, ova being first produced, and passed into the infrabranchial
chamber—the ‘ white-sick’ stage—and then, after an interval,

1 St. Jumes’s Gazette, 6th January, 1893.
2 Also at Arcachon (W. A. Herdman, Nature, 1893, p. 269).
3 See especially Hoek, Tijdschr. Ned. Dierk. Vereen, Suppl. Deel, i. 1883.

IV FALL OF THE SPAT , i AL 23

spermatozoa being formed and fecundating these ova—the
‘black-sick’ stage. In this latter view the oyster is first
female and then male, and is, both morphologically and physio-
logically, hermaphrodite. The old view, that ‘black-sick’
oysters are the male, and ‘white-sick’ the female, is therefore
quite incorrect.

The ova, in their earliest stage, consist of minute oval
clusters of globules floating in a transparent mucus. They
pass from the ovary into the gills and folds of the mantle, and
are probably fecundated within the excretory ducts of the ovary,
before arriving in the mantle chamber. In this stage the oyster
is termed ‘ white-sick.” In about a fortnight, as the course of
development proceeds, the fertilised ova become ciliated at one
end (the so-called veliger stage, p. 151), and soon pigment appears
in various parts of the embryos, giving them a darker colour,
which varies from greyish to blue, and thus the white-sick oyster
becomes ‘black-sick. When the black spat emerge, they are
still furnished with cilia for their free-swimming life. This is
of very short duration, for unless the embryo finds some suit-
able ground on which to affix itself within forty-eight hours, it
perishes. As the spat escapes from the parent oyster, which
shghtly opens its valves and blows the spat out in jets, it
resembles a thick cloud in the water, and is carried about at the
mercy of wind and tide. April to August are the usual spawning
months, warm weather being apparently an absolute necessity
to secure the adhering of the spat. A temperature of 65° to 72°
F. seems requisite for their proper deposit. Thus on a fine,
warm day, with little wind or tide running, the spat will fall
near the parents and be safely secured, while in cold blustering
weather it will certainly be carried off to a distance, and pro-
bably be altogether lost. The number of young produced by
each individual has been variously estimated at from 300,000 to
60,000,000. Either extreme seems enormous, but it must be
remembered that besides chmatal dangers, hosts of enemies—other
Mollusca, fish, and Crustacea—beset the opening career of the
young oyster.

As soon as the spat has safely ‘fallen, it adheres to some
solid object, and loses the cilia which were necessary for its
swimming life. It begins to grow rapidly, increasing from
about 5', inch in diameter to about the size of a threepenny

VOL: Tit I

I14 FALL OF THE-SPAT——POISONOUS OYSTERS CHAP.

piece in five or six months, and in a year to 1 inch in
diameter. Roughly speaking, the best guide to an oyster’s age
is its size; 1t 1s as many years old as it measures inches across.

The oyster is at its prime at the age of five; its natural life
is supposed to be about ten years. The rings, or ‘shoots’ on a
shell are not—as is frequently supposed—marks of annual
growth; cases have been noticed where as many as three
‘shoots’ were made during the year.

An oyster is furnished, on the protruding edges of the
mantle, with pigmented spots which may be termed ‘visual
organs, though they hardly rise to the capacities and organisation
of real ‘eyes.’ But there is no doubt that they are sufficiently
sensitive to the action of light to enable the oyster to apprehend
the approach of danger, and close his doors accordingly. ‘ How
sensitive, notes Mr. W. Anderson Smith,’ ‘the creatures are to the
light above them; the shadow of the iron as it passes overhead
is instantaneously noted, and snap! the lps are firmly closed.’

The geographical distribution of Ostrea edulis extends from
Triinen, in Norway, close to the Arctic circle, to Gibraltar and
certain parts of the Mediterranean, Holland, and N. Germany to
Heligoland, and the western shores of Sleswick and Jutland. It
occurs in Iceland, but does not enter the Baltic, where attempts
to colonise it have always failed. Some authorities regard the
Mediterranean form as a distinct species.

The literature of oyster-cookery may be passed over in
silence. The curious may care to refer to M.S. Lovell’s Hdzble
British Mollusks, where no less than thirty-nine different ways
of dressing oysters are enumerated. It may, however, be worth
while to add a word on the subject of poisonous oysters. Cases
have been known where a particular batch of oysters has,
for some reason, been fatal to those who have partaken of them.
It is possible that this may have been due, in certain instances,
to the presence of a superabundance of copper in the oysters,
and there is no doubt that the symptoms detailed have often
closely resembled those of copper poisoning. Cases of poisoning
have occurred at Rochefort through the importation of ‘ green
oysters’ from Falmouth. It would no doubt be dangerous ever
to eat oysters which had grown on the copper bottom of a ship.
But copper is present, in more or less minute quantities, in very

1 Benderloch, p. 136.

Iv CULTIVATION OF THE MUSSEL IN FRANCE 5

many Mollusca, and it is more probable that a certain form
of slow decomposition in some shell-fish develops an alkaloid
poison which is more harmful to some people than to others,
just as some people can never digest any kind of shell-fish2
These alkaloid developments from putrescence are called
ptomaines. In confirmation of this view, reference may be
made to a case, taken from an Indian Scientific Journal, in
which an officer, his wife, and household ate safely of a basket of
oysters for three days at almost every meal. The basket then
passed out of their hands, not yet exhausted of its contents, and
a man who had already eaten of these oysters at the officer’s
table was afterwards poisoned by some from the same basketful.

The cultivation of the common mussel (Mytilus edulis 1.) is
not practised in this country, although it is used as food in the
natural state of growth all round our coasts. The French
appear to be the only nation who go in for extensive mussel
farming. The principal of these establishments is at a little
town called Esnaudes, not far from La Rochelle, and within
sight of the Ile de Ré and its celebrated oyster parks. The
secret of the cultivation consists in the employment of ‘ bouchots,
or tall hurdles, which are planted in the mud of the foreshore,
and upon which the mussel (la moule, as the French call it)
grows. ‘The method is said? to have been invented as long ago
as 1235 by a shipwrecked Irishman named Walton. He used
to hang a purse net to stakes, in the hope of capturing sea birds,
He found, however, that the mussels which attached themselves
to his stakes were a much more easily attainable source of food,
and he accordingly multiplied his stakes, out of which the
present ‘bouchot’ system has developed. The shore is simply a
stretch of liquid mud, and the bouchots are arranged in shape
like a single or double V, with the opening looking towards the
sea. The fishermen, in visiting the bouchots, glide about over
the mud in piroques or light flat-bottomed boats, propelling
them by shoving the mud with their feet, Each bouchot is now
about 450 yards long, standing 6 feet out of the mud, making
a strong wall of solid basket-work, and as there are altogether at
least 500 bouchots, the total mussel-bearing length of wall is
nearly 130 miles.

1 This is the view of E, Ray Lankester, Quart. Journ. Mier. Sc. xxvi. 80.
2 De Quatrefages, Rambles of a Naturalist.

110 ECONOMY OF THE MUSSEL CHAP.

The mussel-spat affixes itself naturally to the bouchots
nearest the sea, in January and February. Towards May the
planting begins. The young mussels are scraped off these
outermost bouchots, and placed in small bags made of old
canvas or netting, each bag holding a good handful of the
mussels. The bags are then fastened to some of the inner
bouchots, and the mussels soon attach themselves by their
byssus, the bag rotting and falling away. They hang in clusters,
increasing rapidly in size, and at the proper time are trans-
planted to bouchots farther and farther up the tide level, the
object being to bring the matured animal as near as possible to
the land when it is time for it to be gathered. This process,
which aims at keeping the mussel out of the mud, while at the
same time giving it all the nutrition that comes from such a
habitat, extends over about a year in the case of each individual.
Quality, rather than quantity, is the aim of the Esnaudes
boucholiers. The element of quantity, however, seems to come
in when we are told that each yard of the bouchots is calculated
to yield a cartload of mussels, value 6 francs, and that the whole
annual revenue is at least £52,000.

In this country, and especially in Scotland, mussels are
largely used as bait for long-line fishing. Of late years other
substances have rather tended to take the place of mussels, but
within the last twenty years, at Newhaven on the Firth of Forth,
three and a half million mussels were required annually to
supply bait for four deep-sea craft and sixteen smaller vessels.
According to Ad. Meyer,’ boughs of trees are laid down in
Kiel Bay, and taken up again, after three, four, or five years,
between December and March, when they are found covered
with fine mussels) The boughs are then sold, just as they are,
by weight, and the shell-fish sent into the interior of Germany.

Mussels are very sensitive to cold weather. In 1874, during
an easterly gale, 195 acres of mussels at Boston, in Lincolnshire,
were killed in a single night. They soon affix themselves to the
bottom of vessels that have lain for any length of time in harbour
or near the coast. The bottom of the Great Hastern steamship
was at one time so thickly coated with mussels that it was esti-
mated that a vessel of 200 tons could have been laden from her.

In some of our low-lying coast districts mussels are a

1 Quoted by Jeffreys, Brit. Conch. i. p. 109.

IV ECONOMY OF THE MUSSEL 17,

valuable protection against inundation. “ An action for trespass
was brought some time ago for the purpose of establishing the
right of the lord of the manor to prevent the inhabitants of
Heacham from taking mussels from the seashore. The locality
is the foreshore of the sea, running from Lynn in a north-
westerly direction towards Hunstanton in Norfolk; and the
nature of the shore is such that it requires constant attention,
and no little expenditure of money, to maintain its integrity,
and guard against the serious danger of inundations of the sea.
Beds of mussels extend for miles along the shore, attaching
themselves to artificial jetties running into the sea, thereby
rendering them firm, and thus acting as barriers against the sea
[and as traps to catch the silt, and thus constantly raise the
level of the shore]. Therefore, while it is important for the
inhabitants, who claim a right by custom, to take mussels and
other shell-fish from the shore, it is equally important for the
lord of the manor to do his utmost to prevent these natural
friends of his embankments and jetties from being removed in
large quantities.” *

The fable that Bideford Bridge is held together by the
byssi of Mytilus, which prevent the fabric from being carried
away by the tide, has so often been repeated that it is perhaps
worth while to give the exact state of the case, as ascertained
from a Town Councillor. The mussels are supposed to be of
some advantage to the bridge, consequently there is a by-law
forbidding their removal, but the corporation have not, and
never had, any boat or men employed in any way with regard
to them.

Poisoning by mussels is much more frequent than by oysters.
At Wilhelmshaven,? in Germany, in 1885, large numbers of
persons were poisoned, and some died, from eating mussels
taken from the harbour. It was found that when transferred to
open water these mussels became innocuous, while, on the other
hand, mussels from outside, placed in the harbour, became
poisonous. The cause obviously lay in the stagnant and
corrupted waters of the harbour, which were rarely freshened by
tides. It was proved to demonstration that the poison was not
due to decomposition ; the liver of the mussels was the poisonous
part. In the persons affected, the symptoms were of three

1M. S. Lovell, Edible Mollusks, p. 49. 2 Science, vii. p. 175.

118 CULTIVATION OF THE SNAIE FOR FOOD CHAP.

kinds, exanthematous (skin eruptions), choleraic, and paralytic.
Cases of similar poisoning are not unfrequent in our own
country, and the circumstances tend to show that, besides the
danger from mussels bred in stagnant water, there is also risk
in eating them when ‘out of season’ in the spawning time.

Whelks are very largely employed for bait, especially in the
cod fishery. The whelk fishery in Whitstable Bay, both for
bait and for human food, yields £12,000 a year. Dr. Johnston,
of Berwick, estimated that about 12 million limpets were
annually consumed for bait in that district alone. The cockle
fishery in Carmarthen Bay employs from 500 to 600 families,
and is worth £15,000 a year; that in Morecambe Bay is worth
£20,000.

Cultivation of Snails for Food; use as Medicine.—It was
a certain Fulvius Hirpinus who, according to Pliny the elder,’
first instituted snail preserves at Tarquinium, about 50 B.c. He
appears to have bred several species in his ‘cochlearia, keeping
them separate from one another. In one division were the
albulae, which came from Reate; in another the ‘ very big snails’
(probably H. lucorum), from Illyria; in a third the African
snails, whose characteristic was their fecundity; in a fourth
those from Soletum, noted for their ‘nobility.’ To increase the
size of his snails, Hirpinus fed them on a fattening mixture of
meal and new wine, and, says the author in a burst of enthusiasm,
‘the glory of this art was carried to such an extent that a
single snail-shell was capable of holding eighty sixpenny pieces.’
Varro” recommends that the snaileries be surrounded by a
ditch, to save the expense of a special slave to catch the
runaways. Snails were not regarded by the Romans as a
particular luxury. Pliny the younger reproaches® his friend
Septicius Clarus for breaking a dinner engagement with him, at
which the menu was to have been a lettuce, three snails and two
eggs apiece, barley water, mead and snow, olives, beetroot, gourds
and truffles, and going off somewhere else where he got oysters,
scallops, and sea-urchins. In Horace’s time they were used as a
gentle stimulant to the appetite, for

“?Tis best with roasted shrimps and Afric snails
To rouse your drinker when his vigour fails.” 4

TEST MING xan Oo. 2 De re rustica, ii. 14. 3 Epistles, i. 15.
4 Hor. Sat. II., iv. 58, tr. Conington.

IV CULTIVATION OF THE SNAIL FOR FOOD 119

Escargotieres, or snail-gardens, still exist in many parts of
Europe, eg. at Dijon, at Troyes and many other places in
central and southern France, at Brunswick, Copenhagen, and
Ulm. The markets at Paris, Marseilles, Bordeaux, Toulouse,
Nantes, ete., are chiefly supplied by snails gathered from the
open country, and particularly from the vineyards, in some of
which Heliz pomatia abounds. In the Morning Post of 8th
May 1868 there is an account of the operation of clearing the
celebrated Clos de Vougeot vineyard of these creatures. No less
than 240 gallons were captured, at a cost in labour of over 100
francs, it being estimated that these snails would have damaged
the vines to an extent represented by the value of 15 to 20 pipes
of wine, against which may be set the price fetched by the snails
when sold in the market.

It is generally considered dangerous to eat snails at once
which have been gathered in the open country. Cases have
occurred in which death by poisoning has resulted from a neglect
of this precaution, since snails feed on all manner of noxious
herbs. Before being sent to table at the restaurants in the great
towns, they are fattened by being fed with bran in the same way
as oysters.

The Roman Catholic Church permits the consumption of
snails during Lent. Very large numbers are eaten in France
and Austria at this time. At the village of Cauderon, near
Bordeaux, it is the proper thing to end Carnival with especial
gaiety, but to temper the gaiety with a dish of snails, as a
foretaste of Lenten mortification.

The following species appear to be eaten in France at the
present day: H. pomatia, aspersa, nemoralis, hortensis, aperta,
pisana, vermiculata, lactea. According to Dr. Gray, the glassmen
at Newcastle used to indulge in a snail feast once a year, and a
recent writer informs us that H. aspersa is still eaten by working
people in the vicinity of Pontefract and Knottingley But in
this country snails appear to be seldom consciously used as an
article of food; the hmitation is necessary, for Lovell tells us
that they are much employed in the manufacture of cream, and
that a retired (!) milkman pronounced it the most successful
imitation known.

Preparations made from snails used tobe highly esteemed as

1 Roberts, Zoologist, 1885, p. 425.

XO) SNAILS AS MEDICINE CHAP.

a cure for various kinds of diseases and injuries. Pliny the elder
recommends them for a cough and for a stomach-ache, but it is
necessary “to take an uneven number of them.”! Five African
slugs, roasted and beaten to a powder, with half a drachm of
acacia, and taken with myrtle wine, is an excellent remedy for
dysentery. Treated in various ways, snails have been considered,
in modern times, a cure for ague, corns, web in the eye, scorbutic
affections, hectic fevers, pleurisy, asthma, obstructions, dropsy,
swelling of the joints, headache, an impostume (whitlow), and
burns. One of Pliny’s remedies for headache, which competes
with the bones of a vulture’s head or the brain of a crow or an
owl, is a plaister made of slugs with their heads cut off, which is
to be applied to the forehead. He regards slugs as immature
snails, whose growth is not yet complete (nondum perfectae).
Lovell states that “a large trade in snails is carried on for
Covent Garden market in the Lincolnshire fens, and that they
are sold at 6d. per quart, being much used for consumptive
patients and weakly children.”

The custom still seems to linger on in some parts of the
country. Mr. E. Rundle, of the Royal Cornwall Infirmary, gives
his experience in the following terms: “I well remember, some
twelve years since, an individual living in an adjoining parish
[near Truro] being pointed out to me as ‘a snail or slug eater.’
He was a delicate looking man, and said to be suffering from
consumption. Last summer I saw this man, and asked him
whether the statement that he was a ‘snail eater’ was true: he
answered, ‘Yes, that he was ordered small white slugs—not
snails—and that up till recently he had consumed a dozen or
more every morning, and he believed they had done him good.’
There is also another use to which the country people here put
snails, and that is asan eye application. I met with an instance a
few weeks since, and much good seemed to have followed the use.” ?

A reverend Canon of the Church of England, whose name I
am not permitted to disclose, informs me that there was a belief
among the youth of his native town (Pontypool, in Monmouth-
shire) that young slugs were ‘good for consumption, and that
they were so recommended by a doctor who practised in the
town. The slugs selected were about 3 inch long, “such as may
be seen crawling on the turf of a hedge-bank after a shower of

I Hast. Nat. xxx. 15, 119) 2 Science Gossip, 1891, p. 166.

1V PRICES PAID FOR SHELLS 121

rain.” They were “placed upon the tongue without any previous
preparation, and swallowed alive.” My informant himself in-
dulged in this practice for some time, “not on account of any
custatory pleasure it afforded, but from some vague notion that
it might do him good.”

A colleague of mine at King’s College tells me that the country
people at Ponteland, near Morpeth, habitually collect Limax
agrestis and boil it in milk as a prophylactic against consump-
tion. He has himself frequently devoured them alive, but they
must be swallowed, not scrunched with the teeth, or they taste
somewhat bitter.

Snails have occasionally fallen, with other noxious creatures,
under the ban of the Church. In a prayer of the holy martyr
Trypho of Lampsacus (about 10th cent. A.D.) there is a form of
exorcism given which may be used as occasion requires. It
runs as follows: “O ye Caterpillars, Worms, Beetles, Locusts,
Grasshoppers, Woolly-Bears, Wireworms, Longlegs, Ants, Lice,
Bugs, Skippers, Cankerworms, Palmerworms, Snazls, Earwigs,
and all other creatures that cling to and wither the fruit of the
grape and all other herbs, I charge you by the many-eyed
Cherubim, and by the six-winged Seraphim, which fly round the
throne, and by the holy Angels and all the Powers, ete. etc., hurt
not the vines nor the land nor the fruit of the trees nor the
vegetables of the servant of the Lord, but depart into the
wild mountains, into the unfruitful woods, in which God hath
given you your daily food.”

Prices given for Shells.— Very high prices have occasionally
been given for individual specimens, particularly about thirty or
forty years ago, when the mania for collecting was at its height.
In those days certain families, such as the Volutidae, Conidae, and
Cypraeidae, were the especial objects of a collector’s ardour, and
he spared no expense to make his set of the favourite genus as
complete as possible. Thus at Stevens’ auction-rooms in Covent
Garden, on 21st July 1854, one specimen of Conus cedo nulla
fetched £9:10s., and another £16, a C. omaicus 16 guineas,
C. victor £10, and C. gloria maris, the greatest prize of all,
£43:1s. At the Vernéde sale, on 14th Dec. 1859 two Conus
omaicus fetched £15 and £22, and aC. gloria maris £34. At
the great Dennison sale, in April 1865, the Conidae fetched
extravagant prices, six specimens averaging over £20 a-piece.

122 PRICES PAID FOR SHELLS CHAP. IV

Conus cedo nullt went for £18 and £22, C. omaicus for £12,
C. malaccanus for 10 guineas (this and one of the cedo nulli
being the actual specimens figured in Reeve’s Conchologia
Iconiea), C. cervus for £19 and C. gloria maris for £42. On
9th May 1866 a Cypraca Broderipii was sold at Stevens’ auction-
rooms for £13, and at the Dennison sale a Cypraea princeps
fetched £40, and C. guttata £42. The Volutidae, although not
quite touching these prices, have yet done fairly well. Mr.
Dennison’s Voluta fusiformis sold for £6:15s., V. papillaris for
£5, V. cymbiola for £5:15s., V. reticulata for 8 guineas, and two
specimens of the rarest of all Volutas, V. festiva, for £14 and
£16, both being figured in the Conchologia. At the same
sale, two unique specimens of Oniscia Dennisoni fetched £17
and £18 respectively, and, at the Vernéde sale, Ancillaria
Vernedet was bought for £6:10s, and Voluta piperata for
£712 108.

A unique specimen of a recent Plewrotomaria (quoyana
F. and B.) was purchased by Miss de Burgh in 1873 for 25
guineas, and another species of the same genus (adansoniana
Cr. and F.), of extraordinary size and beauty, is now offered for
sale for about £100.

Bivalves have never fetched quite such high prices as uni-
valves, but some of the favourite and showy genera have gone
near to rival them. On 22nd June 1869, at Stevens’, Pecten
solaris fetched £4:5s., P. Reevit £4:88.,, and Cardita varia
5 guineas. Mr. Dennison’s specimens of Pecten subnodosus sold
for £7, of Corbula Sowerbyi for £10, of Pholadomya candida
for £8 and £13, while at the Vernéde sale a Chama damicornis
fetched £7.

CEEAPT ER, ¥

REPRODUCTION——DEPOSITION OF EGGS——DEVELOPMENT OF THE
FERTILISED OVUM——DIFFERENCES OF SEX—DIOECIOUS AND
HERMAPHRODITE MOLLUSCA——DEVELOPMENT OF FRESH-WATER
BIVALVES.

REPRODUCTION in the Mollusca invariably takes place by means
of eges, which, after being developed in the ovary of the female,
are fertilised by the spermatozoa of the male. As a rule, the
egos are ‘laid, and undergo their subsequent development apart
from the parent. This rule, however, has its exceptions, both
among univalve and bivalve Mollusca, a certain number of which
hatch their young from the egg before expelling them. Such
ovoviviparous genera are Melania, Paludina, Balea, and Coeliaxis
among land and fresh-water Mollusca, and Cymba and many
Littorina amongst marine. The young of Melania tuberculata,
in Algeria, have been noticed to return, as if for shelter, to the
branchial cavity of the mother, some days after first quitting it.
Isolated species among Pulmonata are known to be ovovivi-
parous, eg. Patula Coopert, P. Hemphilli, and P. rupestris,
Acanthinula harpa, Microphysa vortex, Pupa cylindracea and
muscorum, Clausilia ventricosa, Opeas dominicensis, Rhytida in-
aequalis, etc. All fresh-water Pelecypoda yet examined, except
Dreissensia, are OVOViviparous.

The number of eggs varies greatly, being highest in the
Pelecypoda. In Ostrea edulis it has been estimated at from
300,000 to 60,000,000; in Anodonta from 14,000 to 20,000;
in Unio pictorum 200,000. The eggs of Doris are reckoned at
from 80,000 to 600,000, of Zoligo and Sepia at about 30,000
to 40,000. Pulmonata lay comparatively few eggs. Arion ater

has been observed to lay 477 in forty-eight days (p. 42). Nests

Ny yyal EGGS OF LAND PULMONATA CHAP.

ot Helix aspersa have been noticed, in which the number of eggs
varied from about 40 to 100. They are laid in little cup-
shaped hollows at the roots of grass, with a little loose earth
spread over them. The eggs of Zestacella are rather large, and
very elastic; if dropped on a stone floor they will rebound
sharply several inches. The Cochlostyla of the Philippines lay
their eggs at the tops of the great forest trees, folding a leat
together to serve as a protection.

The eges of the great tropical Bulimus and Achatina,
together with those of the Jlacrodn
eroup of Helia (Helicophanta, Acavus,
Panda) are exceedingly large, and the
number laid must be decidedly less
than in the smaller Pulmonata. Lu/i-
mus oblongus, for imstance, from Bar-
bados, lays an egg about the size of a

i sparrow’s (Fig. 38), Achatina sinis-
Fia. 38.—Newly-hatched young = spn wee es
and ege of Bulimus oblongus trorsa as large as a pigeons. The

Mill., Barbados. Natural Cingalese Helix Waltont when first

ee hatched is about the size of a full-
erown H. hortensis. There is, in the British Museum, a speci-
men of the egg of a Bulimus from 8. America (probably maximus
or popelairanus) which measures exactly 12 inch in length.

The Limnaeidae deposit their eggs in irregular gelatinous
masses on the under side of the leaves of water-plants, and on
all kinds of débris.

The achiglossa or marine carnivorous families lay their
egos in tough leathery or bladdery capsules, which are frequently
jomed together in shapes which differ with the genus. Each
capsule contains a varying number of ova. The cluster of egg
capsules of Buccinum undatum is a familiar object on all our
sandy coasts. The capsules of Purpura lapillus are like delicate
pink grains of rice, set on tiny stalks. They are not attached to
one another, but are set closely together in groups in sheltered
nooks of the rocks. A single Purpura has been observed to pro-
duce 245 capsules! Busycon lays disc-shaped capsules which
are all attached at a point in the edge to a cartilaginous band
nearly 3 feet in length, looking like a number of coins tied
to a string at equal distances from one another. In Jlurex
erinaceus the egg capsules are triangular, with a short stalk.

vo EGGS OF MARINE GENERA ; 125

They are deposited separately in clusters of from 15 to 150, there
being about 20 ova in each capsule. It appears that all the
species of the same genus have by no means the same method
of depositing their eggs, nor do they always produce eges of at
all similar size or shape. Thus, of two British species of Nassa,

Fic. 39.—Various forms of spawn
in Prosobranchiata: A and D,
Pyrula or Busycon ; B, Conus ;
C, Voluta musica; E, Amputl-
daria (from specimens in the
British Museum); all x 4%.

N. reticulata lays egg-capsules in shape like flattened pouches
with a short stalk, and fastens them in rows to the leaves of
Zostera; M. inerassata, on the other hand, deposits soltary
capsules, which are shaped like rounded oil-flasks. Neptunea
untiqua lays its eggs in bunched capsules, ike Buce. wndatum
(Fig. 40), but the capsules of N. gracilis are solitary.

In .Vatica the egos are deposited in what looks like a thick
piece of sand-paper, curled in a spiral form (Fig. 41). The sand
is agglutinated by copious mucus into a sort of sheet, and the

y
5

eges are let into this, sometimes (V. heros) in regular quincunx
form. Janthine attaches its eggs to the under side of its float
(Fig. 42). The Trochidae deposit their eggs on the under side
of stones and sea-weeds, each ovum being contained in a separate
capsule, and all the capsules glued together into an irregular
mass of varying size. The female of Galerus chinensis hatches

126 VARIOUS FORMS OF SPAWN CHAP.

her egos by keeping them between her foot and the stone she
adheres to. They are laid in from 6 to 10 capsules, connected
by a pedicle and arranged like the petals of a rose, with 10 to 12

Fic. 40.—Egg-capsules of, A, Nassa Fic. 41.—Spawn of a species of
reticulata L. x %3 B, Buccinuin Natica (from a specimen in the
undatum L. x %3 C, Neptunea British Museum) x 3.

antiqua L. x4.

eggs in each capsule. Those Littorina which are not ovovivi-
parous deposit their spawn on sea-weeds, rocks, and stones.
The eggs are enveloped in a glairy mass which is just firm
enough to retain its shape in the water; each ege has its own

FL
\
— = = >
SSS 3S SS

<= i SSS
ON NATO.

(0)

Fic. 42.—Ianthina fragilis Lam. FL, float ; O, ova; Pr, proboscis ; Br, branchiae ;
F, foot. (Quoy and Gaimard.)
globule of jelly and is separated from the others by a very thin
transparent membrane.!
Chiton marginatus, when kept in captivity, has been noticed?
1 Jeffreys, Brit. Conch. iii. p. 355. _~W. Clark, Mag. Nat. Hist. xvi. p. 446.

Vv SPAWN O8 CHITON AND OF THE CEPHALOPODA W227,

to elevate the posterior part of the girdle, and to pour out a
continuous stream of flaky white matter like a fleecy cloud,
which proved to be of a glutinous nature. It then discharged
ova, at the rate of one or two every second, for at least. fifteen
minutes, making a total of 1500 to 1500, each being about
roo inch diameter. The ova were shot into the glutinous cloud,
which seemed to serve as a sort of nidus to entangle the ova and
prevent them being carried away. The subsequent development
was rapid, and in seven days the young Chiton was hatched,
being then about 5!) inch long. Lovén has described the same
species as laying its eggs, loosely united in clusters of seven to
sixteen, upon small stones. There is probably some mistake about
the identification, but the observation illustrates the’ varying
methods of oviposition among allied forms.

Not very much is known with regard to the ovipositing
of the Cephalopoda, especially those which inhabit deep water.
Masses of ova arranged in
very various forms have occa-
sionally been met with float-
ing in the ocean, but it is
next to impossible to deter-
mine to what species, or even
genus, they belong."

In Loligo punetata the
ova are contained in small
cylindrical cases measuring 3
to 4 in. by J in, to the

: ee . Fic. 43.—Egg-capsules of A, Sepia elegans
number of about 250 ova in Orb., and B, Octopus vulgaris Lam.

each case. Hundreds of these
cases are attached together like a bundle of sausages or young
carrots, and the movements of the embryos within can be dis-
tinetly noted. Sepia officinalis lays large black pear-shaped
capsules, each of which is tied to some place of attachment by a
kind of ribbon at the wpper end of the capsule, the whole form-
ing a large group like a bunch of grapes. Octopus vulgaris
deposits thousands of small berry-shaped ova, attached to a string
which runs along the centre of the mass (Fig. 43).

The so-called shell of the female Argonauta is nothing more

1 Examples will be found in Journ. Linn. Soc. Zool. xi. p. 90; Ann. Sc. Nat.

>
xx. p. 472; Zeit. wiss. Zool. xxiv. p. 419.

128 CURIOUS FORMS OF EGG-LAYING CHAR.

than a form of protection for the ova, and is in no sense homo-
logous to the ordinary molluscan shell. The ova consist of a
large granulated mass, attached to a many branched stem; they
are contained in the spire of the shell, in contact with the
posterior part of the body of the mother, but sometimes project
externally beyond the coil of the spire.

Certain species possess the curious property of laying their
eggs on the outside of their own shells. Buccinopsis Dalei is
not unfrequently found decorated with its own ege capsules.
Possibly this species, which lives on oozy ground, finds this
the only secure place of attachment for its progeny. Meritina
fluviatilis has a similar habit, and so have many other species of
Neriting and Navicella. It is not quite clear, in the latter cases,
whether the eggs are laid by the specimens on whose shell
they are found, or whether they are deposited by others. In
either case, perhaps the shell is the safest place for them in the
rapid streams which both genera frequent. Specimens of Hydrobia
ulvae taken on the wet sands at the mouth of the Dee, are
found to have several lttle rounded excrescences scattered over
the surface of the shell. These, on examination, are found to
be little masses of small sand-grains, in the centre of which
is a clear jelly containing segmenting ova or young embryos.
Here again, in all probability, the shell is the only comparatively
stable object, in the expanse of shifting sands, on which the egos
can be laid.t

The pulmonate. genus Libera, which occurs on a few of the
island groups in the Central Pacific, is remarkable for the habit
of laying its eggs within its own cavernous umbilicus, which is
narrowed at the lower part. The eggs number from four to six,
or the same number of very young shells may be seen closely
packed in the cavity, each being in shape exactly ike a young
Planorbis. This constriction of the umbilicus does not occur till
the formation of the last two whorls, ze. till the animal is sexually
mature. Some species, but not all, provide for the safety of their
eges more completely by forming a very thin shelly plate, which
nearly closes the umbilical region, and breaks away or is absorbed
to facilitate the escape of the young shells.”

Union of Limax.— With regard to the act of union itself,

1 Herdman, Proc. Liverp. Biol. Soc. iii. p. 30.
2 Garrett, Journ. Ac. Nat. Sc. Phil. viii. (1880).

Vv PERIODICITY IN BREEDING 129

the method in certain species of Limax deserves special notice.
L. maximus has been observed at midnight to ascend a wall or
some perpendicular surface. A pair then crawl round and round
one another emitting a quantity of mucus which at length forms
a patch, 2 to 24 inches in diameter. When this acquires con-
sistency the pair begin to twist round each other in corkscrew
form, and detach themselves from the wall, hanging by a cord
of the thickened mucus, about 8—15 inches long, and still twist-
ing round each other. The external generative organs are then
protruded and copulation takes place, after which the bodies
untwist, separate, and crawl up the cord again to the wall.

Periodicity in Breeding.—JIn the marine Mollusca, the
winter months appear to be the usual time for the deposition of
egos. Careful observations have been made on the Mollusca
occurring at Naples,? and the general result seems to be that for
all Orders alike the six winter months from November to April,
roughly speaking, are the breeding time. Scarcely any forms
appear to breed habitually in August, September, or October.
On our own coasts, Nudibranchiata come in shore to deposit
their ova from January to April. Purpura lapillus may be
observed depositing ova all the year round, but is most active
from January to April. Buccinwm undatum breeds from October
to May; Lzttorina all the year round.

The land Mollusca exhibit rather more periodicity than the
marine. In temperate climates they breed exclusively in the
summer months. In the tropics their periods are determined
by the dry and rainy seasons, where such occur, otherwise they
cohabit all the year round. According to Karl Semper, the
snails of the warm Mediterranean region arrive at sexual maturity
when they are six months old, ze. before they are fully grown.
After a rest of about three months during the heat of summer, a
second period of ovipositing occurs.’ Helix hortensis and H.
nemoralis ascend trees, sometimes to a height of forty feet, when
pairing.4

Hybridism as the result of union between different species of
Mollusca is exceedingly rare. Lecoq once noticed’ on a wall at
Anduze (Gard) as many as twenty specimens of Pupa cinerea

1 J. Bladon, Zoologist, xvi. p. 6272.
2 Lo Bianco, M7’. Zool. Stat. Neap. viii. p. 414. 3 Animal Life, pp. 126, 135.
+ R. Rimmer, Land and Fresh- Water Shells, p. 119. 5 Journ. de Conch, ii. p. 245.

VOL. III K

130 DEVELOPMENT OF THE OVUM CUAP,

united with Clausilia papillaris. No offspring seem to have
resulted from what the professor calls ‘this innocent error, for
the wall was carefully scrutinised for a long time, and no hybrid
forms were ever detected.

The same observer noticed, in the Luxembourg garden at Paris,
and M. Gassies has noticed! at various occasions, union between
Feliz aspersa and nemoralis, H. aspersa and vermiculata, between
Stenogyra decollata and a Helix (sp. not mentioned), H. variabilis
and pisana, H. nemoralis and hortensis. In the two latter cases
a hybrid progeny was the result. It has been noticed that these
unions generally took place when the air was in a very electric
condition, and rain had fallen, or was about to fall, abundantly.

Of marine species Littorina rudis has been noticed? in union
both with Z. obtusata and with ZL. littorea, but no definite facts
are known as to the result of such unions.

Self-impregnation (see p. 44).

Development of the Fertilised Ovum.—tThe first stages in
the development of the Mollusca are identical with those which
occur in other classes of animals. The fertilised ovum consists of
a vitellus or yolk, which is surrounded with albumen, and is
either contained in a separate capsule, or else several, sometimes
many, ova are found in the same capsule, only a small proportion
of which ultimately develop. The germinal vesicle, which is
situated at one side of the vitellus, undergoes unequal segmenta-
tion, the result of which is usually the formation of a layer of
small ectoderm cells overlying a few much larger cells which
contain nearly the whole of the yolk. The large cells are then
invaginated, or are simply covered by the growth of the ectoderm
cells. The result in either case is the formation of an area, the
blastopore, where the inner cells are not covered by the ectoderm.
The blastopore gradually narrows to a circular opening, which, in
the great majority of cases, eventually becomes the mouth. The
usual differentiation of germinal layers takes place, the epiblast
eventually giving rise to the epidermis, nervous system, and
special sense organs, the hypoblast to the liver and to the middle
region of the alimentary tract, the mesoblast to the muscles, the
body cavity, the vascular, the excretory and reproductive systems.
The next, or trochosphere (trochophora) stage, involves the forma-

1 Journ. de Conchyl. iii. p. 107.
* Jeffreys, Brit. Conch. iii. p. 359 ; Sauvage, Jowrn. de Conchyl. xxi. p. 122.

Vv TROCHOSPHERE AND VELIGER STAGES ey

tion of a circlet of praeoral cilia, dividing the still nearly spherical
embryo into two unequal portions, the smaller of which consists
sunply of the prostomium, or part in front of the mouth, the
larger bearing the mouth and anus.

So far the series of changes undergone by the embryo are not
peculiar to the Mollusca; we now come to those which are
definitely characteristic of that group. The stage next succeed-
ing the development of the trochosphere is the definitive forma-
tion of the velwm, a process especially characteristic of the
Gasteropoda and Pelecypoda, but apparently not occurring in the
great majority of land Pulmonata.

The circlet of cilia becomes pushed more and more towards

Fic. 44.—Veligers of Dentaliui entalis L.: A, longitudinal section of a larva 14 hours
old, x 285; B, larva of 37 hours, x 165; C, longitudinal section of larva of 34
hours, x 165; m, mouth; v v, velum. (After Kowalewsky).

the anterior portion of the embryo, the cilia themselves become
longer, while the portion of the body from which they spring
becomes elevated into a ridge or ring, which, as a rule, develops
on each side a more or less pronounced lobe. The name velwm
is appled to this entire process of ciliated ring and lobes, and
to the area which they enclose.

In this so-called veliger stage, the velum serves, in the first
place, to cause rotation of the larva within the egg-capsules, and,
after hatching, as an organ of locomotion. As a rule, the velum
disappears entirely in the adult mollusc after the free-swimming
stage is over, but in the common Limnaea stagnalis it persists,
losing its cilia, as the very prominent circum-oral lobes. Simul-
taneously with the-development of the velum, and in some cases
earlier, appear the rudiments of the shell-gland and of the foot,

VELIGER STAGE CHAP.

~
LoS)
bo

the latter being situated on the ventral side, between the mouth
and anus, the former on the dorsal side, behind the velum, and
above the surface of the eventual visceral sac. Thus the prime
characteristics of the veliger stage, subsequent to the appearance

Fia. 45.—Veliger of Patella vulgata Ita. 46.—Developed larva of Cyclas cornea L. :

L., 130 hours old: 7, rudimentary br, rudimentary branchiae ; by, byssus ; 7,
foot ; op, operculum ; sh, shell; foot ; m.e, mantle edge; sh, shell. (After
v, v, Velum. (After Patten, highly Ziegler, highly magnified.)

magnified. )

of the velum itself, are the development of the visceral sac and
shell-gland on the upper, and of the foot on the under side.
According to Lankester the primitive shell-gland does not, as a

Fia. 47.—A, Advanced
veliger of Dreissensia :
J, foot; m, mouth; sh,
shell; v7, velum. (After
Korschelt and Heider,
much enlarged.) B,
Veliger of a Pteropod
(Tiedemannia) : op, oper-
culum; sh, shell; »,
velum. (After Krohn,
much enlarged).

rule, directly give mse to the shell of the adult molluse, but
becomes filled up by a horny substance, and eventually disappears ;

5
?

the permanent shell then forms over the surface of the visceral
hump from the original centre of the shell-gland. It is only in

Vv TYPES OF SEXUAL’ DIFFERENCE 13

[Ss)

Chiton, and possibly in Limax, that the primitive shell-sac is
retained and developed into the final shell-forming area, which
is much wider, and extends to the edges of the mantle. Within
the velar area first appear the rudiments of the tentacles and eyes ;
when these become developed the velum atrophies and disappears.

Several of these veligers when captured in the open sea have
been mistaken for perfect forms, and have been described as such.
Thus the larva of Dolium has been described as Macgillivrayia,
that of a Purpura as Chelotropis and Sinusigera, that of
Aporrhais pes pelecani as Chiropteron, that of Marsenia conspicua
as Brownia, Echinospira, and Calcarella.

Cephalopoda.—The embryonic development of the Cephalopoda
is entirely distinct from that of all other Mollusca. The
segmentation of the vitellus
is partial, and the embryo is
furnished with a vitelline
sac, which is very large in
the majority of cases (Fig.
uo) Lhere “as “no free-
swimming stage, but the
embryo emerges from the
egg fully developed.

Differences of Sex.—In
the Mollusca there are two

main types of sexual differ- Fic. 48.—'Two stages in the development of
ence: (1) sexes separate (dioe- Loligo vulgaris Lam.: a, a, first, and a2, do,

; 30 Cire second pairs of arms; 07, branchiae, seen
cious type), (11) sexes united through m, mantle ; e, e, eyes ; fi, fins ; fu,

in the same individual (her- ae v.s, vitelline sac, (After Kowal-
ewsky.

maphrodite type).
In some cases—e.g. certain Pelecypoda—what is practically
a third type occurs. The animal is hermaphrodite, but the male
and female elements are not developed simultaneously, de. the
same individual is at one time female, at another male.
1. The sexes are separate in
All Cephalopoda.
Gasteropoda Amphineura (except Neomeniidae).
Gasteropoda Prosobranchiata (except Valvata and some

species of Marsenia).
Scaphopoda.
Many Pelecypoda.

134 TYPES OF SEXUAL DIFFERENCE CHAP.

2. The sexes are united in
Gasteropoda Opisthobranchiata.
Gasteropoda Pulmonata.
Certain Pelecypoda.*

In the dioecious Mollusca, sexual union is the rule, but is by
no means universal. In some instances,—e.g. Vermetus, Magilus,
Patella, Haliotis, Crepidula, Chiton, the Scaphopoda—the form
and habits of the animal do not admit of it; in others (many
Trochus) a male copulative organ is wanting. When this is the
case, the male scatters the spermatozoa freely ; the majority must
perish, but some will be carried by currents in the direction of the
female.

When the sexes are separate, the female is frequently larger
than the male. This is markedly the case in Littorina, Buccinum,
and all the Cephalopoda ; in Argonauta the difference is extreme,
the male not being more than + the size of the female.

Those hermaphrodite Mollusca which are capable of sexual
union (Gasteropoda, Pulmonata and Opisthobranchiata) are con-
veniently divided into two sections, according as (1) there are
separate orifices for the male and female organs, or (2) one orifice
serves for both. To the former section (Digonopora”) belong the
Limnaeidae, Vaginulidae, and Onchidiidae, and many Opistho-
branchiata, including all the Pteropoda; to the latter (Jono-
gonopora”) nearly all the Nudibranchiate Opisthobranchiata, and
all the rest of the Pulmonata. In the latter case during union,
mutual impregnation takes place, and each of the two individuals
concerned has been observed (compare p. 42) to deposit eggs. In
the former, however, no such reciprocal act can take place, but
the same individual can play the part of male to one and female
to another, and we sometimes find a string of Limnaea thus
united, each being at once male and female to its two adjacent
neighbours.

The Reproductive System.—Broadly speaking, the comph-
cated arrangements which are found in Mollusca resolve themselves
into modifications of three important factors :—

(a) The gonads or germ-glands, in which are developed the

1 Hermaphroditism seems to occur in (a) whole families, e.g. Anatinidae and the
Septibranchia ; (b) genera, e.g. Cyclas, Pisidiwm ; (c) single species, e.g. in the
generally dioecious genera Ostrea, Pecten, Cardium.

2 dtw, two; pdvos, single ; yévos, semen ; mépos, passage.

Vv GENERATIVE ORGANS OF DIOECIOUS MOLLUSCA 135

ova and the spermatozoa. These glands are generally known as
the ovary in the female, the sperm-gland or ¢estis in the male.

(>) The channels which provide for the passage of the seminal
products ; namely, the oviduct in the female, the vas deferens or
sperm-duct in the male.

(c) The external generative organs.

Dioecious Mollusca.—The common Littorina obtusata will
serve as a typical instance of a dioecious prosobranchiate, exhibit-
ing the simplest form of organs. In the female the ovary, a
lobe-shaped body, is embedded in the liver. An oviduct with

Fic. 49.—Generative and other organs
of Littorina obtusata L., female.

A, anus. M,
Br, branchia.

Fic. 50.—Generative and other organs
of Littorina obtusata L., male.

A, anus. M, muscle of attach-
Br, branchia. ment.

muscle of
attachment.

Buc, buccal mass.
H, heart.

Hep, hepatic duct.
I, continuation of

O’, female orifice.
Od, oviduct.
Oes, oesophagus.
Ov, ovary.

H, heart.
I, intestine.
Li, liver.

Pe, penis.
Te, testis.
VD, vas deferens.

(After Souleyet.)

oesophagus Ra, radula.
Ki, kidney. St, stomach.
Li, liver. U, uterus.

(After Souleyet. )

many convolutions conveys the ova into the wferus, an oblong
chamber which consists simply of a dilatation of the oviduct. The
ova descend into the uterus, which is sometimes furnished with a
seminal pouch. In this seminal pouch, or above it, in the oviduct,
the ova come into contact with the spermatozoa. The lower part
of the uterus secretes a gelatinous medium (or capsule, as the case

136 GENERATIVE ORGANS OF DIOECIOUS MOLLUSCA CHAP.

may be) in which the fertilised ova become enclosed previous to
exclusion. In position the oviduct abuts on the kidney, while the
uterus is in close proximity to the rectum, and the female external
orifice is found close to the anus, within the branchial cavity.

The male organs of Zittorina are more simple. The fes¢is is
lodged, like the ovary, in the liver; the vas deferens is, like the
oviduct, convoluted, and eventually traverses the right side of the
neck, emerging near the right tentacle, and terminating in the
penis or external copulative organ (Fig. 50).

This system prevails, with but slight modifications in detail,
throughout the prosobranchiate Gasteropoda. The most important
modification is the passage of the seminal products in certain cases
(many of the Diotocardia) through the right kidney, with which
the oviduct and vas deferens always stand in close relation. The
same arrangement occurs in the Scaphopoda and some Pelecypoda.

The penis varies greatly in form and size. In the Strombidae
(see Fig. 99) and Buccinidae (Fig. 62) it is very large and promi-
nent; in Littorina it is somewhat spinulose at one side; in
Paludina a portion of it is lodged in the right tentacle, which
becomes atrophied and much more obtuse than the tentacle on
the left side.

Spermatozoa.—The shape of the spermatozoa and of the
ova in Mollusca is of the usual type. In Paludina, Ampullaria,
and certain species of Murex two types of spermatozoa occur,
one hair-like, the other worm-like, three times as long as the
former, and not tapering at one end. The former type alone
take part in fertilisation, and penetrate the ovum. It has been
suggested that these worm-like spermatozoa are a kind of
incipient ova, and indicate a possible stage in commencing
hermaphroditism. And, since the nearest allies of the Proso-
branchiata (in which these types occur) are hermaphrodite (7.e.
the Opisthobranchiata and Pulmonata), it is not unreasonable to
suppose that the Prosobranchiata should show some tendency
towards hermaphroditism in their genital glands.

Cephalopoda.—tThe special characteristic of the reproductive
organs in female Cephalopoda is the development of various glands,
some of considerable size, in connexion with the ovary and
oviduct. Sepia, Loligo, and Sepiola are furnished with two large
nidamental glands, which open into the mantle cavity independ-

1 Von Brunn, Arch. Mikr. Anat. xxiii. p. 418.

Vv THE HECTOCOTYLUS ARM IN CEPHALOPODA 137

ently of the oviduct. Their purpose is to produce a viscid mucus,
which envelops the ova at the moment of their emission and
eventually hardens into the egg-capsules. A pair of accessory
nidamental glands occur in Sepia, as well as a pair of smaller
glands situated on the oviduct itself.

In many of the male Cephalopoda the vas deferens is long
and dilated at its outer end into a glandular reservoir, within
which are formed the spermatophores, or narrow cylindrical
packets which contain a very large number of spermatozoa.
When charged, the spermatophores pass into what is known as
Needham’s sac, where they remain until required for use.
These spermatophores are a very characteristic part of the
reproductive arrangements in the Cephalopoda. The male of
Sepia has been noticed to deposit them, during union, upon the
buccal membrane of the female. During the emission of the ova
by the female, the spermatophores, apparently through the
agency of a kind of spring contained at one end, burst, and
scatter the spermatozoa over the ova.

The Hectocotylus Arm.—Perhaps the most remarkable
feature in the sexual relations of all the Mollusca is the so-
called hectocotylus of the Cephalopoda. In the great majority of
the male Cephalopoda, one of the ‘arms, which is modified for
the purpose in various ways and to a greater or less extent, be-
comes charged with spermatophores, and sometimes, during union,
becomes detached and remains within the mantle of the female,
preserving for some considerable time its power of movement.

The hectocotylus is confined to the dibranchiate Cephalopoda,
and its typical form, 7.e. when part of the arm becomes disengaged
and left with the female, occurs only in three genera of the
Octopodidae,viz. Argonauta, Ocythoe (Philonexis), and Tremoctopus.
In all of these, the male is many sizes smaller than the female.
In Argonauta the third arm on the left side becomes hectocoty-
lised. At first it is entirely enveloped in a kind of cyst, in such
a way that only a small portion of the tip projects; subsequently
the cyst parts asunder, and allows the arm to become expanded
to its full length, which considerably exceeds that of the other
arms. At a certain point the acetabula or suckers terminate,
and the remainder of the arm consists of a very long, tapering,
sometimes thread-lke filament, which is pointed at the extreme
tip. It is not yet known how the spermatophores find their way

138 TUE HECTOCOTYLUS ARM IN CEPHALOPODA CHAP.

into the hectocotylus, or how the hectocotylus impregnates the
ova of the female. The arm thus affected is not always the
same. In 7remoctopus it is the third of the right side, in the
Decapoda the modification usually affects the fourth of the left.
This singular property of the male Cephalopoda has only
recently been satisfactorily explained. It is true that Aristotle,
more than twenty-two centuries ago, distinctly stated that certain

Fic. 51.—Male of Ocythoe tubercu-
lata Raf. ( = Philonexis catenu-
latus, Fér.), Mediterranean,
showing three stages, A, B,
and C, in the development of
the hectocotylus arm: h.cy,
hectocotylus still in the cyst ;
c'y’, spoon-shaped cyst at the
end of the arm when freed ;
th, thread-like organ freed by
the rupture of cy’. Natural
size. From specimens in the
British Museum.

of the arms were modified for sexual purposes. Speaking of
what he calls the polypus (which appears to represent the Octopus
vulgaris of the Mediterranean), he says: ‘It differs from the
female in having what the fishermen call the white sexual organ
on its arm;’ again, ‘Some say that the male has something of a
sexual nature (aido.@dés Tv) on one of its arms, that on which
the largest suckers occur; that this is a kind of muscular
appendage attached to the middle of the arm, and that it is

Vv THE HECTOCOTYLUS ARM IN CEPHALOPODA 139

entirely introduced within the funnel of the female.’ Unfor-
tunately the word translated by introduced is corrupt, and can
only be restored conjecturally. He again remarks, ‘The last of
the arms, which tapers to a fine point and is the only whitish
arm, it uses 1n sexual union.’ !

The typical hectocotylus seems to have entirely escaped
notice until early in the present century, when both Delle Chiaje
and Cuvier described it, as detected within the female, as a
parasite, the latter under the name of Hectocotylus octopodis
Kolliker, in 1845—49, regarded the hectocotylus of Zremoctopus
as the entire male animal, and went so far as to discern in it an
intestine, heart, and reproductive system. It was not until 1851
that the investigations of Vérany and Filippi confirmed a
suggestion of Dujardin, while H. Miller, in 1855, completed the
discovery by describing the entire male of Argonauta.

In all genera of dibranchiate Cephalopoda except Argonauta,
Ocythoe, and Tremoctopus, one of the arms is sexually modified in
various ways, but never becomes so much prolonged, and is never
detached and left with the female. In Loligo Forbesii Stp. the
fourth arm on the left has 23 pairs of regularly developed aceta-
bula, which then lessen in size and disappear, being replaced by
long pedunculated papillae, of which there are about 40 pairs.
In Loligo vulgaris Lam. and L. Pleit Orb. 18 or 19 pairs of
acetabula are regularly formed, and then occur 40 pairs of papillae,
as in Forbesit. In other species of Loligo (gahi Orb., brevis BL,
brasiliensis Orb.) only the outer row of suckers becomes modified
into papillae after about the 20th to the 22nd pair. In Sepio-
teuthis sepioides the modification is the same as in the Loligo
last mentioned, but the corresponding arm on the right side is so
covered with acetabula towards its extreme end, that it is thought
that it in some way co-operates with the hectocotylised left arm.

In Octopus, the third arm on the right side is subject to
modification. This arm is always shorter than the corresponding
arm on the other side, and carries fewer suckers, but is furnished
at the extreme tip with a peculiar kind of plate, which connects
with the membrane at the base of the arm by a channel of skin,
which probably conveys the spermatophores up to the tip.

1 Hist. Anim. v. 6 and 12, iv. 1, ed. Bekker, 1887.
**On pourra constater si ce ne seraient pas des parties détachées de quelque cépha-
lopode dans le but de servir a le fécondation,’ Hist. Nat. Helminthes, 1845, p. 482.

140 HERMAPHRODITE MOLLUSCA, GENERATIVE ORGANS cuap.

In Octopus vulgaris, the species referred to by Aristotle, the
hectocotylsed arm is short, thin in its outer half and pointed at
the extremity, while the fold of skin is very white, and gives
the arm an appearance of being divided by a cleft at the side.
At the same time, an unusual development of one or two suckers
on the arm is not uncommon.!

Fic. 52.—Octopus lentus Baird, N. Atlantic, showing the peculiar formation of the
hectocotylus arm, i.a. (After Verrill, x 3.)

It is believed that in the Tetrabranchiate Cephalopoda
(Nautilus) a union of the four inner ventral arms may correspond
functionally to the hectocotylising of the arm in the Dibranchiates.

Hermaphrodite Mollusca.—(«) Monogonopora.—tThe repro-
ductive system in the hermaphrodite Mollusca is far more compli-
cated than in the dioecious, from the union of the male and female
organs in the same individual. As a type of the Monogonopora,
in which a single orifice serves for both male and female organs,
may be taken the common garden snail (Helix aspersa), the
accompanying figure of which is drawn from two specimens
found in the act of union (Fig. 53).

Beginning from the inside and proceeding outwards we have
firstly the hermaphrodite gland or ovo-testis (H.G.), a yellowish
white mass of irregular shape, embedded in the liver (1.) and
forming part of its spiral but not reaching quite to the apex.
Within this gland are developed the ova and spermatozoa. The
former are rather large round cells, produced within the outer
_wall of the gland, while the spermatozoa, which are produced in
the more central part, are threadlike bodies, generally agere-
gated in small bundles. From the hermaphrodite gland the ova

1 Steenstrup, dan. Mag. Nat. Hist. (2), xx. p. 81 f.

vV GENERATIVE ORGANS OF HELIX I4t

and spermatozoa pass through the upper part of the hermaphrodite
duct (#.D.), which is always more or less convoluted. Below
the convoluted portion, the duct opens into the albumen gland
(A.G.), a large linguiform mass of tissue which becomes dilated
at the time of pairing, and secretes a thick viscid fluid which
probably serves to envelop the ova. Up to this point both
the male and female elements follow the same course, but

Fic. 538.—Genitalia of Helix aspersa
Miiller, drawn from two indivi-
duals in the act of union, from a
dissection by F. B. Stead.

A.G, albumen gland.

C, coecum.

Cr, crop.

D.S, dart sac.

E, eye (retracted)

Fl, tlagellum.

H.D, hermaphrodite duct.
H.DF, ditto, female portion,
H.DM, ditto, male portion.
H.G, hermaphrodite gland.
L, liver.

M.G, M.G, mucous glands.
Ov, oviduct.

P.S, penis sac.

R.M, retractor muscle of penis.
Sp, spermatheca.

V, vagina.

V.D, vas deferens.

on their exit from the albumen gland they diverge. The herma-
phrodite duct becomes greatly enlarged, and is partially divided
by a kind of septum into a male and female portion. . These run
parallel to one another, the larger or female portion (H.DF.),
through which the ova pass (and which is sometimes termed the
uterus) being dilated into a number of puckered folds, while the
smaller or male portion (H.DM.) is comparatively narrow, and
not dilated. At their anterior end, the two portions ef the duct
separate completely from one another, the female portion being
then termed the oviduct (oy.) and the male portion the vas
deferens (Y.D.).

WAZ: FEMALE AND MALE ORGANS OF HELIX CHAP.

Following first the oviduct, we find that it soon widens into
the vagina (v.), which is furnished with a pair of mucous glands
(M.G.), one on each side. These are much branched, and re-
semble little bunches of whitish sea-weed. <A little above the
mucous glands a long tube diverges from the vagina, which is
furnished with a produced coecwm (c.) and a pouch, the spermatheca
(sP.) at the extreme end. In this pouch, and in the duct leading
to it, is stored the spermatophore received in union with another
snail. Just below the mucous glands the vagina is joined by the
dart sac (D.S.), Which is more fully described below. Finally, at
its lower end the vagina unites with the penis sac at a point just
posterior to the common orifice.

Returning now to the male organs, we find that the vas
deferens is the continuation of the male portion of the herma-
phrodite duct, after its final separation from the female portion.
It passes under the retractor muscle of the upper right tentacle,
which has been cut away in the specimen figured, to dissect
it out. Just before the vas deferens widens into the penis sac,
it branches off into a long and tapering tube, the flagellum, in
which the spermatozoa are stored and become massed together
in the long packet known as the spermatophore. The penis sac
(v.8.) is the continuation of the vas deferens beyond the point at
which the flagellum diverges. It joins the vagina at its extreme
anterior end, uniting with it to form the common genital aperture,
which cannot be exactly represented in the figure. The penis
itself lies in the interior of the penis sac, and is a rather long
muscular tube which is protruded during union, but at other
times remains retracted within the sac.

In the Helicidae generally, the form of the generative organs
varies with each separate species, sometimes merely as regards
the size of the different parts, at others in the direction of greater
sunplicity or complication. The mucous glands may be absent,
and the flagellum greatly reduced in size, or absent altogether.

The Dart Sac.—A remarkable part of the reproductive
system in many of the true Helicidae is the so-called dart, Liebes-
pfeil, or telum veneris. It consists of ‘a straight, or curved, some-
times slightly twisted tubular shaft of carbonate of lime, tapering
to a fine point above, and enlarging gradually, more often some-
what abruptly, to the base.’ The sides of the shaft are sometimes
furnished with two or more blades; these are apparently not for

Vv THE DART SAC 143

cutting purposes, but simply to brace the stem. The dart is
contained in a dart sac, which is attached as a sort of pocket
to the vagina, at no great dis-
tance from its orifice. There are
four different forms of sac. It
may be single or double, and each
of these divisions may be bilobed,
each lobe containing one dart at
a time. In Helix aspersa the
dart is about 5°; Im. in length, a

bo

Cc

, nig . . is : . =
and 8. in, in breadth at its base Fic. 54.—Darts of British land snails:
(see I 1e. 54). A, Hyalinia excavata Bean ; B, Helix

om Sa, ; , : hortensis Mill.; ©, Helix aspersa
It appears most probable that — yan, (After Ashford.)

the dart is employed as an ad-

junct to the sexual act. Besides the fact of the position of
the dart sac anatomically, we find that the darts are extruded
and become embedded in the flesh just before or during the act
of copulation. It may be regarded, then, as an organ whose
punctures induce excitement preparatory to sexual union. — It
only occurs in well-grown specimens. When once it begins to
form, it grows very rapidly, perhaps not more than a week being
required for its entire formation.

The dart is almost confined to MHelicidae, a certain number
of exceptions being known which border on Helix. Hyalinia
nitida and excavata are the only British species, not Helices,
which are known to possess it, It has not been noticed to
occur in the slugs, except in the N. American genus Tebenno-
phorus. About one-third of the British Helices are destitute of
the dart.1. HH. rufescens possesses a double bilobed sac, but only
two darts, which le in the lower lobes. It does not use the
darts, and could not do so, from the relative sizes of dart and
sac; it has often been watched when uniting, but the use of the
darts has never been observed. From this it has been inferred
that the darts are degenerate weapons of defence, and that they
were in fact at one time much stronger organs and more often
used.” This theory, however, does not seem consistent with the
whole circumstances of the occurrence, position, and present use
of the darts.

1 ©, Ashford, Journ. of Conch. iii. p. 239, iv. pp. 69, 108.
* W. E. Collinge, Zoologist, 1890, p. 276.

144 HERMAPHRODITE MOLLUSCA, GENERATIVE ORGANS cuap.

Hermaphrodite Mollusca.—()) Digonopora.—aAs an example
of the Digonopora or hermaphrodite Mollusca with separate
generative apertures for the male and female organs, we may
take the common Limnaea stagnalis (Fig. 55). It will be seen
from the figure’ that the relative positions of the hermaphrodite
gland and duct, and of the albumen gland, are the same as in
Helix. When the oviduct parts company from the vas deferens,
it becomes furnished with several accessory glands, one of which
(GLE.) probably serves as a reservoir for the ova, and answers
more or less to a uterus. The tube leading to the spermatheca

Fre. 55.—Genitalia of Limnaea stagnalis
L. (from a dissection by F. B. Stead),
x2.

A.G, albumen gland.

Ac.G, accessory gland.

F.O, female orifice.

G1.E, glandular enlargement.
H.D, hermaphrodite duct.
H.G, hermaphrodite gland.
Li, liver.

M.O, male orifice.

P, penis sac.

Pr, prostate.

R.M, retractor muscle of penis.
Sp, spermatheca.

V.D, vas deferens,

©}. il
\ say,

is short, and there is no divergent coecum. The female orifice
lies near to the external opening of the branchial cavity. The
vas deferens, Which is very long, is furnished with a large prostate
gland. The penis sac is greatly dilated, and there is no flagellum.
The male orifice is behind the right tentacle, slightly in advance
of the female orifice (compare Fig. 102).

Most of the Opisthobranchiata, but not all, have separate sexual
orifices. Numerous variations from the type just described will
be found to occur, particularly in the direction of the develop-

v GENITALIA OF PELECYPODA 145

ment of accessory glands, which are sometimes very large, and
whose precise purpose has in many cases not been satisfactorily
determined.

Pelecypoda.—tIn the dioecious Pelecypoda, which form the
great majority, the reproductive system is simple, and closely
parallel in both sexes. It consists of a pair of gonads, which
are either ovaries or testes, and a pair of oviducts or sperm-
duets which lead to a genital aperture. The gonads are usually
placed symmetrically at the sides or base of the visceral mass.
The oviduct is short, and the genital aperture is usually within
the branchial chamber, thus securing the fertilisation of the ova
by the spermatozoa, which are carried into the branchial chamber
with the water which passes through the afferent siphon.

Hermaphrodite Pelecypoda are rare, the sexes being usually
separate. The following are assured instances: Pecten glaber,
P. jacobaeus, P. maximus, Ostrea edulis, Cardium norvegicum,
Pisidium pusillum, Cyclas cornea, Pandora rostrata, Aspergillum
dichotomum, and perhaps Clavagella. The greater number of
these have only a single genital gland (gonad) on each side,
with a single efferent duct from each, but part of the gland is
male and part female, eg. in the Pectens above mentioned.
Pandora and Aspergillum have two distinct glands, respectively
male and female, on each side, each of the two glands possessing
its separate duct, and the two ducts from each side eventually
opening near one another. It appears probable that the Septi-
branchiata (Cuspidaria, Poromya, Lyonsiella, ete.) must also be
added to the number of hermaphrodite Pelecypoda which have
separate male and female glands.

It is worthy of remark that all the hermaphrodite Pelecypoda
belong to forms decidedly specialised, while forms distinctly
primitive, such as Nucula, Solenomya, Arca, and T'rigonia are all
dioecious. In Gasteropoda similarly, the least specialised forms
(the Amphineura, with the exception of the Neomeniidae, and
the Lhipidoglossa) are dioecious. It is possible therefore that
in the ancestors of the Mollusca the separation of the sexes had
already become the normal type of things, and that hermaphro-
ditism in the group is, to a certain extent, a sign or accompani-
ment of specialisation."

Development of Fresh-water Bivalves.—The vast majority

1 Pelseneer, Comptes Rendus, ex. p. 1081.
VOL. III L

146 DEVELOPMENT OF LARVAL PELECYPODA CHAP.

of fresh-water bivalves either pass the larval stage entirely
within the mother, and do not quit her except in a perfectly
developed form (Cyclas, Pisidium), or assume a mode of develop-
ment in which free larvae indeed occur, but are specially modified
for adaptation to special circumstances (Unio). Cyclas and
Pisidiwm, and no doubt all the kindred genera, preserve their ova
in a sort of brood-pouch within the gills, in which the ova pass
the earlier stages of their development. But, even so, the larva
of these genera retains some traces of its original free-swimming
habits, for a rudimentary velum, which is quite useless for its
present form of development, has been detected in Cyclas.

The larva of Dreissensia (see Fig. 47, A), so far as is at present
known, stands alone among fresh-water bivalves in being free-
swimming, and to this property has been attributed, no doubt
with perfect justice, the fact of the extraordinarily rapid spread
of Dreissensia over the continent of Europe (chap. xvi.). In
‘expelling the ova, the parent slightly opens the shells and then
quickly closes them; shooting out a small point of white shime,
which is in fact a little ball of eggs. The general course of
development is precisely parallel to that of marine Pelecypoda,
ereatly resembling, so far as form is concerned, certain stages in
the growth of the larvae of Modiolaria and Cardium, as figured
by Lovén.t

In June and July the larvae appear in large numbers on the
surface of the water, when in spite of their exceedingly small
size, they can be captured with a fine hand-net. They pass
about eight days on the surface, feeding apparently on minute
floating algae. During this time, the principal change they
undergo is in the formation of the foot, which first appears as
a small prominence midway between the mouth and anus, and
eradually increases in length and flexibility. When the larva
sinks to the bottom, the velum soon disappears entirely, the foot
becomes exceedingly long and narrow, while the shell is circular,
strongly resembling a very young Cyclas.

Larvae of Unionidae.—The early stages of the development
of Unio and Anodonta (so far as the species of North America,
Europe, and Asia are concerned) is of extreme interest, from
the remarkable fact that the young lve for some time para-
sitically attached to certain species of fresh-water fishes. In

1 Kon. Vet. Akad. Handi. 1848, pp. 329-435.

a -

V GLOCHIDIUM OF ANODONTA 147

order to secure this attachment, the larva, which is generally
known as Glochidium, develops a long filament which perhaps
renders it aware of the neighbourhood of a fish, and also a
larval shell furnished with strong hooks by which it fastens
itself to the body of its unconscious host (Fig. 56). According
to some interesting observations made by Mr. O. H. Latter,’
the ova pass into the external gill of the mother, in which is
secreted a nutritive mucus on which they are sustained until they
arrive at maturity and a suitable opportunity occurs for their
‘being born. If this opportunity is deferred, and the Glochidia
mature, their so-called ‘byssus’ becomes developed, and by being

Fig. 56.—A. Glochidiwm immediately after it is hatched: ad, adductor muscle; by,
‘byssus’ cord ; s, sense organs; sh, shell. B. Glochidiwm after it has been on the
fish for some weeks: a.ad, p.ad, anterior and posterior adductors; d/, alimentary
canal ; au.v, auditory vesicle ; br, branchiae ; 7, foot ; mt, mantle. (Balfour.)

entangled in the gill filaments of the parent, prevents their
escaping. It is interesting to notice that, when the nutritive
mucus of the parent is used up, it becomes, as it were, the
turn of the children to provide for themselves a secondary mode
of attachment.

The mother Anodonta does not always retain the Glochidium
until fish are in her neighbourhood. Gentle stirring of the
water caused them to emit Glochidiwm in large masses, if the
movement was not so violent as to cause alarm. The long slimy
masses of Glochidium were observed to be drawn back again within
the shell of the mother, even after they had been ejected to a
distance of 2 or 3 inches.

It is a mistake to assert that the young Glochidivm can swim.
When they finally quit the mother, they sink to the bottom,

1 P, Z, 8. 1891, p. 52.

148 DEVELOPMENT OF GLOCHIDIUM CHAP.

and there remain resting on their dorsal side, with the valves
gaping upwards and the so-called byssus streaming up into
the water above them. There they remain, until a convenient
‘host’ comes within reach, and if no ‘host’ comes within a
certain time, they perish. They are evidently peculiarly sensitive
to the presence of fish, but whether they perceive them by smell
or some other sense is unknown. “The tail of a recently killed
stickleback thrust into a watch-glass containing Glochidiuwm throws
thei all into the wildest agitation for a few seconds; the valves
are violently closed and again opened with astonishing rapidity
for 15—25 seconds, and then the animals appear exhausted and
he placid with widely gaping shells—unless they chance to have
closed upon any object in the water (e.g. another Glochidiwm), in
which case the valves remain firmly closed.”

In about four weeks after the Glochidiwm has quitted its
host, and the permanent shell has made its appearance within
the two valves of the Glochidiuwm, the projecting teeth of the
latter press upon the ventral edge of the permanent shell, at a
point about half way in its lengthward measurement, retarding
the growth of the shell at that particular point, and indenting
its otherwise uninterrupted curve with an irregular notch or dent.
As growth proceeds, this dent becomes less and less perceptible
on the ventral margin of the shell itself, but its effects may
be detected, in well-preserved specimens, by the wavy turn in the
hnes of growth, especially near the umbones of the young shell.

Mr. Latter found that all species of fish with which he
experimented had a strong dishke to Glochidiwm as an article
of food. Sometimes a fish would taste it “just to try,’ but
invariably spit it out again in a very decided manner. The cause
of unpleasantness seemed not to be the irritation produced in
the mouth of the fish by the attempt of the Glochidiwm to attach
itself, but was more probably due to what the fish considered a
nasty taste or odour in the object of his attentions.

The following works will be found useful for further ey of
this portion of the subject :—
F. M. Balfour, Comparative Embryology, vol. i. pp. 186-241.

F. Blochmann, Ueber die Entwickelung von Neritina fluviatilis Miill.: Zeit.
wiss. Zool. xxxvi. (1881), pp. 125-174.

v LIST OF AUTHORITIES 149

L. Boutan, Recherches sur l’anatomie et le développement de Ja Fissurelle :
Arch. Zool. exp. gén. (2) iii. suppl. (1885), 173 pp.

W. K. Brooks, The development of the Squid (Loligo Pealii Les.): Anniv.

Mem. Bost. Soc. Nat. Hist. 1880.
» The development of the oyster: Studies Biol. Lab. Johns
Hopk. Univ. i. (1880), 80 pp.
R. von Erlanger, Zur Entwickelung von Paludina vivipara: Morph. Jahrb.
XVil. (1891), pp. 337-379, 636-680.
bs Fe Zur Entwickelung von Bythinia tentaculata: Mitth. Zool.
Stat. Neap. x. (1892), pp. 376-406.
H. Fol, Sur le développement des Ptéropodes: Arch, Zool. exp. gén. iv.
(1875), pp. 1-214.
» Etudes sur le développement des Mollusques. Hétéropodes : ibid.
v. (1876), pp. 105-158..
» Etudes sur le développement des Gastéropodes pulmonés: ibid.
vill. (1880), pp. 103-232.

. Grenacher, Zur Entwickelungsgeschichte der Cephalopoden: Zeit. wiss.
Zool. xxiv. (1874), pp. 419-498.

. Hatschek, Ueber Entwickelungsgeschichte von Teredo: Arb. Zool. Inst.

Univ. Wien. iii. (1881), pp. 1-44.

. Horst, On the development of the European oyster ; Quart. Journ. Micr.

Sc. xxii. (1882), pp. 339-346.

. Korschelt and K. Heider, Lehrbuch der vergleichenden Entwickelungs-
geschichte der wirbellosen Thiere, Heft iii. (1893), pp. 909-1177 (the
work is in process of translation into English).

A. Kowalewsky, Embryogénie du Chiton polii avec quelques remarques
sur le développement des autres Chitons: Ann. Mus. Hist. Nat. Mars.
Zool. i. (1883), v.

E. Ray Lankester, Contributions to the developmental history of the

Mollusea ; Phil. Trans. Roy. Soc. vol. 165 (1875),
pp: 1-381.

a - Observations on the development of the pond-snail
(Lymnaeus stagnalis), and on the early stages of
other Mollusca: Quart. Journ. Micr. Sc. xiv. (1874),
pp. 365-391.

Observations on the development of the Cephalopoda :*

ibid. xv. (1875), pp. 37—47.

W. Patten, The embryology of Patella: Arb. Zool. Inst. Univ. Wien, vi.
(1886). pp. 149-174.

M. Salensky, Etudes sur le développement du Vermet: Arch. Biol. vi.
(1885), pp. 655-759.

L. Vialleton, Recherches sur les premitres phases du développement de la
Seiche (Sepia officinalis): Ann. Sc. Nat. Zool. (7) vi. (1888), pp. 165—
280.

S. Watase, Observations on the development of Cephalopods: Stud. Biol.

Lab. Johns Hopk. Univ. iv. (1888), pp. 163-183.
5 Studies on Cephalopods: Journ. Morph. iv. (1891), pp. 247-
294.

E. Ziegler, Die Entwickelung von Cyclas cornea Lam.: Zeit. wiss. Zool.

xli. (1885), pp. 525-569.

rh wD WwW

”) ”

CHAPTER VI

RESPIRATION AND CIRCULATION——_THE MANTLE

THE principle of respiration is the same in the Mollusca as in
all other animals. The blood is purified by being brought, in
successive instalments, into contact with pure air or pure water,
the effect of which is to expel the carbonic acid produced by
animal combustion, and to take up fresh supplies of oxygen.
Whether the medium in which a mollusc lives be water or
air, the effect of the respiratory action is practically the
same.

Broadly speaking, Mollusca whose usual habitat is the water
‘breathe’ water, while those whose usual habitat is the land
‘breathe’ air. But this rule has its exceptions on both sides.
The great majority of the fresh-water Mollusca which are not
provided with an operculum (e.g. Limnaea, Physa, Planorbis),
breathe air, in spite of living in the water. They make periodic
visits to the surface, and take down a bubble of air, returning
again for another when it is exhausted. On the other hand
many marine Mollusca which live between tide-marks (e.g. Patella,
Littorina, Purpura, many species of Cerithium, Planaxis, and
Nerita) are left out of the water, through the bi-diurnal recess
of the tide, for many hours together. Such species invariably
retain several drops of water in their branchiae, and, aided by
the moisture of the air, contrive to support lte until the water
returns to them. Some species of Littorina (e.g. our own L. rudis
and many tropical species) live so near high-water mark that at
neap-tides it must frequently happen that they are untouched
by the sea for several weeks together, while they are frequently
exposed to a burning sun, which beats upon the rocks to which
they cling. In this case if appears that the respiratory organs

CHAP. VI MODES OF RESPIRATION ra5

will perform their functions if they can manage to retain an
extremely small amount of moisture.'

The important part which the respiratory organs play in the
economy of the Mollusca may be judged from the fact that the
primary subdivision of the Cephalopoda into Dibranchiata and
Tetrabranchiata is based upon the number of branchiae they
possess. Further, the three great divisions of the Gasteropoda
have been named from the position or character of the breathing
apparatus, viz. Prosobranchiata, Opisthobranchiata and Pulmonata,
while the name Pelecypoda has hardly yet dispossessed Lamelli-
branechiata, the more familiar name of the bivalves.

Respiration may be conducted by means of—(a) Branchiae or
Gills, (6) a Lung or Lung cavity, (¢c) the outer skin.

In the Pelecypoda, Cephalopoda, Scaphopoda, and the great
majority of the Gasteropoda, respiration is by means of branchiae,
also known as ctenidia,?7 when they represent the primitive Mol-
luscan gill and are not ‘secondary’ branchiae (pp. 156, 159).

In all non-operculate land and fresh-water Mollusca, in the
Auriculidae, and in one aberrant operculate (Amphibola), respira-
tion is conducted by means of a lung-cavity, or rarely by a true
lung, whence the name Pulmonata. The land operculates
(Cyclophoridae, Cyclostomatidae, Aciculidae, and Helicinidae) also
breathe air, but are not classified as Pulmonata, since other points
in their organisation relate them more closely to the marine
Prosobranchiata. Both methods of respiration are united in
Ampullaria, which breathes indifferently air through a long
siphon which it can elevate above the surface of the water, and
water through a branchia (see p. 158). Stphonaria (Fig. 57) is
also furnished with a lung-cavity as well as a branchia. Both
these genera may be regarded as in process of change from an
aqueous to a terrestrial life, and in Siphonaria the branchia is to
a great extent atrophied, since the animal is out of the water, on
the average, twenty two hours out of the twenty-four. In the allied
genus Gadinia, where there is no trace of a branchia, but only a

! The result of some experiments by Professor Herdman upon Littorina rudis,
tends to show that it can live much better in air than in water, and goes far to support
the view that the species may be undergoing, as we know many species must have under-
gone (see p. 20), a transition from a marine to a terrestrial life. It was found that
marked specimens upon the rocks did not move their position for thirty-one successive
days (Proc. Liverp. Biol. Soc. iv. 1890, p. 50).

* Diminutive of x7eés, a comb.

152 RESPIRATION BY THE SKIN CHAP.

Fia.57.—A, Siphonaria gigas,
Sowb., Panama, the animal
contracted in spirit: gr,
siphonal groove on right
side. B, Gadiniu peru-
viand, Sow)., Chili, shell
only: g7, mark of siphonal
groove to right of head.

t hig

organisation exactly analogous to that of Cyclophorus,
process may be regarded as practically completed.

Respiration by means of the skin, without the development
of any special organ, is the
simplest method of breathing
which occurs in the Mollusca.
In certain cases, e.g. Hlysia, Li-
mapontia, and Cenia among the
Nudibranchs, and the parasitic
Entoconcha and Entocolax, none
of which possess breathing organs
of any kind, the whole outer
surface of the body appears to
perform respiratory functions. In
others, the dorsal surface 1s cov-
ered with papillae of varied size
and number, which communicate
with the heart by an elaborate
system of veins. This is the case
with the greater number of the
Aeolididae (Fig. 58, compare Fig.
5, C), but 1t 1s curious that when
the animal is entirely deprived of
; ~~ these papillae, respiration appears

Fia. 58.—Aeolis despecta Johnst., British ‘ : :
coasts. (After Alder and Hancock.) to be carried on without inter-

ruption through the skin.

Tn the development of a distinct breathing organ, it would
seem as if progress had been made along two definite lines, each

”

1 Stoliczka, quoted in Jowrn. de Conch. xviii. p. 452.

VI DEVELOPMENT OF A BREATHING ORGAN 153

resulting in the exposure of a larger length of veins, i.e. of a
larger amount of blood, to the simultaneous operation of fresh
air or fresh water. Either (@) the skin itself may have developed,
at more or less regular intervals, elevations, or folds, which gradually
took the form of papillae, or else (4) an inward folding, or ‘in-
vagination, of the skin, or such a modification of the mantle-
fold as is described below (p. 172) may have taken place,
resulting in the formation of a cavity more or less surrounded
by walls, within which the breathing organs were ultimately
developed. Sometimes a combination of both processes seems to
have occurred, and after a papilliform organ has been produced,
an extension or prolongation of the skin has taken place, in
order to afford a protection to it. Respiration by means of a
lung-cavity is certainly subsequent, in point of time, to respiration
by means of branchiae.

The branchiae seem to have been originally paired, and
arranged symmetrically on opposite sides of the body. It is not
easy to decide whether the multiple form of branchia which
occurs In Chiton (Fig. 59), or the simple form as in Fissurella

ay

THEI

Sl

i

ini

Fic. 60.—Sissurella virescens Sowb.,

Panama, showing position of the
Fic. 59.—Chiton squamosus L., Bermuda : branchiae: Br, branchiae ; E, E, eyes :

A, anus ; Br, branchiae ; M, mouth. F, foot; M, mantle; T, T, tentacles.
(Fig. 60), is the more primitive. Some authorities hold that
the multiple branchia has gradually coalesced into the simple,
others that the simpie form has grown, by serial repetition,
into the multiple. There appears to be no trace of any inter-
mediate forms, and, as a matter of fact, the multiple branchia is

154 BREATHING ORGANS IN AMPHINEURA _ CHAP.

found only in the Amphineura, while one or rarely two (never
more) pairs of branchiae, occur, with various important modi-
fications, in the vast majority of the Mollusca.

Amphinevra.—In Chiton the branchiae are external, forming
a long row of short plumes, placed symmetrically along each side
of the foot. The number of plumes, at the base of each of which
lies an osphradial patch, varies from about 70 to as few as
6 or 7. When the plumes are few, they are confined to the
posterior end, and thus approximate to the form and position of
the branchiae in the other Amphineura. In Chaetoderma, the
branchiae consist of two small feather - shaped bodies, placed
symmetrically on either side of the anus, which opens into a sort
of cloaca within which the branchiae are situated. In Weomenia
the branchiae are still further degraded, consisting of a single

— —

F1a. 61.—Terminal portions of the Amphineura, illustrating the gradual degradation
of the branchiae, and their grouping round the anus in that class. A, Chiton
(Hemiarthrum) setulosus Carp., Torres Str.; B, Chiton (Leptochiton) benthus Hadd.,
Torres Str.; ©, Chaetodermu ; D, Neomenia; a, anus; br, br, branchiae; k, kh,
kidneys ; p, pericardium. (A and B after Haddon, © and D after Hubrecht.)

bunch of filaments lying within the cloaca, while in Proneomenia
there is no more than a few irregular folds on the cloaca-wall
(Fig. 61).

In the Prosobranchiata, symmetrically paired branchiae ocew
only in the Fissurellidae, Haliotidae, and Pleurotomaridae, in the
former of which two perfectly equal branchiae are situated on
either side of the back of the neck. These three families taken
together form the group known as Zygobranchiatat In all other
families the asymmetry of the body has probably caused one of
the branchiae, the right (originally left), to become aborted, and
consequently there is only one branchia, the left, m the vast
majority of marine Prosobranchiata, which have been accordingly

1 Géyov, a yoke, from the symmetrical position of the branchiae.

VI BREATHING ORGANS IN PROSOBRANCHIATA 155

eroupedas Azygobranchiata. Even in Haliotis the right branchia
is rather smaller than the left, while the great size of the attach-
ment muscle causes the whole branchial cavity to become pushed
over towards the left side. In those forms which in other respects
most nearly approach the Zygobranchiata, namely, the Trochidae,
Neritidae, and Turbinidae, the branchia has two rows of filaments,
one on cach side of the long axis, while in all other Proso-
branchiata there is but one row (see Fig. 79, p. 169).

In the great majority of marine Prosobranchiata the branchia
is securely concealed within a chamber or pouch (the respiratory
cavity), Which is placed on the left dorsal side of the animal,
generally near the back of the neck. For breathing purposes,
water has to be conveyed into this chamber, and again expelled
after it has passed over the branchia. In the majority of the
vegetable-feeding molluscs (e.g. Lit-
torina, Cerithium, Trochus) water
is carried into the chamber by a
shuple prolongation of one of the
lobes or lappets of the mantle, and
makes its exit by the same way,
the incoming and outgome currents
being separated by a valve - like
fringe depending from the lobe.
In the carnivorous molluscs, on the
other hand, a regular tube, the
branchial siphon, which is more
or less closed, has been developed
from a fold of the mantle surface,
for the special purpose of con-
ducting water to the branchia. y,, 69. putlia laevissima Gmel..

After performing its purpose there, showing branchial siphon § ; F, F, F,
foot ; OP, operculum; P, penis ;
Pr, proboscis; T, T, tentacles.
through the siphon, but 1s con- (After Quoy and Gaimard.)

the spent water does not return

ducted towards the anus by vibra-

tile cilia situated on the branchiae themselves. In a_ large
ntunber of cases, this siphon is protected throughout its entire
leneth by a special prolongation of the shell called the cand.
Sometimes, as in Buccinum and Purpura, this canal is little more
than a mere notch in the ‘mouth’ of the shell, but in many of
the Muricidae (e.g. IZ haustellum, tenuispina, tribulus) the canal

156 BREATHING ORGANS IN PROSOBRANCHIATA CHAP.

becomes several inches long, and is set with formidable spines
(see Fig. 164, p. 256). In Doliwm and Cassis the canal is very
short, but the siphon is very long, and is reflected back over the
shell.

The presence or absence of this siphonal notch or canal forms
a fairly accurate indication of the carnivorous or vegetarian
tendencies of most marine Prosobranchiata, which have been, on
this basis, subdivided into Siphonostomata and Holostomata. But
this classification is of no particular value, and is seriously
weakened by the fact that Matica, which is markedly ‘holo-
stomatous, is very carnivorous, while Cerithiwm, which has a
distinct siphonal notch, is of vegetarian tendencies.

In the Zygobranchiata the water, after having aerated the
blood in the branchiae, usually escapes by a special hole or holes
in the shell, situated either at the apex (/ssurella) or along the
side of the last whorl (Haliotis). In Pleurotomaria the shit
answers a similar purpose, serving as a sluice for the ejection of
the spent water, and thus preventing the inward current from
becoming polluted before it reaches the branchiae (see Fig.
eo; Pp. -2.010)).

In Patella the breathing arrangements are very remarkable.
In spite of their apparent external similarity, this genus possesses
no such symmetrically paired plume-shaped branchiae as /’%s-
surella, but we notice a circlet of gill-lamellae, which extends
completely round the edge of the mantle. It has been shown by
various authorities that these lamellae are in no sense morpho-
logically related to the paired branchiae in other Mollusca, but
only correspond to them functionally. The typical paired
branchiae, as has been shown by Spengel, exist in Patella in a
most rudimentary form, being reduced to a pair of minute yellow
bodies on the right and left sides of the back of the ‘neck.’ <A
precisely similar abortion of the true branchiae, and special
development of a new organ to perform their work, is shown
in Phyllidia and Pleurophyllidia (see below under Opistho-
branchiata). This circlet of functional gills in Patella has there-
fore little systematic value, being only developed in an unusual
position, like the eyes on the mantle in certain Pelecypoda, to supply
the place of the true organs which have fallen into disuse. Accord-
ingly Cuvier’s class of Cyclobranchiata, which included Patella
and Chiton, has no value, and has indeed long been discarded.

VI BREATHING ORGANS IN PROSOBRANCHIATA WS Hy

In Chiton the gills never extend completely round the animal,
but are always more or less interrupted at the head and anus.
They are the true gills, the plumes being serially repeated in the

same way as the shell plates.

Fic. 64. — Patella vulgata L., seen from
the dorsal side after the removal of the
shell and the black pigment covering
the integument ; the anterior portion of

Fic. 65.—Patella vulgata I.., seen from the the mantle is cut away or turned back :
ventral side: 7, foot; g./, circlet of gill a, anus; br, br, remains of the true
lamellae ; m.e, edge of the mantle ; mv, branchiae (ctenidia) ; 7, intestine ; %, 2’,
attachment muscle ; s/, slits in the same ; kidneys ; k.ap, their apertures on each
sh, shell; v, vessel carrying aerated blood side of the anus; /, liver; m, m, mantle;
to the heart ; v’, vessel carrying blood from mu, attachment muscles, severed in re-
the heart ; ve, small accessory vessels. moval of shell ; ¢, ¢, tentacles.

In the land Prosobranchiata (Cyclostomatidae, Cyclophoridae,
Aciculidae, Helicinidae) which, having exchanged a marine for
an aerial life, breathe air instead of water, the branchia has
completely disappeared, and breathing is conducted, as in the
Pulmonata, by a lung-cavity. In certain genera of land oper-
culates, e.g. Pupina, Cataulus, Pterocyclus, a slight fissure or tube
in the last whorl (see Fig. 180, p. 266) serves to introduce air
into the shell, which is perhaps otherwise closed to air by the oper-
culun. In Aulopoma, which has no tube, the operculum adimits
free circulation of air. In certain other Cyclostomatidae the apex
is truneated, and air can enter there. De Folin closed with wax
the aperture of Cyel. elegans, and found that on placing it in a
pneumatic machine, the shell gave off air through its whole sur-
face. On the other hand, Cylindrella and Stenogyra decollata,

158 BREATHING OF AMPULLARIA CHAP.

on being submitted to the same test, showed that the truncated
part alone was permeable by air.

Fischer and Bouvier have made some interesting observations
on the breathing of a species of Ampullaria (insularwm Orb.).
The species has, in common with all Ampullaria, two siphons,
but while the right siphon is but shghtly developed, the left is
very long, almost twice as long as the
shell (see Fig. 65). The animal, when
under the water, lengthens its siphon,
brings the orifice to the surface, and by
alternately raising and depressing its head
produces in the pulmonary sac movements
of ex- and inspiration; these are repeated
about ten or fifteen times at reeular
intervals of from six to eight seconds,
a method of respiration strongly resem-
bling that of the Cetacea. At the same
time, branchial respiration takes place.
If powdered carmine is added to water,

the particles are seen to enter the bran-

De ae Pee ae chial cavity by the siphon and pass out
water ; B, breathing air; Si, by the short right siphon. Sometimes
ae Sige the animal remains under water for
pansion, performing the part hours without rising to the surface to
Se aea Ree es inspire air. In Valvata (Fig. 66) the
branchia 1s very large, and projects like

a leaf or fan above the shell on the left side; on the correspond-
ing position on the right side is a long filiform appendage, which
some have regarded as representing the other branchia.
Opisthobranchiata.—A true branchia occurs only in the Tecti-
branchiata and the Ascoglossa. It hes on the right side, and is
usually more or less external, being partly covered sometimes by
the shell (as in Umbrella, Fig. 5), sometimes by a fold of the
‘mantle. In the Pteropoda (which are probably derived from the
Tectibranchiata), all the Thecosomata, with the exception of
Cavolinia, have no specialised branchia, but probably respire
through portions or the whole of the integument. In the
Gymnosomata an accessory branchia has in many cases been de-
veloped at the posterior end of the body. Pneuwmodermon alone
has both lateral and posterior branchiae well developed, Clione

VI BREATHING ORGANS IN OPISTHOBRANCHIATA 159

and Halopsyche are destitute of either,
families have one branchia, sometimes la

Certain of the Nudibranchiata possess
no special breathing organs, and pro-
bably respire through the skin (4/ysia,
Limapontia, Cenia, Phyllirrhoé). The
majority, however, have developed sec-
ondary branchiae, in the form of promi-
nent lobes or leaf-like processes (the
cerata), which are carried upon the back,
without any means of protection. These
cerata are, as a rule, of extreme beauty
and variety of form, consisting sometimes
of long whip-hke tentaculae, in other
cases of arborescent plumes of fern-like

while the four remaining
teral, sometimes posterior.

Fie. 66.— Valvata piscinalis
Miill. : 67, branchia ; fi, fila-
ment ; 7./, foot lobes. (After
Boutan. )

leafage, in others of curious bead-like appendages of every imagin-

able shape and colour. In Doris they lie

Fic. 67.—Doris (Archidoris)
tuberculata L., Britain: «a,

at the posterior end of the

anus ; br, branchiae, sur- Fia. 68. — Pleurophyllidia Tineata
rounding the anus ; m, male Otto, Mediterranean : a, anus ; U7,
organ ; 7h, 7h, rhinophores, secondary branchiae ; mm, mouth ;
xe: s.0, sexual orifice.

body, in a sort of rosette, which is generally capable of retraction

intoa chamber. In Phyllidia and Plew

ophyllidia these secondary

branchiae lie, as in Patella, on the lateral portions of the mantle.

1 Pelsenecer, ‘ Challenger’ Reports, v

ol. xxiii. part. Ixvi.

160 BREATHING ORGANS IN PULMONATA CHAP.

The Scaphopoda in all probability possess neither true nor
secondary branchiae.

Pulmonata.—When we use the term ‘lung, it must be
remembered that this organ in the Mollusca does not correspond,
morphologically, with the spongy, cellular ling of vertebrates ;
it simply performs the same functions. The ‘lung, in the
Mollusca, is a pouch or cavity, lined with blood-vessels which
are disposed over its vaulted surface in various patterns of
network. The pulmonary sac or cavity is therefore a better
name by which to denote this organ.

It seems probable, as has been already shown (pp. 18-22),
that all Pulmonata are ultimately derived from marine forms
which breathed water by means of branchiae. Thus we find inter-
mediate forms, such as Siphonaria, possessed of both a branchia
and a pulmonary sac, the former being evanescent, while in
Gadinia and Amphibola it has quite disappeared. In the vast

Fic. 69.—Geomalacus maculosus Allm., 8. Tveland: P.O, pulmonary orifice.

majority of Pulmonata no trace of a branchia remains ; its function
is performed by a chamber, always situated at the right side of
the animal, and generally more or less anterior, admitting air by
a narrow aperture which is rhythmically opened and closed. In
Arion and Geomalacus (Fig. 69) this aperture is in the front of the
right side of the ‘shield’ in Zimaz (Fig. 71) in the hinder part,
in Testacella (Fig. 20) it is near the extremity of the tail, under
the spire of the shell; in Janel/a it is on the middle of the right
edge of the shield (Fig. 70). If a specimen of Helia aspersa,
or better, of H. pomatia, is held up to the light, the beautiful
arborescent vessels, with which the upper part of the pulmonary
chamber is furnished, can be clearly seen by looking through the
aperture as it dilates. It is only in the Auriculidae that an
actual spongy mass of lung material appears to exist. When in
motion, a Helix inspires air much more frequently than when
at rest. Temperature, too, seems to affect the number of inspira-
tions; it appears doubtful whether, during hibernation, a snail

VI BREATHING ORGANS IN PULMONATA Mont

breathes at all. In any case, the amount of air required to
sustain life must be small.

With regard to the respiration of fresh-water Pulmonata there
appears to be some difference of opinion. It is held, on the one
hand, that the Limnaeidae only respire air, making periodic visits
to the surface to procure it, and that they perish, if prevented
from doing so, by asphyxiation. If, we are told,’ as a Limnaca
is floating on the surface of the water in a glass jar, a morsel of
common salt be dropped upon its outstretched foot, it will sink

Fic. 70.—Janella hirudo Fig. 71.—Limaz maximus L.: PO, pulmonary
Fisch., N. Caledonia : orifice. x %.
G, generative orifice ; P,
pulmonary orifice ; T, T,
tentacles. (After Fis-
cher.)
heavily to the bottom, emitting a stream of air from its pulmon-
ary orifice. On recovering from the shock, it will anxiously
endeavour to regain the surface, but will have some difficulty
in doing so, owing to its now much greater specific gravity.
When it succeeds, it creeps almost out of the water, and exposes
its respiratory orifice freely to the air. If the experiment is
repeated several times on the same individual, it becomes so much
weakened that it has to be taken out of the water to save its
1 Zoologist, xii. p. 4248.
VOL. LE M

162 BREATHING OF DEEP-WATER LIMNAEA CHAP.

life. Moquin-Tandon, on the other hand, is strongly of opinion !
that there is no absolute necessity for Limnaea to obtain air by
rising to the surface, and that, if prevented from emerging, it can
obtain air from the water. When covered in by a roof of ice,
Limnaea has not been observed to suffer any inconvenience.
Moquin-Tandon kept Z. glabra and Planorbis rotundatus in good
health under 20 mm. of water for eighteen and nineteen days,
and relates a case in which Physa was kept alive under water
for four days, and Planorbis for twelve. Young specimens, both
of Limnaea and Planorbis, do not rise to the surface for a supply
of air; they are hatched with the pulmonary cavity full of water.

It is probable, therefore, that Limnaeidae are capable, on
occasion, of respiration through the skin. Some authorities are
of opinion that certain long and narrow lamellae, situated within
the pulmonary sac, are employed for the purpose of aqueous
respiration. -Ancylus, which never makes periodic excursions to
the surface, perhaps respires by receiving into its pulmonary
chamber the minute quantities of oxygen given off by the
vegetation on which it feeds.

Limnaeidae taken from a great depth of water, eg. from 130
fathoms in the lake of Geneva, have been examined by Forel.’
The pulmonary sac is full of water, but there is no transformation
of organs, no appearance of a branchia, to meet the changed cir-

cumstances of their environment. Doubtless a good deal of
respiration is done by the skin; being soft and vascular,
it respires the air dissolved in the water. Forel cites cases

of Limnaew living at much shallower depths, which come to
the surface once, and then remain below for months. The
oxygen of this supply must soon have become exhausted, and the
animals, discontinuing for a time the use of the pulmonary
chamber, must have respired through the skin. Shallow-water
Limnaea, according to the same authority, remain beneath the sur-
face during cold weather; when warm weather returns they rise
to the surface to take ina supply of air. Since the water at great
depths is always very cold, there is no need for the Limnaea living
there to rise to the surface at all.

It is a curious fact that Limnaea, which have been respiring
by the skin for the whole winter, should suddenly, on the first
warm days of summer, take to rising to the surface and breathing

1 Mollusques de France, i. p. 81. * N. Denk. Schw. Ges. xxix. (2) p. 196 f.

VI EXPERIMENTS ON BREATHING OF HELIX 163

air. But exactly the same phenomenon is shown in the case of
Limnauea from great depths. Placed in an aquarium, they
immediately begin rising to the surface and inspiring air; in
other words, they experience instantaneously a complete trans-
formation of their respiratory system.

In Onchidium, a land pulmonate which has retrogressed to an
amphibious or quasi-marine mode of life, there is no organ which
represents the pulmonary or branchial cavity, the so-called lung
being only a cavity of the kidney. Respiration is, however,
conducted by the skin as well, and by the dorsal papillae."

Land Mollusca can sustain, for a considerable time, complete
deprivation of atmospheric air. Helices placed in an exhausted
receiver show no signs of being inconvenienced for about 20 hours,
and are able to survive for about two or three days. If detained
under water, they are very active for about 6 hours, then become
motionless, the body swells, owing to the water absorbed, and
death ensues in about 36 hours. Immersion for only 24 hours
is generally followed by recovery. In the latter case, the cause
of death is not so much deprivation of air as compulsory absorp-
tion of water by the skin. The amount of water thus taken up
is surprising. Spallanzani found that a Helia which weighed 18
grammes increased in weight by 134 grammes after a prolonged
immersion. Even slugs enclosed in moist paper gained more
than 2 grammes in the course of half an hour. Experiment has
shown that the amount of carbonic acid gas produced by respira-
tion stands in direct relation to the amount of food consumed.
Four pairs of snails were taken which had recently awakened
from their winter sleep and had eaten heartily, and an equal
number, under the same circumstances, which had been prevented
from eating. It was found that the first four pairs produced, in
consuining a given amount of oxygen, 11, 9, 10, and 13 parts
respectively of carbonic acid, while the second set produced, in
consuming the same amount of oxygen, only 4, 8, 7, and 9 parts
of carbonic acid. Hibernating Helices, if weighed in December
and again in April, will be found to have lost weight, due to the
expiration of carbonic acid. Owing to the difficulty of experi-
ment, opinions vary as to the absolute temperature of snails. It
appears to be established that several snails, if placed together in
a tube, raise the temperature one or two degrees C., but as a rule,

2 Bergh, Morph. Jahrb. x. p. 172. 2 Pp. Fischer, Jowrn. de Conch. ix. p. 101.

164 POSITION OF BRANCHIAE IN PELECYPODA CHAP.

the temperature of a solitary Helix differs very slightly from that
of the surrounding air. Increased activity, whether in respiration
or feeding, is found to raise the temperature.

W. H. Dall, writing of the branchia in Pelecypoda, remarks *
that there can be no doubt that its original form was a simple
pinched-up lamella or fold of the skin or mantle. This, elongated,

Fia. 72. — Cardium
edule L.: A, anal ;
B, branchial siphon ;
F, foot. (After
Mobius. )

becomes a filament. Filaments united by suitable tissue, trussed,
propped, and stayed by a chitinous skeleton, result in the forms,
wonderful in number and complexity, which puzzle the student
to describe, much more to classify.

In Pelecypoda the branchiae are placed on each side of the
body, between the mantle and the visceral mass. They le in a

Fia. 73.—NScrobicularia piperata Gmel., in its natural position in the sand: A, efferent
or anal siphon ; B, afferent or branchial siphon. (After Mobius.)

chamber known as the branchial cavity. Leading into this
cavity, and behind it, are, as a rule, two tubes or siphons, one of
which conducts water to the branchiae, while the other carries it
away after it has passed over them. The lower is known as the
branchial or afferent siphon, the upper as the anal or efferent
siphon (see Figs. 72 and 73). The action of these siphons
can readily be observed by placing a little carmine in water,

1 Bull. Mus. C. Z. Harv. xviii. p. 434,

VI THE SIPHONAL APERTURES 165

near to the siphonal apertures of an Anodonta or Unio. In
many cases (e.g. Psammobia, Tellina, Mya, genera which burrow
deeply in sand) both the siphons are exceedingly long, sometimes
considerably longer than the whole shell. In some cases the two
tubes are free throughout their entire length, in others they be-
come fused together before their entrance within the shell (Fig.
74). In other genera, which do not burrow (e.g. Ostrea, Pecten,
Arca, Mytilus), the siphons are rudimentary or altogether absent
(Fig. 75).

The number and arrangement of the branchiae varies con-

Fic. 74.—Solecurtus strigillatus L., Fie. 75.—Mytilus edulis L., attached by its byssus

Naples: s.af, afferent siphon ; (By) to a piece of wood: F, foot; S, anal siphon,
s.ef, efferent siphon, the two the branchial siphon being below it and not
uniting in SS externally to the closed. (After Mobius.)

shell. x4.

siderably. It appears probable that the different degrees of
complication of the gill indicate degrees of specialisation in the
different groups of Pelecypoda, in other words, assuming that a
simpler form of gill precedes, in point of development, a more
complicated form, the nature of the gill may be taken as indicat-
ing different degrees of removal from the primitive form of
bivalve.

166 THE GILL IN PELECYPODA CHAP.

1. The simplest form of gill (Wucula, Leda, Solenomya, ete.) is
that which consists (Fig. 76, A, compare Fig. 100, p. 201) of two
rows of very short, broad, not reflected filaments, the rows being
placed in such a way that they incline at right angles to one
another from a common longitudinal axis. The filaments are not
connected with one another, nor are the two leaves of each gill
united at any point. (Protobranchiata.)

2. In the Anomiidae, Arcadae, Trigoniidae, and Mytilidae each
gill consists of two plates or rows of much longer filaments, which
consequently occupy a much larger space in the mantle cavity

D

Fic. 76.—Morphology of the branchiae of Pelecypoda, seen diagrammatically in section :
A, Protobranchiata; B, Filibranchiata; C, Eulamellibranchiata ; D, Septi-

branchiata ; e, e, external row of filaments ; 7, 7, internal row of filaments ; e’, ex-

ternal row or plate folded back ; 7’, internal row folded back ; 7, foot ; m, mantle ;

s, septum ; v, visceral mass. (From A. Lang.)
(Fig. 76, B). Unable to extend beyond the limits of the mantle,
filaments are reflected or doubled back upon one another, those
of the external plate being reflected towards the outside, those of
the internal plate towards the inside. Each
separate filament is not connected with the
filament next adjacent, except by surface
cilia situated on small projections on the
sides of the filaments, and interlocking with
the cilia of the adjacent filament. The two
superposed plates or leaves of the gill may or
= may not be united by cords running between
' 1) the two parts ofa filament. (/ilibranchiata.)
Fic. 77. —Four gill fila- 3. In the Pectinidae, Aviculidae, and
highly nee ae Ostreidae a further development takes
ciliary junctions; f, place. The filaments of each gill are
filament. (After Peck.) : : ; sae
reflected in the same way as in the Mili-
branchiata, but the part thus reflected may become completely

RANGOON
jupsncants!|
YOGOOWON'

VI THE GILL IN PELECYPODA G7

united or ‘coneresce’ with the mantle on the exterior and
with the base of the foot on the interior side. The leaves of
each gill plate, which have thus become doubled (the gills being
apparently two instead of one on each side), are folded or crum-
pled, and the filaments are modified at the re-entrant angles of
the fold. (Pseudolamellibranchiata.)

4, In all the remaining Pelecypoda, except class 5, in other
words, in the very large majority of families, the filaments are
either reflected, as in (3), or
simple ; but the process of con-
erescence is so far advanced
that the adjacent filaments are
always intimately connected
with one another in such a
way as to admit the passage
of the blood; and the leaves
Gineach eill-plate (Fig. 76, C) Fic. 78.—Transverse section of portion of

: an outer gill plate of Anodonta, highly
are united by eross channels in magnified: i, inner lamella; iJ’, outer

a similar way. (EHulamelli- jange vertical vessel. (Aftcr Peck.)
branchiata.)

5. In certain of the Anatinacea alone (Cuspidaria, Lyonsiella,
Poromya, Silenia) the gills are transformed into a more or less
muscular partition, extending from one adductor muscle to the
other (Fig.76, D), and separating off the pallial chamber into two
distinct divisions, which communicate by means of narrow slits
in the partition. (Septibranchiata.)

Thus the process of gill development in the Pelecypoda
appears to lead up from a simple to a very complex type. In
its original form, at all events in the most primitive form known
to us, the gill is a series of short filaments, quite independent of
one another, strung in two rows; then the filaments become
longer and double back, while at the same time they begin to

show signs of adhesion, as yet only superficial, to one another.
In a further stage, the reflected portions become fused to the
adjacent surfaces of the foot and mantle, while the interlamellar
junctions serve to lock the two gill-plates together; finally, the
mere ciliary junction of adjacent filaments is exchanged for inti-
mate vascular connection, while the gill-plates as a whole become
closely fused together in a similar manner.

This theory of origin is strengthened by closer observa-

168 RELATIONS BETWEEN BRANCHIAE AND HEART CHAP.

tion of the phenomena of a single group. Taking the Septi-
branchiata as an instance, we find that in Lyonsiella the branchiae
unite with the mantle in such a way as to form two large pallial
chambers, the structure of the branchiae being preserved, and
their lamellae covering the partition. A further stage is
observed in Poromya. There, a similar partition exists, but it
has become muscular, preserving, however, on each side two
groups of branchial lamellae, separated one from the other by a
series of slits, which form a communication between the two
pallial chambers. A further stage still is seen in Silenia. There
the same muscular partition exists, but the branchial lamellae on
either side have disappeared, the slits between the two chambers,
which occur in Poromya, still persisting, but separated into
three groups. Cuspidaria represents the last stage in the
development. In the ventral chamber there appears nothing at
all corresponding to a branchia; the surface of the partition
appears perfectly uniform, but on careful examination three little
separate orifices, remains of the three groups of orifices in Stlenia,
are observed."

Relation between Branchiae and Heart—The object of the
branchiae being, as has been already stated, to aerate the blood
on its way to the heart, we find that the heart and the branchiae
stand in very important structural relations to one another.
When the branchiae are in pairs, we find that the auricles of the
heart are also paired, the auricle on the right and left sides being
supplied by the right and left branchiae respectively. This is
the case with the Dibranchiate Cephalopods (Argonauta, Octopus,
Loligo, etc.), the Zygobranchiate Prosobranchs (/issurella, Hali-
otis), and all Pelecypoda. In the Amphineura (Chiton, etc.) there
are two auricles corresponding to the two sets of multiple
branchiae. In the case of the Tetrabranchiate Cephalopods
(Nautilus) there are four auricles corresponding to each of the
four branchiae. Compare Fig. 79, A, B, C, D, E.

On the other hand, when the branchia is single, or when both
branchiae are on the same side, and one is aborted and functionless,
the auricle is single too, and on the same side as the branchia.
This is the case with the Tectibranchiate Opisthobranchs (Phaline,
Scaphander, ete.), all the Pectinibranchiate Prosobranchs (Rachi-
glossa, Taenioglossa, and Ptenoglossa), and the other Azygobran-

1 Pelseneer, Comptes Rendus, cvi. p. 1029.

VI CIRCULATORY SYSTEM 169

chiate Prosobranchs (Trochidae, Neritidae, ete.). In the last case
the right auricle exists, as well as the left, but is simply a closed

Fia. 79.—Diagram illustrating the relations between branchiae, heart, and aorta in the
Mollusca: A, In Chiton ; B, Pelecypoda; C, Dibranchiate Cephalopoda; D, Tetra-
branchiate Cephalopoda ; E, Prosobranchiata Zygobranchiata ; F, Prosobranchiata
Azygobranchiata ; G, Prosobranchiata Monotocardia ; H, Opisthobranchiata Tecti-
branchiata: 1, Ventricle ; 2, Auricle; 3, Aorta; 3a, Cephalic aorta; 36, Visceral
aorta ; 3c, Posterior aorta, (From A. Lang. )

sac, the coalescing of the two gills on the left side having thrown
all the work upon the left auricle. Compare Fig. 79, F, G, H.

Circulatory System.

All Mollusca, without exception, possess a circulatory system
of more or less complexity. The centre of the system is the heart,
which receives the aerated blood from the breathing organs, and
propels it to every part of the body. In the Scaphopoda alone
there appears to be no distinct heart.

The heart may consist simply of a single auricle and vent-
ricle, and an aorta opening out of the ventricle. From the
aorta the blood is conveyed to the various parts of the body by
arteries. Veins convey the blood back to the breathing organs,
after passing over which it returns by the branchial or pulmonary
vein to the heart, thus completing the circuit.

170 CIRCULATORY SYSTEM CHAP.

As regards position, the heart is situated within the pericardium,
a separate chamber which in the Pelecypoda, Cephalopoda, and
the bilaterally symmetrical Gasteropoda lies on the median line,
while in the asymmetrical Gasteropoda it is on one or other of the
sides of the body, usually the right. The veins connected with
the branchiae, and consequently the auricle into which they open,
are situated behind the ventricle in the Opisthobranchiata (whence
their name), while in the Prosobranchiata they are situated on
Front of the ventricle.

The number of auricles corresponds to the number of branchiae.
Thus there is only one auricle in the great majority of Proso-
branchiata (which are accordingly classified as Monotocardia),
and also in the Opisthobranchiata, while the Pulmonata have a
single auricle corresponding to the pulmonary chamber. There
are two auricles in the Amphineura, in a small group of Gastero-
poda, hence known as Diotocardia, in all Pelecypoda, and in the
Dibranchiate Cephalopoda. In the Tetrabranchiate Cephalopoda
alone there are four auricles corresponding to the four branchiae.

A single aorta occurs only in the Amphineura and in the
Tetrabranchiate Cephalopoda. In all the other groups there are
two aortae, leading out of the anterior and posterior ends of the
ventricle in Pelecypoda and Dibranchiate Cephalopoda, while a
single aorta leads out of the posterior end alone, and subsequently
bifurcates, in most of the Gasteropoda. One aorta, the cephalic,
supplies the front part of the body, the oesophagus, stomach,
mantle, etc.; the other, the visceral aorta, supplies the posterior
part, the liver and sexual organs.

The general circulatory system in the Mollusca has not yet
been thoroughly investigated. As a general rule, the blood driven
from the ventricle through the aorta into the arteries, passes, on
reaching the alimentary canal and other adjacent organs, into a
number of irregular spaces called Jacwnae. These in their turn
branch into sinuses, or narrow tubes covered with muscular tissue,
which penetrate the body in every direction. In the Dibranchiate
Cephalopoda true capillaries are said to occur, which in some cases
form a direct communication between the arteries and veins.
According to some authorities! capillaries and veins exist in
certain Pelecypoda in connexion with the intestinal lacunae, but
this again is regarded by others as not established. A similar

1 E.g. Kollmann, Zeit. wiss. Zool. xxvi. p. 87.

Vl COMPOSITION OF THE BLOOD AN

difference of opinion occurs with regard to the precise function of
the foot-pore which occurs in many Mollusca, some holding that
it serves as a means for the introduction of water into the blood-
vascular system, while others regard it as a form of secretion
gland, the original purpose of which has perhaps become lost.

Blood.—As a rule, the blood of the Mollusca—.e. not the cor-
puscles but the liquor sanguinis—is colourless, or slightly tinged
with blue on exposure to the air. This is due to the presence
of a pigment termed haemocyanin, in which are found traces of
copper and iron, the former predominating. Haemoglobin, the
colouring matter of the blood in Vertebrates, is, according to Lan-
kester,! of very restricted occurrence. It is found—(1) in special
corpuscles in the blood of Solen legumen (and Arca Noae); (2) in
the general blood system of Planorbis ; (3) in the muscles of the
pharynx and jaws of certain Gasteropoda, e.g. Limnaea, Paludina,
Littorina, Chiton, Aplysia.. This distribution of haemoglobin is
explained by Lankester in reference to its chemical activity ;
whenever increased facilities for oxidisation are required, then it
may be present to do the work. The Mollusca, being as a rule
otiose, do not possess it generally diffused in the blood, as do the
Vertebrata. The actively burrowing Solen possesses it, and
perhaps its presence in Planorbis is to be explained from its re-
spiring the air of stagnant marshes. Its occurrence in the
pharyngeal muscles and jaws of other genera may be due to the
constant state of activity in which these organs are kept.?

According to Tenison- Woods ® a species of Arca (trapezia Desh.)
and two species of Solen, all Australian, have red blood. It is
suggested that in these cases the habits of the animal (the Solen
burrowing deeply in sand, the Arca in mud) require some highly
oxidising element, surrounded as the creature is by ooze. In Arca
peaata (N. America) the blood is red, the animal being familiarly
known as the ‘bloody clam.’ Burrowing species, however, are
not all distinguished by this peculiarity. Tenison-Woods finds
red fluids in the buccal mass of many Gasteropoda, e.g. in species
of Patella, Acmaea, Littorina, Trochus, Turbo, giving the parts the
appearance of raw meat.

1 Proc. Roy. Soc. 1873, p. 70.

2 Griesbach (Arch. mikr. Anat. xxxvii. p. 22) finds haemoglobin in several
bivalves, e.g. Poromya granulata, Tellina planata, Arca Noae, and Pectunculus
glycimeris.

3 Trans. Roy. Soc. N. S. Wales, xxii. p. 106.

172 THE MANTLE AND MANTLE CAVITY CHAP.

The Mantle

On the dorsal side of the typical molluscan body, between the
visceral sac and the shell, lies a duplicature of the integument,
generally known as the mantle. The depending sides of the
mantle, which are usually somewhat thickened, enclose between -
themselves and the body mass a chamber of varying size and
shape, called the mantle cavity, which communicates freely with
the external air or water, and encloses and furnishes a protection
for the organ or organs of respiration. On its upper or dorsal
surface the mantle is closely applied to the shell throughout its
whole extent, the cells with which it is furnished secreting the
materials from which the shell is formed (see p. 255). The whole
mantle is capable, to some degree, of secreting shelly matter, but
the most active agent in its production is the mantle edge or
margin.

In the Prosobranchiata the mantle cavity, for reasons which
have already been explained, is found on the left side of the
animal, its front portion being in many cases produced into a
tubular siphon. Within the mantle cavity are found, besides the
branchia, the anus, the apertures of the kidneys, and the
osphradium. In the Pulmonata the mantle fold encloses a so-
called lung-cavity. The front edge of the mantle coalesces with
the integument of the neck in such a way as to enclose the
cavity very completely, the only communication with the outer
air being by means of the contractile breathing or pulmonary
aperture on the right side. In the Tectibranchiate Opistho-
branchs the mantle fold is inconsiderable, and is usually
not of sufficient extent to cover the branchia, while in the
Nudibranchs, which have no true branchiae, it disappears
altogether.

In the Pelecypoda the mantle cavity is equally developed on each
side, enclosing the two sets of branchiae. The mantle may thus
be regarded as consisting of two equal portions, which form a sort
of lining to the two valves. The lower or ventral portion of the
mantle edges may be simple, or provided with ocelli (Pecten, Arca),
tentacles, cilia (Lima, Lepton), or doubled folds. The two portions
of the mantle touch one another along the whole line of the
edge of the two valves, and, although thus in contact, may remain
completely separate from one another, or else become permanently

VI FUSION OF MANTLE. EDGES IN PELECYPODA MW 7h

united at one or more points. This fusion of the mantle edges
corresponds to important changes in the organisation of the
animal as a whole. The anal and branchial siphons are no more
than prolongations of the mantle edges on the posterior side into
a tubular form. These ‘siphons’ exhibit the siphonal form more
distinetly according as the adjacent portions of the mantle become
more definitely fused together.

This progressive fusion of the mantle edges may be taken as
indicating definite stages in the development of the Pelecypoda.
A perfectly free mantle edge, joined at no point with the edge
of the adjacent mantle, occurs in Nucula, Arca, Anomia, and
Trigonia (see Fig. 80, A, B). Here there is nothing in the

v.0
Fic. 80.—Diagram illustrating the various stages in the closing of the mantle in Pelecy-
poda: A, mantle completely open ; B, rudiments of siphons, mantle still completely
open ; C, mantle closed at one point; D, mantle closed at two points, with com-
plete formation of siphonal apertures ; E, development of siphons, ventral closure
more extended ; F, mantle closed at three points, with fourth orifice: 7, foot; s.a,

s.b, anal and branchial siphons ; 1, 2, 3, first, second, and third points of closure of
mantle. (After A. Lang.)

nature of a siphon, either anal or branchial; in other words, no
contrivance exists to prevent the spent water which has passed
over the branchiae from becoming mixed with the fresh water
which is to reach them. When the mantle edges are fused at
one point only, this is invariably on the middle part of the
posterior side, thus separating off an anal opening which may
become prolonged into a tube-like form. At the same time the
adjacent underlying portions of the mantle edges draw together,
without actually coalescing, to form an opening for the incurrent
stream of water, the rudiments of the ‘branchial siphon’ (Fig. 80,C).
This is the case with most Mytilidae (see Fig. 75) with Car-
dita, Astarte, and Pisidium. In the next stage the branchial

174 MANTLE REFLECTED OVER THE SHELL CHAP.

opening is separated off by the concrescence of the mantle edges
beneath it, and we have the mantle united in two places, thus
forming three openings, the ventral of which is the opening for
the protrusion of the foot (Fig. 80, D). This is the case in
Yoldia, Leda, the majority of the Eulamellibranchiata (e.g. Lucina,
Cyrena, Donax, Psammobia, Tellina, Venus, Cardium, Mactra), and
all Septibranchiata. In Chama and Tridacna the fused portions
of the mantle become more extended, and in Pholas, Xylophaga,
Teredo, Pandora, and Lyonsia this concrescence takes places over
the greater length of the whole mantle edge, so that the mantle
may be regarded as closed, with the exception of the three
apertures for the foot and the two siphons (Fig. 80, E).

In certain genera there occurs, besides these three apertures, a
fourth, in the lne of junction between the pedal and branchial
orifices. It appears probable that this fourth orifice (which has
been regarded by some as an inlet for water when the siphons are
retracted), stands in relation to the byssal apparatus (Fig. 80, F).
In Lyonsia, for instance, a thick byssus protrudes through the
orifice, which is large and open. In Solen, Lutraria, Glycimeris,
Cochlodesma, Thracia, Aspergulum, and a few more genera, which
have no byssus, the orifice is very small and narrow. It is
possible that in these latter cases, the byssal apparatus having
become atrophied, the orifice has been correspondingly reduced
in size."

Mantle Reflected over the Shell.—lIt is sometimes the case
that the mantle edges tend to double back over the external sur-
face of the shell, and to enclose it to a greater or less extent.
When this process is carried to an extreme, the edges of the
reflected mantle unite, and the shell becomes completely internal.
We see an incipient stage of this process in Cypraea and Mar-
ginella, Where the bright polish on the surface of the shell is due
to the protection afforded by the lobes of the mantle. A con-
siderable portion of the shell of Scutws is concealed in a similar
way, while in Cryptochiton, Lamellaria, and Aplysia the shell is
more or less completely enclosed. Among Pulmonata, it is possible
that in forms hke Vitrina, Parmacella, Limax, and Arion, we
have successive stages in a process which starts with a shell com-
pletely external, as in Helix, and ends, not merely by enveloping the
shell in the mantle, but by effecting its disappearance altogether.

1 Pelseneer, Comptes Rendus, ex. p. 154.

VI MANTLE REFLECTED OVER THE SHELL E75

In Vitrina and some allied genera we have a type in which the
mantle lobes are partly reflected over the shell, which at the
same time exhibits rather less of a spiral form than in Heliz.
In the stage represented by Parmacella, the mantle edges have
coalesced over the whole of the shell, except for a small aperture
immediately over the spire; the nucleus alone of the shell is
spiral, the rest considerably flattened. In Zimaax the shell has
become completely internal, and is simply a flat and very thin
plate, the spiral form being entirely lost, and the nucleus repre-
sented by a simple thickening at one end of the plate. In Arion,
the final stage, we find that the shell, being no longer needed as
a protection to the vital organs, has either become resolved into
a number of independent granules, or else has entirely dis-
appeared.

Some indications of a similar series of changes occur in the
Pelecypoda. The mantle edge of Lepton is prolonged beyond the
area of the valves, terminating in some cases in a number of
filaments. In Galeomma and Scintilla the valves are partially
concealed by the reflected mantle lobes, and in a remarkable form
recently discovered by Dall! (Chlamydoconcha) the shell is com-
pletely imbedded in the mantle, which is perforated at the
anterior end by an orifice for the mouth, and at the posterior
end by a similar orifice for the anus. In all these cases,
except Lepton, it is interesting to notice that the hinge teeth
have completely disappeared, the additional closing power gained
by the external mantle rendering the work done by a hinge un-
necessary. It is quite possible, on the analogy of the Gaster-
opoda mentioned above, and also, it may be added, of the
Cephalopoda and other groups, that we have here indicated the
eventual occurrence of a type of Pelecypoda altogether deprived
of valves, a greatly thickened mantle performing the part of a
shell.”

The following works will be found useful for further study of
this portion of the subject :-—

F. Bernard, Recherches sur les organes palléaux des Gastéropodes proso-
branches: Ann. Se. Nat. Zool. (7) ix. (1890), pp. 89-404.

1 Science, iv. p. 50.

2 Pp. Fischer, Jowrn. de Conchyl. (3) xxvii. p. 201.

176 AUTHORITIES CHAP. VI

G. Cuvier, Le Régne animal (ed. V. Masson) ; Mollusca, Text and Atlas.

C. Grobben, Beitrage zur Kenntniss des Baues von Cuspidaria (Neaera)
cuspidata Olivi, nebst Betrachtungen tiber das System der Lamelli-
branchiaten ; Arb. Zool. Inst. Wien, x. (1893), pp. 101-146.

E. Ray Lankester, Encyclopaedia Britannica, 9th ed., vol. xvi. (1883),
‘Art. ‘ Mollusca.’

A. Ménégaux, Recherches sur la circulation des Lamellibranches marins:
Besancon, 1890.

K. Mitsukuri, On the structure and significance of some aberrant forms of
Lamellibranchiate gills: Q. Journ. Micr. Sc., N.S. xxi. (1881), pp.
595-608.

H. L. Osborn, On the gill in some forms of Prosobranchiate Mollusca :
Stud. Biol. Lab. Johns Hopk. Univ. iii. (1884), pp. 37-48.

R. Holman Peck, The structure of the Lamellibranchiate gill: Q. Journ.
Mier. Se., N.S. xvii. (1877), pp. 43-66.

P. Pelseneer, Contributions 4 l’étude des lamellibranches: Arch. Biol. xi.
(1891), pp. 147-312.

CHAPTER, Wil

ORGANS OF SENSE: TOUCH, SIGHT, SMELL, HEARING——THE FOOT——
THE NERVOUS SYSTEM.

Organs of Sense: I. Touch.

TACTILE organs, although occurring in some of the Mollusca, do not
appear to attain special or marked development, except in a few
cases. The whole surface of the skin, and particularly of the
foot, is very sensitive to the slightest impression. Nearly all
Gasteropoda are furnished with at least two cephalic tentacles,
projecting like horns from each side of the fore part of the head.
At or near the base of these are generally situated the eyes.
In the Helicidae the eyes are situated, not at the base, but at
the apex of the tentacles, and in that case—except in Vertigo—
a second pair of shorter tentacles appears beneath the longer
pair. It frequently happens that several senses are centred in
a single organ, thus the upper tentacles of snails not only
carry the eyes and serve to a certain extent as tactile organs,
but they also carry the organs of smell.

The edges of the mantle, which are sometimes specialised
into lobes, appear to be keenly sensitive to touch in all
Gasteropoda.

In Cypraea (Fig. 81) these lobes, or tentaculae, are a
prominent feature of the animal, and also in certain genera of
the Trochidae (Fig. 82). In most of the carnivorous land
Pulmonata—e.g. Testacella, Rhytida, Ennea—there are developed,
under the lower pair of tentacles, and close to the mouth, large
labial palps or feelers. These are connected with the cerebral
ganglion by a very large nerve, and may therefore be supposed
to be of extreme sensitiveness. In some of the large carnivorous

VOL. III N

7S ORGANS OF TOUCH CHAP.

forms (Glandina, Aerope, compare Fig. 21, p. 54) these palpae are of
ereat size, and curl upwards like an enormous pair of moustaches.

Fic. 81.—Cypraea moneta L., showing tentaculae at Fic. 82.—Monodonta canali-

edge of mantle, which partly envelopes the shell: fera Lam., New Ireland,
Si, siphon; M, M, mantle; F, foot; T’, tenta- showing mantle lobes.
culae at edge of mantle. (After Quoy and Gai- (After Quoy and Gai-
mard). x d. mard.)

When a Glandina seizes its prey, the palpae (see Fig. 83) appear
to enfold it and draw it in towards the mouth.

It is in the Opisthobranchiata that the organs of touch
attain their maximum development. Many of this group are
shell-less or possess a small internal shell, and accordingly, in the
absence of this special form of defence, a multiplied sense of
touch is probably of great service. Thus we
find, besides the ordinary cephalic tentacles,
clusters or crowns of the same above the head
of many Nudibranchiata, with lobe-like pro-
longations of the integument, and tentacular

_ processes in the neighbourhood of, or surround-
Fic. 83.—Glandina ~. : aes

seizing its prey, Ng the branchiae (see Figs. 58 and 84), or even

with buccal papil- projecting from the whole upper surface of the

lae turned back. :

(Strebel.) body (Fig. 5, C).

In the Pelecypoda, the chief organs of touch
are the foot, which is always remarkably sensitive, especially towards
its point, the labial palps on each side of the mouth, and the
siphons. In certain cases the mantle border is prolonged into a
series of threads or filaments. These are particularly noticeable
in Pecten, Lepton, and Lima (Fig. 85), the mantle lobes of the
common L. hians of our own coasts being very numerous, and of
a bright orange colour. In many genera—e.g. Unio, Mactra—
this sensibility to touch appears to be shared by the whole
mantle border, although it is not furnished with any special
fringing. The ‘arms’ of the Cephalopoda appear to be keenly

se TASTE IN SNAILS 179

sensitive to touch, and this is particularly the case with the
front or tentacular pair of arms, which seem to be employed in

Fic. 84.—I/dalia Leachit A. and H., British seas ; br, branchiae. (After
Alder and Hancock.)

an especial degree for exploration and investigation of strange
objects.

Taste.—The sense of taste 1s no doubt present, to a greater
or less extent, in all the head-bearing Mollusca. In many of
these a special nerve or nerves has been discovered in the
pharynx, connecting with the cerebral
ganglion; this no doubt indicates the
seat of the faculty of taste. The Mol-
lusca vary greatly in their hkings for
different lands of food. Some seem
to prefer decaying and highly odorifer-
ous animal matter (Buccinwm, Nass),
others apparently confine themselves
to fresh meat (Purpura, Natica,

: Tere Pauly ; ;
Testacella), others again, although natu- ¥1¢. 85.—Zima squamosa Lam.,
S © Naples, showing tentacular

rally vegetarian, will not refuse flesh lobes of mantle (£, t); a, anus;
on occasion (Limax, Helis). Dia COINS ass SENS Sgt
2 ze branchiae ; 7, foot ; sh, shell.

Mr. W. A. Gain! has made some
interesting experiments on the taste of British land Mollusca, as

evidenced by the acceptance or rejection of various kinds of food.
He kept twelve species of Arion and Limax, and eight species of
Helix in captivity for many months, and tried them with no less
than 197 different kinds of food, cannibalism included. Some

1 Journ. of Conch. vi. p. 349 ff.

180 POSITION OF THE EYES CHAP.

curious points came out in his table of results. Amalia gagates
appears to be surprisingly omnivorous, for out of 197 kinds of
food it ate all but 25; Arion ater came next, eating all but 40.
Limax arborum, on the other hand, was dainty to a fault, eating
only seven kinds of food, and actually refusing Swedes, which every
other species took with some avidity. Certain food was rejected
by all alike, e.g. London Pride, Dog Rose, Beech and Chestnut
leaves, Spruce Fir, Common Rush, Liverwort, and Lichens ; while
all, or nearly all, ate greedily of Potatoes, Turnips, Swedes,
Lettuces, Leeks, Strawberries, Boletus edulis, and common
grasses. Few of our common weeds or hedgerow flowers were
altogether rejected. Arion and Limax were decidedly less
particular in their food than Helix, nearly all of them eating
earth-worms and puff-balls, which no Helia would touch. Arion
cater and Limax maximus ate the slime off one another, and
portions of skin. Cyclostoma elegans and Hyalinia nitida
preferred moist dead leaves to anything else.

IL. Sight.

Position of Eyes.—In the majority of the head-bearing
Mollusca the eyes are two in number, and are placed on, or in
the immediate neighbourhood of the head. Sometimes they are
carried on projecting tentacles or ‘ommatophores, which are
either simple (as in Prosobranchiata) or capable of retraction

Fic. 86.—A, Limnaea peregra Miill. ; e, e, eyes; é, ¢, tentacles: B, Helix nemoralis
Miill. ; e, e, eyes ; ¢, ¢, tentacles ; p.o, pulmonary orifice.

like the fingers of a glove (Helix, etc.). Sometimes, as in a large
number of the marine Gasteropoda, the eyes are at the outer base
of the cephalic tentacles, or are mounted on the tentacles them-
selves, but never at the tip (compare Fig. 60, p. 153 and Fig. 98,

VII ORGANISATION OF THE EYE 18I

p. 199). In other cases they are placed somewhat farther back, at
the sides of the neck. The Pulmonata are usually subdivided into
two great groups, Stylommatophora and Basommatophora (Fig.
86), according as the eyes are carried on the tip of the large
tentacles (Helix, and all non-operculate land shells), or placed at
the inner side of their base (Limnaea, Physa, ete.). In land and
fresh-water operculates, the eyes are situated at the outer base of
the tentacles.

In the Helicidae, careful observation will show that the eyes
are not placed exactly in the centre of the end of the tentacle,
but on its upper side, inclining shghtly outwards. The eye is
probably pushed on one side, as it were, by the development. of
the neighbouring olfactory bulb. The sense of smell being far
more inportant to these animals than the sense of sight, the
former sense develops at the expense of the latter.

Organisation of the Molluscan Bye.——The eye in Mollusca
exhibits almost every imaginable form,
from the extremely sunple to the
elaborately complex. It may be, as in
certain bivalves, no more than a pig-
mented spot on the mantle, or it may
consist, as in some of the Cephalopoda,
of a cornea, a sclerotic, a choroid, an
iris, a lens, an aqueous and vitreous
humour, a retina, and an optic nerve, or
of some of these parts only.

In most land and fresh-water Mol-
lusca the eye may be regarded, roughly
speaking, as a ball connected by an
exceedingly fine thread (the optic nerve)

Fic. 87.—Eye of Helix pomatia

with a nerve centre (the cerebral gang- L., retracted within — the
“a 7, 6 Se alee - Sveti tentacle ; c, cornea; ep, epi-
lion). In Paludina this ball is elliptic, thelial layer; Z, lens: op.n,
in Planorbis and Neritina it is drawn optic nerve; 7, retina. (After

‘ : Simroth.)
out at the back into a conical or pear

shape. In Helix (Fig. 87) there is a structureless membrane,
surrounding the whole eye, a lens, and a retina, the latter
consisting of a nervous layer, a cellular layer, and a layer of
rods containing pigment, this innermost layer (that nearest the
lens) being of the thickness of half the whole retina.

Comparing the eyes of different Gasteropoda together, we find

182 STAGES OF DEVELOPMENT IN THe EVIE CHAP.

that they represent stages in a general course of development.
Thus in Patella the eye is scarcely more than an invagination
or depression in the integument, which is lined with pig-
mented and retinal cells. The next upward stage occurs in
Trochus, where the depression becomes deeper and_ bladder-
shaped, and is filled with a gelatinous or crystalline mass, but
still is open at the top, and therefore permits the eye to be

Fic. 88.—EHyes of Gasteropoda, showing arrest of development at successive stages: A,
Patella ; B, Trochus; ©, Turbo; D, Murex ; ep, epidermis ; 7, lens ; op.n, optic
nerve ; 7, retina; v./, vitreous humour. (After Hilger.)

bathed in water. Then, as in Zurbo, the bladder becomes
closed by a thin epithelial layer, which finally, as in some Murex,
becomes much thicker, while the ‘eyeball’ encloses a lens (Fig.
88), which probably corresponds with the ‘vitreous humour’ of
other types.

In Nautilus the eye is of a very simple type. It consists of
a cup-shaped depression, with a small opening which is not
quite closed by the integument. The retina consists of cells

VII EYE OF CEPHALOPODA 183

which line the interior of the depression, and which communicate
directly with the branches of the optic nerve, there being no
iris or lens. This type of eye,
it will be observed, corresponds
exactly with that which occurs
in Patella. It appears also to
correspond to a stage in the
development of eyes in the
Dibranchiata (e.g. Octopus, Sepia,
Loligo). Uankester has shown '
that in ZLoligo the eye first
appears as a ridge, enclosing an
oval area in the integument.
By degrees the walls of this
area close in, and eventually
join, enclosing the retimal cells
within the chamber im which
the lens is afterwards developed ee Se ee Ee
(Fig. 89). It thus appears that enclosing .0.c, primitive optic cham-
in some cases the development ae a fe eng oF pas
of the eye is arrested at a point ci, ci, ciliary body ; 1, rudimentary
which in other cases only forms Tens ag Ee Deu CT Crep a neeter)
a temporary stage towards a higher type of organisation.

The developed eye in the dibranchiate Cephalopods consists
of a transparent cornea, which may or may not be closed over

Fic. 90.—Eye in
A, Loligo ; B, He-
liz or Limax; C,
Nautilus : «.0.¢,
anterior optic
chamber ; ¢, cor-
nea; int. integu-
ment ; ir, iris; J,
lens; 7’, external
portion of lens ;
op.n, optic nerve ;
op.g, optic gang-
lion ; p.0.c, poste-
rior optic cham-
ber; 7, retina.
(After Grenacher.)

the front of the lens. 3ehind the cornea is a narrow chamber
(the anterior optic chamber) which is continued for three parts

1 Quart. Journ. Mier. Sc. N.S. xv. p. 37.

184 VISUAL POWERS OF CEPHALOPODA CHAP.

round the whole circle of the eye, and into which project the
front portion of the lens and the folds of the iris. Throughout
its whole extent, the anterior optic chamber is lined by the
integument, the portion of which on the inner side is the
choroid. The lens is divided into an outer and inner seg-
ment by a thin membrane, and is supported by the ciliary
body which forms a continuation of the retina. The main
portion of the lens lies within the posterior optic cham-
ber, at the back and sides of which is found the retina
(Grenacher).

There can be no doubt that the Cephalopoda use their eyes to
observe, but there is nothing to show that any other Mollusca
use their eyes for this purpose, the sense of smell in their case
largely taking the place of visual observation. Madame Jeannette
Power once saw! the Octopus in her aquarium holding a fragment
of rock in one of its arms, and watching a Pinna which was
opening its valves. As soon as they were perfectly open, the
Poulpe, with incredible address and promptitude, placed the stone
between the valves, preventing the Pinna from closing again,
upon which it set about devouring its victim. ‘The next day
the Poulpe was seen, after crushing some TZellina, to stretch
himself down close by a Zriton nodiferus, and watch it atten-
tively. After four hours the Zviton emerged from its shell,
when the Octopus sprang upon it, and surrounded it with its
arms.

Powers of Vision in Land Mollusca.—The Helicidae are un-
doubtedly very short-sighted. Seldom emerging from their retreats
except in twilight and darkness, they are naturally myopic, and
see better in a subdued than in a bright light. Experiment has
shown that a Helix can perceive an object better at 6 centimetres
distance in a weak light than at 4 or 5 millimetres in a strong
one. Oyclostoma elegans and Paludina vivipara are comparatively
long-sighted, perceiving objects at a distance of 20 to 30
centimetres. The increased power of vision is due, in these two
cases, to increased elaboration in the construction of the eye,

1 Ann. Mag. Nat. Hist. (2), xx. p. 386.

2 V. Willem (Arch. Biol. ut infr.) denies this, and declares that Cyclostoma is
only very sensitive to movements. The present writer has often approached, with
the greatest care, a crawling Cyclostoma, but it always withdrew into its shell or fell
to the ground when approached within about 10 or 12 inches.

VII SHORT SIGHT IN SNAILS 185

Paludina possessing a large and almost spherical lens, to which
the vitreous humour closely adheres, while in Cyclostoma the lens
is remarkably hard, and the aqueous humour very abundant.
According to V. Willem,’ the Pulmonata are very sensitive to
the slightest movement of the air or jarring of the surface on
which they crawl, but are so short-sighted as only to perceive a
confused image of a large object at about 1 cm., and to distin-
cuish the form of objects at not more than 1 or 2 mm. The
senses of touch and smell are far more active than that of sight.
A bean-pod enclosed in a narrow glass case and placed before a
hungry snail was not noticed, but when taken out of the case and
placed 8 cm. behind the snail, the latter at once turned towards
it to devour it.

Some interesting experiments were conducted by the same
author with the view of ascertaining whether snails avoid or
court the light. He placed a number of species in different
wooden boxes, which were divided into a light and a dark com-
partment, having previously well soaked the boxes in water to
secure a humid atmosphere and surface, and so induce the snails
to move about. Theresult showed that nearly all species have a
marked predilection one way or the other, but not all in the
same way. SHeliz aspersa, Arion empiricorum, six species of
Timaz, and three of Planorbis, are lovers of darkness, while
H. nemoralis, Succinea putris, and two species of Limnaea are
lovers of hight. Physa fontinalis stands alone in being quite
indifferent.

M. Willem endeavoured further to discover whether any of
the Mollusca possessed ‘dermatoptic perception,’ or the faculty of
perceiving variation of light by means of the skin alone. He
accordingly repeated the above-mentioned experiments, having
previously extirpated the eyes in all cases. The result was
remarkable. In a few instances the experiment was not con-
clusive, but H. aspersa, A. empiricorum, several species of Limaz,
and one Limnaea shunned or sought the light just as they had
done when their eyes were present. A few marine Mollusca
(Littorina ‘littorea, Trochus cinerarius, T. wmbilicatus, Patella
vulgata) were also shown to be exceedingly sensitive to the impact
of a shadow, whether with or without their eyes.

Blind and Eyeless Mollusca.—In a large number of marine

1 Arch. Biol. xii. 1892, p. 57.

186 BLIND AND EYELESS MOLLUSCA CHAP.

Mollusca which habitually creep about half buried in wet sand
(Bullia, Sigaretus, Scaphander, Philine), eyes are altogether absent.
In some species of Natica and Sigaretus,
and in Doris, eyes are developed, but are
enclosed in a thick layer of skin, through
which they can probably do little more than
faintly appreciate different degrees of light
and darkness. Chiton has cephalic eyes in
the embryo, but loses them in the adult
stage. The two great Auricula, A. auris
Judae and A. auris Midae, which habitually
creep about in the liquid mud of mangrove
swamps, have entirely lost their eyes. Cer-
Pe ene: tain pelagic Mollusca seem to have a
vigatus Lam.,a species tendency, which is not easily explained, to
frequenting wet sand, loge their eyes or the power of seeing with
and destitute of ex- ;

ternal eyes; F, ante. them. Thus Janthina has no eyes at all.

te Cae foot. Pteropoda as a rule have no eyes, and the

few that have (Creseis, Cavolinia) possess
only certain pigmented spots placed near to the nervous centres.
In the Heteropoda, however, and the Cephalopoda, many of which
are pelagic, the eyes are unusually large.

Eyes in Deep-sea and Underground Mollusca.—Deep-sea
Mollusca, as a rule, possess no visual organs, or possess them only
in a rudimentary state, but this rule has its exceptions. Dr.
Pelseneer found? no trace of eyes in two species of Plewrotoma
from 1850 and 1950 fath., none in a Fossarus from 1400 f.,
none in a Puncturella from 1540 f. Aremarkable form of Voluta
(Guivillea) from 1600 f. possessed eyes which could hardly be
functional, as they were destitute of pigment, and exhibited other
changes of structure. On the other hand, it is remarkable to
notice that in three different species of Zvrochus from 450 f.,
565 f, and 1375 f, the eyes were pigmented and well
developed.

In land Mollusca which live beneath the surface of the ground
or in absolute darkness, the eyes are generally more or less
modified. Thus in Zestacella, which usually burrows deeply in
the soil, but occasionally emerges into the open air, the eyes are
very small, but distinct and pigmented. Our little Caecilianella

1 *Challenger’ Reports, Zoology, vol. xxvii. part lxxiv. p. 3.

VIL EYES OF ONCHIDIUM AND CHITON 187

acicula, which is never seen above the surface, is altogether
destitute of eyes. A species of Zospewm,a Helia, and a bithynella
from dark caves in Carniola have suffered a similar loss. On the
other hand,a small Hyalinia from a dark cave in Utah (probably
a recent addition to the cave fauna) has the eyes normally
developed.

Eyes of Onchidium.—Many species of Onchidiwm, a naked
land pulmonate which creeps on rocks near high-water mark, are
provided with dorsal eyes of various degrees of organisation, and
in numbers varying up to nearly one hundred. The tropical
Onchidium are the prey of a fish(Pertophthalmus) which skips along
the beach by the aid of its large ventral fins, and feeds principally
on insects and Onchidiwm. Karl Semper suggests’ that the eyes
are of service to Onchidiwm as enabling it to apprehend the
shadow of the approaching Periophthalmus, and defend itself by
suddenly contracting certain glands on the skin and expressing a
liquid secretion which flies into the air like shot and frightens
the Periophthalmus away. This theory—for it is no more than
theory—may or may not be true, but it is remarkable that
Onchidium with dorsal eyes have precisely the same geographical
distribution as Periophthalmus, and that where no Periophthalmus
exists, eg. on our own S.W. coasts, the Onchidiwm are entirely
destitute of dorsal eyes. In those species of Onchidiwm which
have no dorsal eyes, the latter are on the tips of the tentacles, as
in Heliz. The eyes are developed on the head, and afterwards
ascend with the growth of the ommatophores, while in Helia the
ommatophores are formed first, and the eyes developed upon
them.”

Dorsal Eyes in the Chitonidae.—The remarkable discoveries
of Moseley with regard to the dorsal eyes of Chiton were first
published in 1884.2 He happened to notice, while examining a
specimen of Schizochiton incisus, a number of minute black dots
on the outer surface of the shell, which appeared to refract light
as if composed of glass or crystal. These ‘ eyes,’ in all the species
of Chiton yet examined, are restricted to the outer surface of the
exposed area of the shell, never being on the laminae of insertion
or on the girdle. In certain sub-genera of Chiton the eyes are
scattered irregularly over the surface, in others they are arranged

1 Animal Life, p. 372 f. 2 Bergh, Morph. Jahrb. x. p. 172.
3 Ann. Mag. Nat. Hist. (5) xiv. p. 141.

188 EYES OF CHITON CHAP.

symmetrically in rows diverging from the apex of each plate, but
in old specimens the eyes towards the apices are generally
rubbed off by erosion or abrasion. Moseley regarded the occur-
rence of scattered eyes as indicating an original stage of develop-
ment, when the eyes were at first disposed irregularly all over the
surface of the shell; the gathering into regular rows showing a
later stage.

The eyes appear to be invariably more numerous on the
anterior plate. Thus in Corephium aculeatum there are about

Fic. 92.— Dorsal eyes of

Chitonidae, showing
the various forms
of arrangement in
the first and fourth
valvesof1,1a,Acan-
thopleura spinigera
Sowb., E. Indies, x
2; 2,20, Tonicia sue-
zensis Reeve, Suez,
x 3; 3, 3a, Acan-
thopleura granulata
Gmel., W. Indies,
x2; 4, 4a, Tonicia
lineolata, Fremb.,
Chilis 25 Eirom
specimens in the
Museum of Zoology,
Cambridge.

12,000 in all, of which more than 3000 are on the anterior
plate. In Schizoehiton they are arranged in very symmetrical
rows, six of which are situated on the anterior, and only
two, sometimes only one, on the central plates. In Tonicia
marmorata the eyes are sunk in little cup-shaped depressions
of the shell, possibly to escape abrasion. As regards shape
and size, in Ch. incisus they are circular, and about 3s inch in
diameter, this being the largest size known; in Ch. spiniger and
Ch. aculeatus they are oval, measuring about gh X goo mech.
There are no eyes in Chiton proper, nor in Mopalia, Maugeria,

VII EYES IN BIVALVE MOLLUSCA 189

Lorica, and Ischnochiton.. None of our English species appear
to possess them.”

Eyes in Bivalve Mollusca.—Some, possibly most, of the
Pelecypoda possess, in the larval state, true paired eyes at the oral
end of the body. These become aborted as the animal develops,
since that part of the body becomes entirely screened from the
light by the growth of the shell. To compensate for their loss,
numerous ocellz, or pigmented spots sensitive to the action of light,
are in many cases developed on different parts of the mantle,
functionally corresponding to the ‘eyes’ of Chiton described
above. As in Chiton too, we have here an interesting series of
instances 1n which true eyes have suffered total obliteration,
through disuse, and, as if to restore to the animal in some
measure its lost sense, visual organs of a low power have sub-
sequently been developed and are now observed in various stages
of specialisation.

Concentration of Eyes in Special Parts of the Mantle.—
Sharp has shown? that in several species of Ostrea, Cardium,
Anomia, Lima, Avicula, Arca, and Tellina pigmented cells, with
a highly refractive cuticle, are scattered over a considerable
portion of the mantle. Experiment has proved the powers of
‘vision, 7.¢. of sensitiveness to different degrees of light, possessed
by these organs. In Dreissena polymorpha, Tapes decussatus, and
two species of Venus these cells are concentrated on that particu-
lar part of the mantle which is not always covered by the shell,
ze. the siphon, but since the siphon can be completely retracted
within the shell, there is no special provision for their protection.
A further step is shown in the case of Mya arenaria, where the
siphon is scarcely capable of complete retraction. Here, while
some of the pigment cells are scattered about over the surface of

1 The nature of the grouping of the eyes into rows varies considerably in different
species. Asa rule, the rows radiate from the beak, but occasionally they run par-
allel to the girdle. In Yonicia lineolata Fremb., they are grouped, as it were, under
the shelter of strongly marked longitudinal wavy lines.

* Shell-Eyes in other Mollusca.—The Rey. J. E. Tenison-Woods (Zrans. Linn.
Soc. NV. S. Wales, xxii. p. 106) is of opinion that ‘shell-eyes’ are by no means con-
fined to the Chitonidae, but that, in fact, multiplicity of eyes of this kind is the
rule rather than the exception among the Mollusca. He finds (1) exceedingly minute
and numerous ‘ eyes’ on the outer surface of the shell in both univalves and bivalves ;
(2) large and solitary ‘eyes’ in the shell substance ; (3) eyes on the mantle lobes in
both univalves and bivalves ; (4) eyes on the opercula.

3 Mitth. Stat. Zool. Neap. v. p. 447 ff.

19O EYES IN BIVALVE MOLLUSCA CHAP.

the siphon, the majority are placed in grooves at the base of the
siphonal tentacles, forming an intensely black band round them.
A higher stage still is shown in Solen vagina, S. ensis, and Mactra
solidissima, where the cells are situated only in the siphonal
grooves, which are more or less specialised in numbers and com-
plexity.

Arca Noae, according to Patten, is very sensitive to any
sudden change in the amount of light fallimg upon its mantle-
edge. A faint shadow cast upon it by the hand is sufficient to
cause it to close its valves quickly, but always one or two
seconds afterwards, the promptitude in all cases depending upon
the depth of the shadow. Sensitiveness in this direction was
found to depend greatly upon the vitality of the animals them-
selves, since it always became less in those specimens which had
been kept for long in confinement. A shadow was not always
necessary to make them close. An ordinary black pencil, if
approached within two or three inches with extreme caution,
produced the same result, while a glass rod brought within the
same distance, and even moved rapidly to and fro, appeared to
cause no alarm. Sensitiveness to change in intensity of light
was experimentally noticed by the same author in the case of
Ostrea, Mactra, Avicula (to a special extent), and Cardium. It
is very remarkable to find that increased elaboration in the
structure of the eyes does not necessarily carry with it imcreased
sensitiveness, 7.e. higher visual powers. Avicula, which is only
provided with a few scattered ommatidia, which would entirely
escape the notice of any one who had not seen them better de-
veloped elsewhere, was considerably more sensitive to heht and
shade than Arca, with its eyes of conspicuous size and much
more perfect organisation, instantly contracting the mantle
upon the impact of a shadow so faint as to be invisible to the
experimenter.!

Visual Faculties of Solen and Ostrea—The visual power of
Solen may be exemplified by any one who is walking along
almost any of our sandy bays at extreme low-water mark. If
the day be warm and sunny, numbers of Solen will be seen
raising themselves an inch or two out of their holes; but if you
wish to catch them you must approach very cautiously, and on
no account allow your shadow to fall upon them, or they will

1 W. Patten, Mitth. Zool. Stat. Neap. vi. (1886) pp. 546, 605 f.

VII EYES) IN PECTEN AND ARCA IQI

pop down into their burrows in an instant, and it is vain to
attempt to dig them out. ‘How sensitive, remarks Mr. W.
Anderson Smith, with reference to oysters,! ‘the creatures are to
the light above them; the shadow [of the boat] as it passes over-
head is instantaneously noted, and, snap! the lps are firmly closed.’

Ocelli of Pecten.—In Pecten and Spondylus the ocelli are
remarkably large and prominent, shining lke precious stones, and
are placed along the two edges of the mantle so as to receive the
light when the shell gapes (Fig. 93). In Pecten opercularis,
jacobaeus, and maximus their number varies from 80 to 120.
In Spondylus gaederopus, a very inequivalve shell, 60 have been
counted on the right or fixed valve, and 90 on the left or upper
valve. Each ocellus is con-
nected, by means of its
optic nerve, with the large
circumpalleal nerve, and so
with the branchial gan-
glion. They possess a cornea,
lens, choroidea, and optic ye
nerve, and, according to Fic. 93.—Pecten opercularis L., showing the
Hickson 2 bear a consider- ocelli on the two edges of the mantle.
able resemblance to the vertebrate type of eye. In spite of this,
the power of vision in these genera does not appear at all superior
to that of other Pelecypoda.

According to the elaborate investigations of Patten, the
‘eyes’ in Area occur upon the middle or ‘ophthalmic’ fold of
the mantle-edge, which is thickened at the end to admit of their
reception. Along
this is ranged a row
of dark brown spots
of various _ sizes,
which are larger at
the anterior and
posterior ends of the

: —= ae mantle - edge, — but
Fig. 94.—Compound eyes (c.e) of Arca barbata L.; m./, : re ee
Gite 2 sie
mantle fold ; omm, ommatidia. (After Patten.) smaller and more

numerous towards
the middle. These brown spots, or ‘eyes’ are many of them
compound, being made up of the fusion of a number of

1 Benderloch, p. 136. * Quart. Journ. Micr. Soc. xx. p. 448.

192 ORIGIN OF FUNCTIONAL EYES CHAP.

ommatidia (from 10 to 80) into one large round eye, which is
generally elevated above the surface of the surrounding epithe-
lum. Sometimes these eyes themselves tend to fuse together. In
one specimen of Arca Noae, 133 of these faceted eyes were
counted in one mantle border, and 102 in the other.

There can be lttle doubt that the development of these
functional eyes, or sensitive spots, in bivalve Mollusca, is due to
special needs. They appear to be entirely absent in fresh-water
bivalves (with the exception of Dreissensia, which is obviously a
marine genus recently become fresh-water), while they are most
abundant in genera living between tide marks (Solen, Mya,
Mactra), and most highly specialised in a genus that is, for a
bivalve, of singularly active habits (Pecten). Now genera living
in sand between tide marks, as the three above-mentioned genera
are in the habit of doing, and also protruding their siphons,
and occasionally a considerable portion of their shells, out of their
burrow, are manifestly very much at the mercy of their watchful
enemies the gulls, and anything which would enable them to
apprehend the approach of their enemies would be greatly to
their advantage. Here, perhaps, lies the explanation of the
ereater elaboration of these pigmented spots in littoral genera, as
compared with those inhabiting deeper water. Pecten, again, a
genus distinguished by great activity, which can ‘fly’ for con-
siderable distances in the water by flapping its valves together
and expelling the water from the apertures at either side of the
hinge, may be greatly assisted by its ocelli in directing its flight
so as to escape its enemies.

IIL. Smell

The sense of smell—touch at a distance, as Moquin-
Tandon has called it—-is probably the most important sense
which the Mollusca possess, and is unquestionably far more
valuable to them than that of sight. Any one who has ever
enjoyed the fun of hauling up lobster pots will recollect that
part of the contents was generally a plentiful sprinkling of
Buccinum, Nassa, and Natica, attracted by the smell of the
stinking piece of fish with which the trap was baited. Accord-
ing to Mr. J. 8. Gibbons,! Bullia rhodostoma congregates in

1 Quart. Journ. of Conch. i. p. 368.

VII POWER OF SMELL IN MOLLUSCA 193

hundreds on gigantic medusae which are stranded on the sandy
bays near the Cape of Good Hope. Dr. J. G. Jeffreys says? that
quantities of the common Neptunea antiqua “are procured on the
Cheshire coast by the fishermen placing a dead dog on the sands
at low-water mark during spring tides. The bait is then com-
pletely covered with stones, which are piled up like a cairn. On
the next turn of the tide the heap of stones is visited, and the
whelks are found on the surface in great numbers, having been
apparently attracted by the smell of the bait, but unable to get
at it.” Mr. W. A. Lloyd kept specimens of Wassa reticulata in
a tank in the sand, at the bottom of which they usually remained
buried. If a piece of meat of any kind were drawn over the
sand, the Nassa would appear above the surface in a few minutes.
Half-picked beef or mutton bones, if placed in the tank, were
covered in a few minutes. In fact, no animal matter, whether
living or dead, could be introduced without the Wassa smelling
it, and coming up to see what they could get.’

Any one can experiment for themselves on the olfactory
powers of our common snails or slugs. Moquin-Tandon records *
two interesting cases, one communicated to him by letter, the
other occurring to himself. His correspondent, a M. Parenteau,
was one day walking along a dusty high-road, when he noticed,
near the middle of the road, an empty bean-pod and two Arions
eating it. Attributing the meeting of feeders and food to mere
chance, he was walking on, when he noticed a second bean-pod,
and, about two yards away from it, a third Arion, hurrying
straight towards it. When the Arion had yet more than a yard
to traverse, M. Parenteau picked up the bean and put it in his
pocket. The Arion stopped, raised its head, and turned in every
direction, waving its tentacles, but without advancing. M.
Parenteau then carried the bean to the other side of the road,
and put it in a small hole behind a piece of stone. The Arion,
after a moment’s indecision, started off straight for the bean.
Again the position of the precious morsel was changed, and
again the Arion made for it, this time without being further
tantalised. M. Moquin-Tandon noticed, one rainy day in the
botanical gardens at Toulouse, two Limaz maximus approaching
a rotten apple from different directions. He changed the position

1 British Conchology, i. p. xxviii.
2 Science Gossip, 1865, p. 259. 3 Mollusques de France, i. p. 130.

VOL. II O

194 POSITION OF SMELL-ORGANS CHAP.

of the apple several times, placing it at a sufficient distance, to
be sure they could not see it, but they always hit it off correctly,
after raising their heads and moving their long tentacles in every
direction. It then occurred to him to hold the apple in the air,
some centimetres above the head of the Limax. They perceived
where it was, raised their heads and lengthened their necks,
endeavouring to find some solid body on which to climb to their
food.

Several of the land Mollusca have the power of exhaling a
disagreeable smell, Hyalinia alliaria smelling strongly of garlic,
and Stenogyra decollata of laudanum; but this need not be any
argument for the sense of smell in the creatures themselves.

Position of Olfactory Organs in Pulmonata.— Most authori-
ties are of opinion that the olfactory organs are situated in the
tentacles. _Moquin-Tandon considered that in the Helicidae and
Limacidae the sense of smell is confined to the little knob or
elevation at the end of the longer tentacles, close to the eye. He
found that when he cut off these tentacles both in Zimaz and
Arion, the creatures were quite unable to discover the whereabouts
even of strongly-scented food. The same author believed that
in the Basommatophora the sense of smell was present in the
whole of the tentacle, which is covered with an exceedingly
sensitive ciliated epithelium. Lacaze-Duthiers, however, places
the olfactory sense in this group at the outer side of the base
of the tentacles, near to the eyes. Some authorities! deny that
the Helicidae have the olfactory organ at the tip of the tentacles,
and locate it in a pedal gland near the mouth, which contains
conspicuous sensitive cells. A Helia whose tentacles had been
removed manifested its repulsion to the smell of spirits of tur-
pentine, while another Helix, which was unmutilated, did not
object to the turpentine being held between its tentacles.
Altogether, then, the exact position of the smell organ in the
Helicidae must be considered as not yet thoroughly determined.
Sumroth holds thet the sense of smell is distributed over the
whole soft integument, and is especially concentrated in the
feelers, and in the neighbourhood of the respiratory orifice.

Tn nearly all marine Mollusca yet examined, the organ of smell
or osphradvum is in situation intimately connected with the
breathing organs, being generally placed near their base, with the

1 E.g. Sochaczewer, Zcits. wiss. Zool. xxxvy. p. 30. 2 Zool. Anz. 1882, p. 472.

VII THE OSPHRADIA 195

object, apparently, of testing the quality of the water before it
passes over the branchiae. It consists of a patch of the
epithelium, modified in a special manner, and connected by its
own nerve with one of the visceral gangha.

An osphraditum does not necessarily occur in all genera; for
instance, it has not been detected in Fissurella. It is most
highly specialised in the Conidae, and in the carnivorous
Gasteropoda generally. In BLuccinum undatum, tor instance, it 1s
very large indeed, and, from its plumed form, has sometimes
been mistaken for an accessory branchia (Fig. 95). In Haliotis
it is paired, one lying in close proximity to each of the two
branchiae, but in Zurbo it
is single, corresponding to
the single branchia. In
Chiton there is an osphra- .
dium at the base of each
separate gill filament, mak-
ing a total of twenty or
more on each side. Its

SHC : y 3, Fic. 95.—Buccinum undatum ., deprived of
‘ - 2) e ‘ ?
position In Physu and in its shell, showing the relative position of

Cyclostoma will be seen by branchia (67) and osphradium (0s) ; m, mucous
: oom ~ glands ; s, siphon. The portion of the mantle
reference to 198. 105 and covering the osphradium has been removed.
104 (p. 205). In the Pele-
cypoda the osphradia are paired, and lie adjacent to the posterior
adductor muscle, close to the hinder end of the axis of the branchiae.
In the Tetrabranchiate Cephalopoda there are two osphradia, placed
between the bases of the two pairs of gills. In the Dibranchiates
on the other hand, a groove above the eyes has been regarded as
the seat of the organ of smell. This groove contains sensory-and
ciated cells, and appears to be connected with a special nerve
centre of its own, which ultimately is derived from the cerebral
ganglion. |
Searcely any instances of the exercise of the sense of smell on
the part of bivalve Mollusca have been recorded. Something of
the sort, however, seems to have been present in a case related by
Mr. R. L. King’ A skull of a fox had been placed in a small
ditch in order to soak, and after a few days, when taken out, was
found to be covered with Pisidium pusillum to the number of
at least two hundred, which had been probably attracted from the

1 Zoologist, iv. p. 1266,

196 POWERS OF HEARING CHAP.

water in the immediate neighbourhood by the smell of the
decaying flesh.

IV. Hearing

Experiments made with a view to ascertain whether the
Mollusca are sensitive to noises have usually led to the con-
clusion that they are deaf to very loud sounds. This is the
more curious, because an undoubted auditory apparatus has been
discovered in a large number of genera. In the case of an
experiment, it is not easy to be sure that the animal is not
affected, at least in part, by the shock or jar, rather than by the
actual sound. In some experiments, however, conducted at the
Plymouth Marine Biological Laboratory, Mr. Bateson found 1
that Anomia could be made to shut its shell by smearing the
glass of the tank with the finger in such a way as to make a
creaking sound. It was evident that the cause of alarm was not
the jarring of the solid framework of the tank, for the same
result occurred when the object on which the Anomia were
fixed was suspended in the water by a thread. It was found
that the sound had to be of a particular pitch to excite the
attention of the mollusc.

As a rule the organ of hearing is nothing more than a small
vesicle or sac (the ofocyst), filled with a fluid secretion, in which
are suspended one or usually more calcareous concretions known as
otoliths. By means of cilia, which connect with sense-cells, these
otoliths are given a peculiar movement or oscillation in the
medium in which they are suspended. The number of the
otoliths varies in different genera and species; there are several
hurdreds in Arion and Limaz, about a hundred in Helix
pomatia, nemoralis, hispida, arbustorum, rotundata, Succinea
putris, and Limnaea stagnalis ; about fifty in Planorbis contortus
and Physa fontinalis, only one in Cyclostoma elegans. The number
increases with age. In young specimens of Limn. stagnalis
as few as ten, nine, and seven have been noticed.”

The otocysts are always paired, and, in Gasteropoda, are
placed close to the pedal gangha. The acoustic nerve, however,
has been shown by Lacaze-Duthiers to connect with the cerebral
ganglia in certain cases. The otocysts are never on the surface

1 Journ. Mar. Biol. Ass. N.S. i. p. 217.
2 Moquin-Tandon, Moll. de France, i. p. 133.

VII POSITION AND FORMATION OF THE OTOCYSTS 1) 7/

of the body and are rarely connected with it by any passage or
tube; it is probable therefore that sound reaches them simply
through the medium of the tissues.

In the Pelecypoda the otocyst is similarly situated near the

fs

»

AP OSCE
Fic. 96.—Illustrating the otocyst in A, Anodonta, B, Cyclas ; ot, otolith; a, 6, ¢, ¢,
cellular layers surrounding the chamber ; ¢7, cilia on interior walls of chamber :

C, an otolith crushed. (After Simroth.)
pedal ganglion, and is probably (though this has not yet been
proved) similarly connected with the cerebral. There is only a
single otolith. Pelseneer finds’ in Nuculidae alone a free com-
munication between the otocyst and the exterior. Anodonta has
been observed ? to withdraw its foot imto the shell at the noise
of an opening door, a loud voice, or a shrill whistle, whether in
a basin of water or lying on a study table.

Delage extirpated the otocysts in certain Octopoda, and
obtained some unexpected results. He found that remarkable
effects were produced upon the animal’s powers of locomotion, so
that it was unable to preserve its proper balance in the water
when in rapid motion, but its body was forced to undergo a form
of rotation more or less pronounced. He concluded that the
otocysts must possess, besides their auditory functions, a power
which stands in some relation to the proper orientation of the
body in locomotion, a power which is not wholly supplied by
sight and touch alone. The otocysts may thus regulate locomo-
tion by stimulating muscular acts which tend to keep the body
in the straight line during the process of movement.’

1 Zool. Jahrb. Anat. iv. (1890) p. 501. 7 Baudon, Rév. Mag. Zool. 1852, p. 575.

° Arch. Zool. Exp. Gén. (2) v. 1887, p. 2; compare also C. H. Hurst, Natural
Science, li, pp. 350, 421.

198 . THE FOOT CHAP,

The Foot

One of the most characteristic organs of the Mollusca is the
foot, which, under one form or another, occurs throughout the
whole phylum. The foot is a thickening, on the ventral side,
of a portion of the integument of the animal, modified to serve
different forms of motion. It attains its maximum relative area
in the Chitonidae, many Nudibranchs, and the slugs generally,
in nearly all of which there is no portion of the body which is
not subtended by the foot. Here too it presents the form of a
regular disc or ellipse, which is more or less produced. In many
cases, however, the foot becomes modified im such a way that
we are enabled to recognise well-marked anterior and posterior
portions, which have received the name of propodiuvm and meta-

—_J™ Fe _ —— .
Le ~~ oA
/ sap

Fic. 97.—Sigaretus laevigatus Lam., showing excessive development of the propodium
(pr) and metapodium (met) in a molluse living in sand (the shell, which covers
only the liver and adjacent parts, has been removed); /, liver; s.ap, aperture
of proboscis, here deflected from the median line; ¢, ¢, tentacles. (After Quoy and
Gaimard. )

podium respectively, while the intervening central portion is
termed the mesopodiwm.

The propodimn is most strongly developed in genera which
crawl about in wet sand, eg. Natica, Sigaretus, Oliva, Harpa,
Scaphander (Figs. 97 and 98, and compare Fig. 91). In such eases
it seems to serve as a sort of fender or snow-plough, to push the
sand away on both sides of the path the animal is traversing.
In some species of Sigaretus the propodium becomes as it were
banked up against the head and proboscis, which are thus
unnaturally elevated, or tend to disappear altogether. Bul/ia
(Fig. 62), which crawls about rapidly on wet sand, appears
to attain its object by a wide extension of the foot on all sides,
and so slides over the sand instead of ploughing through it;

VII PROPODIUM AND METAPODIUM 199

the little lappets at the end of the ‘tail’ probably serve as
rudders.

In Melampus and Pedipes the propodium is marked off by
a groove across the ventral surface. When the animal is in
motion it first advances the propodium and then pulls the rest
of the foot after it with the looping gait of certain caterpillars.
In many Cyclostomatidae this groove, instead of being transverse,
is longitudinal, and the animal advances first the right and then
the left segment of the foot, which gives it a swaying motion
from side to side.

Upon the metapodium lies the operculum, when it oceurs.
As a rule the metapodium is not sharply marked off from the
rest of the foot. In Strombus (Fig. 99) it becomes erected

= i

Fic. 98.—Oliva textilina Lam., showing how the front part of the foot (/) is developed
into a sort of fender, the propodium (pr); e, e, eyes; m.ap, front appendage of
mantle; m.ap’, hinder appendage of mantle, folded into the suture when the
animal is at rest ; s?, siphon; ¢, ¢, tentacles. (After Quoy and Gaimard.)

into a sort of hump or column, on the top of which the opercu-

lum is situated.

The epipodium is a prominent fold or border, which occurs
upon the upper edge of the foot in most Diotocardia. In
Haliotis it is of considerable breadth, and is covered by a
number of lobes which spring from a moss-like prolongation of
the skin. From the epipodium are developed the lateral tenta-
culae of Monodonta (Fig. 82, p. 178), and of other subgenera of
the Trochidae.'

In the Opisthobranchiata the lateral edges of the foot (the
parapodia) are frequently produced into broad folds or wing-
like extensions, which in many cases tend to fold over the shell,
and, in conjunction with the mantle, eventually imbed it
altogether. By the wavy motion of the parapodia the animal is

1 Compare Pelseneer, Bull. Sct. Fr. Belg. (3) xix. pp. 107, 182.

200 MODIFICATIONS OF THE FOOT CHAP.

enabled to progress through the water. The paired natatory
lobes of the Pteropoda are simply the parapodia of the Tecti-
branchs modified for swimming purposes.

It is in the Heteropoda, Pteropoda, and most of all, the Cephalo-
poda, groups which have, for the most part, exchanged a crawling
for a swimming life, that the modifications of the foot are most
considerable. In Oxygyrus and Atlanta, for instance, the
propodium and metapodium are sharply distinguished from the
mesopodium, and no doubt have acquired, as a means of pro-
pulsion, the power of separate movement, the animal swimming
with these portions of the foot uppermost. In Carinaria and

Fig. 99. — Strombus lentigi-
nosus Lam., showing the
modified form of the foot
(f): @ @ eyes on their
pedicels ; mp, metapodium ;
op, operculum; p, penis ;
pr, proboscis ; ¢, ¢, tentacles.
(After Quoy and Gaimard. )

Pterotrachea the metapodium has probably become continuous
with the long axis of the body, while the so-called ‘foot’ with
its sucker represents only the original propodium. In the
Cephalopoda the arms and funnel represent the modified foot,
the sides of which are prolonged into a number of very long
specialised tentaculae. In the adult Cephalopod some of the
arms have assumed a position in advance of the mouth, the latter
being in fact surrounded by a cirele of arms. But in the
Cephalopod embryo the mouth opens as in the Gasteropoda, 7.e.
in advance of the arms, and it is only gradually that it becomes
encircled by them. Arms and funnel alike are found to be
innerved from the pedal ganelion.'

1 Pelseneer, Arch. Biol. viii. p. 728.

VII MODIFICATIONS OF THE FOOT 201

The pointed axe-shaped foot, which is characteristic of the
majority of Pelecypoda, is doubtless derived from a form more
akin to the flattened ‘sole’ of the Gasteropoda. A foot with
something of this disc-shaped base actually occurs in some of the
Nuculidae, the parapodia being furnished with pleats which
recall similar formations in other Orders (Fig. 100). The principal
modifications of the foot are due to its employment as a
burrowing organ. In genera which burrow but shghtly it is
small and feebly developed, while in genera which habitually
excavate, it becomes the largest and strongest organ of the body.
At the same time it has a tendency to shift its position from the

Fic. 100.—YVoldia limatula Say,
Greenland, showing the short
plumed branchiae (47, 67), the
gasteropodous foot (7), and
the large labial palps (/.p,
.p): A, as seen from the ven-
tral margin; B, from the left
side, with the mantle turned
back ; a.m, position of an-
terior adductor muscle; 7,
intestine; @, liver; m, m,
mantle,

ventral to the anterior margin, accompanied by a corresponding
narrowing of the shell, until it arrives at the position seen in
Mollusca of the shape of JJya, Pholas, and Solen. In sedentary
or attached genera, e.g. Pecten, Chama, Ostrea, the foot tends to
become aborted.

The byssus gland, secreting a byssus of horny threads, is
characteristic of many Pelecypoda, and may be observed by any
one in the common mussel. It occurs in the larvae of many
species which do not possess a byssus in the adult stage. The
pedal gland of many Prosobranchiates, which secretes a tough and
almost thread-like slime, is possibly homologous with the byssus
gland of bivalves.

Nervous System

The Mollusca possess a nervous system, which usually consists
of a number of nerve centres or ganglia, linked together by bands
(the commissures) and sending out thread-like nerves which
ramify into the various organs. The character of the nervous

202 NERVOUS SYSTEM—-GASTEROPODA CHAP.

system varies greatly in different groups, ranging as it does from
a condition of extreme complexity, in which the ganglia are
numerous and the commissures equally so, to that of considerable
simpheity, in which ganglia are almost entirely absent.

The most important ganglia are (1) the cerebral, which are
always placed above or on either side of the mouth, and from
which proceed the nerves of the eyes and tentacles ; (2) the pedal,
which in Gasteropoda are situated below the oesophagus, in
Pelecypoda at the base of the foot, and from which the nerves of
the foot and sometimes the acoustic nerve arise; (3) the plewral,?
whose position varies considerably, but is always below the
oesophagus and shehtly above the pedal ganglia; these innervate
the mantle, branchiae, heart, and viscera generally.

Gasteropoda.—The simplest form of nerve system as thus
understood occurs in the Amphineura, and more particularly in
the Chitons. Here we find four longitudinal nerve-cords, parallel
to one another for nearly the whole length of the mollusc. The
two exterior cords probably represent the pleural, the two interior
the pedal nervous system. There being no head or tentacles, but
sunply a mouth at the anterior end, the cerebral ganglia do not
exist, but they are represented by the curved ring formed by the
massing together of the two nerve-cords on each side. The only
distinct gangha are a pair of buccal gangha (which are developed
on a pair of commissures which pass forward from the cerebral
mass and innervate the lips and buccal region), and a much
smaller group, the sublingual. The two pedal cords are united by
a number of transverse parallel connectives, which recall similar
modes of connection in the Chaetopod worms and in Arthropoda.

This quadruple set of nerve-cords is characteristic of all the
Amphineura, but the absence of ganglia is most marked in the
Chitons. In Proneomenia and Neomenia there is a distinct
cerebral ganglion, formed by the massing of the two ganglia into
one, while in Proneomenia the lateral cords are joined to the
pedal, as well as the pedal to one another, by connectives. In
Chaetoderma the cerebral ganglia, though adjacent, are distinct,
and both the pedal and lateral cords connect directly with them,
while there are no transverse connectives.

' Also known as /abial and supra-oesophageal ganglia.
2 Wivén, however (K. Sv. Vet. Ak. Handl. xxiv. 1892, No. 12), describes trans-
verse connectives in Chaetoderma.

VII NERVOUS SYSTEM—GASTEROPODA ZO?

The remaining three great divisions of Gasteropoda, namely,
the Prosobranchiata, Opisthobranchiata, and Pulmonata, may be
regarded as comprising two distinct types of nervous condition,
according as the loop formed by the two visceral nerve cords is
twisted over itself, forming a figure of 8, or continues straight
and uncrossed. In the former case, we get the condition known
as streptoneurous, in the latter that as euthyneurous.' The
Euthyneura include the whole of the Opisthobranchiata ’ and
Pulmonata, the Streptonewra all the Prosobranchiata.

c

c
Tt U 1 L
jie pe
B Cc

Fic. 101.—Nervous system of the Amphineura: A, Proneomenia ; B, Neomena ; C,
Chaetoderma; D, Chiton; c, cerebral ganglia; 7, l, lateral cords ; pc, posterior
commissure ; s, sublingual commissure or ring, with ganglia; v, v, pedal cords.
(After Hubrecht. )

The simplest form of nervous system in the euthyneurous
Gasteropoda occurs in the Opisthobranchiata. The cerebral,
pleural, and pedal ganglia tend to become concentrated in a ring-
like form, united by short commissures at the posterior end of
the pharynx. The visceral loop is in some cases long, and the
two or three visceral ganglia are then situated at its posterior
extremity. The nervous system of the Pulmonata is of a similar
type, the visceral loop being often much shorter, and tending to
draw in towards the central group of ganglia. The tentacular
and optic nerves are, as usual, derived from the cerebral gang-
lion, with which also the otocysts are probably connected by
rather long nerves. A pair of buccal gangha innervate the
buccal mass, and are united by commissures with the right
and left cerebral ganglia. The osphradial nerve springs from one

1 grperrés, twisted ; evdvs, straight.

* With the exception of Actacon, which is streptoneurous (Bouvier, Comptes
Rendus, exvi. p. 68).

204 STREPTONEURA AND EUTHYNEURA CHAP.

of the ganglia on the visceral loop, the osphradium itself
being situated (in Limnaea) immediately above the pulmonary
orifice and adjacent to the anus (Fig. 102). This massing
of the gangla is still better illustrated by the accompanying
figure of Physa (Fig. 103), in which the animal is represented as
if transparent, so that the gangha and nerves are seen through
the tissues.

Of the streptoneurous Gasteropoda, the nervous system of

Fic. 102.—I. Nervous system of

Limnaea stagnalis L. ‘he

oesophagus has been cut and

pulled forwards through the
nerve-collar, so as to expose
the lower surface of the buccal
mass (dissected by F. B. Stead).

B.M, buceal mass.

B.G, buccal, C.G, cerebral, Os.G,
osphradial, Pe.G, pedal
ganglia,

P1.G, pleural ganglia.

Op.N, optic, Os.N, osphradial,
Te.N, tentacular nerve.

Ot, otocyst; V.L, visceral loop.

R, rectum, dotted in to show
its position relative to the

osphradium.
. Right side of the head of Zim-
naea stagnalis. The over-

hanging flap of the mantle has
been cut in the middle line,
and the right half twisted
back, so as to expose the pul-
monary orifice, ete. The points
A A on the mantle edge were
continuous before the mantle
was cut; the line BA is part
of the free edge of the mantle.

An, anus; F, female genera-
tive orifice ; J, portion of jaw ;
M, male generative orifice under
right tentacle ; Os, osphradium ;
P.O, pulmonary orifice.

Fissurella and Haliotis shows distinct points of similarity to that
of the Amphineura. The pedal nerves are united by transverse
commissures throughout their entire length, while a double com-
missure unites the cerebral ganglia to the mass from which the
pedal nerves proceed. In the great majority of the Streptoneura
the ganglia (except the visceral) are more concentrated and the
commissures are consequently much shorter. The accompanying
figure of Cyclostoma, in which the animal is represented as in that
of Physa just described, illustrates this grouping of the ganglia,

VII STREPTONEURA AND EUTHYNEURA 205

the twist of the visceral loop, and the position of the visceral
ganglion at its posterior end.

Scaphopoda.—In the Scaphopoda the nervous system resem-
bles that of the Pelecypoda, The cerebral and pleural ganglia le
close together, while the pedal ganglia are placed in the anterior
part of the foot, connected with the cerebral gangha by long

ml

Fic. 108.—Nervous system of Physt Fic. 104.— Example of a streptoneurous

acuta Drap., showing the massing Gasteropod (Cyclostoma elegans Drap.) :
of the ganglia at the hinder end of C.g, c.g, cerebral ganglia ; e, e, eyes; 0s,
the pharynx: e, e, eyes; m, mouth ; osphradium ; of, ot, otocysts; p.g, p.g,
m.l, m.l, mantle lappets ; 0.f, female pedal ganglia ; pl.g, pl.g, pleural ganglia ;
generative orifice; o.m, male gen- sp.g, supraintestinal ganglion ; sb.g, sub-

erative orifice ; os, osphradiun. intestinal ganglion ; tm, tentacle nerve ;
(After Lacaze-Duthiers. ) v.g, visceral ganglion. (After Lacaze-
Duthiers. )

commissures ; the visceral loop is rather long, and the two vis-
ceral ganglia are adjacent to the anus.

Pelecypoda.—The nervous system in the Pelecypoda is the
simplest type in which well-marked ganglionic centres occur. The
ganglia are few, symmetrically placed, and are usually at a con-
siderable distance apart. There are, as a rule, three distinct pairs
of ganglia, the cerebral (cerebro-pleural), pedal, and visceral. The
cerebral are formed by the fusion of the cerebral and pleural
ganglia, which however, in some cases (Protobranchiata) continue
distinct.1. They lie above or on each side of the mouth, united

1 This fusion of the cerebral and pleural ganglia and the consequent union of the

206 NERVOUS SYSTEM IN PELECYPODA CHAP.

by a commissure of varying length. Another pair of com-
missures unites them with the pedal ganglia, which are placed
at the base of the foot, and are usually very close together,
sometimes (as in Anodonta) becoming partially fused. The
length of these commissures de-
pends upon the distance between
mouth and foot; thus they are
very long in Mya and Jodiola,
and very short in Pecten.~ In
cases Where the foot is rudimen-
tary or becomes aborted through
disuse (e.g. Ostrea), the pedal
ganglia may dwindle or disappear
altogether. The visceral gangha
are on the ventral side of the
posterior adductor muscle, beneath
the recttwn, and innervate the
branchiae, osphradia, and the
whole of the visceral sac. A pair
of cerebro - visceral commiussures
TGs 105.—Nervous system of Pelecy-" traverses the base of the foot,

poda: <A, Teredo: B, Anodonta ; : , :

C, Pecten; a, a, cerebral ganglia; Surrounding it with a compara-

b, pedal ganglia ; c, visceral ganglia. 4; : : as
4 ee) : Se) AV r gsnor Oop ae) ave 0”
(ists Ceneatane tively short loop (compare Fig

106, eve’), while a long commis-
sure, which runs round the entire edge of the mantle, and sup-
plies branching nerves to the mantle border and siphons (Fig.
106, ¢.v.c), may also connect the visceral and cerebral gangha.
Cephalopoda.—In the Cephalopoda the concentration of
ganglia attains its maximum, and may perhaps be regarded as
approaching the poimt at which a definite brain may be said to
exist. Another point of distinction is the formation of special
small ganglia upon the nerve cords in different parts of the body.
In the Tetrabranchiata (Nautilus) the cerebral and pedal gangha
form a broad ring which surrounds the oesophagus, the former
giving out the optic nerves, with their special optic ganglion, and
a pair each of buccal and pharyngeal gangha, the latter the
nerves of the arms and funnel. The visceral loop is still present
in the form of a separate band, which innervates the branchiae,

cerebro-pedal and pleuro-pedal commissures can be recognised by sections of the mass
(Pelseneer, Comptes Rendus, exi. p. 245).

VII NERVOUS SYSTEM IN PELECYPODA ZOW,

osphradia, and viscera generally, forming a special genital gane-
lion in connection with the reproductive organs. ‘The principal
ganglia of the Dibranchiata are still more concentrated, even
the visceral loop being possibly united with the rest in forming
an unbroken mass in which scarcely any trace of commiussures

SS

\\\
lp i Wy
/ a / ey y py) W\i =
CVC —- f \ Pe
/ / eo
“t pay are ea < 1
or: cV.c

Fic. 106.—Nervous system of Cardium edule L.: a.m, anterior adductor muscle ; 67,
branchiae ; brn, branchial nerve 3 c.g, ¢.g, cerebral ganglia ; c.p.c, cerebro-pedal
commissure ; ¢.v.c’, cerebro-visceral commissure ; ¢.v.c, cerebro-visceral commissure
of mantle ; 7.p, labial palps ; m, mouth ; .g, pedal ganglion; p.m, posterior adductor
muscle ; v.g, visceral ganglion. (After Drost, x 3.)

can be detected. The pedal ganglion becomes separated into
two portions, one of which innervates the arms, the other the
funnel. Two peculiar gangha (the stellate ganglia) supply a
number of branching nerves to the mantle.

E. L. Bouvier, Systeme nerveux, morphologie générale et classification des
Gastéropodes prosobranches: Ann, Se. Nat. Zool. (7) i. 188%,
pp. 1-510.
J. Brock, Zur Neurologie der Prosobranchier: Zeit. wiss. Zool. xlviil.
1889, pp. 67-83.
O. Biitschli, Bemerkungen iiber die wahrscheinliche Herleitung der Asym-
metrie der Gasteropoda, etc.: Morph. Jahrb, xii. 1886, pp. 202-222.
B. Haller, Zur Kenntniss der Muriciden. I. Anatomie des Nervensystems :
Denksch. Math. Nat. Kl. Ak. Wien, xlv. 1882, pp. 87-106.
7 Untersuchungen tber marine Rhipidoglossen. II. Textur des
Centralnervensystems und seiner Hiillen: Morph. Jahrb.
xi, 1885, pp. 319-436.

208 AUTHORITIES CHAP. VII

H. Grenacher, Abhandlungen zur vergleichenden Anatomie des Auges: Abh.
Naturf. Gesell. Halle, xvi. 1884, pp. 207-256; xvil. 1886, pp. 1-64.
A. P. Henchman, ‘!ne Origin and Development of the Central Nervous
System in Limax maximus: Bull. Mus. C. Z. Harv. xx. 1890,
pp. 169-208.
V. Hensen, Ueber das Auge einiger Cephalophoren : Zeit. wiss. Zool. xv.
1865, pp. 157-242.
C. Hilger, Beitrage zur Kenntniss des Gasteropodenauges: Morph. Jahrb. x.
1885, pp. 352-371.
Lacaze-Duthiers, Otocystes ou Capsules auditives des Mollusques (Gastéro-
podes) : Arch, Zool. Exp, Gén. i. 1872, pp. 97-166.
Du systeme nerveux des Mollusques gastéropodes pulmonés
aquatiques : ibid. pp. 437-500.

P. Pelseneer, Recherches sur le systeme nerveux des Ptéropodes: Arch, Biol.
vil. 1887, pp. 93-130.

Sur la valeur morphologique des bras et la composition du
systtme nerveux central des Cephalopodes: Arch. Biol. viii.
1888, pp. 723-756.

H. Simroth, Ueber die Sinneswerkzeuge unserer einheimische Weichthiere :

Zeit. wiss. Zool, xxvi. 1876, pp. 227-348.
J. W. Spengel, Die Geruchsorgane und das Nervensystem der Mollusken :
Zeit. wiss. Zool. xxxv. 1881, pp. 3338-383.

” ”

CHAPTER VIII

THE DIGESTIVE ORGANS, JAW, AND RADULA: EXCRETORY ORGANS

THE digestive tract, or, as it is often termed, the alimentary canal
or gut, is a very important feature of the Mollusca. It may be
regarded as consisting of the following parts: (1) a mouth or oral
aperture; (2) a throat or pharynx; (3) an oesophagus, leading into
(4) a stomach, (5) an intestine and rectum, ending in (6) an
anus.

The primitive positions of mouth and anus were presumably
at the anterior and posterior ends of the animal, as in the
Amphineura and symmetrical Mollusca generally. But the
modifications of original molluscan symmetry, which have already
been referred to (p. 154, compare pp. 245, 246), have resulted in
the anus becoming, in the great majority of Gasteropoda, twisted
forward, and occupying a position on some point in the right
side in dextral, and in the left in sinistral species.

The process of digestion, as the food passes from one end of
the tract to the other, is performed by the aid of the secretions
of various glands, which open into the alimentary canal at
different points in its course. The principal of these are the
salivary glands, situated on the pharynx and oesophagus, and
the liver, biliary or hepatic gland, connecting with the stomach.
With these may be considered the anal and ink-glands, which, in
certain genera, connect with the terminal portion of the rectum.

1. The mouth is generally, as in the common snail and _peri-
winkle, placed on the lower part of the head, and may be either
a mere aperture, circular or semicircular, in the head-mass, or, as
is more usual, may be carried on a blunt snout (compare Fig. 6,
p. 10, and Fig. 68, p. 159), which is capable of varying degrees
of protrusion. From the retractile snout has doubtless been

VOL. Il P

210 THE PROBOSCIS, PHARYNX, AND JAWS CHAP.

derived the long proboscis which is so prominent a feature of
many genera (compare Figs. 1, B, and 99), and in some (eg.
Mitra, Dolium) attaims a length exceeding that of the whole
body. As a rule, Mollusca provided with a proboscis are carniv-
orous, while those whose mouth is on the surface of the head
are vegetable feeders, but this rule is by no means invariable.
The mouth is thickened round the aperture into ‘lips, which are
often extensile, and appear capable of closing upon and grasping
the food. In the Pelecypoda the mouth is furnished, on each side,
with a pair of special external lobes, the ‘ labial palps, which appear
to be of a highly sensitive nature, and whose object it is to collect,
and possibly to taste, the food before it passes into the mouth.

2. The Pharynx, Jaws, and Radula.—lnmediately behind the
lips the mouth opens into the muscular throat, pharynx, or
buccal mass. The pharynx of the Glossophora, i.e. of the
Gasteropoda, Scaphopoda, and Cephalopoda, is distinguished from
that of the Pelecypoda,' by the possession of two very characteristic
organs for the rasping or trituration of food before it reaches the
oesophagus and stomach. These are (a) the jaw or jaws, and
(b) the radula, odontophore, or lingual ribbon. The jaws bite
the food, the radula tears it up small before it passes into the
stomach to undergo digestion. The jaws are not set with teeth
like our own; roughly speaking, the best idea of the relations of
the molluscan jaw and radula may be obtained by imagining our
own teeth removed from our jaws and set in parallel rows along
a greatly prolonged tongue.”

In nearly all land Pulmonata the jaw is single, and is placed
behind the upper lip. Ifa common feliz aspersa be observed
crawling up the inside of a glass jar, or feeding on some succu-
lent leaf, the position and action of the jaw can be readily dis-
cerned. It shows very black when the creature opens its mouth,
and under its operation the edge of a lettuce leaf shows a regular
series of little curved indentations, in shape not unlike the semi-

1 There is practically no pharynx in the Pelecypoda, the mouth opening directly
into the oesophagus.

2 Ladere, to serape ; ddovs, tooth ; Pépew, to carry.

® ‘The mechanism of the radula has been dealt with by Geddes, Zrans. Zool, Soc.
x. p. 485. Riicker has observed (Ber. Oberhess. Gesell. Nat. Heilk. xxii. p. 207)
that the radula in Helix pomatia is the product of five rows of cells; the use of the
first row is uncertain, the second forms the membrane of the radula, while rows
three to five originate the teeth.

VIII THE JAW IN PULMONATA Zit

circular bites inflicted by a schoolboy upon his bread and butter.
The jaw of Helix (Fig. 107, B) is arched in shape, and is
strengthened by a number of projecting vertical ribs. That of
Limaz (A) is straighter, and is slightly striated, without vertical
ribs. In Bulimulus (C) the arch of the jaw is very conspicuous,
and the upper edges are always denticulated ; in Orthalicus there
is a central trangular plate, with a number of overlapping plates
on either side; in Succinea (E) there is a large square accessory
plate above the jaw proper. The form of the jaw is peculiar not

Fic. 107.—Jaws of
various Pulmon-
ata: A, JLimazx
(gagates Drap.,
Lancashire, x 15);
B, Helix (acutis-
sima Lam., Ja-
maica, x 15); 'C;
Bulimulus — (de-
pictus Reeve,
Venezuela, x 20);
D, Achatina
(fulica Fer. ,Mau-
rae) 4 7) Ley
Succinea (elegans
Riss., Aral Dis-
IoC 5S B10) B 13h
Limnaea — (stag-
nalis L., Cam-
bridge, x 30).

only to the genus but to the species as well. Thus the jaw of
H. aspersa is specifically distinct from that of H. pomatia, and
that of H. nemoralis is distinct from both. Wiegmann has
observed? that in young Arion, Limax, and Helix, the jaw
consists of two pieces, which coalesce by fusion in the adult,
thus indicating a stage of development in advance of the double
jaw which is found in most of the non-pulmonate Mollusca. In
all fresh-water Pulmonata there are two small accessory side
plates besides the jaw proper (Fig. 107, F).

Nearly all the non-carnivorous Prosobranchiata, land, fresh-
water, and marine alike, are provided with two large lateral jaws.

1 Jahrb. Deut. Malak. Gesell. iii. p. 193.

212 JAWS IN PROSOBRANCHIATA AND OPISTHOBRANCHIATA cu.

Many of these are sculptured with the most elaborate patterns,
and appear to be furnished with raised teeth, like a file. In the

YOR
x Wns :
XY RX

Fic. 108.—Jaws of A, Triton australis Lam., Sydney ; B, Ampullaria fasciata Reeve.
Demerara; C, Calliostoma punctulatum Mart., New Zealand; D, Cyclophorus
atramentarius Sowb., Sanghir; all x 15.

>
ONY
SO

Fic. 109.—Jaws of A, Chromodoris gracilis Ther.,x 15; B, Scyllaea pelagica L., x 7;
C, Pleurobranchus plumula Mont., x10; D, Plewrobranchaea Meckelit Lam., x 3.

Nudibranchiata the jaws are of great size and beauty of orna-
mentation (Fig. 109).

VIII THE RADULA 213

The carnivorous genera, whether marine (e.g. Conus, Murex,
Buccinum, Nassa) or land (eg. Testacella, Glandina, Streptaxis,
Ennea), are entirely destitute of jaws, the reason probably being
that in all these cases the teeth of the radula are sufficiently
powerful to do the work of tearing up the food without the aid
of a masticatory organ as well. Jaws are also wanting in the
Heteropoda, and in many of the Nudibranchiata and Tecti-
branchiata.

In the Cephalopoda the jaws, or ‘beaks, as they are called,
are most formidable weapons of attack. In shape they closely
resemble the beaks of a parrot, but the hook on the dorsal side
of the mouth does not, as in birds, close over the lower hook,
but fits under it. Powerful muscles govern these mandibles,
which must operate with immense effect upon their prey (Fig. 110).

The Radula.'—When the food has passed beyond the opera-

1 The whole of the radulae and jaws figured in this work are taken from the
original specimens in the collection of the Rev. Prof. H. M. Gwatkin, who has
always been ready to give me the run of his cabinets, which probably contain the
finest series of radulae in the world. To his kindness I owe the following descrip-
tion of the process of mounting: ‘‘ The first step is to obtain the radula. Dissection
is easy in species of a reasonable size. On opening the head from above, so as to
lay open the floor of the mouth, the radula itself is seen in most of the marine
species, though in others it is contained in a sort of proboscis ; and in the Pulmonata
and others the student will find the buccal mass, with commonly a brown mandible
at its front end, and the lingual ribbon in its hinder part. The teeth may be recog-
nised by their silvery whiteness, except in a few cases like Patella and Chiton, where
they are of a deep brown colour. When obtained, the radula may be cleaned by
boiling in a solution of caustic potash. There is no risk of injury if the solution is
not too strong.

‘* Smaller species may be treated more summarily. The proboscis, the buccal mass,
or even the whole animal may be thrown into the potash solution and boiled till
scarcely anything is left but the cleaned radula. Remains of animals dried inside
the shell may be similarly dealt with, after soaking in clean water. With a little
care, this process will answer for shells down to the size of Ancylus or Rissoa. The
very smallest (Carychiwm, Tornatellina, Skenea, etc.) must be crushed on the slide
and boiled on it, after removing as much as possible of the broken shell. The
radula can then be searched for under the microscope, and washed and mounted on
the slide.

“«The student must be warned that though the general process is simple, there
are difficulties in particular cases. In the Pulmonata, for example, membranes on
both sides of the radula need careful removal. Murex, Purpura, and most of the
Taenioglossa have the side teeth folded down over the central, so that the arrangement
is not well seen till they have been brushed back. The Cones, again, have no basal
membrane at all, so that if the potash is not used with great care, the single teeth
will fall asunder and be lost. Perhaps the worst case is where a large animal has
a radula as small as that of a Rissoa like Turriteila, Harpa, or Struthiolaria, or

214 FUNCTIONS AND POSITION OF RADULA CHAP.

tion of the jaw, it comes within the province of the radula, the
front part of which perhaps co-operates to a certain extent with

Fic. 111.—Patella vulgata ., show-
ing the normal position of the
radula, which is doubled back in

B a bow; the shell has been re-
moved, and the whole visceral
mass is turned forward, exposing
the dorsal surface of the muscular
foot: gr, longitudinal groove on
this surface; 7, 7, intestine; J,

Fig. 110.—Jaws of Sepia : A, in situ liver ; mM, ™, mantle edge ; Mu,
within the buceal mass, several of muscles (cut through) fastening the
the arms having been cut away ; visceral mass to the upper sides of

B, removed from the mouth and the foot ; ov, ovary; 7, radula; uf,

slightly enlarged. upper or dorsal surface of the foot.

the jaw in performing the biting process. The function of the

where the radula is almost filmy in its transparency, like those of Actacon and the
small Scalaria.

‘“When once the radula is laid out, the mounting is commonly easy. Canada
balsam makes it too transparent. Fluids may be used, and are almost necessary for
thick radulae like those of large Chitons ; but the best general medium is glycerine
jelly. It runs under the cover glass by capillary attraction, and may be boiled
(though only for a moment) to get rid of air bubbles. It should then be left un-
finished for several weeks. If cracks appear, the reason is either that the jelly is a
bad sample, or that it has been boiled too long, or (commonly) that the object is too
thick ; and there is not often any difficulty in remounting. I have no serious com-
plaint of want of permanence against the medium, if I may speak from a pretty
wide experience during the last twenty years.”

VIII TEETH OF THE RADULA 215

radula as a whole is to tear or scratch, not to bite; the food
passes over it and is carded small, the effect being very much the
same as if, instead of dragging a harrow over the surface of a
field, we were to turn the harrow points upwards, and then drag
the field over the harrow.

The radula itself is a band or ribbon of varying length and
breadth, formed of chitin, generally almost transparent, some-
times beautifully coloured, especially at the front end, with red
or yellow.’ It lies enveloped in a kind of membrane, in the floor
of the mouth and throat, being quite flat in the forward part, but
usually curving up so as to line the sides of the throat farther
back, and in some cases eventually forming almost a tube. The
upper surface, z.e. the surface over which the food passes, is covered
with teeth of the most varied shape, size, number, and disposition,
which are almost invariably arranged in symmetrical rows.
These teeth are attached to the cartilage on which they work by
muscles which serve to erect or depress them; probably also the
radula as a whole can be given a forward or backward motion, so
as to rasp or card the substances which pass over it.

The teeth on the front part of the radula are often much
worn (Fig. 112), and probably fall away by degrees, their place
being taken by others successively pushed up from behind. At
the extreme hinder end of the radula the teeth are in a nascent
condition, and there are often as many as a dozen or more
scarcely developed rows. Here, too, lie the cells from which the
teeth are originally formed.

The length and breadth of the radula vary greatly in different
genera. In Littorina it is very narrow, and several times the
length of the whole animal. It is kept coiled away like a
watch-spring at the back of the throat, only a small proportion
of the whole being in use. I have counted as many as 480 rows
in the common Littorina littorea. In Patella it is often longer
than the shell itself, and if the radula of a large specimen be
freshly extracted and drawn across the hand, the action of the
hooks can be plainly felt. In Aerope, the Turbinidae generally,
and Haliotis it is very large. In Zurritella, Aporrhais, Cylichna,

' The substance both of the jaw and radula is neither crystalline nor cellular, but
laminated. Chitin is the substance which forms the ligament in bivalves, the
‘pen’ in certain Cephalopoda, and the operculum in many univalves. Neither
silica nor keratine enter into the composition of the radula.

216 SIZE OF RADULA——PRESENCE OR ABSENCE, CHAP.

Struthiolaria, and the Cephalopoda it is small in proportion to
the size of the animal. In the Pul-
monata generally it is very broad,
the length not exceeding, as a rule,
thrice the breadth; in most other
groups the breadth is inconsider-
able, as compared to the length.

The radula is wanting in two
familes of Prosobranchiata, the
Hulimidae and Pyramidelldae,
which are consequently grouped
together as the section Gymno-
glossa. It is probable that in

these cases the radula has aborted
Fic. 112.—Example of a front portion : ; : ;
of. a radula (Cantharus ringens through disuse, the animals hay-

Reeve, Panama), much worn by use. ing taken to a food which does not

ee require trituration. Thus several
genera contained in both these families are known to live para-
sitically upon various animals—Holothurians, Echinoderms, ete.—
nourishing themselves on the juices of their host. In some cases,
the development of a special suctorial proboscis compensates for
the loss of radula (see pp. 76-77). In Harpa there is no radula in
the adult, though it is present in the young form. No explana-
tion of this fact has yet been given. It is also absent in the
Coralliophilidae, a family closely akin to Purpura, but invariably
parasitic on corals, and probably nourished by their exudations.
There is no radula in Huxtoconcha, an obscure form parasitic on
the blood-vessels of Synapta, or in Neomenia, a genus of very low
organisation, or in the Tethyidae, or sea-hares, or in one or two
other genera of Nudibranchiata.

The number of teeth in the radula varies greatly. When the
teeth are very large, they are usually few in number, when small,
they are very numerous. In the carnivorous forms, as a rule, the
teeth are comparatively few and powerful, while in the phyto-
phagous genera they are many and small. Large hooked and
sickle-shaped teeth, sometimes furnished with barbs like an
arrow-head, and poison-glands, are characteristic of genera which
feed on flesh; vegetable feeders, on the contrary, have the teeth
rounded, and blunter at the apex, or, if long and narrow, so
slender as to be of comparatively lttle effect. Genera which are

VIII NUMBER AND ARRANGEMENT OF TEETH Zig;

normally vegetarian, but which will, upon occasion, eat flesh, e.g.
Limax and Hyalinia, exhibit a form of teeth intermediate
between these two extremes (see Fig. 140, A).

In Chaetoderma there is but one tooth. In Aeolis coronata
there are about 17, in A. papillosa and Elysia viridis about 19,
in Glaucus atlanticus about 21,in Fiona nobilis about 28. In
the common whelk (Buccinum undatum) there are from 220 to
250,in the common periwinkle about 5500. As many as 8343
have been counted in Limnaca stagnalis, about 15,000 in Helix
aspersa (that is, about 400,000 to the square inch), about 30,000
in Limax maximus, and as many as 40,000 in Helix Ghies-
breghti, a large species from Mexico; they are very numerous
also in Nanina, Vitrina, Gadinia, and Actaeon. But Umbrella
stands far and away the first, as far as number of teeth is con-
cerned. In both U. mediterranea and U. indica they entirely
battle calculation, possibly 750,000 may be somewhere near the
truth.

The teeth on the radula are almost invariably disposed in
a kind of pattern, exactly like the longitudinal rows of colour
in a piece of ribbon, down the centre of which runs a narrow
stripe, and every band of colour on one side is repeated in the
same relative position on the other side. The middle tooth of
each row—the rows being counted across the radula, not longi-
tudinally—is called the central or rachidian tooth; the teeth
next adjacent on each side are known as the laterals, while the
outermost are styled wncini or marginals. As a rule, the dis-
tinction between the laterals and marginals is fairly well indi-
cated, but in the Helicidae and some of the Nudibranchiata it is
not easy to perceive, and in these cases there is a very gradual
passage from one set to the other.

The central tooth is nearly always present. It is wanting in
certain groups of Opisthobranchiata, some of the carnivorous
Pulmonata, and in the Conidae and Terebridae, which have lost
the laterals as well. Voluta has lost both laterals and marginals
in most of the species, and the same is the case with Harpa. In
Acolis, Elysia, and some other Nudibranchiata the radula consists
of a single central row. Other peculiarities will be described
below in their proper order.

The extreme importance of a study of the radula depends
upon the fact, that in each species, and a fortiori in each genus

218 VALUE IN CLASSIFICATION CHAP.

and family, the radula is characteristic. In closely allied species
the differences exhibited are naturally but slight, but in well-
marked species the differences are considerable. The radula,
therefore, serves as a test for the distinction of genera and species.
For instance, in the four known recent genera of the family
Strombidae, viz. Strombus, Pteroceras, Rostellaria, and Terebellum,
the radula is of the same general type throughout, but with dis-
tinct modifications for each genus; and the same is true, though
to a lesser extent, for all the species hitherto examined in each
of the genera. These facts are true for all known genera, differ-
ences of the radula corresponding to and emphasising those other
differences which have caused genera to be constituted. The
radula therefore forms a basis of classification, and it is found
especially useful in this respect in dealing with the largest class
of all, the Gasteropoda, and particularly with the chief section of
this order, the Prosobranchiata. Thus we have—

(a) Toxoglossa
| (b) Rachiglossa
Monotocardia + (c) Taentoglossa
(d) Ptenoglossa
(e) Gymnoglossa
(f) Rhipidoglossa
(g) Docoglossa +

Prosobranchiata

Diotocardia

(a) Toxoglossa.—Only three families, Terebridae, Conidae, and
Cancellariidae, belong to this section. There is no central tooth,
and no laterals, the radula consisting simply of large marginals
on each side. In Conus these are of great size, with a blunt
base which contains a poison-gland (see p. 66), the contents of
which are carried to the point by a duct. The point is always
singly and sometimes doubly barbed (Fig. 116). When extracted,
the teeth resemble a small sheaf of arrows (Figs. 113,115). A re-
markable form of radula, belonging to Spirotropis (a subgenus of
Drillia, one of the Conidae), enables us to explain the true history
of the radula in the Toxoglossa. Here there are five teeth in a
row, a central tooth, and one lateral and one marginal on each
side, the marginals being very similar in shape to the character-
istic shafts of the Conidae (Fig. 114). It is evident, then, that
the great mass of the Toxoglossa have lost both their central

1 +6Zov, arrow ; paxus, ridge, sharp edge ; rawvia, ribbon ; mryvés, winged ; yupurds,
bare ; puis, fan ; doxds, beam.

VIII FORMULAE OF TEETH 219

and lateral teeth, and that those which remain are true uncini
or marginals. Spirotropis appears to be the solitary survival of
a group retaining the primitive form of radula.

The arrangement of teeth in all these sections is expressed
by a formula applicable to each transverse row of the series.
The central tooth, if present, is represented by 1, and the laterals
and marginals, according to their number, on each side of the

Fria. 114.—Portion of radula of Spiro-
tropis carinata Phil., Norway. x70.

Fic. 113.—Radula of Bela turricula Mont. Fic. 115.—Kight teeth from the radula
x 70. of Terebra caerulescens Lam. x 60.

central figure. Thus the typical formula of the Toxoglossa 1s
1.0.0.0.1, the middle 0 standing for the central tooth which 1s
absent, and the 0 on each side of it for the absent laterals; the
1 on each extreme represents the one uncinus in each row.
Thus the formula for Spirotropis, which has also one lateral on
each side and a rachidian or central tooth, is 1.1.1.1.1. Often
10500 -4y chiles

the formula is given thus: — , where 30 and 42

>
vw “=

stand for the average number of rows of teeth in Conus and
Spirotropis respectively ; the same is sometimes expressed thus :
OOO Seo aed et S42.

BAO) RADULA OF THE RACHIGLOSSA CHAP.

(b) The Rachiglossa comprise the 12 families Olividae, Harpi-
dae, Marginellidae, Volutidae, Mitridae, Fasciolariidae, Turbinel-
lidae, Buccinidae, Nassidae, Columbellidae, Muricidae, and

Fic. 117.—Portion of the radula of Melongena
vespertilio Lam., Ceylon, x 30

Fic. 116.—A_ tooth
from the radula
of Conus imperi-
alis L., 8. Pacific,
x 50, showing
barb and poison
duct. Fre. 118.—Portion of the radula of Eburna japonica

Sowb., China. x 30.

Fic. 119.—Portion of the
radula of Murex regius
Lam., Panama. x 60.

Corallophilidae. Certainly most and probably all of these
families are or have been carnivorous, the Coralliophilidae being
a degraded group which have become parasitic on corals, and
have lost their teeth in consequence. The characteristics of the

VIIL RADULA OF THE RACHIGLOSSA 2,

iS)
|

group are the possession of a central tooth with from one cusp
(Boreofusus) to about fourteen (Bullia), and a single lateral more
or less cuspidate, the

outer cusp of all being
generally much
largest. Thus in MZelon-
gena respertilio( Fig. 117)

the central tooth

cuspid, the central cusp
being the smallest, while

the

is tri-

Fic. 120.—Portion of the radula of Imbricaria

the laterals are bicuspid ; marmorata Swains, x 80.

in Hburna japonica (Fig.

118) the central tooth is 5-cusped, the two outer cusps being much
the smallest. The teeth, on the whole, are sharp and hooked,

Fic. 121.—Three rows
of teeth from the
radulaof Masciolaria
trapezium Lam. x

40.

with a broad base and formidable cutting edge. In the Olividae,
Turricula, Buceinopsis, and the Muricidae the laterals are unicuspid

Fig. 122.—Six teeth
from the radula of
Cymbium diadema
Lam., Torres Strait.

owe

and somewhat degraded (Fig. 119). In Mitra
and the Fasciolariidae they are very broad and
finely equally toothed like a comb (Figs. 120,
121). The whole group is destitute of marginals.

Several remarkable peculiarities occur.
Harpa loses the radula altogether in the adult.
In the young it has lost only the laterals, and
consists of nothing but the central tooth.
Marginella has no laterals; the central tooth
is small and comb-shaped, with blunt cusps.
In Voluta the laterals are generally lost, but
in Volutomitra and one species of Voluta}
they are retained. The central tooth usually

has three strong cusps, and is very thick and coloured a deep red

1 V. concinna, according to Schacko (Conch. Mitth. i. p. 126, Pl. xxiv. f. 5); the
lateral is large, strong, unicuspid on a broad base.

i)
NO
NO

DEGRADED AND ABNORMAL RADULA CHAP.

or orange (Fig. 122); in the subgenus Amoria it is unicuspid,
in shape rather like a spear-head with broadened wings; in
Volutolyria it is of a different
type, with numerous unequal den-
ticulations, something like the
laterals of Jhtra or Fasciolaria.
Of the Mitridae, Cylindromitra
has lost the laterals. Among the
Buecinidae, Buccinopsis possesses
a curiously degraded radula, the
central tooth having no cusps, but
being reduced to a thin basal
plate, while the laterals are also
weakened. This degradation from
the type is a remarkable feature
among radulae, and appears to be
characteristic, sometimes of a whole

B family, e.g. the Columbellidae (Fig.
Fic. 123.—Examples of degraded forms 123, B), sometimes of a genus,

of radula: A, Cantharus pagodus .. 5 yea Cet AA bea ee Soop
Reeve, Panama (nascent end), x 40 ; SOmetimes again of a single species.

A’, same radula, central and front Thus in Cantharus (a subgenus of
portion; B, Coluimbella varia Sowb., Dire t] pad ulancia tenpienianl
Panamiaakco 0. uccinum) the radula is typical in
the great majority of species, but im
C. pagodus Reeve, a large and well-grown species, it is most remark-
ably degraded, both in the central and lateral teeth (Fig. 123, A).
This circumstance is the more singular since C. pagodus lives at
Panama side by side with C. ringeus and C. insignis, both of which

Fic. 124.—Three rows of the radula of Sistrum spectrum Reeve, Tonga. x 80.
The laterals to the right are not drawn in.
have perfectly typical radulae. It is probable that the nature of
the food has something to do with the phenomenon. — Thus Sistrum
spectrum Reeve was found to possess a very aberrant radula, not of
the common muricoid type, but with very long reed-lke laterals.
This singularity was a standing puzzle to the present writer,

VIII RADULA OF THE TAENIOGLOSSA 22:3

until he was fortunate enough to discover that S. spectrum,
unlike all other species of Sistrum, lives exclusively on a branch-
ing coral.

The dental formula for the Rachiglossa is thus 1.1.1, except
in those cases where the laterals are absent, when it is 0.1.0.

(¢) The Taenioglossa comprise 46 families in all, of which the
most important are Tritonidae, Cassididae, Cypraeidae, Strom-
bidae, Cerithiidae, Turritellidae, Melaniidae, Littorinidae,
Rissoidae, Paludinidae, Ampullarudae, Cyclophoridae, Cyclostoma-

Fic. 125.—Portion of the radula of Cassis sulcosa Born., x 40. The marginals
to the right are not fully drawn.
tidae, and Naticidae. The radula is characterised by a central
tooth of very variable form, the prevailing type being multi-
cuspid, the central cusp the largest, on a rather broad base; a
single lateral, which is often a broad plate, more or less cusped,
and two uncini, rather narrow, with single hooks, or slightly

Fig. 126.—Four rows of teeth
from the radula of Vermetus
grandis Gray, Andamans.
x 40.

eusped. The accompanying figures of Cassis, Vermetus, and
Cypraea, and those of Littorina and Cyclophorus given on pp.
20, 21, are good examples of typical taenioglossate radulae.

In Homalogyra the radula is much degraded, the central
tooth is large and triangular on a broad base, the lateral is
represented only by a thin oblong plate, and the uncini are
absent. In some species of Jeffreysia the uncini are said to be
absent, while present in others. Lamellaria has lost both its
uncini, but the radula of the allied Velutina is quite typical. A
peculiar feature in this group is the tendency of the marginals
to increase in number. A stage in this direction is perhaps seen

224 RADULA OF THE TAENIOGLOSSA CHAP.

in Ovula, Pedicularia, and the Cyclostomatidae. Here the outer-
most of the two marginals is by far the larger and broader, and
is strongly pectinated on its upper edge; in the Cyclostomatidae

Fic. 127.—Two rows of the
radula of Cypraea tigris L.
xo0:

the pectinations are rather superficial; in Ovula (where both
marginals are pectinated) they are decidedly deeper ; in Pedicu-
laria they are deeper still, and make long slits in the tooth,
tending to subdivide it altogether. In Zwrritella the number of
marginals is said to vary from none (in 7. acicula) to three (7.
triplicata), but the fact wants confirmation. Solariwm is an
aberrant form, possessing simply a number of.long uncini, which
recall those of Conus or Pleurotoma, and is therefore hard to
classify; the allied Zorinia has a radula which appears allied
to Ovula or Pedicularia. In Triforis the teeth are identical
throughout, very small, about 27 in a row, tricuspid on a square
base, cusps short.

The normal formula of the TYaenioglossa is 2.1.1.1.2; in
Lamellaria, 1.1.1; in Triforis, 15.1.18, or thereabouts.

(ad) Ptenoglossa.—tThis
section consists of two
families only, which cer-
tainly appear remarkably
dissimilar in general habits
and appearance, viz., the
Janthinidae and Scalarii-
dae. In all probability
their approximation is
only provisional. The

Fic. 128.—Portion of the radula of Zanthina radula which in Lanthina
communis Lam. x 40. :

is very large, and in
Scalaria very small, possesses an indefinite number of long hooked

VIII RADULA OF THE PTENOGLOSSA, ETC. 225

teeth, of which the outermost are the largest. The central
tooth, if present (it does not occur in Lanthina), is the smallest
in the series, and thus recalls the arrangement in some of the
carnivorous Pulmonata (p. 252). In Lanthina the radula is
formed of two large divisions, with a gap between them down
the middle.

The formula is 0.1.0 or 0.0.00 according as the central
tooth in Scalaria is or is not reckoned to exist.

(e) Gymnoglossa.—tIn the absence of both jaw and radula it is
not easy to classify the two families (Kulimidae and Pyrami-
dellidae) which are grouped under this section. Fischer regards
them as modified Ptenoglossa; one would think it more natural
to approximate them to the Taenioglossa.

Fic. 129.—Portion of the radula of Margarita umbilicalis Brod., Labrador.
x 75 and 300.

(7) Rhipidoglossa.—This section consists of seventeen families,
the most important being the Helicinidae, Neritidae, Turbinidae,
Trochidae, Haliotidae, Pleurotomariidae, and Fissurellidae. The
radula is characterised by—

(1) The extraordinary development of the uncini, of which
there are so many that they are always reckoned as indefinitely
numerous. They are long, narrow, hooked, and often cusped at
the top, and crowded together like the ribs of a fan, those at the
extreme edge not being set straight in the row, but curving
away backwards as they become smaller; in Solariella alone,
where there are from five to ten, can they be counted.

(2) The varying number of the laterals. The average

VOls I Q

“©

226 RADULA OF THE RHIPIDOGLOSSA CHAP.

number of these is five on each side; in some cases (Livona)
there are as many as nine, in some (Neritopsis) only three. The
lateral next to the uncini (which is specially large in the
Neritidae, and is then known as the capituliform tooth) is
regarded by some authorities as the first uncinus, by others as
the sole representative of the laterals, the teeth on the inner
side of it being reckoned as multiplied central teeth. Accord-
ing to this latter view, Zivona will have as many as seventeen
central teeth. Taking five as the average number of ‘ laterals,’
we shall have the following different ways of constituting the
rhipidoglossate formula, the first being that to which preference
Ise Ven; evs ——
(1) ©.5.1.5.00, we one central, five laterals, including
the ‘last lateral’ tooth.
(2) (o.1).4.1.4.(1.00 ), regarding the ‘last lateral’ as. first
uncinus, but specialising it by a number.
(3) o.1.(4.1.4). 1.00 , regarding the ‘last lateral’ as the only
lateral.
In the Neritidae and the derived fresh-water genera (Veritina,
Navicella) the first lateral, as well as the capituliform tooth, is

Fic. 130. —Portion of the radula of Nerita albicilla L., Andaman Is., with central tooth
highly magnified : ¢c, c, the capituliform tooth. x 40.

very large, and in shape rather like the blade bone of a shoulder
of mutton; the intervening laterals are very small. In
Neritopsis (a degraded form) the central tooth and first lateral
are entirely wanting. In the neritiform land-shells (/felicina,
Proserpina) the first lateral is no larger than the others, while
the capituliform tooth is enormous. Hydrocena is a very
aberrant and apparently degraded form; the laterals between the
first and the capituliform tooth are all wanting. In Haliotis,
Scissurella, and Pleurotomaria the five laterals are of fairly equal

VIII RADULA OF THE DOCOGLOSSA 227

size; in Fissurella we again meet with a large capituliform
tooth, with very small laterals.

(yg) The Docoglossa are in direct contrast with the Rhipido-
glossa in possessing few and strong teeth, instead of many and
weak. There are only three families, Acmaeidae, Patellidae,
and Lepetidae. In some of the Acmae-
idae there are not more than two
teeth in a row, while in no species are
there more than twelve. The radula
is, however, very long; there are as
many as 180 rows in Patella vulgata.
The teeth are thick, generally of a
very deep red horn colour, rather
opaque. The cartilage in which they
are set is remarkably thick, and in
some species whose teeth are very Fic. 131.—Portion of the radula
few a considerable portion of this car- ie si ae nore a
tilage is left quite bare.

Although the teeth are so few, the arrangement is by no
means simple. The special feature of the group is the multipli-
cation of identical centrals. Of these there are two in Aemaea,
and four, as a rule, in Patella. Thus in these two genera there is
seldom an absolutely central tooth. Either laterals or marginals
are liable to be lost, but there are never more than two of either
in Acemaea, and never more than two laterals and three marginals
in Patella. Thus the formula varies from 0.0.01 +0+1).0.0 in

Fic. 132.—Two rows of
the radula of Ptero-
trachea mutica Les.,

Naples, x 60.

Pectinodonta, 2.2(1+0+1).2.2 in Collisellina (both Acmaei-
dae), to 3.2.(14+0+1).2.3 in Patinella, and 3.1.(2+0+4 2).1.3
in Patella proper. In the Lepetidae there is an absolutely
central tooth, which appears to be made up of the coalescence of
several teeth, no laterals, and about two marginals; formula,

2.011 :0,2.

228 RADULA OF HETEROPODA AND AMPHINEURA CHAP.

The radula of the eteropoda is quite characteristic, and
shows no sign of affinity with any other Prosobranchiate. The
central tooth is large, broad, tricuspid, and denticulated on a
broad base; the single lateral is strong, often bicuspid; the
two marginals simple, long, falciform; formula, 2.1.1.1.2
(Pio. 13:2),

Amphineura. — («) Polyplacophora—tThe radula of the
Chitonidae is quite unique. It resembles that of the Docoglossa
in being very long, and composed of thick and dark horn-
coloured teeth. The number of teeth, however, is considerably

Fic. 133.—A, Portion of the radula of Chiton (Acanthopleura) spiniger Sowb., Anda-
mans, x 30; B, portion of the radula of Dentalium entalis L., Clyde, x 50.

greater, amounting almost invariably to seventeen in each row.
There are three rather small central teeth, the two outer of these
being similar ;: next comes a very large lateral (the major lateral),
usually tricuspid, which is followed by two much smaller laterals,
which are scarcely more than accessory plates; then a very large
and arched marginal (the major uncinus), at the outer side of
which are three accessory plates. Some consider there is only
one central tooth, and count the two small teeth on each side of
it as laterals.

Thus the formula is either (8+1).(24+1).8.(14+2).(14+3
or (38 +1).(24+14+1).1.24+14+2).(14+3).

(b) Aplacophora.—oOf this rather obscure order, Chaetoderma
has a single strong central tooth, Neomenia has no radula.

VIII RADULA OF OPISTHOBRANCHIATA 229

Proneomenia and Lepidomenia have about twenty faleiform
teeth, much larger at one end of the radula than the other;
formula, 0.1.0.

Opisthobranchiata.—The radula of the Opisthobranchiata
is exceedingly variable in shape, size, and number and character
of teeth. Not only do allied families differ greatly from one
another, but allied genera often possess radulae widely distinct

Fic. 134.—Two teeth from the radula of
Aeolis papillosa L. x 55.

in plan. Thus, among the Polyceridae, Goniodoris has no central
tooth, one large lateral and one marginal (form. 1.1.0.1.1);
Doridunculus the same, with five marginals (form. 5.1.0.1.5);
Lamellidoris one each of median, laterals and marginals
(1.1.1.1.1); Ldalia, Aneula, and Thecacera the same as Goniodoris ;
Crimora several each of laterals and marginals. Even species of
the same genus may differ; thus the formula for Aeolis papillosa
is 0.1.0, but for Ae. Landsbergi 1.1.1; for Philine aperta 1.0.1,
but for Philine pruinosa 6.0.6.

It must not be forgotten, however, that a simple repetition of
the same tooth, whether lateral or marginal, does not necessarily
constitute an important characteristic, nor does the presence or
absence of a central tooth. In most of the cases mentioned above,
the difference in the number of laterals and marginals is due to
the multiplication of identical forms, while the central tooth, when
present, is often a mere plate or narrow block without cusps,
whose presence or absence makes little difference to the character
of the radula as a whole.

There appear to be three well-marked types of radula among
the Opisthobranchiata.

(a) Radula with a single strong central tooth, rows few.

24 VO) RADULA OF OPISTHOBRANCHIATA CHAP.

This form is characteristic of the Aeolididae, Fionidae, Glaucidae,
Dotoidae, Hermaeidae, Elysiidae (Fig. 135), and Limapontiidae.
In the Aeolididae it is sometimes accompanied by a single
lateral. The same type occurs in Oxynoe, and in Lobiger (=
Lophocercus).

(0) Radula with the first lateral very strongly developed.
This type may take the form of (1) a single lateral, no central or
marginals, e.g. Onehidoris, Scaphander (Fig. 137, A) Philine
(certain species), Ringicula, or (2) first lateral strongly developed,
and repeated in succeeding laterals (2-6) on a smaller scale, e.g.
Philine (certain species). A few marginals are sometimes added,

Ira. 1385.—Radula of Elysia Fic. 136.—Portion of the radula
viridis Mont. «40. Type of Gadinia peruviana Sowd.,
(a). Chili. 250. ‘Type (c).

e.g. in Polycera, Lamellidoris (where there is a degraded central
tooth, Fig. 137, B), Zdalia, and Aneula.

(c) Radula with an indefinite number of marginals, laterals
(if present) merging into marginals, central tooth present or
absent, inconspicuous, teeth all very small. This type of radula,
among the Nudibranchiata, is characteristic of certain subgenera
of Doris (e.g. Chromodoris, Aphelodoris, Casella, Centrodoris), of
Hypobranchiaca and Pleurophyllidia ; among the Tectibranchiata,
of Actaeon, many of the Bullidae, Aplustrum, the Aplysudae,
Pleurobranchus, Umbrella and Gadinia (Figs. 1386 and 137, C).

In the Pteropoda there are two types of radula. The Gymno-
somata, which are in the main carnivorous, possess a radula with a
varying number (4-12) of sickle-shaped marginals, central tooth
present or absent. In the Thecosomata, which feed on a vegetable
diet, there are never more than three teeth, a central and
marginal on each side ; teeth more or less cusped on a square base.

VIII RADULA OF PULMONATA PAC I

Pulmonata.—The radula of the Testacellidae, or carnivorous
land Mollusca, is large, and consists of strong sickle-shaped teeth
with very sharp points, arranged in rows with or without a
central tooth, im such a way that the largest teeth are often on
the outside, and the smallest on the inside of the row (as in
Rhytida, Fig. 139). The number and size of the teeth vary.
In Testacella and Glandina, they are numerous, consisting of
from 30 to 70 in a row, with about 50 rows, the size through-
out being fairly uniform. In Aerope they are exceedingly large,

Fic. 137.—Portions of theradula
of Opisthobranchiata, illus-
trating types (4) and (c); A,
Scaphander lignarius L.; A’,
one of the teeth seen from
the other side, x 40; B,
Lamellidoris bilamellata L.,
Torbay, x 60; C, Hydatina
physis L., E. Indies, x 75.

and only eight in a row, the outermost marginal being probably
the largest single tooth in the whole of the Mollusca. The
central tooth is always obscure, being, when present, simply a
weaker form of the weakest lateral; in genera with only a few
teeth in a row it is generally absent altogether.

The first family of jaw-bearing snails, the Selenitidae, is
distinctly intermediate. The possession of a jaw relates it to
the main body of Helicidae, but the jaw is not strong, while the
teeth are still, with the exception of the central, thoroughly
Testacellidan. The central tooth is quite rudimentary, but it is

232 RADULA OF PULMONATA CHAP.

something more than a mere weak reproduction of the marginals.
There are no true laterals. The Limacidae show a further stage
in the transition. Here the central tooth has a definite shape of
its own, tricuspid on a broad base, which is more or less repeated
in the first laterals; these, as they approach the marginals,

ip Fia. 138. — Portion
of the radula of
Glandina trun-

cata Gmel. x 49.

=——

gradually change in form, until the outer marginals are again
thoroughly Testacellidan.’ This is the general form of radula,
varied more or less in different genera, which occurs in Nanina,
Helicarion, Limax, Parmacella, and all the subgenera of Zonites.
It is certain that some, and probable that all of these genera will,

Fia. 139.— Portion
of the radula of
Rhytida Kraussit
Pir sy eeauncas
2D:

on occasion, eat flesh, although their usual food appears to be
vegetable. The jaw is more powerful than in the Selenitidae, but
never so large or so strongly ribbed as in Helix proper.

When we reach the Helicidae, we arrive at a type of radula

1 In some cases (e.g. Hyalinia inornata) the laterals are very few, while in Zonites
laevigatus the first side tooth is more of a marginal than a lateral.

VII RADULA OF PULMONATA 2a

in which the aculeate form of tooth—so characteristic of the
Agnatha—disappears even in the marginals, and is replaced by
teeth with a more or less quadrate base; the laterals, which are
always present, are intermediate in form between the central and
the marginals, and insensibly pass into the latter. In size and
number of cusps the first few laterals resemble the central tooth ;
in the extreme marginals the cusps often become irregular or
evanescent. As a rule, the teeth are set squarely in the rows,
with the exception of the extreme marginals, which tend to slope
away on either side. In some Helicidae there is a slight approxi-
mation to the Zonitidae in the elongation of the first marginals.

The above is the type of radula occurring in the great family
Helicidae, which includes not only Helix proper, with several
thousand species, but also Arion, Bulimus, Ariolimax, and other
genera. The jaw is almost always strongly transversely ribbed.

In the Orthalicidae (Fig. 140, C) the teeth of the radula,
instead of being in straight rows, slope back at an angle of about
45 degrees from the central tooth. The central and laterals are
very similar, with an obtuse cusp on rather a long stem; the
marginals become bicuspid.

In the Bulimulidae, which include the important genera
Placostylus, Amphidromus, Partula, Amphibulimus, and all the
groups of South American Bulimulus, the jaw is very char-
acteristic, being thin, arched, and denticulated at the edges, as if
formed of numerous narrow folds overlapping one another. The
radula is like that of the Helicidae, but the inner cusp of the laterals
is usually lengthened and incurved. In Partula the separation
between laterals and marginals is very strongly marked.

The remaining families of Pulmonata must be more brieily
described. In the Cylindrellidae there are three distinct types of
radula: (a) Central tooth a narrow plate, laterals all very
curiously incurved with a blunt cusp, no marginals (Fig. 140, D);
(6) radula long and narrow, central tooth as in (a), two laterals,
and about eight small marginals ; (¢) much more helicidan in type,
central and laterals obtusely unicuspid, marginals quite heli-
cidan. Type (c) is restricted to Central America, types (a) and
(b) are West Indian.

Pupidae: Radula long and narrow; teeth of the helicidan
type, centrals and laterals tricuspid on a quadrate base, marginals
very small, cusps irregular and evanescent. This type includes

234 RADULA OF PULMONATA CHAP.

Anostoma, Odontostomus, Buliminus, Vertigo, Strophia, Holospira,
Clausilia, and Balea.

Stenogyridae, including Achatina, Stenogyra, and all its sub-
genera: Central tooth small and narrow, laterals much larger,
tricuspid, central cusp long, marginals similar, but smaller.

Achatinellidae: Two types occur; (a) teeth in very oblique
rows, central, laterals, and marginals all of the same type, base
narrow, head rather broad, with numerous small denticles
(Achatinella proper, with Auriculella and Tornatellina, Fig.

A
CAPR Aarne
SMRAAARIMPNITY ey PPD = +y]
B ots

Fic. 140.—Portions of the radula of A, Hyalinia nitidula Drap., Yorkshire, with central
tooth, first lateral, and a marginal very highly magnified ; B, Helix pomatia L.,
Kent, showing central tooth, laterals, and one extreme marginal, the two former
also highly magnified ; ©, Orthalicus undatus Brug., Trinidad, with three laterals
highly magnified ; D, Cylindrella rosea Pfr., Jamaica, central tooth and laterals,
the same very highly magnified ; E, Achatinella vulpina Fér., Oahu, central tooth
(c) and laterals, the same highly magnified.

140, E); () central tooth small and narrow, laterals bicuspid,
marginals as in Helix (Amastra and Carelia).

Succinetdae : Central and laterals helicidan, bi- or tricuspid on
a quadrate plate, marginals denticulate on a narrow base; jaw
with an accessory oblong plate.

Junellidae : Central tooth very small, laterals and marginals
hike Achatinellidae (a).

Vaginulidac: Central, laterals, and marginals unicuspid
throughout, on same plan.

Onchidiidae: Rows oblique at the centre, straight near the

VIII RADULA OF PULMONATA 25

edges; central strong, tricuspid; laterals and marginals very
long, faleciform, arched, unicuspid.

Auriculidae: Teeth very small; central narrow, tricuspid on
rather a broad base ; laterals and marginals obscurely tricuspid on
a base hke Suecined.

Limnaecidae: Jaw composed of one upper and two lateral
pieces ; central and lateral teeth resembling those of Helicidae ;
marginals much pectinated and serriform (Fig. 141. A). In

sia FRAO ARP

a
\ vye/

Nat HHT
ae \\\\ \\ SUD WU F 4
1d. 141.—Portions of the radula of
A, Limnaea stagnalis L., with the
central tooth and two first laterals,
and two of the marginals, very
highly magnified; B, <Ancylus
; fluviatilis Miill., with two of the
Oe marginals very highly magnified ;
C, Physa fontinalis L., with cen-
tral tooth and two of the marginals

very highly magnified.

i
'
1
'
i
1
'

Ancylus proper the teeth are of a very different type, base
narrow, head rather blunt, with no sharp cusps, teeth similar
throughout, except that the marginals become somewhat pec-
tinated (Fig. 141, B); another type more resembles Limnaea.
Physidae: Jaw simple, but with a fibrous growth at its
upper edge, which may represent an accessory plate; radula
with very oblique rows, central tooth denticulate, laterals and

236 RADULA OF SCAPHOPODA AND CEPHALOPODA CHAP.

marginals serriform, comb-lke, with a wing-like appendage at
the superior outer edge (Fig. 141, C).

Chilinidae : Central tooth small, cusped on an excavated tri-
angular base, marginals five-cusped, with a projection as in
Physa, laterals comb-lhke, serrations not deep.

Amphibolidae: Central tooth five-cusped on a broad base,
central cusp very large; two laterals only, the first very small,
thorn-like, the second like the central tooth, but three-cusped ;
laterals simple, sabre-shaped.

Scaphopoda.—In the single family (Dentaliidae) the radula is
large, and quite unlike that of any other group. The central
tooth is a simple broad plate; the single lateral is strong, arched,
and slightly cusped ; the marginal a very large quadrangular plate,
quite simple; formula, 1.1.1.1.1 (Fig. 133, B).

Cephalopoda.—The radula of the Cephalopoda presents no
special feature of interest. Perhaps the most remarkable fact about
it is its singular uniformity of structure throughout a large number
of genera. It is always very small, as compared with the size of
the animal, most of the work being done by the powerful jaws,
while the digestive powers of the stomach are very considerable.

The general type of structure is a central tooth, a very few
laterals, and an occasional marginal or two; teeth of very uniform
size and shape throughout. In the Dibranchiata, marginals are
entirely absent, their place being always taken, in the Octopoda,
by an accessory plate of varying shape and size. This plate
is generally absent in the Decapoda. The central tooth is, in
the Octopoda, very strong and characteristic; in Eledone and
Octopus it is five-cusped, central cusp strong; in <Argonauta
unicuspid, in Zvemoctopus tricuspid. The laterals are always
three in number, the in-
nermost lateral having a
tendency to assume the
form of the central. In
Sepia the two inner laterals

-are exact reproductions of
Fic. 142.—Portion of the radula of Octopus tetra- the central tooth: in Ele-
cirrhus D. Ch., Naples, x 20. : ? =u

done, Sepiola, Loligo, and

Sepia, the third lateral is falciform and much the largest.
In Nautilus, the only living representative of the Tetra-
branchiata, there are two sickle-shaped marginals on each side,

VIII SALIVARY GLANDS 2:37.

each of which has a small accessory plate at the base. The two
laterals and the central tooth are small, very similar to one
another, unicuspid on a square base.

Salivary glands are found in most Glossophora. They occur in
one or two pairs on each side of the pharynx and oesophagus, the
duct usually leading forwards and opening into the anterior part
of the pharynx (see Figs. 143, 144). They are exceptionally
large in the carnivorous Gasteropoda. In certain genera, eg.
Murex, Dolium, Cassis, Pleuwrobranchus, the secretions of these
glands are found to contain a considerable proportion (sometimes
as much as 4°25 per cent) of free sulphuric acid. This fact was

hip iy

Fic. 143.—Alimentary canal of Helix uspersa L.: a, anus; b.d, b.d’, right and left
biliary ducts ; 6.m, buccal mass ; ¢, crop; h.g, hermaphrodite gland ; 7, intestine ;
i.o, opening of same from stomach (pyloric orifice); 7, /’, right and left lobes of
liver ; m, mouth; oe, oesophagus; 7, rectum; s.d, salivary duct; s.g, salivary
gland ; st, stomach; ¢, left tentacle. (After Howes and Marshall, slightly
modified. )

first noticed by Troschel, who, while handling a Doliwm galea at
Messina, saw the creature spit a jet of saliva upon a marble slab,
which immediately produced a brisk effervescence. A number
of the genera thus provided bore through the shells of other
Mollusea and of Echinoderms, to prey upon their soft tissues, and
it is possible that the acid assists in the piercing of the shell by
converting the hard carbonate of lime into sulphate of hme,
which can easily be removed by the action of the radula.’’ In
the majority of the Cephalopoda there are two pairs of salivary
glands, one lying on each side of the mouth, the other on the
middle of the oesophagus.

3. The Oesophagus.—That part of the alimentary canal which

1 Semon, Biol. Centraibi. ix. p. 80.

238 THE OESOPHAGUS CHAP.

lies between the pharynx and the stomach (in Pelecypoda
between the mouth and stomach) is known as the oesophagus.
Its exact limits are not easy to define, since in many cases the
tube widens so gradually, while the muscular structure of its walls
changes so slowly that it is difficult to say where oesophagus
ends and stomach begins. As a rule, the oesophagus is fairly

Fie. 145. —Gizzard of Scaphander
lignarius L.: A, showing posi-
tion with regard to oesophagus
(oe) and intestine (7), the latter
being full of comminuted frag-
ments of food ; p, left plate ; p’,
right plate; p.ac, accessory
plate; B, the plates as seen from
the front, with the enveloping
membranes removed, lettering
asin A. Natural size.

| Hh Mey

Fra. 144.—Alimentary canal, etc.,
of Sepia officinalis L.: a,
anus; 6.d, one of the biliary
ducts ; 6.m, buccal mass ; ¢,
coecum ; 7, ink-sac ; 7.d, duct 4
of same; j, jaws; ./, lobes Fic. 146.—Section of the stomach of

of the liver ; oe, oesophagus ;
pP, pancreatic coeca; 7, rec-
tum ; s.g, salivary glands ; st,

Melongena, showing the gastric plates
(g.p, g.p,) for the trituration of food ;
b.d, biliary duct; g.g, genital gland ;

stomach. (Froma specimen in
the British Museum. )

7, intestine ; 7, liver; oe, oesophagus ;
st, stomach. (After Vanstone.)
simple in structure, and consists of a straight and narrow tube.
In the Pulmonata and Opisthobranchiata it often widens out
inte a ‘crop, which appears to serve the purpose of retaining a
quantity of masticated food before it passes on to the stomach.
In Octopus and Patella the crop takes the form of a lobular
coecum. In the carnivorous Mollusca the oesophagus becomes
complicated by the existence of a varying number of glands, by

VII THE STOMACH AND ITS APPENDAGES 239

the action of which digestion appears to begin in some cases
before the food reaches the stomach proper.

4. The Stomach.—At the posterior end of the oesophagus lies
the muscular pouch known as the stomach, in which the digestion
of the food is principally performed. This organ may be, as in
imax, no more than a dilatation of the alimentary canal, or it may,
as is usually the case, take the form of a well-marked bag or pocket.
The two orifices of the stomach are not always situated at opposite
ends; when the stomach itself is a simple enlargement of the wall
of one side of the alimentary canal, the cardiac or entering orifice
often becomes approximated to the orifice of exit (pyloric orifice).

The walls of the stomach itself are usually thickened and
strengthened by constrictor muscles. In some Nudibranchs
(Seyllaea, Bornella) they are lined on the inside with chitinous
teeth. In Cyclostoma, and some Bithynia, Strombus, and Trochus
there is a free chitinous stylet within the stomach.! In Melon-
gena (Fig. 146) the posterior end of the oesophagus is provided
with a number of hard plate-like ridges, while the stomach is
lined with a double row of cuticular knobs, which are movable
on their bases of attachment, and serve the purpose of triturating
food? Aplysia has several hard plates, set with knobs and spines,
and similar organs occur in the Pteropoda. But the most formid-
able organ for the crushing of food is possessed by the Bullidae,
and particularly by Scaphander (Fig. 145). Here there is a
strong gizzard, consisting of several plates connected by powerful
cartilages, which crush the shells, which are swallowed whole.

Into the stomach, or into the adjacent portions of the digestive
tract, open the ducts which connect with the so-called liver.
The functions of this important organ have not yet been
thoroughly worked out. The liver is a lobe-shaped gland of a
brown-gray or light red colour, which in the spirally-shelled
families usually occupies the greater part of the spire. In the
Cephalopoda, the two ducts of the liver are covered by append-
ages which are usually known as the pancreatic coeca ; the biliary
duct, instead of leading directly into the stomach, passes into a
very large coecum (see Fig. 144) or expansion of the same,

' According to Moquin-Tandon (dModl. de France, i. p. 44) this process in Bithynia
is attached by one end to the wall of the stomach. Vivipara, with two jaw pieces,
does not possess this stylet ; Bithynia, which does possess it, has no jaw.

2 J. H. Vanstone, Journ. Linn. Soc. xxiv. p. 369.

240 THE LIVER AND HYALINE STYLET CHAP.

which serves as a reservoir for the biliary secretions. At the
point of connexion between the coecum and stomach is found a
valve, which opens for the issue of the biliary products into the
stomach, but closes against the entry of food into the coecum.
In most Gasteropoda the liver consists of two distinct lobes,
between which are embedded the stomach and part of the
intestine. In many Nudibranchiata the liver becomes ‘ diffused ’
or broken up into a number of small diverticula or glands con-
necting with the stomach and intestine. The so-called cerata
or dorsal lobes in the Aeolididae are in effect an external liver,
the removal of which to the outside of the body gives the crea-
ture additional stomach-room.

The Hyaline Stylet—In the great majority of bivalves the
intestine is provided with a blind sac, or coecum of varying
leneth. Within this is usually lodged a long cylindrical body
known as the hyaline or crystalline stylet. In a well-developed
Mytilus edulis it is over an inch in length, and in Mya arenaria
between two and three inches. The bladder-like skin of the
stylet, as well as its gelatinoid substance, are perfectly trans-
parent. In the Unionidae there is no blind sac, and the stylet,
when present, is in the intestine itself. It is said to be present
or absent indifferently in certain species.

The actual function performed by the hyaline stylet is at
present a matter of conjecture. Haseloff’s experiments on
Mytilus edulis tend to confirm the suggestion of Mobius, that
the structure represents a reserve of food material, not specially
secreted, but a chemical modification of surplus food. He found
that under natural conditions it was constantly present, but that
specimens which were starved lost it in a few days, the more
complete the starvation the more thorough being the loss; it
reappeared when they were fed again. Schulze, on the other
hand, believes that it serves, in combination with mucus secreted
by the stomach, to protect the intestine against laceration by
sharp particles introduced with the food. W. Clark found that
in Pholas the stylet is connected with a light yellow corneous
plate, and imagined therefore that it acts as a sort of spring to
work the plate in order to comminute the food, the two together
performing somewhat the function of a gizzard."

1 Biol. Centralbl. vii. p. 683; SB. Ges. Nat. Fr. 1890, p. 42; Mag. Nat. Hist.
(2) v. 1850, p. 14.

VIII AMSUS, JONANESMANS:

241

5. and 6, Lhe Intestine, Rectum, and Anus.—The intestine,
the wider anal end of which is called the rectum, almost invari-

ably makes a bend forward on leaving the stomach.

is the case in the Cephalopoda, Scaphopoda,
and the great majority of Gasteropoda. The
exceptions are the bilaterally symmetrical
Amphineura, in which the anus is terminal,
and many Opisthobranchiata, in which it is
sometimes lateral (Fig. 68, p. 159), sometimes
dorsal (Fig. 67). The intestine is usually
short im carnivorous genera, but long and
more or less convoluted in those which are
phytophagous. In all cases where a bran-
chial or pulmonary cavity exists, the anus is
situated within it, and thus varies its posi-
tion according to the position of the breath-
ing organ. Thus in Helix it is far forward
on the right side, in Zestacella, Vaginula, and
Onchidium almost terminal, in Patella at the
back of the neck, shghtly to the right side
(Fig. 64, p. 157).

In the rhipidoglossate section of the Dioto-
cardia (Zrochus, Haliotis, etc.) the rectum
passes through the ventricle of the heart, a
fact which, taken in conjunction with others,
is evidence of their relationship to the
Pelecypoda.

In nearly all Pelecypoda the intestine is
very long and convoluted, being sometimes
doubled forward over the mouth. Towards
its terminal part it traverses the ventricle of
the heart, except in Ostrea, Anomia, Teredo,
and a few more. The anus is always at the
posterior end of the animal, adjacent to and
slightly above the adductor muscle.

Anal glands, which open into the rectum
close to the anus, are present in some Proso-
branchiata, eg. Murex, Purpura. In the

This

fi) |_f/

Fie. 147.—Ink-sae of

Sepia, showing its re-
lation to the rectum:
a, anus; ad, duct of
sac; tg, ink - gland ;
%.7, portion of the sac
which serves as a re-
servoir for the ink ; 0,
orifice of ink-gland ; 7,
rectum ; sp, double set
of sphincter muscles
controlling upper end
of duct. (Modified
from Girod. )

Cephalopoda the anal gland becomes of considerable size and
importance, and is generally known as the ink-sac (Fig. 147);

VOL. III

R

242 THE KIDNEYS CHAP.

it occurs in all known living genera, except Nautilus. The ink-
sac consists of a large bag generally divided into two portions, in
one of which the colouring matter is secreted, while the other
acts as a reservoir for its storage. A long tube connects the
bag with the end of the rectum, the mouth of the tube being
controlled, in Sepia, by a double set of sphincter muscles.

The Kidneys

The kidneys, nephridia, renal or excretory organs, consist
typically of two symmetrical glands, placed on the dorsal side of
the body in close connexion with the pericardium. Hach kidney
opens on the one hand into the mantle cavity, close to the anus
(see Fig. 64, p. 157), and on the other, into the pericardium.
The venous blood returning from the body passes through the
vascular walls of the kidneys, which are largely formed of cells
containing uric acid. The blood thus parts with its impurities
before it reaches the breathing organs.

The kidneys are paired in all cases where the branchiae are
paired, and where the heart has two auricles, ¢.e. in the Amphi-
neura, the Diotocardia (with the exception of the Neritidae), the
Pelecypoda, and all Cephalopoda except Nautilus, which has
four branchiae, four auricles, and four kidneys. In other Gastero-
poda cnly one kidney survives, corresponding to the left kidney
of Zygobranchiate Gasteropods.

Besides their use as excretory organs the kidneys, in certain
groups of the Mollusca, stand in very close relation to the genital
glands. In some of the Amphineura the generative products,
instead of possessing a separate external orifice of their own, pass
from the genital gland into the pericardium and so out through
the kidneys (see Fig. 61 C,D, p. 154). In the Diotocardia it is
the right kidney alone which serves, besides its excretory func-
tions, as a duct for the emission of the generative products, the
left kidney being at the same time greatly reduced in size.
Thus in Patella the left nephridium is small, the right being
much larger; both function as excretory organs, but the right
serves as a mode of conveyance for the seminal products as well.
In certain Pelecypoda (eg. Yoldia, Avicula, Modiola, Pecten,
Spondylus) the genital glands communicate directly, and with a

1 yeppos, kidney.

VIII AUTHORITIES 24:3

similar object, with the renal pouch on the same side of the
body, but in the majority of cases the orifices are distinct.

The following memoirs will be found useful for further study
of this portion of the subject :—

D. Barfurth, Ueber den Bau und die Thiatigkeit der Gasteropodenleber :
Arch. Mikr. Anat. xxii. (1883), pp. 473-524.

Th. Behme, Beitrige zur Anatomie und Entwickelungsgeschichte des Harn-
apparates der Lungenschnecken : Arch. Naturges. iv. (1889), pp. 1-28.

R. Bergh, Semper’s Reisen im Archipelago der Philippinen; Nudibran-
chiata: Theil 1. Band ii. (1870-78), Band iii. (1880-1892).

W. G. Binney, Terrestrial Air-breathing Mollusks of the United States:

Bull. Mus. C. Z. Harv. iv. (1878), 450 pp.

On the Jaw and Lingual Membrane of North American
Terrestrial Pulmonata: Proc. Ac. Nat. Se. Philad. (1875),
pp. 140-243.

J. T. Cunningham, The renal organs (Nephridia) of Patella: Quart. Journ.

Mier. Se. xxiii. (1883), pp. 369-375.

bs ;. Note on the structure and relations of the kidney in
Aplysia: Mitth. Zool. Stat. Neap. iv. (1883), pp.
420-428.

R. von Erlanger, On the paired Nephridia of Prosobranchs, ete.: Quart.
Journ. Micr. Se. xxxiil. (1892), pp. 587-623.

H. Fischer, Recherches sur la Morphologie du Foie des Gastéropodes: Bull.
Scient. France Belg. xxiv. (1892), pp. 260-346.

C. Grobben, Morphologische Studien tiber den Harn- und Geschlechtsapparat,

sowie die Leibeshohle, der Cephalopoden: Arb. Zool. Inst.
Wien, v. (1884), pp. 179-252.

" Die Pericardialdruse der Gasteropoden: ibid. ix. (1890), pp.
35—56.

B. Haller, Beitrage zur Kenntniss der Niere der Prosobranchier : Morph.
Jahrb. xi. (1885), pp. 1-53.

A. Hancock, On the structure and homologies of the renal organ in the
Nudibranchiate Mollusca: Trans. Linn. Soc. xxiv. (1864), pp. 511-
530.

A. Kohler, Microchemische Untersuchung der Schneckenzungen: Zeits.
Gesamm. Naturw. viii. (1856), pp. 106-112.

Ad. Oswald, Der Riisselapparat der Prosobranchier: Jena. Zeits. Naturw.
N.F. xxi. (1893), pp. 114-162.

R. Perrier, Recherches sur Vanatomie et Vhistologie du rein des Gastéro-
podes prosobranches : Ann. Sc. Nat. Zool. (7), vill. (1889), pp. 61-315.

C. Semper, Reisen im Archipelago der Philippinen ; Land Pulmonata:
Theil ii. Band iii. (1870-77).

C. Troschel, Das Gebiss der Schnecken: Berlin, 1856-1892.

W. G. Vigelius, Ueber das Excretionssystem der Cephalopoden: Nieder).
Arch. Zool. v. (1880), pp. 115-184.

”

CHAPTER IX

THE SHELL, ITS FORM, COMPOSITION AND GROWTH—DESIGNATION
OF ITS VARIOUS PARTS

THE popular names of ‘shells, ‘shell-fish, and the lke, as
commonly applied to the Mollusca, the intrinsic beauty and
erace of the shells themselves, resulting in the passion for their
collection, their durability and ease of preservation, as compared
with the non-testaceous portion,—all these considerations tend
to unduly exalt the value of the shell as part of the organism as
a whole, and to obscure the truth that the shell is by no means
the most important of the organs.

At the same time it must not be forgotten that the old
systems of classification, which were Based almost entirely on
indications drawn from the shell alone, have been strangely little
disturbed by the new principles of arrangement, which depend
mainly on structural points in the animal. This fact only tends
to emphasise the truth that the shell and animal are in the
closest possible connection, and that the shell is a living part of
the organism, and is equally sensitive to external influences.

A striking instance of the comparative valuelessness of the
shell alone as a primary basis of classification is furnished by the
large number of cases in which a limpet-shaped shell is assumed
by genera widely removed from one another in cardinal points of
organisation. This form of shell occurs in the common limpet
(Patellidae), in Ancylus (Limnaeidae), Hemitoma (Fissurellidae),
Cocculina (close to Trochidae), Umbrella and Stphonaria (Opis-
thobranchiata), while in many other cases the limpet form is
nearly approached.

Roughly speaking, about three-quarters of the known Mollusca,
recent and fossil, possess a univalve, and about one-fifth a bivalve

CHAP. IX POSITION OF THE SHELL 245

shell. In Pholas, and in some species of Zhracia, there is a small
accessory hinge plate ; in the Polyplacophora, or Chitons, the shell
consists of eight plates (see Fig. 2, p. 8), usually overlapping. <A
certain proportion of the Mollusca have no shell at all. In many
of these eases the shell has been present in the larva, but is lost
in the adult.

The shell may be

(1) Hxternal, as in the great majority of both univalves and
bivalves.

(2) Partly external, partly internal ; eg. Homalonyx, Hem-

Fic. 148.—Aplustrum aplustre Fia. 149.—Sigaretus laeviga-
L., Mauritius, showing the tus Lam., showing shell
partly internal shell (8); F, partially immersed in the
foot ; LL, cephalic lappets ; foot; F, anterior pro-
TT, double set of tentacles. longation of the foot.
(After Quoy and Gaimard. ) (After Souleyet. )

phillia, some of the Naticidae, Scutum, Acera, Aplustrum
(Figs. 148 and 149).

(3) Internal ; eg. Philine, Gastropteron, Pleurobranchus,
Aplysia, Limax, Arion, Hyalimax, Parmacella, Lamellaria,
Cryptochiton, and, among bivalves, Chlamydoconcha,

(4) Absent ; e.g. all Nudibranchiata and Aplacophora, many
Cephalopoda, a few land Mollusca, e.g. all Onchidiidae, Philomycus,
and Vaginula.

The Univalve Shell— In wunivalve Mollusca the normal form
of the shell is an elongated cone twisted into a spiral form round
an axis, the spiral ascending to the left. Probably the original
form of the shell was a simple cone, which covered the vital
parts like a tent. As these parts tended to increase in size, their

246 VARIOUS FORMS OF THE SPIRAL CHAP.

position on the dorsal side of the animal caused them gradually
to fall over, drawing the shell with them. The result of these
two forces combined, the increasing size of the visceral hump,
and its tendency to pull the shell over with it, probably resulted
in the conversion of the conical into the spiral shell, which
eradually came to envelop the whole animal. Where the
visceral hump, instead of increasing in size, became flattened, the
conical shape of the shell may have been modified into a
simple elliptical plate (e.g. Zimax), the nucleus representing the
apex of the cone. In extreme cases even this plate dwindles
to a few calcareous granules, or disappears altogether (Arion,
Vaginula).

Varieties of the Spiral.— Almost every conceivable modifi-

Fic. 150.—Examples of shells with A, a flattened
spire (Polygyratia) ; B, a globose spire (Vatica) ;
C, a greatly produced spire (Zerebra).

cation of the spiral occurs, from the type represented by Gena,
Haliotis, Sigaretus, and Lamellaria, iv which the spire is practi-
eally confined to the few apical whorls, with the body-whorl
inordinately large in proportion, to a multispiral form lke
Terebra, with about twenty whorls, very gradually increasing in
size.

As a rule, the spire is more or less obliquely coiled round
the axis, each whorl being partially covered, and _ therefore
hidden by, its immediate successor, while the size of the
whorls, and therefore the diameter of the spire as a whole,
increases somewhat rapidly. The effect of this is to produce
the elevated spire, the shell of six to ten whorls, and the wide
aperture, of the normal type of mollusc, the whelk, snail, peri-
winkle, ete.

1 VARIOUS FORMS OF THE SPIRAL Ziv

Sometimes, however, the coil of the whorls, instead of being
oblique, tends to become horizontal to the axis, and thus we
have another series of gradations of form, from the excessively
produced spire of Zerebra to the flattened dise of Planorbis,
Polygyratia, Euomphalus, and Ammonites. The shell of many
species of Conus practically belongs to the latter type, each whorl
folding so closely over its predecessor that the spiral nature of
the shell is not perceived until it is looked at at right angles to
the spire.

In some cases the regularly spiral form is kept, but the
whorls are completely disconnected ; e.g. some Scalaria, Spirula ;

Fig. 151. — Examples of shells Fic. 152.—Example of a shell
with disconnected whorls ; whose apical whorls alone are
A, Cyathopoma cornu Mf., coiled, and the remainder pro-
Philippines; B, Cylindrellu duced in a regular curve.
hystrix Wright, Cuba. (Both (Cyclosurus Mariet Morel.,
x 4.) Mayotte. )

among fossil Cephalopoda, Gyroceras, Crioceras, and Ancyloceras ;
and, among recent land Mollusca, Cylindrella hystria and Cyatho-
poma cornu (Fig. 151). Sometimes only the last whorl becomes
disconnected from the others, as in Rhiostoma (see Fig. 180, p.
266), Teinostoma, and in the fossil Ophidioceras and Macroscaphites.
Sometimes, again, not more than one or two whorls at the apex
are spirally coiled, and the rest of the shell is simply produced or
coiled in an exceedingly irregular manner, e.g. Cyclosurus, Lituites,
Orygoceras, Siliquaria (Fig. 153), Vermetus. In Coecum (Fig.
170, p. 260) the spiral part is entirely lost, and the shell becomes
simply a cylinder. In a few cases the last whorl is coiled irregu-
larly backwards, and is brought up to the apex, so that the animal
in crawling must carry the shell with the spire downwards, as in

248 FORMS OF THE SPIRAL CHAP.

Anostoma (Fig. 154), Opisthostoma (Fig. 208, p. 309), Stropho-
stoma, and Hypselostoma (Fig. 202 A, p. 502).

Some genera of the Capulidae, in which the shell is of a
broadly conical form or with scarcely any spire, develop an
internal plate or process which serves the purpose of keeping the

Fra. 153.—Siliquaria anguina Lam., show- Via. 154.—Anostoma globulosum Lam.,
ing scalariform coil of upper whorls and Brazil. (After P. Fischer.)

irregular extension of the lower.

animal within the shell, and does the work of a strong attachment
muscle. In Mitrularia this process takes the form of a raised
horseshoe ; in Crucibulum it is cup-shaped, with the edge free all
round; in Galerus, Ergaea, Crepipatella, and Trochita we get a

Fia. 155.—Various forms of the internal plate in Capulidae: A, Calyptraea (Mitru-
laria) equestris Lam., E. Indies; B, Crucibulum scutellatum Gray, Panama ; C,
Ergaea plana Ad., and Reeve, Japan; D, Galerus chinensis L., Britain ; E, Crepi-
patella dilatata Lam., Callao; F, Trochita maculata Quoy, N. Zealand ; G, Crepi-
dula fornicata Lam., N. America.

series of changes, in which the edge of the cup adheres to the
interior of the shell, and then gradually flattens into a plate. In
Crepidula proper this plate becomes a regular partition, covering
a considerable portion of the interior (Fig. 155 G). Hipponyx
secretes a thin calcareous plate on the ventral surface of the foot,

IX SINISTRAL SHELLS 249

which intervenes hke an operculum between the animal and the
substance to which it adheres.

Sinistral, or Left-handed Shells—The vast majority of uni-
valve spiral shells are normally dewtral, i.e. when held spire
uppermost, with the aperture towards the
observer, the aperture is to the right of the
axis of the spire. If we imagine such a
shell to be a spiral staircase, as we ascended
it we should always have the axis of the
spire to our left.

Sinistral or ‘reversed’ forms are not
altogether uncommon, and may be grouped
under four classes :—

(1) Cases in which the genus is normally
sinistral ; (2) cases in which the genus is
normally dextral, \ut certain species are

normally sinistral ; (3) cases in which the
shell is indifferently deatral or sinistral ;
(4) cases in which both genus and species
are normally dextral, and a sinistral form is an abnormal

Fic. 156.— Fulgur perver-
sum L., Florida, x 4.

monstrosity.

In all cases of sinistral monstrosity, and all in which a sinistral
and dextral form are interchangeable (sections 3 and 4 above),
the position of the apertures of the internal organs appears to be
relatively affected, 2.c. the body is sinistral, as well as the shell.
This has been proved to be the case in all specimens hitherto
examined, and may therefore be assumed for the rest. The same
uniformity, however, does not hold good in all cases for genera
and species normally sinistral (sections 1 and 2). As a rule, the

Fic. 157.—Illustration of the gradation of forms in Ampullaria between a dextral
(A) and an ultra-dextral species (F).
anal and genital apertures are, in these instances also, to the left,
but not always. In Spirialis, Limacina, Meladomus, and Lanistes
the shell is sinistral, but the animal is dextral. This apparent
anomaly has been most ingeniously explained by Simroth, Von

250 ULTRA-DEXTRAL AND ULTRA-SINISTRAL SHELLS cunap.

Ihering, and Pelseneer. The shell, in all these cases, is not
really sinistral, but wltra-dextral. Imagine the whorls of a
dextral species capable of being flattened, as in a Planorbis, and
continue the process, still pushing, as it were, the spire down-
wards until it occupies the place of the original umbilicus,
becoming turned completely ‘inside out, and we have the whole
explanation of these puzzling forms. The animal remains
dextral, the shell has become sinistral. A convincing proof of
the truth of this is furnished by the operculum. It is well
known that the twist of the operculum varies with that of the
shell; when the shell is dextral, the operculum is sinistral, with
its nucleus near the columella, and vice versd. In these ultra-
dextral shells, however, where it is simply the method of the
enrolment of the spire that comes in question, and not the
formation of the whorls themselves, the operculum remains
sinistral on the apparently sinistral shell.

The reverse case to this, when the shell is dextral but the
orifices sinistral, is instanced by the two fresh-water genera
Pompholyz (from N. America), and Choanomphalus (L. Baikal).
A similar transition in the enrolment of the whorls may be
confidently assumed to have taken place, and the shells are
styled wltra-sinistral.

Yet another variation remains, in which the embryonic form
is sinistral, but the adult shell dextral, the former remaining
across the nucleus of the spire. This is the case with
Odostomia, Eulimella, Turbonilla, and Mathilda, all belonging to the
Prosobranchiata, with Actaeon, Tornatina, and Actaeonina among
the Opisthobranchs, and Melampus alone among Pulmonates.

Monstrosities of the Shell.— Abnormal growths of the
shell constantly occur, some of them being scarcely noticeable,
except by a practised eye, others of a more serious nature,
involving an entire change in the normal aspect of the creature.
Scalariform monstrosities are occasionally met with, especially
in Helix and Planorbis, when the whorls become unnaturally
elevated, and sometimes quite disjomed from one another ;
carinated monstrosities develop a keel on a whorl usually smooth ;
acuminated monstrosities have the spire produced to an extreme
length (Fig. 158); sinistral monstrosities (see above) have the
spire reversed: dwarfs and giants, as in our own race, are occa-
sionally noticed among a crowd of individuals.

IX MONSTROSITIES OF THE SHELL 251

More serious forms of monstrosity are those which occur in
individual cases. Mr. S. P. Woodward once observed? a specimen
of an adult Helix aspersa with a second, half-crown individual
fixed to its spire, and partly embedded in the suture of the body
whorl. The younger snail had died during its first hibernation,
as was shown by the epiphragm remaining in the aperture, and
its neighbour, not being able to get free of the incubus, partially
enveloped it in the course of its growth. In the British Museum
two Littorina littorea have become entangled in a some-
what similar way (Fig. 160 B), possibly as a result of embryonic

Fra. 158.—Monstrosities of NVeptunea an- Fic. 159.—Monstrosities of Littorina
tiqua L., and Buccinum undatum 1.., rudis Mat, The Fleet, Weymouth.
with a greatly produced spire (from (After Sykes.)

specimens in the Brit. Mus.)

fusion. Double apertures are not uncommon” in the more
produced land-shells, such as Cylindrella and Clausilia (Fig.
160 A). In the Pickering collection was a Helix hortensis
which had crawled into a nutshell when young, and, growing
too large to escape, had to carry about this decidedly extra shell
to the end of its days. A monstrosity of the cornucopia form,
in which the whorls are uncoiled almost throughout, is of exceed-
ingly rare occurrence (Fig. 161).

Some decades ago ingenious Frenchmen amused themselves
by creating artificial monstrosities. #7. aspersa was taken from
its shell, by carefully breaking it away, and then introduced into
another shell of similar size (4. nemoralis, vermiculata, or

1 Ann. Mag. Nat. Hist. (2) xvi. p. 298.

2 See, for instance, Quart. Journ. Conch. i. p. 340 (Cyl. Raveni): Jahrb. Deut.
Malak. Gesell. 1879, p. 98 (Clausilia dubia).

Ziy2 CHEMICAL COMPOSITION OF THE SHELL CHAP:

pisana). At the end of several days attachment to the columella
took place, and then growth began, the new shell becoming soldered
to the old, and the spiral part of the animal being protected by
a thin calcareous envelope. A growth of from one to two
whorls took place under these conditions. The individuals so
treated were always sordid and lethargic, but they bred, and
naturally produced a normal aspersa offspring.’ In the British

Fic. 160. — Monstrosities with two Fia, 161, —Cornucopia-
apertures: A, Cylindrella agnesi- shaped monstrosity
ana C. B. Ad., Jamaica; B, of Helix aspersa,
Littorina littorea (from specimens from Ilfracombe.
in the British Museum). (British Museum. )

Museum there is a specimen of one of these artificial unions of a
Helix with the shell of a Limnaea stagnalis.

Composition of the Shell.—The shell is mainly composed
of pure carbonate of lime, with a very sheht proportion of phos-
phate of lime, and an organic base allied to chitin, known as
conchiolin. The proportion of carbonate of lime is known to
vary from about 99 p.c. in Strombus to about 89 p.ec. in Turri-
tella. Nearly 1 p.c. of phosphate of lime has been obtained from
the shell of Helix nemoralis, and nearly 2 p.c. from that of Ostrea
virginica. The conchiolin forms a sort of membranous frame-
work for the shell; it soon disappears in dead specimens, leaving
the shell much more brittle than it was when alive. Carbonate
of magnesia has also been detected, to the extent of ‘12 p.c. in
Telescopium and ‘48 p.c. in Neptunea antiqua. <A trace of silica
has also occasionally been found.

’ Cailliaud, Journ. de Conchyl, vii. p. 231; Gassies, ibid. p. 44.

1x CHEMICAL COMPOSITION OF THE SHELL 253

When the shell exhibits a crystalline formation, the carbonate
of lime may take the form either of calcite or aragonite. The
calcite crystals are rhombohedral, optically uniaxal, and cleave
easily, while the aragonite cleave badly, belong to the rhombic
system, and are harder and denser, and optically biaxal. Both
classes of crystal may occur in the same shell.

Two main views have been held with regard to the formation
and structure of the shell—(1) that of Bowerbank and Carpenter,
that the shell is an organic formation, growing by interstitial
deposit, in the same manner as the teeth and bones of the higher
animals; (2) that of Réaumur, Eisig, and most modern writers,
that the shell is of the nature of an excretion, deposited like
a cuticle on the outside of the skin, being formed simply of
a number of calcareous particles held together by a kind of
‘animal glue.’ Leydig’s view is that the shell of the Monoto-
cardia is a secretion of the epithelium, but that in the
Pulmonata it originates within the skin itself, and afterwards
becomes free.’

According to Carpenter, when a fragment of any recent shell
is decalcified by being placed in dilute acid, a definite animal
basis remains, often so fine as to be no more than a membranous
film, but sometimes consisting of an aggregation of ‘cells’ with
perfectly definite forms. He accordingly divides all shell struc-
ture into cellular and membranous, according to the characteristics
of the animal basis. Cellular structure is comparatively rare ; it
occurs most notably in Pinna, where the shell is composed of a
vast multitude of tolerably regular hexagonal prisms (Fig. 162 B).
Membranous structure comprises all forms of shell which do not
present a cellular tissue. Carpenter held that the membrane
itself was at one time a constituent part of the mantle of the
mollusc, the carbonate of lime being secreted in minute ‘cells’
on its surface, and afterwards spreading over the subjacent
membrane through the bursting of the cells.

The iridescence of mnacreous shells is due to a_ peculiar
lineation of their surface, which can be readily detected by a
lens. According to Brewster, the iridescence is due to the
alternation of layers of granular carbonate of lime and of a very
_ thin organic membrane, the layers very slightly undulating.
Carpenter, on the other hand, holds that it depends upon the

1 Arch. Naturgesch. xlii. p. 209.

254 STRUCTURE OF THE SHELL CHAP.

disposition of a single membranous layer in folds or plaits, which
he more or less obliquely to the general surface, so that their
edges show as lines. The nacreous type of shell occurs largely
among those Mollusca which, from other details in their organisa-
tion, are known to represent very ancient forms (eg. Nucula,
Avicula, Trigonia, Nautilus). It is also the least permanent, and
thus in some strata we find that only casts of the nacreous shells
remain, while those of different constitution are preserved entire.

Porcellanous shells (of which the great majority of Gastero-
poda are instances) usually consist of three layers, each of which
is composed of a number of adjacent plates, hke cards on edge.
The inclination of the plates in the different layers varies, but
that of the plates in the inner and outer layer is frequently the

Fic. 162.—A, Section of shell of Unio; a, periostracal layer ; 6, prismatic layer ; ¢,
nacreous layer. B, Horizontal section of shell of Pinna, showing the hexagonal
prisms.

same, thus if the plates are transverse in the middle stratum,
they are longitudinal in the inner and outer strata, and, if
longitudinal in the middle, they are transverse in the other two.
Not uncommonly (Fig. 163 B) other layers occur. In bivalves
the disposition and nature of the layers is much more varied.

In Unio the periostracal or uppermost layer is very thin;
beneath this is a prismatic layer of no great depth, while the
whole remainder of the shell is ‘nacreous (Fig. 162 A). Many
bivalves show traces of tubular structure, while in the Veneridae
the formation and character of the layers approaches closely to
that of the Gasteropoda. Further details may be gathered from
Carpenter’s researches.!

1 Dro W. B. Carpenter, Rep. Brite Ass, xii: p. 715 xiv. p. 15 Xvi. ps 9dG aes:
Bowerbank, Z'rans. Micr. Soc. i. p. 123; Ehrenbaum, Zeit. wiss. Zool. xli. p. 1.

IX DEPOSITION AND FORMATION OF SHELL 255

Formation of Shell'—The mantle margin is the principal
agent in the deposition of shell. It is true that if the shell be
fractured at any point, the hole will be repaired, thus showing
that every part of the mantle is furnished with shell-depositins
cells, but such new deposits are devoid of colour and of periostra-
eum, and no observation seems to have been made with regard to

y
Cc

the layers of which they are composed. As a rule the mantle,
except at its margin, only serves to thicken the innermost layer
of shell.

It is probable that the carbonate of lime, of which the shell
is mainly composed, is separated from the blood by the epithelial
cells of the mantle margin, and takes the crystalline or granular
form as it hardens on exposure after deposition. The three
layers of a porcellanous shell are deposited successively, and

SS

ah

Fic. 163.—Sections of shells. A, Conus: a, outer layer ; >, middle prismatic layer, with
obliquely intersecting laminae above and below ; ¢, inner layer. B, Oliva: a, outer
layer; 6, layer of crossed and curved laminae ; ¢, prismatic layer, succeeded by
layer of laminae at right angles to one another; d, inner layer. C, Cyprauea: a,
outer layer; 6, middle layer; c, inner layer.

the extreme edge of the mouth, when shell is forming, will
contain only one layer, the outermost; a little further in, two
layers appear, and further still, three. The pigment cells which
colour the surface are situated at the front edge of the mantle
margin.

Shelly matter is deposited, and probably secreted, not only by
the mantle, but also insome genera by the foot. This is certainly
the case in Cymbium, Oliva, Ancillaria, Cassis, Distortio, and
others, in several of which the foot is so large that the shell
appears to be quite immersed in it.”

1 See also p. 258. * J. E. Gray, Phil. Trans. 18388, p. 774 f.

256 SCULPTURE AND ORNAMENTATION CHAP.

The deposition of shell is not continuous. Rest periods occur,
during which the function is dormant; these periods are marked
off on the edge of the shell, and are known as lines of growth.
In some cases (Murex, Triton, Ranella), the rest period is marked
by a decisive thickening of the lip, which persists on the surface
of the shell as what is called a varia (see p. 263).

The various details of sculpture on the exterior surface of the
shell, the striae, ribs, nodules, imbrications, spines, and other
forms of ornamentation are all the product of similar and

Fic. 165.—Neritina longi-
sping Réel. Mauritius.
(Operculum removed. )

Fia. 164.—Murex tenuispina L., Ceylon.
x 8.

corresponding irregularities in the mantle margin, and have all
been originally situated at the edge of the hp. Spines, e.g. those
ot Murex and Pteroceras, are first formed as a hollow thorn, cleft
down its lower side, and are afterwards filled in with solid matter
as the mantle edge withdraws. What purpose is served by the
extreme elaboration of these spiny processes in some cases, Can
hardly be considered as satisfactorily ascertained. Possibly they
are a form of sculptural development which is, in the main, pro-

1X GROWTH OF THE SHELL 257

tective, and secures to its owners immunity from the attacks of
predatory fishes.

‘Attached’ genera (e.g. Chama, Spondylus) when living on
smooth surfaces have a flat shell, but when affixed to coral and
other uneven surfaces they become very irregular in shape. The
sculpture of the base on which they rest is often reproduced in
these ‘attached’ shells, not only on the lower, but also on the
upper valve, the growing edge of which rests on the uneven
surface of the base. Oysters attached to the branches of the
mangrove frequently display a central convex rib, modelled on the
shape of the branch, from which the plaits of sculpture radiate,
while specimens fixed to the smooth trunk have no such rib.
Crepidula, a genus which is in the habit of attaching itself to
other shells, varies in sculpture according to that of its host.
Sometimes the fact may be detected
that a specimen has lived on a
ribbed shell when young, and on
a smooth one when old, or vice
versd. A new genus was actually
founded by Brown for a Capulus
which had acquired ribs through
adhesion to a Pecten. A specimen
of Hinnites giganteus in the British
Museum must at one period of its
erowth have adhered to a surface on

Fic. 166.—A specimen of Anomia

which was a Serpula, the impression ephippium L., Weymouth, taken
of which is plainly reproduced on upon Pecten maximus, the sculp-

‘ : ae ture of which is reproduced on
the upper valve of the Hinnites. the upper valve of the Anomia,

Growth of the Shell.—No- aml em ons yume, sno
thing very definite is known with
regard to the rate of growth of the shell in marine Mollusca.
Under favourable conditions, however, certain species are known
to increase very rapidly, especially if the food supply be abundant,
and if there is no inconvenient crowding of individuals. Petit
de la Saussaye mentions? the case of a ship which sailed from
Marseilles for the west coast of Africa, after being fitted with an
entirely new bottom. On arriving at its destination, the vessel
spent 68 days in the Gambia River, and took 86 days on its
homeward voyage. On being cleaned immediately on its return

1 J, E. Gray, Phil. Trans. 1833, p. 774 f. > Journ. de Conchyl. iv. p. 424.
VOL. III 5S

258 GROWTH OF THE SHELL CHAP.

to Marseilles, an Avicula 78 mm. and an Ostrea 95 mm. long

(both being species peculiar to W. Africa) were taken from its
keel. These specimens had therefore attained this growth in at
most 154 days, for at the period of their first attachment they
are known to be exceedingly minute. P. Fischer relates’ that in
1862 a buoy, newly cleaned and painted, was placed in the basin
at Arcachon. In less than a year after, it was found to be
covered with thousands of very large Mytilus edulis, 100 mm.
x 48 mm., the ordinary size on the adjoining banks being only
about 50 to 60 x 30 mm.

Some observations have already been recorded (p. 40) on
the growth of Helix aspersa. In the summer of 1858, which was
very dry, especially in the south of France, the young Helices
born that year were still very small in August. About the end
of that month abundant rain came on, and in four or five days
young Hf. variabilis, H. pisana, and H. aspersa, eating without cessa-
tion, as if to make up for lost time, grew more than a centimetre
of shell. The lip of a young arbustorwm has been observed to
have grown, at the end of the first week in the season’s growth,
3 mm., at the end of the second week, 6°25 mm., the third,
11-5 mm., and the fourth 12°5 mm., with a finished lip.

Careful observation has shown that in the growth of the shell
of Helix aspersa the periostracum is first produced; it is covered
with hyaline globules, 10—12 mm. in diameter, which persist even
in the oldest shells. Calcareous matter is deposited on the
internal face of the new periostracum, at some distance from the
margin. It is secreted by a white zone or band of cells bound-
ing the entire breadth of the mantle as applied to the peristome.
Immediately behind the white zone are a series of pigment cells
which not only give the shell its colour but complete the
calcification of the shelly matter laid down by the white zone.
When the animal has attaimed its full growth and the lip is
finished off, the white band and the periostracum cells completely
cusappear, and only such cells persist as contribute to the internal
thickening of the shell. Shell growth, in this species, is very
rapid. Ifa portion of the pulmonary sac is laid bare, by remov-
ing a fragment of shell, at the end of 145 or 2 hours there may
be detected a delicate organic membrane covering the hole,
and strewn with crystals of carbonate of lime. This thickens

1 Journ. de Conchyl. xii. p. 3. 2 T. Scott, Journ. of Conch., 1887, p. 230.

IX GROWTH OF THE SHELL 259

with great rapidity, and soon fills up the hole with solid matter.
For two consecutive months an animal, deprived of food, has been
known to reproduce this membrane daily after its removal every
morning! Prof. Schiedt has found that oysters, if deprived of
the right valve and exposed to the light, not only develop brown
pigment over the whole exposed surface of mantle and branchiae,
but actually succeed in part in reproducing the valve and hinge.’

Deposit of Additional Layers of Shell—Mollusca possess the
power of thickening the interior of the shell, by the deposit of
successive layers. This is frequently done in self-defence
against the attacks of boring Mollusca, sponges, and worms.
Cases may often be noticed of Ostrea, Spondylus, and other
sedentary molluscs, which, unable to escape the gradual assaults
of their foes, have provided against them by the deposit of fresh
shelly matter. A somewhat similar plan is adopted to provide
against intrusion by way of the aperture.
Pearls are, in many cases, the result of
shell deposition upon the eggs or even the
body of some intrusive parasite (Jistoma,
Filaria, ete.), and are, in some countries,
artificially produced by the introduction of
fragments of sand, metal, etc., into living
Unio and Anodonta. Little joss images ree emer eee ea
are made in India and China, the nacre Cape of Good Hope, into
on which is produced by thrusting them Niece AL reese
inside living Unionidae. come introduced. The

A specimen of Helix rosacea, in the at eee
British Museum, into whose shell a piece grass with a shelly layer.

f oras : 1] bec: eae ant@en. nRYe (From a specimen in the
of grass somehow became introduced, has — pyitis Museum.)

partitioned it off by the formation of a
sort of shelly tunnel extending throughout its entire length
(Fig. 167).

Absorption of Internal Portions.—Certain genera have the
remarkable property of absorbing, when they become adult, the
internal portions of the whorls and the greater part of the
columellar axis. The effect of this is to make the shell, when
the process is complete, no longer a spiral but a more or less
produced cone, and it is found that in such cases the viscera of

1M. de Villepoix, Comptes Rendus, exiii. p. 317.
* Proc. Ac. Nat. Sc. Phil. 1892, p. 350.

260 ABSORPTION OF INTERNAL PARTS—DECOLLATION cuap.

the spire lose their spiral form, and take the shape of the cavity
in which they lie. Amongst the genera in which this singular
process takes place are Nerita,' Olivella, and Cypraea
amongst marine forms, and nearly the whole of
the Auriculidae ?(Fig. 168). Conus reduces the in-
ternal subdivisions of the spire to extreme thin-
ness. It is noticeable that these genera are all
of considerable thickness of shell, and it is per-
haps the result of the whole energy of the animal
being directed to the formation of its external
protection that the internal walls of the spire
become atrophied and eventually disappear.
Decollation.—In certain genera, when the
Fic. 168.—Awri- :
nila Judae Shell becomes adult, the animal ceases to occupy
rear eee the upper whorls, which accordingly die and drop
ance of the Off, the orifice at the top having meanwhile been
partitions of the closed by a shelly deposit. Such shells are termed
whorls, which : :
are represented @ecollated. In some land genera decollation 1s

by dotted lines. 4}, pyle - = pipe SAN Re nk + ( Ades a
(After Fischer.) the rule, eg. in Cylindrella (Fig. 169), Huecalo

dium, and Rumina, as well as in many species of
the brackish water genera, Z’rwncatella, Cerithidea, and Quoyia.

Fria. 169.—A, Decollated (adult) Fic. 170.—Development of Coecum: A,
form, and B, perfect (young) showing the gradual formation of
form of Cylindrella nobilior septa; a, apex; ap, aperture; ss,
Ad., Jamaica ; the dotted first septum; s’s’, second septum.
line shows where decollation (After de Folin.) B, Adult form of
takes place. C. eburneum Ad., Panama. x6&.

Stenogyra (Rumina) decollata, a common shell in the south of

1 Mr. B. B. Woodward has recently pointed out (P. Z. 8. 1892, p. 528) a very
remarkable method of shell absorption and growth in Velates and certain other
Neritidae.

2 The only exception appears to be Pedipes, while in Cassidula and Sewrabus the
absorption is partial (Crosse and Fischer, Jowrn. de Conch. Xxx. p. U7 it).

Tx DEVELOPMENT OF FISSURELLA, CYPRAEA, ETC. 261

Europe, has been noticed to bang its upper whorls violently
against some hard substance, as if to get rid of them.

Fra. 171.—Four stages in the growth of Fisswrella, showing how the spire gradually
disappears and the marginal slit becomes an apical hole, A, B, C, highly magni-
fied, D, natural size. (After Boutan.)

Special Points in the Growth of Certain Genera.—In the
young of Coecum the apex is at first spiral, but as growth
proceeds and the long tube begins to form, a septum is produced
at the base of the apex, which soon drops off. Soon afterwards,
a second septum forms a little farther down, and a second piece
drops off, leaving the shell in the normal cylindrical form of the
adult (Fig. 170). The development of Fisswrella is of extreme
interest. In an early stage it possesses a spiral shell, with a slit
on the margin of the outer
lip of the last whorl. As
erowth advances, — shelly
matter is deposited on both
margins, which results in
the slit becoming a_ hole
and the spire a mere cal-
losity, until at last they
appear to coalesce in the
apex of the adult shell (Fig.
1 TL). The singular forma- Fic. 172.—Three stages in the ate of Cypraen
neOr Magilus Se ae Sea L. (From specimens taken at
chilus have already been
described (pp. 75, 76). Cypraea, in the young stage, is a thin

spiral shell with a conspicuous apex. As growth proceeds, the

262 DEVELOPMENT OF €CYPRAEA, ANOMIA, ETC. CHAP.

surface of the whorls, which are nearly enveloped by two large
lobes of the mantle, becomes overlaid with new layers of shelly
matter, until eventually the spire becomes embedded, and ulti-
mately disappears from view (Fig. 172).

Patella, when young, has a nautiloid shell (see Fig. 45, p.
134), but it is a remarkable fact that we are entirely ignorant, in
this commonest of molluscs, of the transition stages which convert
the nautiloid into the familiar conical shell. The young shell of
Pteroceras is deceptively unlike the adult, and is entirely devoid
of the finger-like processes which are so characteristic of the
genus (chap. xiv.).

Among the bivalve Mollusca, Anomia in a young stage is
not to be distinguished from Ostrea. Soon a small sinus appears

on the ventral margin, which

gradually deepens and, as the

S shell grows round it, forms a

hole for the byssus, eventually

becoming fixed beneath the um-

bones (see Fig. 173). In Yeredo

the two valves of the shell proper,

~ which is very small, become

lodged in a long calcareous tube

Fic. 173.—Development of the byssus-or op cylinder, which is generally

plug-hole in Anomia. (After Morse.) 58

open at both ends (see Chap. xvi.).

In Aspergillum a somewhat similar cylinder is developed, but

the valves are soldered to the tube, and form a part of it, the

tube itself being furnished, at the anterior end, with a disk, which

is perforated with holes lke the rose of a watering-pot. In

Clavayella the left valve alone becomes soldered to the tube,

while the right valve is free within it (see Chap. xvi.). Fistulana

encloses the whole of its shell in a long tapering tube, which is
not at any point adherent to the shell.

Terms employed to denote various Parts of the Univalve
Shell —The apex is the extreme top of the spire, and generally
consists of the embryonic shell, which may often be recognised
by its entire want of sculpture.. When the embryonic shell
happens to be large, the apex is often mammillated, eg. in Fusus,
Neptunea, and some Turbinella; in the Pyramidellidae it 1s
sinistral.

The suture is the line of junction between any two successive

A

ove PANTS OF ib UNIVALVE SHEL 263

whorls. It may be deep, and even channelled, or very shallow,
as in Fig. 150 B (p. 246).

The spire is the whole series of whorls except the last or
body whorl. A whorl is a single revolution of the spiral cone
round the axis. The spire may be swbulate (as in Terebra, Fig.
150 C), turretted (Scalaria), depressed (Polygyratia, Fig. 150 A),

Chokey ese
-~ spire
suture ----- :
varix ;
he posterior canal (if present)
umbilicus

- outer lip

columella

anterior canal “s. mouth or aperture

Fic. 174.—Illustrating the technical terms applied to the various parts of a
univalve shell.

conical (Trochus), globose (Ampullaria, Natica, Fig. 150 B), with
almost all conceivable gradations between these types. The
number of whorls is best counted by placing the shell
mouth downwards, and reckoning one for every suture that
occurs between the extreme anterior point of the shell and
the apex.

The mouth or aperture may be (a) entire, as in Helvz,
Natica, Ampullaria, when its peristome or margin
is not interrupted by any notch or canal, or (/)
prolonged at its anterior and sometimes also
at its posterior end into a canal. The anterior
canal serves as a protection to the siphon,’ the
posterior canal is mainly anal in function, and
corresponds, in part, to the hole of Fisswrella,
the shit in Plewrotoma and Hmarginula, and the Pre, 175.—Anal
row of holes in Haliotis. The mouth presents slit in Beuro-
every variety of shape, from the perfect circle
in Cyclostoma and Trochus, to the narrow and prolonged slit in

Conus and Oliva.
The right margin of the mouth (the left, in sinistral shells) is

1 Strombus and Pteroceras (see Fig. 99, p. 200) exceptionally develop a siphonal
notch which is distinct from the anterior canal.

264 PARTS OF THE UNIVALVE SHELL CHAP.

termed the outer lip or labrum, the left margin the inner lip,
labium, or columella lip." In young shells the outer lip is
usually thin and unfinished, while in the adult it is generally
thickened into a rib, or furnished with more or less prominent
teeth, or given an inward or outward curve. In some genera,
especially the Strombidae, the outer lip of the adult develops
long finger-like processes, which sometimes attain an extra-
ordinary size (Chap. xiv.). As growth proceeds, these marginal
teeth and ribs are either dissolved and disappear, or are perma-
nently incorporated, in the shape of varices, with the framework
of the shell. Some shells, e.g. Matica, Turritella, Actacon, have

Fic. 176.—Solarium perspectivum Fic. 177.—Section of Turbinella
Lam., from the under side. pyrum L., showing the plicae
on the columella and the growth

of successive whorls.

a permanently unfinished outer lip, even in the adult stage.
The columella lip varies in shape with the mouth as a
whole; thus it may be straight, as in Conus, or excavated,
as in Sigaretus, Struthiolaria, and Bulla. Frequently it is
continued by part of the body whorl, as in Ficula, Doliwm, and
Fasciolaria.

The folds or plaits on the columella, which are often charac-
teristic of the genus or even family (e.g. Fasciolariidae, Mitridae,
Turbinellidae) are not merely external, but continue down the

1 The columella, as distinct from the colwmella lip, is the solid pillar of shell

round which the whorls are coiled (Fig.177), the lower, or anterior portion of which
alone is usually visible.

Ix THE SLIT 265

whole spire (see Fig. 177, which also shows how successive fresh
growths have thickened the columella).

The whorls may be wound in a spiral, which is either hollow,
as in Solarium, or quite compact, as in Oliva, Terebra, Cypraea,
with every possible intermediate grade. This concavity, which
varies in depth and width, is known as the wmbilicus, and shells
are accordingly spoken of as deeply (eg. most Trochidae and
Naticidae), narrowly (eg. Lacuna, Littorina), or widely (e.g.
Solarium) uwmbilicated. When the spiral is quite flat, as in
Planorbis and some Helix, the umbilicus vanishes entirely.
Shells in which the whorls are so compactly coiled on an
ascending spiral that there is no umbilicus, are termed imper-
Jorate.

The Slit—Many shells are furnished with a slit in the last
whorl, which opens, in most cases, on the outer lip, and is some-

Fic. 178.—The slit in A, Hemitoma, B, Emarginula, C, Macroschisma, D, Craniopsis,
E, Puncturella, F, Fissurella,

times of considerable depth, at others a mere notch. In the
patelliform shells it is always in front of the apex. The function
of the slit appears to be mainly anal, the excretory products
being thus allowed to escape by a passage of their own, without
soiling the clean water taken in by the branchiae. The posterior
canal of some Gasteropoda probably performs a similar function.
In the adult Fisswrella the slit becomes an apical hole (see Fig.
178 F), in the allied genera it is either immediately in front of
the spire (Puncturella), or half-way between the spire and the
anterior margin (Rimula), or on the margin and well marked
(Emarginula), or a mere indentation of the margin (Hemitomc).
In Pleurotomaria it is exceptionally long, and is well marked in
Bellerophon, Schismope, Scissurella, Murchisonia, and Pleurotoma
(where it is sutural). In Haliotis and Polytremaria it is replaced
by a series of holes, which are closed up as the animal grows
past them. Some of these holes (at least in Haliotis) certainly

266 LHD SLIt—— TE UB ED ORE RNCUIC ATES CHAP.

serve the purpose of admitting water to the branchiae, while
others are anal. In Trochotoma
there are only two holes, united by
a harrow fissure.

The Tubed Land Operculates,—A
eroup of the Cyclophoridae, which is
restricted to Further India and the
great Malay Islands, has developed
a remarkable sutwral tube on the
exterior of the last whorl, near
the aperture. A similar tube, but
more obscure, exists in Alycaeus.
Several stages in the development
DE eRe es eee of this tube may be noticed, begin-

B, Pleurotomaria, C, Schismope, Ding with the elevation of part of

D, Polytremaria, B, Haliotis (not the peristome into a simple irregu-

drawn to scale). ; 5 5

lar shelly plate, which is continued,
first into a short, and then into a long tube, which becomes
soldered to the shell; finally, the tube becomes free, and the
anterior part of the last whorl is disconnected from the spire
(Fig. 180 A-D).

It is singular that the tube does not appear to be of any use
to the animal, since its internal extremity, in the complete form,

Fra. 180.—Development of the tube in the tubed operculates : A, Pterocycus rupestris
Bens. ; B, Opisthoporus birostris Pir. ; ©, Spiraculum travancoricum Bedd.; D,
Rhiostoma Houset Pir.

is closed, and does not communicate with the interior of the

whorl. It may be presumed, however, that in origin the tube

served as a means of conveying air to the animal when the
operculum was closed. The holes in the peristome of Pupina,

Cataulus, and Anostoma (Fig. 154) may be compared.

IX THE OPERCULUM 267

The Operculum.—The operculum is a cuticular development
of a group of cells situated on the dorsal
side of the foot, exactly over the terminal
point of the fibres of the columellar muscle.
It is so situated that in crawling it is
generally carried free of the shell, some-
times at the extreme upper end of the foot,
more usually somewhat nearer to the shell
(Fig. 181). In Pterocyclus it is pushed back
into the umbilicus when the animal is in
motion.

The operculum is present in nearly all
land, fresh-water, and marine Prosobran-
chiata, absent in all Opisthobranchiata 11 pig 191, gpamna ees
the adult state, except Actaeon, and in all Lam., E. Indies. F,

. . foot; OP, operculum ;
> mate taal ‘ > ’ I! >
I ulmonata, except Am ph bola. It has been Pe vceniae ie ened
lost in the following marine Prosobran- T, tentacles, with eyes

at their base. (After
Souleyet. )

cliata: many Cancellariidae and Conidae,
Oliva (though present in Olivella~ and
Ancilla), Harpidae, Marginellidae, Voluta proper (though pre-
sent in V. musica), nearly all Mitridae, Cypraeidae, Dolidae,
Ianthinidae ; and, of land genera, in Proserpinidae. It is evident,
therefore, that its presence or absence is of limited value in
classification. In some species of Ampullaria and Natica it
is horny, in others shelly. Dall found that in a number of
specimens of Volutharpa ampullacea, 15 p.c. had opercula, 10
p.c. traces of the operculigenous area, but no operculum, the rest
no trace of either. Monstrosities of Buccinum undatum some-
times occur, which have two, or in rare cases three opercula.

As a rule, the operculum exactly fits the mouth of the shell.
But in cases where the mouth is very large (e.g. Conus, Strombus,
Concholepas, some Bullia), it only covers a very small portion
and is quite inadequate as a protection (Fig. 62,p.155). Again,
when the shell has assumed a more or less limpet-shaped form,
and habitually adheres to flat surfaces without much occasion for
locomotion, the operculum becomes degraded and is probably ou
the way to being lost altogether. This is the case with Navi-
cella (a modified WVerita, see Fig. 13, p. 17), Concholepas (a modi-
fied Purpura), Sigaretus (a modified Natica). Probably the more
completely patelliform shells of Crepidula, Haliotis, Fissurella,

268 THE OPERCULUM CHAP.

and Patella have reached the stage at which the operculum has
been lost entirely. In Wavicella, besides becoming degraded, the
operculum has actually become partly internal, and apparently
serves the purpose of separating the viscera from the upper
part of the foot, something like the shelly plate in Crepidula.
This explains why the operculum in this genus is polished on
both sides.!

Some authors have imagined that the operculum is homo-
logous (a) to the second valve in Pelecypoda, (>) to the byssus.
It differs, however, morphologically from the former in the
essential point of not being produced by the mantle, and from
the latter in not being produced by a special gland.

As regards shape and formation, the operculum has usually
a more or less well-marked nucleus which may be central (e.g.
Livona), subcentral (Ampullaria), lateral (Purpura), or terminal

Turbo Turbo Livona Ampullaria Natica
(Sarmaticus) (Callopoma)

Frc. 182.—Various forms of opercula.

(Pyrula). As a rule, both the inner and outer surfaces are fairly
flat, but in Zorinia, Cyathopoma, and Pterocyclus the outer sur-
face is elevated and conically spiral, in some Turbo (e.g. Sarmati-
cus) it is covered with raised tubercles resembling coral, while in
others (e.g. Callopoma) it is scored with a deep trench. -Aulo-
poma, a land genus peculiar to Ceylon, has a paucispiral oper-
culum with hollow whorls, deceptively like a Planorbis ; it fits
over the aperture instead of into it. In Zivona and most
Trochidae the operculum is cartilaginous and multispiral. In
Strombus it is narrow, curved, and often serrated like a leaf
on one of the edges; in Conus it is narrowly oblong and rather
featureless; in Zittorina, paucispiral and always cartilaginous.
1 J. E. Gray, Phil. Trans. 1838, p. 812.

IX PARTS OF THE SHELL IN BIVALVES 269

In many cases (e.g. Paludina) there is no true spiral form, but
the striae are concentric to a nearly central nucleus, and thus
give the appearance of a spiral. The evolution of the oper-
culum in Navicella from Nerita has already been illustrated (p.
10). Neritopsis has a very remarkable operculum, the striated

Pyrula Purpura Littorina Aulopoma Torinia Neritopsis Conus
x¥ x3 Strombus x2

Fic. 183.—Various forms of opercula.
appendage of which locks behind the columella of the shell, like
the tooth in the opercula of the Neritidae.

Terms employed to denote various parts of the Bivalve Shell.
—The wmbo, or beak, is the apex of the hollow cone, of which
each valve may be regarded as consisting. This apex is usually
more or less twisted: it is markedly spiral in Jsocardia, Diceras,
some Chama, and especially Requienia, while in Pecten, Lepton,
and others the spiral is altogether absent. As a rule the
umbones point forward, de. towards the anterior end of the
shell. In Donaxv, Nucula, and Trigonia, however, they point
backward. The umbones are generally more or less approxi-
mated, but in Arca they are widely separated.

An equilateral shell is one in which the umbones are more
or less central with regard to its anterior and posterior portion,
while in an inequilateral shell the wnbones are much nearer one
end than the other. On the other hand, equivalve and inequi-
valve are terms used to express the relation of the two valves
to one another as a whole. Thus nearly all bivalve shells are
more or less inequilateral, but a comparatively small proportion
are inequivalve.

The dorsal margin is adjacent to, the ventral margin opposite
to, the umbones. The anterior and posterior margins are respec-
tively the front and hinder edges of the shell.

The muscles which serve to close the valves leave impressions
on the inner surface of each valve. These, when both muscles
are present, are known as the anterior and posterior adductor

74 IO) PARTS OF THE SHELL IN BIVALVES CHAP.

impressions. The impression produced by the muscular edge of
the mantle, which curves downwards and backwards from the
anterior adductor impression, is known as the pallial line. In
shells with only one muscle it is represented by an irregular row
of small marks, or disappears altogether (Ostrea). The pallial
sinus 18 produced by the muscles which retract the siphons,
and is most marked in those genera in which the muscles are
powerful and the siphons large (e.g. Zellina, Mya). It is entirely
absent in genera possessing no retractile siphons.

Fic. 184—Left valve of Venus gnidia L.: Fic. 185.—Right valve of Lucina tigerina

A, anterior, B, posterior, ©, dorsal, L. : A, anterior, B, posterior, ©, dorsal,
D, ventral margin, AB, length, CD, D, ventral margin; AB, length, CD,
breadth of shell. breadth of shell.

a.m, anterior; p.m, posterior adductor a.m, anterior ; p.m, posterior adductor
muscle ; 7, pallial line ; p.s, pallial sinus ; muscles ; p, pallial line; /, ligament; uv,
1, ligament; Zu, lunule; uw, umbo; e¢, umbo ; ¢, cardinal teeth: a.l, p.d, ante-
cardinal teeth ; a.2, anterior lateral tooth ; rior and posterior lateral tooth.

p.l, posterior lateral tooth.

Right and Left Valve-—The simplest way of distinguishing the
valves as right and left is to hold the shell in such a way that
the siphons point towards the observer, and the mouth away
from him; in this position the valve to the right is called the
right valve, and the valve to the left the left valve. If, however,
the animal is not present, it may be remembered that the liga-
ment is nearly always behind the beaks, and that the beaks, as a
rule, point forward, thus the right and left valves can generally
be named by observation of the beaks and ligament. When the
ligament is median to the valves (e.g. Ostrea, Pecten), and the
beaks are not curved, the valves may be recognised by noting the
fact that the impression of the adductor muscle (Gin these cases

SE THE LIGAMENT AND HINGE 27 1

always single) is nearer to the posterior than to the anterior
side. In a similar way the pallial impression, which only forms
a sinus on the posterior side, furnishes a guide to the valves of
Donax, in which the beaks point backward, and of Zellina, in
which the beaks are frequently central.

In the fixed inequivalves (e.g. Chama) it is sometimes the
right, sometimes the left valve which is undermost, but the
fixed valve, whether right or left, is always deep, and the free
valve flat. Ostrea and Anomia are always fixed by the left
valve.

The dwnule is a well-marked area in front of and close to the
wnbones, usually more or less heart-shaped, and
limited by a ridge. Generally it is shallow, but
sometimes, as in Dosinia, Opis, and some Cardium,
deeply impressed. A corresponding area behind
the umbones, enclosing the hgament, is called
the escutcheon (Fig. 186), but it seldom occurs.

The ligament 1s a more or less elastic band,
which unites the two valves along a line adjacent
to the umbones. As a rule, the greater part of
the ligament is external to the shell, but it may Fic. 186. — Venus

: : : subrosirata Lam. :
be entirely internal. It is placed, normally,

és, escutcheon ;
behind the wnbones, but in a few cases, when pee ey
the hinge line is very long (Arca, Pectwnculus), umbones. > ”
it extends in front of them as well. The edges

of the valves, when the ligament is mainly external, are more or
less excavated for its reception. When internal it is generally
contained in a groove or spoon-shaped pit, known as the fossette
(compare Fig. 187).

The ligament consists of two distinct parts, which may occur
together or separately, the external, or ligament proper, and the
internal, or cartilage. Only the external portion can be seen
when the valves are closed. As a rule, the two portions are
intunately connected with one another, the ligament folding over
the cartilage, but in some cases, e.g. Mya, Mactra, where the
cartilage is lodged within the hinge, they are completely discon-
nected (Fig. 187).

In Pecten the external ligament is very thin, and runs along
the dorsal margin, while the internal ligament is large, solid,
and situated in a shallow pit. In Perna, where the hinge is

272 THE LIGAMENT AND HINGE CHAP.

toothless, the ligament is folded into a number of transverse
ridges, which fit into corresponding grooves in the shell.

The hgament proper is inelastic and insoluble in caustic
potash. The cartilage is very elastic, composed of parallel fibres,
shehtly iridescent, and soluble in caustic potash.

The operation of the hgament—using the word as including
the whole lgamental process—is in opposition to that of the
adductor muscles. When the latter
close the valves, they compress the
hgament, an action which its elas-
ticity resists: thus its operation
tends in part towards keeping the
valves open. But when ligament
and cartilage are both fully de-
veloped, they work in opposition to
one another, the ligament, by its.
resistance to compression, prevent-
ing any straining of the adductor

muscles when the valves are open,

Pio, 187 spies ol Aceh vale, amd the cartilage, for the same

King ; ca, cardinals ; U.a, anterior reason, preventing the ventral mar-

Panes aes eae gins of the shell from closing too

ment. rapidly upon one another when the
valves are being shut.

The Hinge-—The valves of Pelecypoda are generally articu-
lated, below the umbones, by a hinge which is furnished, in
the majority of cases, with interlocking teeth, small pits or
depressions in each valve corresponding to the teeth in the
other. The teeth are distinguished as cardinal, or those imme-
diately below the umbo, and lateral, or those to either side of
the cardinals, the latter being also distinguished as anterior and

5

Dy

posterior laterals, according as they are before or behind the
wmbo (Fig. 184). In shells which are tolerably equilateral there
is no difficulty in distinguishing between cardinal and _ lateral
teeth. But when they are very inequilateral, the whole hinge
may share in the inequality of growth, and an anterior lateral
may be thrown backward and simulate a cardinal, or a cardinal
may be thrown backward and simulate a posterior lateral (e.g.
Cardita, Unio, Fig. 188). In many Chama the cardinals are
pushed up into the umbo and become a mere ridge, while the

IX THE LIGAMENT AND HINGE Po If 3

strong anterior lateral becomes nearly central and simulates a
cardinal.

Some bivalves, e.g. Anodonta, Ostrea, Pedum, many Mytilus,
have no hinge teeth at all, in others the laterals are wanting

Fic. 188.—Hinges of A, Cardita semiorbiculata Brug., and B, Unio rectus Lam., show-
ing how, in inequilateral shells, the lateral teeth tend to shift their position. a.m,
anterior adductor, p.m, posterior adductor muscle; ¢, ¢c, cardinal teeth; p./,
posterior lateral teeth ; @, ligament.

(Psammobia, Diplodonta). In the Arcadae the hinge consists of
a number of very similar denticles, which are often serrated like
the teeth of a comb (Fig. 189).

Hinge-teeth are probably, in origin, derived from the crenula-

BITIUVIVHUIIT IVEY 1) a=

BESSNN WANVY NYA SY
=

Fic. 189.—The hinge in Arcadae: Fria. 190.—A, TZridacna scapho Lam.; B
5 * . . . ’ i
A, Nucula Loringt Ang. x 43 Cardium enode Sowb., showing the inter-
’ g § 3° ! ’ TS
B, Arca granosa L.; u.a, um- locking of the ventral margins.
’ J 3 ’ 5 8

bonal area.

tions or ribbings of the surface of the shell, the upper ends of

which impinge upon the dorsal margin and mark it in a way

which is quite recognisable when the shell is thin. Similar

crenulations, resulting in interlocking of the valves, are not
VOL. III Aly

27-4: HINGE-TEETH AND OTHER PROCESSES CHAP.

uncommon upon the ventral margin in certain genera (Fig. 190).
The mechanical effect of these continued riblets, when fitted
together on the opposing valves, would be to prevent the valves
sliding upon one another while closing, or after being closed.
Thus there would be a probability of their surviving, even after
the ribbing had disappeared from the surface of the shell, the
increased strength given by the hinge compensating for, and
making it possible to do without, the extra strength supplied by
the ribs. It is therefore possible that the teeth of the Nuculidae
and Arcadae, which have no distinction between cardinals and
laterals, represent a very ancient type, from which have been evolved
the various forms of hinge in which cardinals and laterals are
distinguished. Even in some forms of Arcadae (comp. Pectun-
culus) we get a hint how the transverse teeth of the typical
Arca may have become transformed into the longitudinal tooth
of the normal lateral.

The developed hinge-teeth, then, ensure the opening of the
valves in one direction; they also secure their accurate closure
upon one another in exactly the same plane. Exposed shells
and gaping siphons matter little to animals which are protected by
their burrowing propensities, but to those which live in material
which can be easily penetrated by their foes, it must be of
advantage to be able to buckle their armour absolutely tight.
The edentulous hinge of Anodonta is a degeneration from a
dentate type, which retains its teeth (¢n Unio, ete.) when subject
to the jar of rapid streams, but tends to lose them in the stiller
waters of canals, lakes, and ponds.

Other processes in the bivalve shell—In Anatina each wnbo
is fissured and strengthened on the inside by a kind of umbonal
plate which carries the ligament. Some forms of Liligna
develop a strong internal umbonal rib, which serves as a buttress
to strengthen the shell. In Pholas the so-called faleiform pro-
cess serves as a point of attachment for the muscles of the foot
and viscera. There is no ligament or hinge-teeth, the place of
the latter being taken by the anterior adductor muscle, which 1s
attached to the hinge-plate, the latter being reflected back into
the shell.

In Septifer the anterior adductor muscle is carried on a
sort of shelf or myophore, and in Cucullaea the posterior

1 W. H. Dall, Amer. Journ. Se. xxxviii. p. 445 f.

IX MEASUREMENT-—THE PERIOSTRACUM 275

adductor is partly raised on a similar and very prominent
formation.

Length and breadth of bivalve shells is variously measured.
Most authorities measure /ength, or ‘antero-posterior diameter,
by a straight lne drawn from the extreme anterior to the
extreme posterior margin, and breadth by a similar line, drawn
from the wnbones to a point, not very clearly marked, on the
opposite ventral margin (see Figs. 184 and 185). Others, less
correctly, reverse these terms. Zhickness is measured by the
extreme distance of the opposite faces of the closed valves. As,
a rule, the length exceeds, and often greatly exceeds, the thick-
ness, but in a few cases—e.g. the Cardissa section of Cardiuvwm—
this is reversed.

The periostracum.—Nearly all shells are covered, at some
period of their growth, by a periostracum,' or surface skin, which
serves the purpose of protecting the shell against the destructive
effects of the chemical action set up by water or air. It also, in
some cases (see p. 258), acts as a kind
of base upon which the shell is de-
posited. In old shells it is commonly
worn away, especially at those parts
which are likely to become abraded.

The form and composition of the
periostracum varies greatly. Some-
times (e.g. Oliva) it is a mere trans-
parent film, at others (Zonites) it is
transparent, but stout and sold. — It
is corneous in Solenomya, covered
with fine hairs in many V/elicidae,
in Conus, Velutina, and Cantharus it

is thick, fibrous, and persistent; 1M py 191. — rriton olewrtiim - Tus,
Trichotropis and some Triton it is Mediterranean, an example of
Prmaiated ihe ma aictles a shell with a stout and hairy
urmished with long bristles on a periostracum. x }.
thick ground (Fig. 191). In fresh-
water shells it is usually rather thick, in order to protect the
shell from the erosive powers of certain kinds of water. In
some cases (Mya, Anatina) the periostracum is continued over the
siphons, so as to form a protection throughout their whole length.
1 The term epidermis, as distinct from periostracum, is properly restricted to the
outer layer of the skin of the mantle and body generally.

276 EROSION OF THE SHELL CHAP. IX

Erosion.—The fresh-water Mollusca generally, and marine
mollusca in a few rare cases (Purpura, Littorina) are subject to
erosion, or decay in the shell substance. In univalves erosion
usually sets in near the apex (Fig. 192), where the life of the
shell may be regarded as weakest, and in bivalves
near the umbones. It is commonest in old shells,
and rarely occurs in the very young. So long as
the periostracum is present to protect the shell,
erosion cannot set in, but when once it has been
removed the shell is hable to the chemical changes
set up in its substance by water. There is
abundant evidence to show that erosion is caused
by pollution of water. Out of many instances
one must suffice. In a certain stream near Boston,
coe. U.S., numbers of Mollusca occurred, the shells of

ample of an Which were very perfect and free from disease.

ee ao Some little way down stream an alkaline manu-

(Melaniacon- factory drained its refuse into the water. At and

ee below this point for some distance every shell was

more or less eroded, most of them seriously.

Farther down, when the alkali refuse became diluted away, the
shells retained their normal condition.'

A small percentage of lime in the water appears to produce
erosion. The result of some experiments by G. W. Shrubsole, in
the investigation of this point, may be tabulated as follows : 2—

Water from ee ee Result.
River Dee, near Chester . 3°00 grs. acted strongly on shells
Wrexham . ; ; . 4°00 grs. a3 = 4
River Dee, near Lianderyel. 0°53 grs. . BA s
Trent Canal ; : . 8°33 grs. no action 5

1 J. Lewis, Proc. Bost. Soc. vi. p. 149. 2 Journ. of Conch. v. p. 66.

CHAPTER X

GEOGRAPHICAL DISTRIBUTION OF LAND AND FRESH-WATER MOL-
LUSCA—_THE PALAEARCTIC, ORIENTAL, AND AUSTRALASIAN
REGIONS

THE Mollusca afford specially valuable evidence on problems of
geographical distribution. This fact is largely due to their
extreme susceptibility to any change in the conditions of life.
Genera which are accustomed to live in a certain temperature
and on certain food, cannot sustain life if the temperature falls or
rises beyond certain limits, or if the required food be not forth-
coming. There is therefore a marked contrast between the
Mollusca of the tropics and of the temperate zones, while different
regions in the same latitude, whether within or without the
tropics, often show great diversity in their fauna. Every region
is thus characterised by its Mollusca. The Mollusca, for instance,
of Australia or of South Africa characterise those countries quite
as much as do the kangaroo and the emu, the hartebeest and the
ostrich ; there is nothing like them anywhere else in the world.
In the Greater Antilles the Mollusca stand out beyond all other
forms of life as characteristic of the islands as a whole, and of
each separate island in particular.

The geographical distribution of the land and fresh-water
Mollusca must be considered quite apart from that of the marine
Mollusca. The sea offers no such serious barriers to the spread
of the latter as the land does to the spread of the former. If we
were to journey to the Azores, and turn our attention to the
Jand-snails, we should find them almost wholly peculiar, while
amongst the sea-shells we should recognise many as occurring
also on our southern coasts, and few that were different from
those of the Mediterranean. The marine Mollusca of the Sand-

27.8 LOCALISATION OF GENERA AND SPECIES CHAP.

wich Islands, in spite of the enormous intervening distance, are
not very different from those of Natal, but the land Mollusca of
the two countries are as widely different as 1s possible to imagine.

Land Mollusea are, as has been remarked, fettered to the soil.
(Juadrupeds, birds, fishes, and reptiles are provided with organs of
inotion which enable them to overpass barriers of various kinds.
Even plants, although themselves incapable of motion, may be
conveyed in every direction by means of seeds, which are either
wafted by the wind or adhere to the skin of animals. But the
Mollusca have no such regular means of transport, and are, in a
large number of instances, limited to districts of a certain
character of soil, or producing certain kinds of vegetation.

The localisation, both of genera and species, occurs all over
the world. The genus Achatinella, which is peculiar to the
Sandwich Islands, is found there in a profusion of species. It
lives in the mountain valleys which radiate from the central
ridge of each island, and each valley is characterised by its own
peculiar set of species. The great carnivorous Glandinu is
restricted to Central America and the adjacent parts of the two
continents, with one or two species in Southern Europe. bulimus
proper is restricted to South America; Achatina to Africa south
of the Sahara; ZVornatellina to the Pacific Islands; Cochlostyla
to the Philippines; Cylindrella and Bulimulus are peculiar to the
New World; Buliminus, Nanina, Scarabus, and Cassidula to the
Old.

Extreme cases of this restriction of habitat sometimes occur.
Thus Limnaea involuta is found only in a single small mountain
tarn in Ireland; Clausilia scalaris along a narrow strip of lime-
stone in Malta; Strophia nana is confined to a few square rods
on an island that is itself a mere dot in the Caribbean Sea; the
genus Camptonyx occurs only in the neighbourhood of Mt. Girnar,
in Gujerat ; and Zantzia in moss on the top of a mountain in
Bourbon.

Attempts to colonise snails in strange localities have usually
resulted in failure, especially when the attempt has involved
serious changes of environment. The common Cochlicella acuta
of our coasts resists all endeavours to establish it beyond a certain
distance from the sea. Snails brought from the Riviera and
placed under almost similar conditions of climate on our own
southern coasts have livea for a while, but have very rarely taken

x ARTIFICIAL TRANSPORT OF SPECIES 27:9

permanent root. Mr. H. W. Kew?’ has collected a good many
of these attempts to acclimatise species, the general success of
which seems to depend almost entirely on a restoration of the
old conditions of life.

At the same time there are certain species which exhibit a
curiously opposite tendency, and which seem capable of flourish-
ing in almost any part of the world, and under the most varied
surroundings. Our own common garden snail (Helix aspersa) is
a striking instance of this adaptability to new conditions. It
has been established, by art or by accident, in Nova Scotia, Maine,
South Carolina, New Orleans, California, Mexico city, Cuba, Hayti,
Cayenne, Brazil, Valparaiso, Cape Town, the Azores, St. Helena,
Mauritius, Loyalty Islands, and Australia. The great Achatina
Jfulica of East Africa has been established first in Mauritius, and
from thence has been carried to the Seychelles and Calcutta.
Flelix lactea, a common Mediterranean species, has been carried
to Teneriffe and Monte Video; Helia similaris, whose fatherland
is Eastern Asia, has been transported to Mauritius, Bourbon, West
Africa, West Indies, Brazil,and Australia; Hnnea bicolor (Eastern
Asia) to India, Bourbon, Mauritius, West Indies; Stenogyra
decollata (Mediterranean basin) to South Carolina; S. Goodallii
(West Indies) to British pineries; Helix hortensis to New Jersey.
Seven common English species (Limaxz gagates, Hyalinia cellaria,
Hf. alliaria, Helix aspersa, H. pulchella, Pupa wmbilicata) have
become naturalised in St. Helena,? and as many as nineteen in
Australia.”

Cases of artificial transport of this kind are readily detected ;
they follow the lines of trade. The snails themselves or their
ova have been accidentally enclosed with plants or mould, or have
adhered to packing-cases, or to hay and grass used in packing.
Thus they constitute no disturbance to the general rule of the
persistent localisation of species and genera, and there is little
fear that the evidence which the geographical distribution of the
Mollusca brings to bear upon the general problems of distribution
will be confused by any intermixture of fauna naturally distinct.

Land Mollusca: Barriers to Dispersal.—The chief natural
barriers to dispersal are extremes of temperature, the sea,
mountain ranges, and deserts. Rivers, however large, seem of

1 The Dispersal of Shells, pp. 182-195. 2 E. A. Smith, P.Z.S. 1892, p, 259,
3 C. T. Musson, Proc. Linn. Soc. N. S. Wales (2), v. p. 883,

280 BARRIERS TO DISPERSAL CHAP.

little effect in checking dispersal. There is no appreciable
difference between the land Mollusca north and south of the
Ganges, or north and south of the Amazon. Living snails, or
their ova, are no doubt transported from one bank to another on
floating débris of various kinds. The barrier offered by the sea
is obvious, and at first sight appears insurmountable; but the
facts with regard to oceanic groups of islands like the Azores
and Canaries (see p. 297) show that even a stretch of salt water
many hundred miles in breadth may be ineffectual in preventing
the dispersal of Mollusca.

Mountain ranges, provided they are too high to be scaled,
and too long to be turned in flank, offer a far more effective
barrier than the sea. Every thousand feet upward means a fall
of so many degrees in the mean temperature, and a change,
more or less marked, in the character of the vegetation. There
is generally, too, a considerable difference in the nature of the
climate on the two sides of a great mountain range, one side
being often arid and cold, the other rainy and warm. The
combined effect of these influences is, as a rule, decisive
against the dispersal of Mollusca. Thus the Helices of Cali-
fornia are almost entirely peculiar; one or two intruders from
states farther east have succeeded in threading their way
through the deep valleys into the Pacific provinces, but not a
single genuine Californian species has been able to scale the
heights of the Cascade Mountains. The land Mollusca of India
are numbered by hundreds; not one penetrates north of the
Himalayas. According to Mr. Nevill,’ the change from the
Indo-Malayan to the so-called European molluscan fauna at the
northern watershed of the Kashmir valley is most abrupt and
distinct; in two days’ march northward, every species is dif-
ferent. Ranges of inferior altitude, such as the Pyrenees, the
Carpathians, or the Alleghanies, may be turned in flank as well
as scaled, and we find no such marked contrast between the
Mollusca on their opposite sides.

The most effective barrier of all, however, is a desert. Its
scorching heat, combined with the absence of water and of
vegetable life, check dispersal as nothing else can. The distri-
bution of the Mollusca of the Palearctic Region is an excellent
instance of this. Their southern limit is the great desert which

1 Scient. Results Sec. Yarkand Exped. “ Mollusca,” pp. 1-16.

x BARRIERS TO DISPERSAL 281

stretches, with scarcely a break, from the west coast of Africa
to the extreme east coast of Asia. The Mediterranean offers no
effectual barrier; shells of southern Europe are found in pro-
fusion in Morocco, Tunis, and Egypt, while all through Siberia
to the extreme of Kamschatka the same types, and even the
same species, of Mollusca occur.

A detailed examination of the means, other than voluntary,
by which Mollusca are transported from one place to another
hardly comes within the scope of this work. Ocean currents,
rivers, floods, cyclonic storms of wind, birds, and even beetles and
frogs, play a part, more or less considerable, in carrying living
Mollusca or their ova, either separately or in connexion with float-
ing débris of every kind, to a distance from their native home.
Accidental locomotion, of one or other of these kinds, combined
with the well-known tenacity of life in many species (p. 37),
may have contributed to enlarge the area of distribution in many
cases, especially in the tropics, where the forces of nature are
more vigorous than in our latitudes. The ease with which
species are accidentally spread by man increases the probability
of such cases occurring without the intervention of human
agency, and numbers of instances may be collected of their
actual occurrence.t

A point, however, which more concerns us here is to remark
on the exceedingly wide distribution of the prevailing forms of
fresh-water Mollusca. It might have been expected that the
area of distribution in the fresh-water forms would be greatly
restricted, since they cannot migrate across the land from one
piece of water to another, and since the barriers between pond
and pond, lake and lake, and one river system and another are,
as far as they are concerned, all but insuperable. We might
have expected, therefore, as Darwin and Wallace have remarked,
to find a great multiplicity of species confined to very restricted
areas, since the possibility of communication with the parent
stock appears, in any given case, to be so exceedingly remote.

As is well known, the exact reverse occurs. The range, not
merely of genera, but even of individual species, is astonishingly
wide. This is especially the case with regard to the Pulmonata
and Pelecypoda. The genera Limnaea, Planorbis, Physa, Ancylus,
Unio, and Cyclas are world-wide. Out of about ten genera of

1 Mr. H. W. Kew, Zhe Dispersal of Shells, has brought together a very large series.

282 WIDE DISTRIBUTION OF FRESH-WATER MOLLUSCA cuap.

fresh-water Mollusca in New Zealand, one of the most isolated
districts known, only one is pecuhar. In South Africa and the
Antilles no genus is peculiar. In the latter case, this fact is
remarkable, when we consider that the same sub-region has at
least ten peculiar genera of operculate land Mollusca alone.

To give a few instances of the distribution of particular
Species : —

Limnaea stagnalis L. occurs in the whole of Europe, and
northern Asia to Amoorland, Turkestan, Afghanistan, North
Persia, and Kashmir; Greenland, North America from the
Atlantic to the Pacific, and from North Canada and British
Columbia as far south as Texas. The distribution of ZL. peregra
Mill, Z. truncatula Mill, and JZ. palustris Mill. is almost
equally wide.

Planorbis albus occurs in the whole of Europe, and northern
Asia to Amoorland, Kamschatka, and Japan; Turkestan, the
Altai-Baikal district, Alaska and Greenland, North Canada, and
the whole of eastern North America.

The distribution of Anodonta anatina L., Cyclas cornea L..,
and Pisidium pusillum Gmel. is almost equally wide.

It is evident that the accidental means of transport mentioned
above are insufficient to account for the facts as we find them ;
we are therefore compelled to seek for further explanation.
Anything in the nature of a current furnishes a ready means
of transport for Mollusca which have obtained a footing in the
upper waters of a river, and there is no difficulty in imagining
the gradual spread of species, through the agency of floods or
otherwise, over a whole river system, when once established at
any point upon it. The feeble clinging power of newly-hatched
Limnaea has often been noticed as contributing to the chances
of their range of distribution becoming extended. Fresh-water
Mollusca, too, or their ova, are exceedingly likely, from their
extreme abundance, to be transported by water-birds, which fly
without alighting from one piece of water to another. Again,
the isolation of one river system from another is, in many
instances, by no means well marked or permanent, and a very
sheht alteration of level will frequently have the effect of
diverting the supplies of one watershed into another. When we
know what enormous oscillations in level have taken place over
practically the whole surface of the globe, we can recognise the

x ATTEMPTS AT EXPLANATION 283

J

probabilhty that the whole river system of the earth has been
mixed up and reconstructed again and again, with a very
thorough blending of adjacent fauna.

It is possible that the very uniform conditions under which
fresh-water Mollusca live may have something to do with the
uniformity of their distribution and the comparative sameness
in their development. There can scarcely be any question that
the environments of fresh-water species are in themselves less
varied and less hable to fluctuation than those of species whose
home is the land. Water is very hke water, all the world over ;
it may be running or motionless, warm or cold, clear or muddy,
but the general tendency is for it to be free from extremes of
any kind. Even if the surface water of a* lake or river freezes,
or becomes unusually hot, there is generally plenty of water at a
lower stratum which maintains a less extreme temperature, and
to which creatures can retire on the first symptoms of a change.
From this two results will follow. Not only will the inhabitants
of a piece of water not be inclined to vary much from the type,
since their whole surroundings, food, etc., continue very much
the same, but, if transported by any accident or cataclysm else-
where, they will be exceedingly likely to arrive at a place which
closely resembles their former home in all essentials. Thus the
tendency for new types to be formed would be constantly
checked, or rather would very seldom arise.

Mr. Belt, while recognising the importance of changes of
level as affecting the distribution of fresh-water species, appears
to regard the operations of such changes from a rather different
point of view to that described above. “I think it probable,”
he writes,’ “that the variation of fresh-water species of animals
and plants has been constantly checked by the want of continuity
of lakes and rivers in time and space. In the great oscillation
of the surface of the earth, of which geologists find so many
proofs, every fresh-water area has again and again been destroyed.

. . Thus species of restricted range were always exposed to
destruction, because their habitat was temporary and their re-
treat impossible, and only families of wide distribution could be
preserved.”

The terrestrial surface of the globe has been divided, as indi-

1 The Naturalist in Nicaragua, p. 334 f.

284 REGIONS OF DISTRIBUTION CHAP.

cating the facts of geographical distribution, into six regions—
the Palaearctic, Oriental, Australasian, Ethiopian, Nearctic, and
Neotropical. To these is sometimes added a seventh, the Neant-
arctic, consisting of Chili and Patagonia (and certain islands of
the south Atlantic); but since the Mollusca of Chili unmistak-
ably form a part of the Neotropical fauna, it seems hardly worth
while to recognise a separate region for those of the extreme
south of South America, which have no peculiar characteristics.

In certain points the exact limits of these regions, as in-
dicated by the Mollusca, will probably not correspond to those
which are marked out by other zoological classes. Wallace’s line,
for instance, does not exist, as far as the Mollusca are concerned.

These regions may be further subdivided into sub-regions,
thus :—

Regions Sub-regions Regions Sub-regions
| Septentrional Central African
Palaearctic ~< Mediterranean Ethiopian South African
Central Asiatic Malagasy
Oriental { Indo-Malay Nearctic { American

| Chinese \ Californian
Antillean

| Papuan Central American

Australasian ~< Australian Neotropical <- Colombian
Polynesian Brazilian
| Chilian

A. The Palaearctic Region

The southern boundary of this region is the northern limit of
the African Sahara, the Mediterranean forming no break what-
ever in its continuity. In Asia this boundary is less well
marked, but roughly corresponds to the southernmost of the vast
ranges of mountains which border the great tablelands of central
Asia. Across Africa the line of desert is well defined; but in
the north-east, as the desert approaches more nearly to the sea,
the African extent of the region is correspondingly narrowed
until it becomes little more than a strip of coast land, scarcely
widening even in Lower Egypt. On the Morocco coast,
Palaearctic land forms penetrate as far south as Cape Nun.’
At its eastern extremity the lne becomes less well defined, but

1 Morelet, Jowrnal de Conch. 1875, p. 194.

x THE PALAEARCTIC REGION 285

probably proceeds along the snowy mountains west of Setchouan,
the Pe-lng and Tan-sia-shan ranges, so as to include all the
high ground of Thibet and of the upper waters of the Hoang-ho,
and ultimately reaches its eastern limit at some point on the
shores of the Sea of Japan.

The region thus includes all Europe, Africa north of the
Sahara, with the Atlantic islands (the Azores, Canaries, etc.), North
Arabia, Asiatic Turkey, the greater part of Persia, Afghanistan,
Thibet, all Asiatic Russia, and a very large portion of the Chinese
empire.

The principal characteristics of the region as a whole are :—

(1) The rich development of Helix, Arion, Limax, Buliminus,
and Clausilia.

(2) The comparative absence of land operculates (see map,
frontispiece). .

(3) The uniform character of the fresh-water fauna.

It is in the southern portion of the region that Helix (in the
sub-genera Macularia, Lberus, Pomatia, and Xerophila) and Buli-
minus (Zebrina, Chondrula, Ena) attain their maximum. In
the north, #ruticicola is the characteristic group; in the
mountainous districts of the south-east, Campylaea, with
Clausilia. The Arionidae have their headquarters in the
damp and warm regions of western Europe, but are rare in the
south. They only approach the Mediterranean coast in Algeria,
near Gibraltar, and in the region between the base of the
Pyrenees and the Maritime Alps, and are very poor in species
throughout Italy and Sardinia. They are absent from almost the
whole of northern Africa, the Mediterranean islands (except
Sardinia), the whole Balkan district, the Crimea, Caucasus, and
western Asia.!

The uniformity of the fresh-water fauna is disturbed only in
the extreme south. <A few species of J/elanopsis with Neritina,
occur in southern Spain and Austria, Galicia, and southern
Russia, while a Melania or two (absent from Spain) penetrate the
south-eastern parts of Europe as far as Germany. Cyrena begins
to replace Cyclas in southern Russia and the Caucasus.

The Palaearctic region falls into three sub-regions :—

(1) The Northern or Septentrional Sub-region, 7.c. the dis-

1 Pollonera, Boll. Mus. Zool. Torino, v. 1890, No. 87.

286 SUBDIVISIONS OF THE PALAEARCTIC REGION CHAP.

trict north of the line formed by the Pyrenees,’ Alps, Carpathians,
and which, passing to the northward of the Aralo-Caspian district,
follows the great central mountain range of Asia until it reaches
the Sea of Japan, perhaps somewhere in the neighbourhood of
Vladivostok.

(2) The Mediterranean Sub-region, 7.c. the countries border-
ing on the Mediterranean, the Black and Caspian Seas, with the
Atlantic Islands.

(3) The Central Asiatic Sub-region, 7.c. Turkestan, Afghani-
stan, Thibet, and probably the districts of Mongolia and
Manchuria.”

(1) The Septentrional Sub-region has been divided by some
writers into two provinces, the European and the Siberian.
There seems, on the whole, but little occasion to separate off
northern Asia, the characteristic of which is, as will be seen
below, rather the gradual disappearance, as we proceed eastward,
of European species and genera, than the development of any
new and peculiar groups. The remarkable fauna of Lake Baikal
stands apart, not only from European, but also from the Siberian
types occurring in its immediate neighbourhood.

On the whole, the Septentrional Sub-region is poor in species
except those which inhabit fresh water. This fact is probably
due to the extreme vicissitudes of temperature which prevail, and
it is interesting to notice that the number of land Mollusca
appears to touch its lowest point in districts where the annual
range of temperature is greatest. On the other hand, in the
western portions of the region, where the climate is moist and
temperature more equable, the Mollusca are considerably more
abundant and varied.

The line which separates the Septentrional from the Mediter-
ranean Sub-region must of necessity be very roughly drawn, and
stragglers from the south will be found to make their way north-
ward, and vice versd, under favouring circumstances of tempera-
ture and geological formation. Jordan has noticed ® that species

1 South and south-western France, however, belong to the Mediterranean Sub-
region.

2 The coast-line of north-east China, including Corea and Japan to north Niphon,
is much more definitely tropical than the adjacent inland districts. The coast-line,
therefore, must be placed in the Oriental Region, while the inland districts belong
to the Palaearctic Region.

3 Biol. Centralbl. ii. p. 208.

x CIRCUMPOLAR SPECIES 287

which in southern countries are not confined to any particular
quality of soil are in more northern latitudes found only on
limestone, which absorbs more heat than other formations. Con-
versely, the higher elevations of the Alps, Pyrenees, and even
Carpathians are like islands in a sea, and support a thoroughly
northern fauna, quite strange to that of the plains below. Thus
Helix harpa Say, a completely boreal shell, which is at home in
Canada, Sweden, Lapland, and the Amoor district, is found on
the Riffel Alp, at a height of 6000 feet.' Vertigo arctica Wall.,
a species abundant in Lapland, North Siberia, Iceland, and Green-
land, occurs on the high Alps of the Tyrol.

Circumpolar Species—A certain number of species are common
to the extreme north both of the Palaearctic and Nearctic regions,
and are, in fact, circumpolar. The number of these species, how-
ever, is so small, not exceeding about 40 species (= 16 genera),
that it seems hardly worth while creating a special sub-
region for their reception, particularly as no genus is peculiar.
At the same time the fact is instructive as illustrating the close
connexion of the northern districts of the two regions, a connexion
which was no doubt more intimate in recent geological times than
it is now.

The circumpolar genera are as follows. The list decisively
sets forth the superior hardiness of the fresh-water as compared
with the land genera :—

Valvata l1sp- Helix . .4sp. Succinea . 1 sp. Physa. LPSp:
Bithynia . 1 ,, Patula. “= 2); Limnaea . 7 ,, Anodonta. 1 ,,
Vitrina 1 ss Epes 23 55 Planorbis. 5 ,, Unio Wes
Hvalinia . 4 ,, Cionella . 1 ,, Aplecta les Pisidiumy = iy,

Great Britain—There are in all about 130 species—83 land,
46 fresh-water ; Limnaea involuta (mountain tarn near Killarney)
appears to be the only pecuhar species. There are 11 Hyalinia,
5 Arion, and 25 Helix, the latter belonging principally to the
sub-genera Nerophila, Tachea, Trichia, and Fruticicola. Three
Testacella are probably not indigenous, but are now so well estab-
lished as to reckon in the total. Of the four Clausilia two reach
Ireland and one Scotland; two do not occur north of the Forth.
There are only two land operculates, one of which (Cyclostoma
elegans) occurs in Ireland but not in Scotland, while the other
(Acicula lineata) reaches the southern counties of Scotland.

' Craven, Jowrn. de Conchyl. (3) xxviii. p. 101.

288 GREAT BRITAIN——FRANCE CHAP.

Several species, e.g. Helia pomatia, H. obvoluta, H. revelata, H.
cartusiana, H. pisana, Buliminus montanus, are restricted to the
more southern or western counties; Geomalacus maculosus is con-
fined to a district in south-western Ireland.

The Pleistocene beds of East Angha contain a number of
species now extinct in these islands, whose occurrence appears to
indicate a warmer climate than the present. Such are Helix
ruderata, H. fruticum, H. incarnata, Clausilia pumila, Unio
littoralis, Hydrobia marginata, and Corbicula fluminalis.

Scandinavian Peninsula—From Norway 121 species in all
are recorded, and 148 from Sweden. The milder climate of
Norway allows many species to reach a considerably higher lati-
tude than in Sweden, thus in Sweden Limax maximus only
reaches 62°, but in Norway 66° 50’ Similarly Arion hortensis
and Balew perversa only reach 63° and 61° respectively in
Sweden, but in Norway are found as far north as 69° and 67°
50’. Clausilia is represented by 9 species in southern Norway ;
one of these is found north of the Arctic circle. There are
4 Pupa, 9 Vertigo, and 11 Hyalinia, but Helix dwindles to 14,
9 of which occur north of the Arctic circle. No land operculates
are found; Cyclostoma elegans, however, occurs in Jutland and
Zealand, which practically form a part of this district.

Iceland.—Hleven species, all Scandinavian, occur. These are
Arion 2, Limaz 1, Helix 2 (arbustorum L. and hortensis Mill., the
latter being found only on the warmer southern coast), Limnaea
1, Planorbis 1, Pisidiwm A.

France.-—The northern, central, and eastern districts belong
to this sub-region, while the southern and western, in which an
entirely new element occurs and many northern forms disappear,
belong to the Mediterranean. Thus, for instance, Helix pomatia
L., H. incarnata Miill., H. fruticum Mill, H. cantiana Mont., #.
strigella Drap., H. rufescens Penn., H. plebera Drap., are not
found in southern France. No detailed enumeration of species
is at present possible, the efforts of a large number of the leading
French authorities being directed to indiscriminate species-making
rather than to the careful comparison of allied forms. Per-
haps the principal difference between the Mollusca of northern
France and those of our own islands is the occurrence of two
species of Pomatias. In the more elevated districts of eastern
France (the Vosges, Jura, western Alps), a certain number of

x FRANCE AND GERMANY 289

species occur which are confined to the high grounds of south
central Europe. Among these are Helix holoserica Stud., H.
personata Lam., H. bidens Chem., H. depilata Drap., H. cobresiana
Alt., H. alpina Faure.

The Pleistocene deposits of the valley of the Somme tell the
same tale as those of eastern England, containing as they do
species and even genera whose northern range is now much more
limited. The Eocene fossils from the Paris beds show most re-
markable relationships to genera now existing in the West Indies
and central America. Others again indicate affinities with India.
Thus we find Ceres, Megalomastoma, and T'udora by the side of
Leptopoma, Faunus and Paludomus.

Germany.—The Mollusca of the plains of northern Germany
are few and not striking, and exhibit little difference from those
of our own islands. In the mountainous districts of the south
and south-east, a number of new
forms occur, amongst which are 3
species of Daudebardia, a remarkable
carnivorous form, with the general
appearance of a Vitrina ; 24 of Clau-

ape. Fo. 0 Fic. 193.—A, Daudebardia brevipes
silia, many Pupa, several Bulominus, ~~ Feér,: sh, shell ; p.o, pulmonary
3 of the Campylaea group of Helix, — ctifice. (After Pfeiffer.) B, shell

: of D. rufa Pfr., 8. Germany.

stragglers from the Italo-Dalmatian
fauna, and 1 of Zonites proper. Our familiar Helix aspersa is
entirely absent from Germany. There are only 4 land oper-
culates—Pomatias 2, Acicula 1, Cyclostoma 1, all of which occur
exclusively in the south. Sithynella and Vitrella, two minute
forms of fresh-water operculates akin to Hydrobia, occur through-
out the district.

Northern Russia and Siberia—This vast tract extends from
eastern Germany to the Amoor district. It is exceedingly poor
in Mollusca, and is chiefly characterised by the gradual disap-
pearance, as we proceed eastward, of European species. There
are a few characteristic Siberian Mollusca, closely alhed_ to
European forms, and in the extreme east a new element is
introduced in the appearance of types which indicate Chinese
attinities. The whole district may be regarded as bounded to the
south by a lne drawn from Lemberg to Moscow, and thence to
Perm; passing south of the Ural mountains, it includes the
whole basins of the rivers Obi, Yenesei, and Lena, coinciding with

VOL. III U

290 NORTHERN RUSSIA AND SIBERIA CHAP.

the vast mountain ranges which terminate to the north the table-
land of central Asia, at the eastern extremity of which it dips
sharply southwards, so as to include the Amoor basin and Corea.

All the larger Helices are wanting, and no land operculates
occur. Helix arbustorum L., H. nemoralis Miull., H. lapicida L.,
H. aculeata Mill, and Hyalinia nitidula Drap., do not appear to
occur east of the Baltic; Arion fuscus Miill., Helix strigella Drap.,
Buliminus obseurus Miill., Clausilia laminata Mont., C. bidentata
Btte., C. plicatula Drap., Viviparus fasciatus Mill, and Neritina
fluviatilis L., do not pass the Urals.

In the Obi district (West Siberia) a further batch of European
species find their easterly linit. Among these are Helix hispida
L., Bithynia tentaculata L., Vivipara vivipara L., Pisidiwm amni-
cum Miill., and Unio tumidus Retz. A few distinctly Siberian
species now appear, e.g. Ancylus sibiricus Gerst., Valvata sibiriea
Midd., and Vitrina rugulosa Koch.

The following are among the European species which reach
eastern Siberia: Hyalinia mitida Miill., Succinea oblonga Drap.,
Planorbis vortex L., spirorbis L., marginatus Drap., rotundatus
Poir., fontanus Light., Valvata piscinalis Mill, Bithynia ventri-
cosa Leach,and Anodonta variabilis Drap. Here first occur such —
characteristic species as Physa sibirica West., P. aenigma West.,
Felix pauper Gld., Hf. Stuaxbergi West., H. Nordenskioldi West.,
Planorbis borealis Lov., Valvata aliena West., Cyclas nitida Cless.,
and C. levinodis West. In the Amoor district a decided
Chinese element makes its appearance in a few hardy forms
which have penetrated northward, e.g. Philomycus bilineatus
Bens., and a few each of the Fruticicola (Chinese) and Acusta
vroups of Helix. Out of 53 species, however, enumerated from
this district, as many as 33, belonging to 18 genera, occur also
in Great Britain.

Lake Baikal.—The Mollusea of Lake Baikal exhibit distinct
characteristics of their own, which seem to indicate the long-
continued existence of the lake in its present condition.
Several entirely peculiar genera occur, which are specialised
forms of Hydrobia, e.g. Baikalia, Liobaikalia, Gerstfeldtia, Dybow-
skia, and Maackia; Benedictia alone extends to the basin of the
Amoor. Choanomphalus, another peculiar and ultra-dextral (p.
250) genus belonging to the Limnaeidae, appears to be related to
the West American Carinifex.

xX SPAIN AND NORTHERN AFRICA 291

(2) The Mediterranean Sub-region is divided into four
provinces: (@) Thé Mediterranean province proper; (b) the
Pontic ; (¢) the Caucasian ; and (d) the Atlantidean province.

(a) The Mediterranean province proper is best considered
by further subdividing it, with Fischer and others, into separate
districts, each of which has certain peculiar characteristics.

G) The Hispano-Algerian district, includes the greater part
of the Iberian peninsula, the Balearic Islands, and northern
Africa from Morocco to Tunis. The extreme western parts of
these districts, including West Morocco, Portugal, Asturias, and
south-west France, under the influence of the moist climate
caused by the Atlantic, show some peculiar features which, in the
view of some, are sufficient to justify their separation from the
rest of the Hispano-Algerian portion. Among these is a marked
development of the slugs, Zestacella, Arion, and Geomalacus, the
latter of which occurs even in south-western Ireland.

Spain.—The principal features are the development of the
Macularia, [berus, and Gonostoma groups of Helix, and the occur-

fh
pp Fie. 194.—A, Parma-

cella Valenciensti
W. and B. x4.
(After Moquin-
Tandon.) A’, shell
of the same, natu-
ral size.

rence of the remarkable slug Parmacella, which is found in many
other parts of the sub-region, and extends eastward as far as
Afghanistan. Clausilia has but few species, mostly in the north.
There are four species of land operculates, one of which is
referred to a genus (Zudora) now living only in the West
Indies, but which occurs in the Eocene fossils of the Paris
basin. In the south there are several species of Welanopsis and
Neritina.

The States of Northern Africa have a thoroughly Mediterranean
fauna, whose facies on the whole shows rather more affinity to
Spain than to Sicily. The Helices of Morocco and Algeria
belong to the same groups as those of southern Spain. Many
are of a dead white colour, the better to resist the scorching
effect of the sun. Fvrussacia is abundant, Geomalacus and Par-

292 NORTHERN AFRICA AND THE SAHARA CHAP.

macella are represented by a single species each, and there is one
Clausilia. According to Kobelt,! the original land connexion
between southern Spain and Morocco must have been much
more extensive than is usually assumed, and probably reached at
least to the meridian of Oran and Cartagena. The Mollusca of
Oran and Cartagena are, according to him, much more closely
related than those of Oran and Tangier, or those of Cartagena
and Gibraltar, but at Cartagena some species, which are charac-
teristic of the Mediterranean coasts from Syria westward, dis-
appear, are absent from the rest of Spain and from Morocco,
but reappear on the south-western coasts of France. These
species may possibly have pushed along that arm of the sea
which, when the Straits of Gibraltar were closed as far as the
latitude of Oran and Cartagena, united in comparatively recent
times the Bay of Biscay with the Gulf of Lions.

The following genera, which do not occur in Spain, have
probably spread into northern Africa as far as Algeria, via
Sicily and Tunis, namely, Glandina (1. sp.), Daudebardia (1
sp.), Pomatias (2 sp.). Tunis shows strong traces of Sicilian
influence, and Kobelt found a colony of snails, of Sicilian affini-
ties, as far west as Tetuan.

The Sahara.—The Algerian Sahara contains, in many places,
a sub-fossil Molluscan fauna which appears to show that the
district has, in quite recent times, undergone a gradual desicca-
tion. The species are mainly fresh-water, including J/elania,
Melanopsis, and Corbicula, with here and there valves of Cardiwm
edule, and indicate, on the whole, an affinity with recent Egyptian,
rather than North African species.
It is probable that a vast series
of étangs, or brackish-water lakes,
once stretched along this region,
and were ultimately connected
with the sea somewhere between

nes eres . Tunis and Eeypt.

Fete Fe de eee (11) Souther 7 F; } vance. — The
Fér.; B, Leucochrow candidissina gouthern portion of France
ae bordering on the Mediterranean

contains many species, especially of Helia, which do not occur in

the centre and north. Amongst these are—

1 Jahrb. Deutsch. Malak. Gesell. viii. p. 278.

x ITALY AND SICILY 293
Leucochroa candidissima Drap. . Helix ciliata Ven.
Hyalinia olivetorum Gmel. » explanata Miill.
Zonites algirus L. » apicina Lam.
Helix rangiana Desh. » cespitum Drap.
», serpentina Fér, »» Lerverii Mich.
» Niciensis Fér, » pyramidata Drap.
., splendida Drap. », trochoides Poir.
» vermiculata Mill. Ferussacia folliculus Gron,
-, Imelanostoma Drap. tumina decollata LL.
»» aperta Born. | Pupa megacheilos C. and J.

Several species of fresh-water Hydrobia (Bithynella) occur.
The district, on the whole, unites certain
characteristics derived from northern Italy
with those of eastern Spain.

Gii) The Jtalo- Dalmatian district in-
cludes Italy and the neighbouring islands
(Corsica, Sardinia, Sicily, Malta), and the
regions at the head and north-eastern shores
of the Adriatic (Carinthia, Carniola, Croatia,
and Dalmatia), the line which separates these py, 196.— Helix (Poma-
latter districts from the fauna of southern ‘«) aperta L, &.
Austria, Bosnia, and Servia being very diffi- ate nae
cult to define.

Ttaly, with the neighbouring islands, has a rich molluscan
fauna. In the sub-Alpine districts of northern Italy the promi-
nent Helix groups are Campylaea, Pomatia, and Anchistoma,
which in the south are generally replaced by Zberus, which here
attains its maximum development. Large Hyalinia are abund-
ant in the north, and Pomatias and Clausilia are frequent all

Fic. 197.—Helizx ( Campylaea) zonata Fic. 198.— Helix (Therus)

Stud., Piedmont. strigata Miill., Florence.
along the Apennines. Sicily has about 250 species, half of
which are peculiar. Helices of the Zberus type abound, but
Campylaea is reduced to two species. Many peculiar forms of
Clausilia oceur, especially a latticed type of great beauty. Ferus-

294 DALMATIA, EGYPT, AND SYRIA CHAP.

sacia and Pupa are well represented, and there are one each of
Glandina and Daudebardia.

Dalmatia and the adjacent districts are chiefly remarkable
for the rich development of Clausilia, which here attains its
maximum (nearly 100 species). The Campylaea section of
Helix is represented by its handsomest forms,
many of which are studded with short
hairs. Here too is the headquarters of
Zonites proper, which stretches westward
as far as Provence, and eastward to Asia
Minor; and also of the single European
Glandina, which has a_ similar eastward
Fre, 199.—A, Clausitia T2DSe but spreads westward through Italy

crassicosta Ben, and Sicily to Algeria, not occurring in

Sere southern France. The land operculates are

matia ; B’, clausilium chiefly represented by Pomatias, and among

ae the fresh-water operculates are a Melania
and a Lithoglyphus, the latter having probably spread from the
basin of the Danube.

Gv) The yypto-Syrian district extends along the south-
eastern shores of the Mediterranean from Tripoli to North Syria,
and eastward to the Euphrates valley. Lower Egypt alone
belongs to this portion, the fauna of Upper Egypt being of an
entirely tropical character, and belonging to the Ethiopian
Region.

Lower Egypt—The Mollusca of Lower Egypt stand in the
unique position of belonging, half to the Palaearctic, and half to
the Ethiopian Region. The land Mollusca are of a distinctly
Mediterranean type, while the fresh-water, directly connected as
they are by the great highway of the Nile with regions much
farther south, contain a large admixture of thoroughly tropical
genera (Ampullaria, Lanistes, Melania, Cleopatra, Corbicula,
Cyrena, Iridina, Spatha, Mutela). The Helices, which are not
numerous, are rather a mixture of circum-Mediterranean species
than of a specially distinctive character. H. desertorwm, how-
ever, belonging to the group Hremophila, is characteristic. There
is a single Parmacella, but the physical features of the country
are unfavourable to the occurrence of such genera as Clausilia,
Pupa, Hyalinia, and the land operculates.

Syria.—The Mollusca, especially in the more mountainous

x THE PONTIC PROVINCE 295

regions of the north, are much more varied and numerous than
those of Egypt. Clausilia is again fairly plentiful, and the
Helicidae are represented by some striking
forms of the sections Levantina, Pomatia,
and Nummulina. Leucochroa las several
curious types with a constricted aperture,
and the Agnatha are represented by Libania,
a peculiar form of Daudebardia. A yromi-
nent feature is the occurrence of a number
of large white Buliminus of the Petraeus
section (Fig. 200). Land operculates appear

to be absent, but Melanopsis and Neritina "pyr & Balmins
are abundant. The Dead Sea contains no Oliv., Beyrout; B,
Mollusca, but Lake Tiberias has a rich Buiminus pC hon

rula) septemdentatus
fauna, including the above-mentioned genera, —_ Roth., Palestine.

with a Corbicula and several Unio.

Upper Mesopotamia appears to possess a mixture of Syrian
and Caucasian forms, including a Parmacella. Lower Mesopo-
tamia has an exceedingly poor land fauna, but is comparatively
rich in fresh-water species, the growing eastern character of
which is shown by the occurrence of several Corbicula and
Pseudodon, and of a Neritina of a distinctly Indian type.

(b) The Pontic province extends from Western Austria to
the Sea of Azof, and includes Austria, Hungary, Roumania, the
Balkan peninsula (so far as it does not form part of the Mediter-
ranean sub-region), the islands of the Greek Archipelago, southern
Russia and the Crimea, and Asia Minor. It thus practically
corresponds to the whole Danube basin, together with the lands
bordering on the Black Sea, except at the extreme east, which
belongs to the Caucasian sub-region. Fischer separates off Greece,
Asia Minor (except the northern coast-line), and the intervening
islands, with Crete and Cyprus, as constituting a portion (Hel-
lado-Anatolic) of the Mediterranean sub-region proper. These
districts, however, appear to possess scarcely sufficient indi-
viduality to warrant their separate consideration.

A prominent characteristic of the Pontic Mollusca is the
ereat abundance of Clausilia and Buliminus. In the islands
east and west of Greece Clausilia forms a large proportion of the
fauna, each island, however small, possessing its own peculiar
forms. The Helices belong principally to the groups Campylaea

296 THE CAUCASUS AND THE CASPIAN SEA CHAP.

(which is very abundant in Austro-Hungary), Pomatia (Greece
and Asia Minor), and Anchistoma. Macularia is comparatively
scarce, but is represented in Greece by one very large form
(Codringtonii Gray). Zonites proper has its metropolis in this
sub-region, and the Danube basin contains one or two species of
Melania and Lithoglyphus. Buliminus is abundant throughout
the sub-region, in the sub-genera Zebrina, Napaeus, Mastus, and
Chondrula. Several striking forms of Zebrina (Ena) are peculiar
to the Crimea.

(c) The Caucasian Province.—The limits of this province
can hardly be exactly defined at present. It appears, however,
to include the whole line of the Caucasus range, Armenia, and
North Persia.

The land Mollusca are abundant and interesting. Among
the carnivorous genera are four species of Daudebardia, a Glandina,
and three peculiar forms of naked slug, Psewdomilax, Trigono-
chlamys, and Selenochlamys. There is a single Parmacella, the
same species as the Mesopotamian, and a good many forms of
Limax, Vitrina and Hyalinia are well represented, and the pre-
dominant groups of Helia are Kulota, Cartusiana, Xerophila, and
Fruticocampylaea, the last being pecuhar. Clausilia and Pupa
are rich in species, together with Buliminus of the Chondrula
type. One Clausilia of the Phaedusa section, together with a
Macrochlamys (Transcaspian only), a Corbicula, and a Cyclotus,
show marked traces of Asiatic affinity. There is one species each
of Acicula and Cyclostoma, and one of Pomatvas.

The Caspian Sea, like Lakes Baikal and Tanganyika, is dis-
tinguished by the possession of several remarkable and peculiar
genera. The sea itself, the waters of which are brackish, is 80
feet below the level of the Black Sea, and is no doubt a relict of
what formed, in earlier times, a very much larger expanse of
water. Marine deposits containing fauna now characteristic of
the Caspian, have been found as far north as the Samara bend of
the Volga. It is probable, therefore, that in Post-pliocene times
an arm of the Aralo-Caspian Sea penetrated northward up the
present basin of the Volga to at least 54° N. The Kazan
depression of the Volga (55° N.) also contains characteristic
Caspian fossils! According to Brusina, the Caspian fauna,

1 Netchayeff, Kazan Soc. Nat. xvii. fase. 5.
* Fauna der Congerien-Schichten, p. 142.

x MADEIRA AND THE CANARIES 297

as a whole, is closely related to the Tertiary fauna of southern
Europe.

Twenty-six species of univalve Mollusca, the majority being
modified forms of Hydrobia, have been described from the Caspian,
namely, Micromelania (6), Caspia (7), Clessinia (3), Nematurella
(3), Lithoglyphus (1), Planorbis (1), Zagrabica (1), Hydrobia (2),
Neritina (2). The bivalves are mostly modified forms of Cardiwm
(Didacna, Adacna, Monodacna), which also occur in estuaries
along the north of the Black Sea. A form of Cardium edule
itself occurs, and numberless varieties of the same species are
found in a semi-fossil condition in the dry or half dry lake-beds,
which are so abundant throughout the Aral district.

(d) Lhe Atlantidean province consists of the four groups of
islands, the Madeiran group, the Canaries, the Azores, and the
Cape Verdes.

The Madeiran group contains between 140 and 150 species
of Mollusca which may be regarded as indigenous, the great
majority of which are peculiar. Only
11 species are common to Madeira and
to the Azores, and about the same
number, in spite of their much greater
proxinuty, to Madeira and the Canaries.
No less than 74 species, or almost
exactly one-half, belong to Helia, and
9 to Patula. A considerable number
of the Helices are not only specifically
but generically peculiar, the genera Fic. 201.—Characteristic land
bearing close relationship to those ae Pe Pe ian

c group: A, Heliz (Irus) laci
occurring in the Mediterranean region. — xiosa Lowe, Madeira; B, Helix

re : : (Hystricella) turricula Lowe,
As a rule they are small in size, but Barts ars Helix( [berus)

often of singular beauty of ornamenta- Wollastont Lowe, Porto Santo ;
; ec 3 =) D, Helix (Coronaria) delphi-
tion. Various forms of Pup are ex- nuloides Lowe, Madeira.

ceedingly abundant (28 sp.), as 1s also
Ferussacia (12 sp.). There are also 53 Clausilia (which genus
occurs on this group alone), and 3 Vitrina (a genus which occurs
on all the groups). The land operculates are represented solely
by 4 Craspedopoma, which is common to all the groups except
the Cape Verdes.

The Canaries have about 160 species, only about a dozen of
which are not peculiar. As many as 75 of these belong to

298 THE ATLANTIC ISLANDS CHAP.

Helix (the sub-genera being very much the same as in the
Madeiran group), and 11 to Patula. There is 1 species of
Parmacella (which occurs in this group alone), and 6 of Vitrina,
of considerable size. A remarkable slug (Plectrophorus) was
described from Teneriffe by Férussac many years ago, but it has
never been rediscovered, and is probably mythical, or wrongly
assigned. Buliminus (Napaeus) has as many as 28 species, all
but one being peculiar, and Merussacia 7. Cyclostoma has two
indigenous species, which, with one Hydrocena and one Craspedo-
poma, make up the operculate land fauna.
The Azores are comparatively poor in Mollusca, having only
52 species, nearly two-thirds of which are peculiar. Heliz has
5 species, Patula 4, and Pupa 8. Ferussacia, so abundant in
Madeira and the Canaries, is entirely absent, its place being
taken by MNapaeus (7 sp.), which is curiously absent from
Madeira, but richly represented in the Canaries. There are 7
Vitrina, while the land operculates consist of one each of
Craspedopoma and Hydrocena. A singular slug (Plutonia), with
an ancyliform internal shell, is said to occur. The group was
long believed to possess no fresh-water Mollusca, but two. species
(one each of Pisidiwm and Physa) have recently been discovered.
The Cape Verdes, owing to the extreme dryness of their
climate, are poor in land Mollusca. There are 11 Helix, nearly
all of which belong to the group Leptaxvis, which is common to
Madeira and the Canaries. erussacia is absent, Buliminus is
represented by a single species, and there are no land operculates.
Ethiopian influence, however, as might be expected from the
situation of the group, is seen in the occurrence of an Hnnea, a
Melania, and an Jsidora.
It will be noticed how httle countenance the molluscan fauna
of these island groups gives to any theory of an Atlantis, any
theory which regards the islands as the remains of a western
continent now sunk beneath the ocean. Had ‘ Atlantis’ ever
existed, we should have expected to find a considerable proportion
of the Mollusca commen to all the groups, and perhaps to Europe
as well, and there would apparently be no reason why a genus
which occurred in one group should not occur in all. As a fact,
we find the species extremely localised throughout, and genera
occur and fail to occur in a particular group without any
obvious reason. All the evidence tends to show that the islands

x CENTRAL ASIA 299

are purely oceanic, and have been colonised from the western
coasts of the Mediterranean, 7.e. from the direction of the prevail-
ing currents and winds.

(3) Central-Asiatic Sub-region.—The countries included in
this vast sub-region are Turkestan, Songaria, Afghanistan, including
the Pamirs, Western Thibet, and probably Mongolia. Kashmir
belongs to the Indian fauna. At present the whole district is very
impertectly known; indeed, it is only at a few points that any-
thing like a thorough investigation of the fauna has been made.
It is therefore almost premature to pronounce any decided opinion
upon the Mollusca, but all the evidence at present to hand
tends to show that they belong to the Palaearctic and not to
the Oriental system. This is especially the case with regard
to the fresh-water Mollusca, many of which are specifically
identical with those occurring in our own islands. A slight
admixture of such widely distributed types as Corbicula and
Melania occurs, but is not sufficient to disturb the general
European facies of the whole. It is possible that eventually
the whole district may be regarded as a sub-region combining
certain characteristics of the eastern portions of the Mediter-
ranean basin with an extension of the septentrional element, due
to higher elevation and more rigorous climate. The principal
features in the land Mollusca appear to be the occurrence of a
number of Buliminus of the Napaeus group, a few Parmacella
(Afghanistan being the limit of the genus eastward), Clausilia,
Pupa, Limax, and Helix, with several stray species of JMucro-
chlamys.

B. The Oriental or Palaeotropical Region

This region includes all Asia to the south of the boundary
of the Palaearctic region, that is to say, India, with Ceylon,
Burmah, Siam, and the whole of the Malay Peninsula, China
proper, with Hainan and Formosa, and Japan south of Yesso.
It also includes the Andamans and Nicobars, and the whole of
Malaysia, with the Philippines, as far eastward as, and includ-
ing Celebes with the Xulla Is., and the string of islands south
of the Banda Sea up to the Ké Is. The Moluccas, in their two
groups, are intermediate between the Oriental and Australasian
regions.

300 THE ORIENTAL REGION CHAP.

In this vast extent of land two distinct centres of influence
are prominent—the Indian and the Chinese. ach is of marked
individuality, but they differ in this essential point, that while
the Chinese element is decidedly restricted in area, being, in fact,
more or less confined to China itself and the adjacent islands,
the Indian element, on the other hand, extends far beyond con-
tinental Asia, and embraces all the Malay islands to their
farthest eastward extent, until it becomes overpowered by the
Papuan and Australian fauna. Upper Burmah, with Siam, forms
a sort of meeting-point of the two elements, which here inter-
mingle in such a way that no very definite line of demarcation
can be drawn between them.

Thus we have—

(a) Indian Province.

(b) Siamese Province.

(c) Malay Province.
re Philippine Province.
{(a) Chinese Province.
\(b) Japanese Province.

k Indo-Malay Sub-Region
Oriental Region |

2. Chinese Sub-Region

The Indo-Malay fauna spreads eastward from its metropolis,
but has practically no westward extension, or only such as may
be traced on the eastern coasts of Africa and the off-lying islands.
There appears to exist no other case in the world where the
metropolis of a fauna is so plainly indicated, or where it lies,
not near the centre, but at one of the ends of the whole area of
distribution.

Comparing the two sub-regions, the Chinese is distinguished
by the great predominance of Helix, while in the Indo-Malay
sub-region Manina and the related genera are in the ascendancy.
In India itself there are only 6 genera of true Helicidae, poorly
represented in point of numbers; in China there are at least
three times this amount, most of them abundant in species.
The Indo-Malay sub-region, on the other hand, is the metropolis
of the Naninidae, which abound both in genera and species. In
the Chinese sub-region Clausilia attains a development almost
rivalling that of S.E. Europe, while in India there are scarcely
a dozen species. A marked feature of the Indo-Malay sub-region
is the singular group of tubed land operculates (Opisthoporus,
Pterocyclus, etc.). In China the group is only represented by
stragglers of Indian derivation, while the land operculate fauna,

x INDIA 301

as a whole, is distinctly inferior to the Indian. Another char-
acteristic group of the Indo-Malay region is Amphidromus, with
its gaudily painted and often sinistral shell; the genus is entirely
absent from China proper and Japan, where its place is taken
by various small forms of the Buliminus group. Fresh-water
Mollusca, especially the bivalves and operculates, are far more
abundant in the Chinese sub-region than in the Indo-Malay.

(1) The Indo-Malay Sub-region.—(a) Zhe Indian Province
proper includes the peninsula of Hindostan, together with Assam
and Upper and Lower Burmah. ‘To the east and extreme north-
east, the boundaries of the province are ill-defined, and the fauna
eradually assimilates with the Siamese on the one hand and the
Chinese on the other. Roughly speaking, the lne of demarca-
tion follows the mountain ranges which separate Burmese from
Chinese territory, but the debatable ground is of wide extent,
and Yiinnan, the first Chinese province over the border, has
many species common with Upper Burmah.

The gigantic ranges of mountains which bound the sub-
region to the north-west and north limit the extension of the
Indian fauna in those directions in a most decisive manner.
There is no quarter of the world, even in W. America, where a
mountain chain has equal effect in barring back a fauna. In
the north of Kashmir, where the great forests end, there is a
most complete change of environment as the traveller gains the
summit of the watershed; but Kashmir itself distinctly belongs
to the Indian and not the Palaearctic system. The great desert
to the south of the Punjab is equally effective as a barrier towards
the west.

The Mollusca of India proper include a very large number of
interesting and remarkable genera. India is the metropolis of
the great family of the Naninidae, or snails with a caudal mucus-
pore, which are here represented by no less than 14 genera and
over 200 species. The genera Macrochlamys, Sitala, Kaliella,
Ariophanta, Girasia, Austenia, and Durgella are at their maxi-
mum. Heliz is scarcely represented, containing only about 30
inconspicuous species (leaving Ceylon out of account). Buliminus
is abundant, especially in the north. The Stenogyridae are
represented by Glessula, which is exceedingly abundant in India,
but has only a few straggling representatives in the rest of the
Oriental region. Among the Pupidae is the remarkable form

302 INDIA CHAP.

Boysia, with its twisted upturned mouth, while Zithotis is a
peculiar form allied to Suecinea, to which group also probably
belongs Camptony«, a limpet-like form with a very small spire,
peculiar to the Kattiawar peninsula. Camptoceras, an extra-
ordinarily elongated sinistral shell, with a loosely coiled spire, is
peculiar to the N.W. Provinces.

Among the fresh-water pulmonates is an Ampullarina, a genus
only known elsewhere from the Fiji Is. and E. Austraha. Crem-
noconchus is a form of Littorina, peculiar to the W. Ghats,
which has habituated itself to a terrestrial life on moist rocks
many miles from the sea. The fresh-water operculates include
the peculiar forms Mainwaringia, from the mouth of the Ganges
(intermediate between JJelania and Paludomus), Stomatodon,

Fic. 202. —Characteristic Indian Mol- Fic. 203. — Streptaxis
lusca: A, Hypselostoma tubiferum . Perroteti Pfr., Nil-
Blanf.; B, Camptoceras terebra Bens. ; ghiri Hills: A, adult;
C, Camptonyx Theobaldi Bens. A’, young form.

Larina, Fossarulus, Tricula, and others. The bivalves are neither
numerous nor remarkable; Velorita, a genus of the Cyrenidae, is
peculiar.

The land operculate fauna of India is singularly rich and
varied. About 25 genera, and at least 190 species, occur. Here
we find the metropolis of Cyclophorus among the larger forms,
and of Diplommatina and Alycaeus among the smaller. A large
proportion of the operculate genera are quite peculiar to the
extreme south of India and Ceylon. The appearance of a few
species of the European genus Pomatias is very remarkable.

The carnivorous genera are poorly represented. A few Hnnea
occur, While Streptaxis is practically confined to the extreme
south and north-east.

x INDIA—CEYLON AND SOUTHERN INDIA 303

Land and Fresh-water Mollusca of India proper

Streptaxis. ... 9 Trachia 12 Limnaea . . 7 Streptaulus 1
Ennea . . . . 8 #£Thysanota 1 Camptoceras . 3 Coptochilus . 3
Helicarion. . . 15 Camaena. 1 Planorbis. .10 Alycaeus . . 49
Girasia. . . . 14 Amphidromus 2 Ampullarina. 1 Lagochilus 1
Austenia . . .11 Boysia 1 Melania . . 17 Cyclophorus . 12
libycush 92 9. - l ) Retracus - 14 Mainwaringia 1 Scalaina 1
Africarion. . . 2 Cerastus . 6 Paludomus . 10 Micraulax. 2
Dursellay S54) Rachis 5 Stomatodon i Jerdonia =). 10
Ariophanta . . 15 Cylindrus 1 Larina. 1 Spiraculum 1
OME 9 0 6 oF eh leibyoE 15 Cremnoconchus 3 Otopoma . 1
Macrochlamys . 78 Hapalus . 4 Fairbankia 2 Cyclotopsis 2
Microcystis . . 7 Clausilia . 10 =‘ Tricula. 1 Georissa 1
Silage ee 20) Subulima ~ 2 Bithynia 9 Modiola 1
Kaliella . . . 35 Opeas. 6 Fossarulus 1 Scaphula. . 1
Hemiplecta . . 15 Glessula. . 49 Stenothyra 3 Unio; 2 5 40
Sesara . . . . 3 Geostilbia 3 Vivipara 4 Solenaia it
Trochomorpha 5 Succinea. . 11 Valvata 1 Cyrena , 18
Trochomorphoides 1 Lithotis 2 Ampullaria 4 Sphaerium 1.
Parmacella (?). 1 Vaginula. 1 Assiminea . 9 Pisidium 5
Tebennophorus . 1 Camptonyx . 1 Acmella 2 Velorita 2
Anadenus . . 4 Coelostele 1 Pomatias . 4 Tanysiphon . 1
Plectopylis. . . 11 Carychium 3 Diplommatina 63 Novaculina 1
Plectotropis 3 Ancylus i> Eupinas = = 1) Nausitora:. 1

The Cingalese district, which almost approaches the character
of a distinct province, presents several remarkable points of
dissimilarity from the rest of India. It consists of the island
of Ceylon, and of a portion of 8S. India whose exact limits have
yet to be defined. It appears, however, that the Western or
Malabar coast, with the hills parallel to it, is more akin to
Ceylon than the Eastern or Coromandel coast. The Travancore,
Malabar, and $8. Canara districts, with the Palnai, Anamalai,
and Nilghiri Hills, are markedly Cingalese, while there seems to
be no distinct evidence of similar relationship on the part of the
Madras or even the Cuddalore district.

Among the principal features of the Cingalese district is the
occurrence of three peculiar genera of Helix, one (Acavus) large
and finely coloured, another (Cori//a) smaller, with a singularly
toothed aperture. While the Coril/a group shows relations with
Plectopylis and other Burmese and Siamese sub-genera Acavus
(Fig. 204) is totally distinct from any other Indian form, and
shows signs of close relationship, in the great size of the
embryonic shell, to the Helices of Madagascar (p. 335). In
Ceylon the group is entirely isolated, and its occurrence, besides

304 CEYLON AND SOUTHERN INDIA CHAP.

decisively separating that island from India, Burmah, and
Siam, forms a most interesting problem in the history of dis-
tribution. Hurystoma, with a single species (4. vittata Miill.),
is also peculiar.

As usual when Helix gains ascendancy, the Naninidae retrogress.
Durgella, Austenia, and Girasia are absent altogether, while
Macrochlamys, Sitala, Kaliella, ete, are present in greatly
diminished numbers. The sub-genus Leddomea is peculiar, a
form directly related to Amphidromus (Siam and Malacca).
The fresh-water operculate Philopotumis is peculiar, but for one

Fic. 204.—Heliz (Aca-
vus) Waltoni Reeve,
Ceylon, showing em-
bryonic shell (emb);
x 2.

species found in Sumatra; while Tanalia is quite peculiar. But
the forms which, next to the Helices, most emphasise the separa-
tion of the Cingalese district are the land operculates. There
are eleven genera or subgenera of land operculates which do not
occur in the rest of India proper. Two (Aulopoma and Cataulus)
are quite peculiar, while the other nine are represented in
Burmah, Siam, and the Malay islands, but not in India. On
the other hand, Diplommatina and Alycaeus, so profusely abun-
dant in India, have not yet been discovered in Ceylon. Among
the slugs, Zennentia is a peculiar genus, whose nearest relation
occurs in the Seychelles.

Genera and Subgenera occurring in the Cingalese District,
but not in N. and Central India

Streptaxis Beddomea Craspedotropis Mychopoma
Tennentia Philopotamis Pterocyclus Cataulus
Acavus Tanalia Aulopoma Nicida
Eurystoma Theobaldius Ditropis Opisthostoma
Corilla Leptopomoides Cyathopoma

The district consisting of Upper Burmah, Peqgu, Tenasserim,

Xx UPPER BURMAH AND PEGU 305

and Aracan, while essentially a part of the Indian province,
contains several Siamese genera which are. not found in India
proper, as well as several which are at present peculiar.
Amongst the former category are, of Helicidae, a single repre-
sentative each of the genera Camaena (Siamese and Chinese) and
Aegista (Chinese). Influence of the same kind is seen in the
increased numbers of Plectopylis (14 sp.) and Plectotropis (5 sp.),
of Clausilia (10 sp.) and Amphidromus (5 sp.),
and of the large tubed operculates (11 sp. in all).
Sesara and Sophina among the Naninidae are strange
to India, while Hyalimaxz is common only to the
Andamans, Nicobars, and Mascarene Is. Hypselo-
stoma (Fig. 202, A) is a most remarkable genus of
the Pupidae, reminding one of Anostoma of the
New World. It is peculiar to the peninsula, but
for one species in the Philippines. Among the
Pupinidae, we have the pecuhar Raphaulus and
Hybocystis (Fig. 205), a very remarkable form, of
which another species occurs at Perak. Two Helicina pig, 205.—mybo-
mark the most westward extension of the genus = ¢ystis gravida

: Bens. Young
on the mainland. In the extreme north of Upper and sadule.
Burmah, Indian and Chinese forms intermingle.

The Burmese district, together with the Indian and Siamese
provinces, is pre-eminently the home of a group of Mollusca,
originally of marine origin, which have permanently habituated
themselves to a brackish or fresh-water existence. They belong
to widely different families, and even Orders. Besides Cremnocon-
chus mentioned above, we have, among the bivalves, Novaculina,
a Solen living in fresh water in the Ganges, Irawadi, and
Tenasserim estuaries; Scaphula, an Arca, one species of which
occurs in the Ganges hundreds of miles above the tideway (see
Fig. 9, p. 14); and Muartesia, a Pholas from the Irawadi Delta.
Clea (which also occurs in Java and Sumatra) is probably an
estuarine Cominella; a Tectura has earned the name jfluminalis
from its exclusive residence in the Irawadi R.; Jravadia is
probably a Rissoina of similar habits, occurring from Ceylon
round to Hong-Kong; Brotia is a Cerithium from an affluent of
the River Salwin, and Canidia is a Nassa, occurring in the
embouchures of rivers from India to Borneo. Nowhere else in
the world is there such a collection—not exhausted by this list

VOL. IIL x

306 THE ANDAMANS AND NICOBARS CHAP.

—of marine forms caught in process of habituation to a fresh-
water or even a land existence.

The Andaman and Nicobar Islands possess no peculiar features
in their land Mollusca. They are closely related to the adjacent
coasts of Lower Burmah. <Amphidromus (2 sp.) occurs in the
Andamans alone, and Clausilia (2 sp.) im the Nicobars alone,
while Hyalimax occurs in both groups. A remarkable Helix
(codonodes Fér.) from the Nicobars appears to find its nearest
relations in the isolated group from Busuanga and Mindoro (p.
315). Land operculates are abundant, in the Nicobars actually
outnumbering the pulmonates (28 to 22). Helicina and Om-
phalotropis, genera characteristic of small islands, are found on
both groups.

(b) The Siamese Province includes the area occupied by the
districts known as Siam, Laos, Cambodia, Cochin China, Annam,
and Tonquin. Along the whole of its northern frontier, the
zoological is no more than a political boundary, while on the
east the mountain ranges which part Siam from Pegu and
Tenasserim are not of sufficient height to offer any effective
barrier to distribution. The province is accordingly qualified to
a considerable extent by Indian and Chinese elements.

Streptaxis is, but for three Hnnea, the sole representative of
the carnivorous genera, and attains its maximum in the Old
World. Partly owing to Chinese influence, the Helicidae, with
11 genera and 46 species, begin to regain their position as
compared with the Naninidae (12 genera, 54 species). Of the
Helicidae, Acusta and Hadra appear now for the first time, and,
with Plectotropis, Stegodera, and Clausilia, form a marked

hm. Chinese element. Amphidromus,

with 33 species, is the most char-

acteristic land pulmonate. Several

genera, whose nucleus of distribu-

tion lies among the islands farther

east, appear to have penetrated as

far as these coasts. Such are Ch/o-

ritis, Camaena, and Obbina among

: the Helicidae, Zrochomorpha, and,

Fic, 206. — Cyclophorus siamensis of the operculates, Helicina.

Sowb., Siam. :

Land operculates are very richly

developed. In all, there are 17 genera and 104 species known.

x SIAM AND CAMBODIA 307

The tubed operculates attain their maximum, and Cyclophorus
is even more abundant than in India. Fresh-water bivalves
abound. Dipsas and Pseudodon are common to China, and Unio
and Anodonta are profusely represented. A curious resemblance
to S. America appears in this group, a single Mycetopus occurring,
the only species not Brazilian, while Arconaia appears very closely
to approach the Hyria of the same locality. Several genera
of the Hydrobia type (Pachydrobia, Jullienia, Chlorostracia) are

peculiar.

Land and Fresh-water Mollusca of the Siamese Province

Streptaxis . . 20 Chloritis. . 8 Faunus 1 Leptopoma . 10
Ennea . 38 Dorcasia. . 1 Bithynia. 9 Lagochilus . 6
Helicarion . 7 Camaena . 5 Wattebledia 1 Pupina A)
Microcystis . 3 Hadra . . 5 Stenothyra . 4 MHybocystis. 3
Sesara (?) 1 Obbina . . 1 Hydrobia 1 <Alycaeus . 6
Medyla . 1 <Amphidromus33 Pachydrobia 9 Cataulus (7). 1
Xesta 4 Bocourtia . 2 Jullienia 6 Diplommatina 2
Macrochlamys. 6 Buliminus . 4 lLacunopsis. 6 Helicina. 4
Kaliella . 5 Hypselostoma 2 Chlorostracia 4 Georissa . 2
Hyalinia (?) 1. Tonkinia 1 Vivipara. . 39 Modiola (f. w.) 2
Hemiplecta. . 14 Clausilia. . 15 Valvata . 1 Dreissensia . 3
Rhysota . 2 Opeas 7 <Ampullaria. 15 Anodonta is
Trochomorpha. 6 Spiraxis (?). 2 Assiminea 7 Mycetopus 1
Trochomorphoides3 Subulina 1 Procyclotus. 6 Pseudodon . 18
Plectopylis . 5 Succinea. 4 Dasytherium 2 Dipsas 4
Stegodera 2 Vaginula 7 Opisthoporus 5 Unio. 64
Plectotropis . 12 Limnaea 7 Rhiostoma 7 Arconaia 1
Trachia . 3. Planorbis 6 Myxostoma. 1 Cyrena 6
Fruticicola . 2 Canidia . .13 Pterocyclus. 7 Batissa 1
Acusta 2 Melania. . 39 Cyclophorus 28 Corbicula . 35

(c) The Malay Province includes the peninsula of Malacca
south of Tenasserim, and the series of islands beginning with
Sumatra and stretching eastward up to the Ké Is., besides
Borneo and Celebes. The Philippines form a separate province.

The Malay province is singularly poor in representative
forms, whether we regard it as a whole or consider the islands
separately. Not a single genus, with the exception of Rhodina
(Malacca), appears to be peculiar. The contrast with the West
Indies is in this respect very striking. Java, for instance,
which is well explored, and almost exactly eleven times the size
of Jamaica, has about 100 species of land Mollusca, while
Jamaica has about 460.

308 MALACCA—-SUMATRA CHAP.

This want of individuality in the land Mollusca .of the Malay
islands is accounted for by a consideration of the sea depths
which separate them from the Asiatic mainland. The accom-
panying map, the red lne on which is intended to show what
would be the result of an elevation of the sea bottom for no
ereater amount tlian 100 fathoms, exhibits clearly the fact that
these islands are practically a part of Asia, a large stretch of very
shallow sea extending between Siam and the greater part of the
north-west coast of Borneo,

In all probability the three great islands of Sumatra, Java,
and Borneo were united with the mainland of Asia, and
with one another, at a period, geologically speaking, com-
paratively recent. This follows from the general uniformity of
their land Mollusca, both as regards one another and as regards
the mainland. Nor do the smaller mem-
bers of the island series—Bah, Lombok,
Sumbawa, Flores, Timor,and Timor Laut—
show any marked individuality in the
possession of peculiar genera. Wallace’s
line is absolutely non-existent, so far as
the land Mollusca are concerned. The
really noticeable break in distribution
comes with the Aru Is., for while the
Tenimber group (Timor Laut, etc.) are decidedly Malay, and the
Ké Is., in the poverty of our information, uncertain, the Aru Is.
are as Papuan as New Guinea itself. The profound depths of the
Banda Sea to the north, and the Timor Sea to the south, appear
to have kept the islands from Flores to Timor Laut free from the
intrusion of any Moluccan or any considerable Australian element.
The Moluccas, as has been already remarked, besides possessing
considerable pecuharities of their own, unite a mixture of the
Malay and Papuan elements, and serve as a sort of debatable
ground for the meeting of the two.

The Malay peninsula is practically another island of some-
what the same shape and general trend as Sumatra, and about
one-half the size. Its general relations—and the remark apples
to the great Sunda Islands as well—appear to be rather more
with Burmah, Tenasserim, and even the Cingalese district, than
with Siam. Points of connexion between Ceylon and Sumatra,
and Ceylon and Borneo, have already (p. 304) been brought out.

\

Hy } i

Fia. 207.—Ariophanta Rum-
phit v. d. B., Java.

Map B. Between pages 308 and 309.

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Map to illustrate the
GEOGRAPHICAL DISTRIBUTION
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x JAVA AND BORNEO 309

It seems not impossible, from the point of view of the land
Mollusea only, that the Sunda Islands may at one time have
stretched much farther into the Bay of Bengal, prolonged, per-
haps, into what are now the Andaman and Nicobar groups,
while Ceylon and the western side of the Deccan, united into one
continuous piece of land, and possibly separated from N. India by
a wide stretch of sea, extended farther eastward in a long island,
or series of islands.

Java, from its Mollusca, does not appear to hold the compara-
tively isolated position which its mammals and birds seem to
indicate. Borneo, on the other hand, is more Siamese than Java
or Sumatra in respect of a group whose metropolis is Siam,
namely, the tubed operculates; for while that section is repre-
sented by 3 species in Sumatra and only 2
in Java, in Borneo it has as many as 19,
Fhiostoma not occurring in the two former
islands at all. Alycaeus, Lagochilus, Pupina,
and Cyclophorus are found throughout, but
Hybocystis (Malacca, 1 sp.) does not quit the
mainland. Borneo is remarkably rich in
land operculates, especially noticeable being
the occurrence (11 sp.) of Opisthostoma
(Fig. 208), a most extraordinary form of
land shell (Ceylon, Siam), of Diplommatina
(17 sp.), and Raphaulus. The occurrence Wicea08=-A. Opens
of a single Papuina (Moluccas eastward) is Cookei E. A. Smith,
very remarkable ce ore

Amphidromus is a genus characteristic G.-A., Borneo. Both
of the great Sunda Islands, attaining its ae
maximum in Java (12 sp.). The Indian Gilessula still has
one species each in Sumatra, Java, and Borneo. One species
of Streptaxis* occurs in Malacca, but Hnnew (3 sp.) reaches as
far east as Borneo and the Philippines. Parmarion, Helicarion,
Ariophanta, and other groups of the Naninidae are well repre-

1 Streptawis is a remarkable instance of a mainland genus. Although abundant

in the Oriental, Ethiopian, and Neotropical regions, it never seems to occur on any
of the adjacent islands, except in the case of Trinidad (1 sp.), which is practically
mainland. Omphalotropis, on the other hand, is the exact reverse of Streptaais
in this respect, occurring all over Polynesia and the Malay Is., as far west as Borneo,
as well as on the Mascarenes, but never, save in a doubtful case from China, on the
mainland of Asia, Australia, or Africa.

310 CELEBES CHAP.

sented. Hemiplecta and Nesta are abundant and large, while the
Rhysota of Borneo contain some huge ‘sinis-
tral forms. Lhodina is a remarkable form
from Malacca, whose exact generic position
is not yet settled. Olausilia has a few species
on all the islands, the last occurring on
Ternate, and a single Papuina (Moluccas
and N. Guinea) occurs in Borneo.

The Jsland of Celebes marks the be-
ginning of a distinct decrease in the Indo-
Malay element. The Naninidae lose ground,
in proportion to the Helicidae, JJacro-

chlamys, for instance, being represented by

Fic. 209.—Aimphidromus _ : : ;
Gee ee Nave. only one species, and Hemiplecta by four.
Other characteristic genera of the Indian
region dwindle, such as Amphidromus, Clausilia, the tubed
operculates, and Cyclophorus, while Sitala, Kaliella, Glessula,
and Plectotropis disappear altogether. , Comparing the total
numbers of Naninidae and Helicidae from Sumatra to New Guinea,

we obtain this interesting result :

Sumatra Java Borneo Celebes Moluceas N. Guinea
Nanina (all genera) 26 32 51 29 36 40
Helix (all genera) a 11 13 14 55 91

It will be noticed that the proportion of Naninidae to Helicidae,
which has been nearly 4 to 1 in Sumatra, falls to 5 to 1 in Java,
and rises again to 4 to 1 in Borneo (showing the essentially con-
tinental character of the island); im Celebes it further falls to 3
to 2, while in the Moluccas the seale turns and Helix has the
advantage by about 8 to 5, and in N. Guinea by more than
2 to 1.

There is the same absence of marked features of individuality
in Celebes as in the islands dealt with above. Not a single
genus is peculiar. The nature of the sea bottom between Borneo
and Celebes, with its indications of a somewhat broad bridge over
an otherwise deep channel of separation, would seem to account
for and suggest the true explanation of the facts as they stand.
At the same time, there are indications of a certain amount of
contrast between N. and 8S. Celebes. The Indian element, which
constitutes the preponderating majority of the fauna, is common
to north and south alike. But the north part of the island, in

x CELEBES—THE MOLUCCAS ST

which Obba and Obbina occur, shows decided relationship with the
Philippines, while the occurrence of three Chloritis and one
Planispira tend to approximate S$. Celebes rather with the
Moluccas.

The islands eastward of Java, from Bal to Timor Laut and
the Tenimber Is., present no trace of individual peculiarities ;
they simply carry on the Indo-Malay fauna as though along a
great peninsula. Even Timor, surrounded as it is on all sides by
sea of profound depth, shows no sign of possessing even one
peculiar genus. Amphidromus, perhaps the most characteristic
of all Indo-Malay genera, occurs throughout, diminishing in
numbers as we go eastward (Bali, Lombok, and Sumbawa 4 sp.,
Timor 2 sp., Timor Laut 1 sp.), while Plectotropis reaches no
farther than Flores and Timor. The tubed operculates are alto-
gether wanting. In Timor Laut we have Moluccan influence
appearing in 3 Ch/loritis, and there is one (supposed) Corasia.
Two Helices of a marked Austrahan type (Ahagada) occur, one in
Flores, the other on Dama I., south-west of Timor. The con-
figuration of the sea bottom (see map) would lead us to believe
that the north-west coast of Australia once stretched a good
deal nearer to these islands.

The Moluccas, taken as a whole, constitute a transition region
between the Indo-Malay and the Papuan faunas, uniting, to a very
considerable extent, the features of both. They fall into two
well-defined groups. The northern, or Ternate group, consists of
Gilolo (Halmahera), Batchian, and the outlying islands as far
south as and including Obi major. The southern, or Amboyna
group consists of Buru, Ceram, Amboyna, and the chain of islands
to the south-east of Ceram, as far as, and including the Keé Is.

The Ternate group shows decidedly closer relations with New
Guinea than the Amboyna group. Thus, among the Helices, the
markedly Papuan genus Papwina is represented by 7 species in
the Ternate group, but by 1 in the Amboyna group. Again, the
Cristigibba section of Planispira, which is a Papuan form, has
4 representatives in the northern group, but only 1 in the
southern. Certain points of connexion with Celebes come out in
the southern group which are wanting in the northern; thus of
Chloritis there are 8 species in Amboyna, 0 in Ternate, 3 in
Celebes.

In the Moluccas the Helicidae, for the first time as we move

312 THE MOLUCCAS CHAP.

eastward from India, gain the ascendancy over the Naninidae, the
numbers being, Heliz 55, Nanina 36. If we take the groups
separately, we find that in the Amboyna grcup the proportion is
22 to 23, while in the Ternate group it is 33 to 13, an addi-
tional proof that the Amboyna group is far less Papuan than the
Ternate. Of Planispira, the most characteristic sub-genus of
Helix, there are 12 species in the Ternate group, and 5 in the
Amboyna. The section Phania, which contains 4 species of the
finest Helices known, is quite peculiar to the Ternate group.
One species of Obbina, a sub-genus markedly Philippine, occurs in
each group. Several of the Indo-Malay land operculates (e.g.
Ditropis) reach their limit here, and here too we have the last
Clausilia (strangely absent from the Amboyna group). Amphi-
dromus is not reported on sufficient authority to warrant its
insertion in the list.

Land Mollusca of the Moluccas. (TY =Ternate, A= Amboyna! group)

Helicarion . 1A _ Cristigibba. 1 A, 4 T Faunus . ura
Euplecta- TAS Obbina: . 3.) A, a Winipara A
Xesta GUA, 4.1 Bhaniay. .. 4T Acmella 1A
Macrochlamys 1A Albersia. . 3 T Diplommatina. 4 A, 2 T
Lamprocystis 4 A,2T Camaena . 1T Registoma . chad
Macrocycloides 4A Papuina. .1A,7T Pupinella 1A
sitala: 7% iA Bupa es. © 3A Callia 2 A
Kaliella. . 3 A,17T Vertigo . 2A Leptopoma 4A, 59.
Trochomorpha3A,3T Clausilia . 1T Lagochilus PASSE ag
Endodonta . 1A Opeas : .4A,4T Ditropis 3 A
Patula 1A Subulina. 1A Cyclotus 4A,6T
Plectotropis . 1'T Tornatellina 1 A Omphalotropis 3A
Eulota 1A Vaginula . 1A Georissa ipa
Chloritis. . 8 A Melania 18 A, 4T Helicina Gras oie

Planispira 5 A, 12 T

(d) The Philippine Province—In the extraordinarily rich
development of their Mollusca, the Philippines form a remark-
able contrast with the poverty of the adjacent Malay islands.
No less than 727 species of land Mollusca alone are known from
the group, amongst which are included some of the finest and
handsomest forms yet discovered. The main features of the
fauna are Indo-Malay, with the addition of a certain Australasian

1 The Amboyna group has been much the better explored. Common to both

groups are one sp. each of Kadliella, Trochomorpha, Opeas, Leptopoma, Cyclotus,
Helicina.

x THE PHILIPPINES S13

element, and a remarkable development of individual character-
istics.

The principal indigenous feature is the profuse abundance of
the genus Cochlostyla, a group of large and elegant land shells,
partly helicoid, partly bulimoid in shape, many of the species of
which are covered with a curious hydrophanous epidermis. They
are in the main of arboreal habits, hyving in the tops of the
enormous forests which cover the greater part of the islands.
As many as 247 species, belonging to 15 sub-genera, have been
described.

The distribution of the sub-genera of Cochlostyla on the

Fic. 210.—Cochlostyla (Chry- Fic. 211. — Cochlostyla (Ortho-
salis) mindoroensis Brod., stylus) Portei Reeve, Luzon.
Mindoro, Philippines. x 2

different islands of the Philippine group affords important
evidence on the geological relation of the islands to one another.
Thus we find Orthostylus and Hypselostyla occurring in the
central islands and $8. Luzon, but not in Mindanao or Mindoro ;
we find Chrysalis peculiar to Mindoro, Prochilus to Mindoro
and the Cuyos, Ptychostyla to Luban, all these being sub-genera
of very marked characteristics. Six out of the fifteen sub-genera
are entirely absent from Mindanao, although occurring on the
islands in the immediate vicinity. The little group Tablas-
tomblon-Sibuyan are entirely deficient in certain sub-genera
which occur on the islands surrounding them on all sides.’

1 A. H. Cooke, P. Z. S. 1892, pp. 447-469.

314 THEY PALE PINES CHAP.

Other forms pecuhar to the Philippmes are Diaphora, a
section of Hnnea with a curi-
ously produced mouth, and
several sub-genera of the
Naninidae( Vitriniconus, Vit-
rinoidea, Hemitrichia). The
great Riysota here find their

metropolis. Another very
= marked group of Helia is

Fic, 212.—Helizx (Obbina) rota Brod.,
Philippines.

Obbina, 19 of the 25 known
species being peculiar.

The Helicidae proper of the Philippines are still held in
check, as in the greater part of the Indian region, by the
Naninidae. The single 7rachia and Plectotropis, and the 2
species each of Plectopylis and Satsuma, indicate affinities with
Indo-China. Further important Indian relationships are seen
in the great Nanina and Cyclophorus, which here attain almost
Indian dimensions; in Kaliella (8 sp.), Sitala (2), Clausilia
(1). Among the operculates we still have 1 Alycaeus and 1
Coptochilus. Singularly enough, several Indian genera which
occur here are not found in the intervening islands of Borneo,
Sumatra, or Java, e.g. Streptaxis, Hypselostoma, Ditropis, Acmella,
and Cyathopoma. The curiously tubed Malay operculates,
Opisthoporus, etc., fail to reach the Philippines proper, although
occurring in Borneo and N. Celebes ; one of them reaches Palawan.
The strikingly Malay genus Amphidromus reaches Palawan, but
no farther (1 sp.), while 2 species reach Mindanao, and one of
these penetrates as far as Bohol and 8. Leyte. Amongst the
slugs, Mariaella occurs again only in the Seychelles, and Vennentia
only in Ceylon.

Land and Fresh-water Mollusca of the Philippines

Streptaxis . 1 Hemiplecta. 11 Trochomorpha 21 Papuina . . I
Ennea . .10 Hemitrichia 15 Endodonta . 1 Phoenicobius. 7
Mariaella . 3 KXesta. . . 2 Plectopylis 3 Cochlostyla 247
Tennentia . 1 Macrochlamys 5 _ Plectotropis 1 Amphidromus 2
Helicarion . 21 Microcystis . 3 Aulacospira 3 Hapalus() . 4
Vitrinopsis 5 Lamprocystis 17 Pupisoma . 1 Hypselostoma 1
Vitrinoidea . 1 Bensonia. . 4 Satsuma 2 Pupa Ae ie!
Rhysota . 17 Vitriniconus 16 Dorcasia 2 -Clausilia; =. ppv
Trochonanina 2 Sitala. . . 2 Chloritis 7 Subulina 3
Euplecta. . 28 Kaliella. . 8 Obbina 19 Prosopeas . 2

—e

x ISLANDS ADJACENT TO THE PHILIPPINES 315
Opeas. . 4 Melania . 50 Hargreavesia. 1 Cyathopoma . 5
Geostilbia 1 Pirena 2; Callia. . . 2 Cyelotus . . 19
Tornalellina 1 Bithynia. 1 Pupinella. . 3 Omphalotropis 3
Succinea . 3 Vivipara. 7 Helicomorpha 4 Helicina . . 18
Vaginula 2 Ampullaria. 5 Coptochilus . 1 Georissa . . 3
Ancylus . 1 Acmella . 2 Alycaeus

Limnaea . 3 Diplommatina4l Leptopoma . 42 Anodonta. . 1
Planorbis 3 Arinia 6 Wagochius .i11 Cyrena. . . 3
Physa 2 Pupina 5 Cyclophorus . 31 Corbicula. . 7

Registoma @ Ditropis . . 7

Islands adjacent to the Philippines.—The Philippines are
connected with Borneo by two distinct ridges or banks of eleva-
tion, which enclose between them the Soo-loo or Mindoro Sea.
There can be little doubt that these ridges represent the
ancient highway of transit, by which Indo-Malay species passed
into the Philippines. The depth of the sea on either side is
profound, ranging from an average of about 1000 fathoms west
of Palawan to 2550 off the south-west coast of Mindanao.

It appears that the fauna of the Soo-loo ridge is definitely
Philippine up to and including Bongao, Sibutu, and Bilatan, the
last islands at the Bornean end of the ridge. On these are found
two species of Cochlostyla and an Obbina.

The Palawan ridge may also be described as more or less
Philippine throughout. One species of Cochlostyla occurs on
Balabac, just north of Borneo, and two on Palawan, but these
are perhaps counterbalanced by the definitely Indo-Malay Amphi-
dromus and Opisthoporus (1 sp. each). At the northern end of
the ridge, on Busuanga and Calamian, the Philippine element
predominates.

Representatives of two remarkable groups of Helix (Camaena
and Phoenicobius) occur along the Palawan ridge and in Mindoro.
The Phoenicobius find their nearest allies in the curious small
group known as Odba, from N. Celebes, the Camaena possibly ina
type of Helix (Hadra) occurring in New Guinea and N.E. Australia.
The only other Helix from the whole of the E. Indies which
bears any resemblance to the Phoenicobius group is H. codonodes
Pfr., which is peculiar to the Nicobars. A few forms assigned to
Camaena also occur in Further India and Siam. It would
appear possible, therefore, that these two isolated groups are a
sort of survival of a fauna which perhaps had once a much
more extended range.

316 CHINA CHAP.

(2) The Chinese Sub-region.—The Chinese Sub-region in-
cludes the whole of China from its southern frontier up to and
including the basin of the Blue or Yang-tse River, together with
the coast district, including Corea, perhaps as far north as Vladi-
vostok, and the outlying islands of Hainan, Formosa, the Loo-
Choo and Bonin groups, and Japan to the north of Niphon. — It
may be divided into two provinces, the Chinese and the Japanese.

(a) The fauna of the Chinese province proper bears, in many
respects, strong marks of relationship to that of India and Siam.
Thus Streptaxis, Helicarion, Macrochlamys, Kaliella, Sitala, Ario-
phanta, Rhysota, Hemiplecta, Diplommatina, Opisthoporus, Ptero-
cyclus, Lagochilus, and Alycaeus all occur, especially in Southern
China. The two points in which the sub-region bears special
marks of individuality are Helix and Clausilia. The sub-genera
of Helix which have their metropolis in China are Satswma,
Cathaica, Aegista, Acusta, Euhadra, Plectotropis, and Plectopylis.
Sinistral forms (compare Fig. 213) are rather prevalent. In
several cases—e.g. Trichia, Gonostoma, Fruticicola—there 1s a
reappearance of forms which appear to belong to well-known
European sub-genera. Clausilia here attains a kind of second
centre of distribution, and is represented by its finest forms,
which belong to several peculiar
sub-genera. The carnivorous Mol-
lusca are not abundant, and are
represented by Rathouisia (a peculiar
genus of naked slug), Hnnea, and
Streptaxis. In the western provinces
Buliminus is abundant in several

Fic. 213.—Helix (Camaena) cica- sub-genera, one of which appears to
tricosa Miill., China.

be the European Napaeus.

There is little which is striking in the operculates, which are
most abundant in the south, and appear to be mainly derived
from Indian and Siamese sources. The occurrence of Helicina
(3 sp.), Omphalotropis (1), Leptopoma (2), and Realia (2), 18
evidence of some influence from the far East. Heudeia is a very
remarkable and quite peculiar form of Helicina with internal
plicae, perhaps akin to the Central American Ceres.

Fresh - water genera are exceedingly abundant, especially
Melania, Unio, and Anodonta. The occurrence of Mycetopus
(a South-American genus) is remarkable. There are several

x CHINA, HAINAN, FORMOSA, AND COREA

LY)

peculiar forms of fresh-water operculates, whose exact position is
hardly yet assured.

Land and Fresh-water Mollusca of the Chinese Province

Rathouisia I -Vrichia .*. 10 Succinea . 8 Leptopoma . 2
Streptaxis 7 Cathaica . . 22 Vaginula. 7 Lagochilus . 10
Ennea . 12 Aegista . .10 Limnaea. 2 Cyclophorus. 18
Parmarion 2 Armandia . 3 _ Planorbis. 6 Coelopoma . 1
Helicarion . 15 Acusta . .15 Melania 44 Pterocyclus . 3
Euplecta . 3 Obbina . . 1 Paludomus 3 Opisthoporus 4
Macrochlamys19 Camaena. . 5. Bithynia . 12 Cyclotus . . 10
Microcystina 2 Euhadra. . 14 Lithoglyphus 3 Scabrina. . 4
Microcystis 7 Plectopylis . 19 Melantho(?). 1 Ptychopoma. 12
Kaliella . . 16 Stegodera . 6 Pachydrobia. 1 Omphalotropis 1
Sitala . 8 Chloritis. . 1 Prososthenia. 2 Realia. . . 2
Ariophanta . 1 Hel. Inc. sed. 39 Stenothyra 2 Pseudopomatias 1
Rhysota 5 Buliminus . 21 Hydrobia. 2 *elicina .. .. 78
Hemiplecta . 1 Buliminopsis 3 Mecongia. 1 Georissa 4
Trochomorpha 2 Buliminidius 3 Oncomelania 9 Heudeia . 1
Limax. 1 Napaeus . .14 Margaracya . 1 Cyelas. 1
Philomycus . 1 Rachis(?). . 4 Rivularia. 4 Corbicula. . 50
Patula. 2 Pupa - « . 10 Delavaya. 1 Unio . 53
Gonostoma . 4 Clausilia. 102 Fenouillia 1 Monocondylaea 1
Metodontia . 2 Opeas. . .12 Vivipara . 34 Anodonta. 55
Vallonia. . 1 LEnuspiraxis . 1 Diplommatina20 Mycetopus 12
Plectotropis . 9 Subulina. . 5 Pupina . . 6 Pseudodon 1
Fruticicola . 11 Stenogyra (?) 12 Alycaeus. . 23 Dipsas. 4
Satsuma . . 14

The island of Hainan, in the extreme south of the sub-region,
has 40 species of Mollusca, 22 of which are peculiar, but there is
no peculiar genus.

The Mollusca of Formosa, although in many cases specifically
distinct, show close generic relationship with those of China.
The characteristic Chinese groups of Helix and Clausilia occur,
and there is still a considerable Indian element in several species
of Streptaxis, Macrochlamys, Kaliella, and Alycaeus. The oc-
currence of two Amphidromus, a genus which, though Siamese,
is not found in China or Hainan, is remarkable.

The peninsula of Corea must undoubtedly be included in the
Chinese sub-region. It is true that the land operculates scarcely
occur, but there are still a number of Clausilia, and several of
the characteristic Chinese groups of Helix are reproduced. In
some points Corea appears to show more affinity to Japan than

318 JAPAN AND NEW GUINEA CHAP.

to China, four of the Helices being specifically identical with
those of Japan, but the peninsula is at present too little explored
for any generalisations to be made as to its fauna in this respect.

(b) Japanese Province—Kobelt distinguishes four groups of
Mollusca inhabiting Japan (a) circumpolar species, actually
occurring in Europe, Siberia, or N. America, or represented by
nearly allied species (these of course do not belong to the
Japanese province as such); () Indo-tropical species; (¢) species
which are Chinese or akin to Chinese; (d) peculiar species, a
mixture of two forms, southern and northern, the latter being
chiefly Hyalinia, Patula, and Fruticicola. Out of a total of 193
Japanese species, at least 164 are peculiar.

The Japanese MHelices belong to sub- genera common to
China (Plectotropis 8, Euhadra 21, Acusta 237); but the
Naninidae scarcely occur at all. The principal feature of the
fauna is the development of Clausilia, which presents some
extraordinarily fine forms. One slug (Philomycus) is identical
with an Indian species. The operculates, which consist mainly
of a few species each of Diplommatina, Cyclophorus, Pupinella,
Pupina, Helicina, and Georissa, belong almost exclusively to the
southern islands Kiu-siu, Sikoku, and southern Niphon. The
three species usually reckoned as Japonia are probably forms of
Lagochilus.

C. The Australasian Region

This region includes all the islands of the Pacific east of the
Moluccas, and falls into three sub-regions—the Papuan, the
Australian, and the Polynesian.

1. The Papuan Sub-region may be divided into—(q) the
Papuan Province proper, which includes New Guinea, with the
Aru Is. and Waigiou, the Admiralty Is, New Ireland, New
Britain, and the d’Entrecasteaux and Louisiade Groups; (0)
the Queensland Province, or the strip of N.#. Australia from
C. York to the Clarence. R. (about 29° S. lat.); (¢) the
Melanesian Province, which includes the New Hebrides, New
Caledonia, with the Loyalty Is. and the Viti Is. The Solomons
form a transition district between the Papuan and Melanesian
provinces, abounding on the cne hand in characteristic Papuan
Helices, while on the other they form the north-western limit of

x NEW GUINEA 319

Placostylus, the group especially characteristic of the Melanesian
province.

(a) The Papuan Province—The molluscan fauna of New
Guinea is the richest and by far the most original of all the
Australasian region. We find ourselves, almost in a moment, in
a district full of new and peculiar forms. New Guinea may be
regarded as the metropolis of the rich Helicidan fauna, which is
also characteristic of the Moluccas to the west, of N. and N.E.
Australiato the south and south-east,andof the Solomons and other
groups to the north-east. Here abound species of Papuina and
Insularia (the latter being quite peculiar), among which are
found, if not the largest, certainly the most finished forms of all
existing Helices. Chloritis (13 sp.), Planispira (5), and Cristi-
gibba (9) are common with the Moluccas, while a_ tropical
Australian element is shown in Pedinogyra (1) and Hadra (4).
Very remarkable, too, is the occurrence of one species of Obbina
and Rhysota, genera which culminate in the Philippines and here
find their most eastward extension ; while a single Corasia serves
to form a link between the Corasza of the Philippines and those
of the Solomon Is., if the latter are true Corasia.

We naturally find considerable traces of a Polynesian element,
which appears to be principally characteristic of the eastern part
of the island. Most noteworthy in this respect is the occur-
rence of Partula (3), Tornatellina (1), Charopa (1), Thalassia
(3). As compared with the true Pulmonata, the operculates are
feebly represented, and the great majority are of a markedly
Polynesian type. Not a single Cyclophorus occurs; Lagochilus,
Alycaeus, and all the tubed operculates, so marked a feature of
the Indo-Malay fauna, are conspicuous by their absence, and the
prevailing genera are Cyclotus, Helicina, and a number of sections
of Pupina. Leptopoma, as in the Philippines, is strongly repre-
sented. Not that an Indo-Malay element is altogether absent.
We still have Yesta (5), Hemiplecta (8), and even Sitala (2), but
the great predominance of Helix seems to have barred the pro-
gress, for the greater part, of the Indian Naninidae.

The slugs appear to be represented by a solitary Vaginula.
A single Perrieria is a very marked feature of union with
(Jueensland, where the only other existing species (P. australis)
occurs. The solitary Rhytida, so far the only representative of
the carnivorous group of snails, emphasises this union still

320 NEW GUINEA AND ARU IS. CHAP.

further. Little is known of the fresh-water fauna. Melania
(28 sp.) is predominant, but on the whole the relations are
Australian rather than Indo-Malay. Ampullaria is wanting,
while a decisive point of similarity is the occurrence of Jsidora
(3 sp.), a genus entirely strange to the Oriental region, but
markedly characteristic of the Australasian.

Land and Fresh-water Mollusca of New Guinea

Rhytida . Il “Thalassia. 3 ‘Calycia; ; 4 Diplommatina 1
Helicarion 2 Ochthephila(?) 1 Partula . 3 Pupna 2? 252
Rhysota . 1 Chioritis. . 13 Pupa. 1 Pupinella .. 3
Hemiplecta. 11 Planispira . 5 Stenogyra 1 Omphalotropis 2
Xesta. 2 Cristigibba . 9 ‘Tornatellina 1 Bellardiella. 2
Microcystis . 3 Insularia 17 _—« Perrieria. 1 Leptopoma . 16
Microcystina 2 Obbina 1 Succinea. L _ Cyclotus: eo
Sitala 2 Albersia . 3 Vaginula 1 Cyelotropis. 5
Oxytes (?) 2 Hadra 4 lLimnaea. 2- Helicina. . 15
Conulus . 1 Pedinogyra . 1 Isidora 3 Umo - 4
Trochomorpha 8 Papuina . 35 Melania . 28 Cyrena 3
Nanina (?) 3 Corasia (?). 1 Faunus . 1 Corbicula 1
Charopa . Ll) Bulimus((@).: 1 Viviparay: 4 Batissa 8

Waigiow is practically a part of New Guinea. Twelve
genera and twenty species of Mollusca are known, eight of the
latter being peculiar. The occurrence of Papuina, Insularia,
and Calycia sufficiently attest its Papuan relationship. Two
species each of Albersia, Chloritis, and Planispira occur."

The Arw Js. are, as we should expect from their position, and
particularly from the configuration of the adjacent sea bottom
(see map), markedly Papuan. At the same time they show un-
mistakable signs of long-continued separation from the parent
island, for of their 36 land Mollusca 15, and of their 20 fresh-
water Mollusca 9 are peculiar. The Papuan element consists in
the presence of Papuina, Albersia, and Cristigibba. Moluccan
influence is not absent, for the three Helicina, the Albersia, and
one Cyclotus are all Moluccan species. The fresh-water fauna
appears to be a mixture of varied elements. The single
Segmentina is common to India, the Glauwcomya to Malacca and
the Philippines, while the single Batissa is also found in New
Zealand.

1 Mysol, with 2 Chloritis, 1 Insularia, 1 Cristigibba, is decidedly Papuan.

x LOUISIADES AND SOLOMON ISLANDS 325

Land and Fresh-water Mollusca of the Arw Islands.

Xesta . 4 Chloritis . 5 Planorbis LV Cyclotus.. = 3
Microcystis . 1 Cristigibba 2 Segmentina. 1 Helicina. . 3
Hyalinia (?). 1 Albersia . 1 Melania. .14 Cyrena 7.2
Trochomorpha 1 Papuina . 4 Leptopoma . 3 Glaucomya . 1
Patula lL Bupa e 2 Moussonia 1 Batissa 1
Eulota 1 Stenogyra 2 Realia i

The Lowisiades, the d’Entrecasteaux, and Trobriand Is., and
Woodlark I., are closely related to New Guinea, containing no
peculiar genera. Each group, however, contains a considerable
proportion of pecuhar species, an indication that their separation
from New Guinea dates from a very distant period. From the
Louisiades are known 34 species in all, 22 of which are peculiar.

The fauna of the Admiralty Js., of New Hanover, and New
Ireland is markedly Papuan, without any especial feature of
distinction. The Admiralty Is. contain 15 sp. Papuina, 7
Chloritis, 1 Planispira, and 1 Corasia. <A single Janella shows
relationship with the New Hebrides and with New Zealand. In
New Ireland Planispira (which is specially characteristic of W.
New Guinea and the Moluccas) has disappeared, but there are 7
Papuina and 6 Chloritis. The essentially Polynesian Partula is
present in both groups.

The prominent feature of the Mollusca of the Solomon Js. is
the extraordinary development of Papuwina, which here cul-
minates in a profusion of species and singularity of form. The
genus is arboreal, crawling on the branches and attaching itself
to the leaves of trees and underwood. Of the 140 land
Pulmonata known from the group, no less than 50, or 36 per
cent, are Papuina. Ten species of Corasia occur, but whether
the shells so identified are generically identical with those of the
Philppines, is not satisfactorily determined. Trochomorpha,
with 22 species, here attains its maximum. Chloritis begins to
fail, but still has 3 species. Indo-Malay influence still appears,
though feebly, in Hemiplecta (3), Xesta (1), and possibly even
Macrochlamys (1). The Rhytida, the 3 Hadra, and possibly
the Paryphanta represent the Australian element. The grow-
ing numbers of Partula (13), the small and inconspicuous land
operculates (only 22 in all, with Helicina very prominent), and
the almost complete absence of fresh-water bivalves, show signs
of strong Polynesian affinities. An especial hnk with the New

VOL. III Y

322 SOLOMON IS. AND QUEENSLAND CHAP.

Hebrides, New Caledonia, and the Viti Is. is the occurrence of
Placostylus (16 sp.). It is very remarkable that this genus
should occur in the Solomon Is. and not in New Ireland. The
occurrence of Streptaxis, if authentic, 1s very noteworthy, the
nearest species being from the Philippines.

Land and Fresh-water Mollusca of the Solomon Islands.

Streptaxis (?) 1 ‘Trochomorpha 22 Merope . . 1 Pupina 4
Rhytida . 1 Nanina (?). . 2 Corasia(?) . 10 Leptopoma 4
Paryphanta(?) 1 Patula. . . 1 _ Placostylus . 16 Omphalotropis 2
Helicarion 2 Thalassia . . 2 Partula . . 18 Cyclotus; 1
Xesta . b Chloritis” ~ . 3 ~ Suecinea., . 1 Cyclotropisyaae2
Macrochlamys 1 Philina. © . 2 Melania . . 18 Helicma 7
Hemiplecta. 3 Hadra. . . 3 Diplommatina 2 Unio 1
Microcystis . 2 Papuina . . 50

(b) The Queensland Province-—The strip of coast-line from Cape
York to the Clarence R. stands apart from the rest of Australia,
and is closely connected with New Guinea. There can be little
doubt that it has been colonised from the latter country, since
an elevation of even 10 fathoms would create (see map) a wide
bridge between the two. Many of the genera are quite strange
to the rest of Australia. Land operculates are abundant, and of
a Papuan type. Several of the characteristic Papuan genera of
Helix (Papuina, Chloritis, Planispira) occur, while Hadra attains

Fic. 214.—Characteristic Aus-
tralian Helices:- A, H.
(Hadra) pomum Pfr.; B,
H. ( Thersites) richmondiana
Bir as:

its maximum. Panda, Pedinogyra, and Thersites are three remark-
able groups in a rich Helix fauna. Parmacochlea is a peculiar
form akin to Helicarion. The carnivorous Mollusca are repre-
sented by Rhytida, Diplomphalus (New Caledonia), and Elaea.
One species of Janella, a slug peculiar to this region, occurs.
The predominant fresh-water genus is Bulinus (Isidora). -Am-
pullaria and Anodonta are entirely absent from Australia and
New Zealand.

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x QUEENSLAND AND NEW CALEDONIA 323

Land Mollusca of the Queensland Province

Diplomphalus 1 = Macroeyelis (?) 1 Helix(ine.sed.)6 Janella. . 1
Rhytida. .10 © Helicella .10 Bulimus(?) 1 Georissa. . 1
Blaea.. . 1 # £Planispira . 8 #Stenogyra . 1 Pupina . . 16
Parmacochlea 1 Hadra . . 51 #£Tornatellina 4 £Hedleya . |
Helicarion . 7 Chloritis poe Bupac, . . 38) ‘Calliast 27
Nanina . . 3 £Pedinogyra. 1 Vertigo . . 4 #£Diplommatina 3
Hyalinia .10 ‘Thersites | Perrieria 1 Ditropis. . 2
Thalassia . 4 Papuina. . 6 £Succinea. . 3 #£Dermatocera 1
Charopa. . 5 Panda .. 2 #£Vaginula . 1 # Helicina. . 8
Patula (?) . 4

(¢) The Melanesian Province includes those islands on which
the remarkable group Placostylus occurs, the metropolis of whese
distribution 1s New Caledonia. These islands are very possibly
the remains of what was once a much wider extent of land.
A single species of Placostylus occurs both on Lord Howe's I.
and in the North I. of New Zealand, but this fact, while
highly interesting as indicating a possible former extension
of land in a south-easterly direction, is hardly sufficient to bring
these islands within the province as now limited. The Solomon
Is., although contaiming Placostylus as far to the west as Faro
L, form, as has been already stated, a transitional district to the
Papuan province.

New Caledonia.—tThe chief features of the Mollusca are the
remarkable development of the helicoid carnivorous genera
Rhytida (30 sp.) and Diplomphalus (13. sp.),
and of Placostylus (45 sp.). There is a stray
Papuina, and a pecuhar form Pseudopartula,
but Helix has almost entirely disappeared.
Polynesian influence is represented by Jicro-
cystis (3 sp.), the so-called Patula (13 sp.,
many of which are probably Charopa), Torna-
tellina (2 sp.), and Helicina (20 sp.). Partula
does not reach so far south, but there are two
species of Janella. The recurrence of JZel-
anopsis (19 sp.), absent from the whole Oriental

region, 18 curious, and forms another link

5 — < : cae : Mra 91%.— Piaeoe .
with New Zealand. The curious sinistral Lim- PF! 215.—Placostylus

caledonicus Pet.,

naea (Isidore), common with Australia and = New Caledonia.
New Zealand, is abundant. gat

The New Hebrides link New Caledonia and the Solomons by

324 THE FIJI IS. AND SOUTH AND WEST AUSTRALIA CHAP.

their possession of the typical heavy Placostylus (5 sp.) of the
former, and the lighter and more elegant Charis (2 sp.) of the
latter. There are 4 Papwina, and Partula is abundant (18 sp.),
but there is no evidence at present that the carnivorous genera
or the Melanopsis and Isidora of New Caledonia occur.

The Fiji Is., by the possession of 14 Placostylus of the Charis
section, which is entirely absent from the adjacent Tonga group,
form the eastern lmit of the province. There appears to be
only a single Partula, but the Polynesian element, especially as
seen in Navicella (8 sp.), Neritina (20 sp.), Helicona (11 sp.),
and Omphalotropis (11 sp.), is very strong. The Microcystis (9
sp.) and 7rochomorpha (14 sp.) are also of a Polynesian type.

(2) The Australian Sub-region includes the whole of Australia
(with the exception of the Queensland province) and Tasmania,
with New Zealand and the off-lying islands. The fauna, from
the prevalence of desert, is scanty, especially in genera. Land
operculates are almost entirely wanting. imax is not indi-
genous, though several species have become naturalised. The
bulk of the fresh-water species belong to /sidora, and it is doubt-
ful whether Physa occurs at all. Unio has a few species, and
also Vivipara, but neither Anodonta nor Ampullaria occur.
There are a few Melania and Neritina.

Tropical South Australia.—The Mollusca are scanty, and
occur chiefly in the neighbourhood of the rivers, the soil being
arid, with no shelter either of trees or rocks. Fresh-water
species predominate, and the rich land fauna of Queensland is
totally wanting. There are no land operculates, 6 Hadra, 1
Bulimus (2), 1 Stenogyra.

West Australia.—Owing to the deserts which bound it, the
Mollusca are very isolated, only one species being common
with N., S., and E. Australia. The chief characteristics are
LIiparus, a form intermediate between Heliz and Bulimus, and,
among the Helices, the group Rhagada. There are no slugs, no
carnivorous snails, and only three land operculates.

Land Mollusca of West Australia.

Lamprocystis 1 Gonostoma. 2 MHadra . . 5 Cyclophorus 2
Hyalinia. . 1 Trachia . 3 Inparus . =. 10 Heliema. ya
Patula . . 7 Xerophila TL) ‘Pupa ers one
Chloritis . 2 Rhagada 8 Succinea. . 3

x EAST AUSTRALIA, TASMANIA, AND NEW ZEALAND 3

In Lastern and Southern Australia (New South Wales,
Victoria, and South Australia) the tropical element, so abundant
in Queensland, almost entirely disappears, the last operculate (a
Helicina) only reaching Port Macquarie, though several species
of Helicarion occur in the extreme south. Hadra is still abun-
dant in New South Wales (18 sp.) and S. Australia (10 sp.), but
becomes scarce in Victoria (2 sp.); New South Wales has also
one Panda and two Thersites. Cystopelta is common with Tas-
mania, and one of the Janellidae (Aneitea) with Queensland.
The carnivorous snails are represented by Rhytida. Caryodes, a
bulimoid group perhaps akin to Liparus, is common with
Tasmania only.

Tasmania.—About 80 species of land Mollusca are known,
not more than 10 being common with Australia. No land
operculates occur; Hndodonta and Charopa are rare, and
Hadra has entirely disappeared, but Pupa and Succinea occur.
Carnivorous genera are represented by Paryphanta, Rhytida, and
Rhenea. Anoglyptaisa peculiar section of Heliz, while Caryodes,
Cystopelta, and Helicarion are common with Australia. Among
the fresh-water Mollusca are a Gundlachia (see p. 345), and some
forms of Amnicola or Hydrobia, one of which (Potamopyrgus) is
common only with New Zealand.t

The Neozealanian Province-—The Mollusca of New Zealand,
with the Kermadec, Chatham, and Auckland Is., are remarkably
isolated. Such genera as Nanina, Partula, Pupa, Stenogyra,
Succinea, Vaginula, Truncatella, Helicina, and Navicella, which
might have been expected to occur, are entirely absent. The
bulk of the land Mollusca are small and obscure forms, perhaps
remains of a very early type, and appear to belong to the
Zonitidae, neither Patula nor Helix occurring at all. The
carnivorous forms are represented by Schizoglossa, a peculiar
genus akin to Daudebardia, by Paryphanta, an extraordinary
group of large shells with a thick leathery epidermis, and by
fthytida and Rhenea. In spite of its extreme isolation, the
general relations of the fauna are partly with New Caledonia,
partly with E. Australia. The occurrence of Placostylus has
already been mentioned (p. 323), and three species of Janella,
a genus which also occurs in Queensland and New Caledonia,

NO
unr

1 See especially C. Hedley, Note on the Relation of the Land Mollusca of Tasmania
and New Zealand, dan. Mag. Nat. Hist. (6) xiii. p. 442.

326 POLYNESIA CHAP.

indicate the same affinity. Otoconcha is peculiar. The fresh-
water Mollusca, besides the J/sidora characteristic of the sub-
region, are partly related to New Caledonia through the oceur-
rence of Melanopsis, partly to Tasmania through Potamopyrgus,
while the peculiar Zatia is possibly akin to Gundlachia (Tas-
mania). The land operculates number only 5 genera and 14
species in all, excluding a doubtful Diplommatina."

Land and Fresh-water Mollusca of the Neozealanian Province

Schizoglossa. 1 Gerontia . 2. Placostylus 1 Melanopsis . 2
Paryphanta . 5 Allodiseus . 10 Carthaea . 1 Potamopyrgus 4
Rhytida 6) Pyrrha = = 1) Vornatellima 1) Paxillus ]
Rhenea 2 'Therasia 7 Janella 3 Lagochilus 7
Helicarion 1 Phenacohelix 3. Latia 2 Omphalotropis 1
Otoconcha ie outeriaee-. 2) sleee-neyhins 2 Realia. 4
Microcystis 1 Flammulina. 13 Limnaea . 5 Hydrocena 1
Trochonanina 1 Laoma . .23 Amphipeplaa 2 Unio... 9
Phacussa . 3 Endodonta . 10 Planorbis. 1 Sphaerium 1
Thalassohelix 5 Charopa . . 28 Isidora 7 Pisidium . 2

Lord Howe's I. is remarkable as containing a Placostylus,
which thus links the island with this province. The remainder
of the fauna is Polynesian, with the exception of a species
(common to the Fijis) of Parmella, a slug akin to Helicarion,
Parmacochlea, and Cystopelta.

(3) The Polynesian Sub-region includes all the island groups
of the central and southern Pacific (except those classified in the
Papuan and Australian sub-regions), from
the Pelews and Carolines in the west to
the Marquesas and Paumotus in the east,
and from the Tonga group in the south
to the Sandwich Is. in the north. It may
be subdivided into (@) the Polynesian pro-
vince proper, and (+) the Hawaiian pro-

Fic. 216. — Characteristic Vince, which includes the Sandwich Is.
Polynesian Mollusca: A, , 7
only.

Achatinella vulpina Fer., nly

Sandwich Is.; B, Par- (a) The general features of the Poly-

tula planilabrum Pease, , es iian A STEERS an ware xen elinap P
Shay ek nesian province are very similar through-
out, although the Mollusca of each island
group are in the main pecular. The species are mostly small

’ Hedley and Suter, Proc. Linn. Soc. N. S. Wales (2), vii. p. 618. Twenty-one
species are ‘‘ introduced.”

x SANDWICH ISLANDS 220,

and obscure. Helix scarcely occurs, its place being taken by
small Zonitidae (Microcystis, Charopa, Trochomorpha, ete.), and
by groups of so-called Patula (Endodonta, Pitys, etc.), the exact
position of which is not yet settled. Libera, remarkable for its
method of ovipositing (p. 128), is peculiar to the Society and
Hervey Is.; Partula is almost universal, attaining its maximum
(40 sp.) in the Society Is.; Zornatellina, Pupa, and Vertigo occur
throughout.

The land operculates consist chiefly of Omphalotropis, Pupina,
Realia, and Helicina. Diplommatina and Palaina are abun-
dant on the Pelews, and a J/oussonia occurs in the Samoa Is.
Ostodes, a small form of Cyclophorus, is found in some of the
southern groups. The fresh-water operculates are JJelania,
Neritina Gncluding Clithon, a sub-genus furnished with spines),
and Navicella; there are no Unionidae, while fresh-water
Pulmonata are very scarce.

(>) The land Mollusca of the Hawaiian province are dis-
tinguished by the possession of four entirely peculiar genera
Achatinella, Leptachatina, Carelia, and Auriculella. More than
300 of the two former genera have been described, every moun-
tain valley of some of the islands having its own peculiar species.
The destruction of the indigenous herbage by goats is rapidly
extinguishing many forms. Partula, and the small land oper-
culates, so characteristic of the other groups, are, with the
exception of Helicina, entirely wanting. The occurrence of one
of the Merope group of Helix (Solomon Is.) is remarkable, and
there is a rich development of Succinea. “ Patula,”’ Microcystis,
Tornatellina, and the other small Polynesian land Pulmonata
are well represented. The presence of Jsidora, absent from the
central Pacific groups, is remarkable, and Hrinna is a peculiar
genus belonging to the Limnaeidae.

CHAPTER. XI

GEOGRAPHICAL DISTRIBUTION OF LAND MOLLUSCA (continued )—
THE ETHIOPIAN, NEARCTIC, AND NEOTROPICAL REGIONS

D. The Ethiopian Region

THE Ethiopian region includes the whole of Africa south of the
Great Desert, and Southern Arabia, together with the outlying
islands, excepting those of the Atlantidean province (p. 297).

Regarded as a whole, the Ethiopian is poorest in land Mollusca
of all the tropical regions. And yet its characteristics are very
remarkable. The entire Achatina group is pecular, and takes,
especially in W. Africa, some curious forms (Columna, Perideris,
Pseudachatina). Carnivorous Mollusca (Hnnea, Gibbus, etc.) are
highly developed, especially in the south and east, the largest
known helicoid form (Aerope) being from Natal. In the posses-
sion of these types of the Agnatha, Africa is more closely related
to the Australasian than to the Oriental region. The true Cyclo-
stoma are entirely peculiar to the region, but are absent from
West Africa.

Fresh-water Mollusca are abundant and characteristic, especi-
ally im and near the Great Lakes. Lanistes, Cleopatra, and
Meladomus, among the operculates, together with JMJutela and
Actheria (Unionidae), Galatea and Fischeria (Cyrenidae), are
peculiar.

In its negative, as well as its positive features, the Ethiopian
region is markedly isolated. Helicidae and Naninidae are equally
deficient, the former, indeed, attaining some numerical predomin-
ance in the extreme south, but the species are nearly all insignifi-
cant in size and colouring. It is only in Madagascar that
Hleliz asserts itself. Arion, Limax, Hyalinia, Clausilia, and a

CHAP. XI CENTRAL AFRICAN SUB-REGION 329

number of other genera abundant along the Mediterranean, are
either altogether absent, or are very scantily represented. Land
operculates, so characteristic of other tropical countries, are almost
entirely wanting. If we disregard the Malagasy sub-region, there
are scarcely forty species of land operculates on the whole
African continent.

The Ethiopian region may be divided into three sub-regions :
(1) the Central African: (2) the South African; (3) the
Malagasy.

(1) The Central African Sub-region is bounded on the north
by the Great Desert, on the east and west by the ocean, and on
the south by a line roughly drawn between the mouth of the
Orange River and Delagoa Bay; it also includes S. Arabia. No
natural features exist which tend to break up this vast district
into areas of independent zoological development. The absence of
long and lofty mountain ranges, the enormous size of the great
river basins, and the general uniformity of climate, equalise the
conditions of life throughout. It will be convenient to break
the sub-region up into provinces, but in most cases no precise
line of demarcation can be laid down.

(a) The Senegambian Province may be regarded as extending
from the mouth of the Senegal River to Cape Palmas. Only 8
genera of land Mollusca are known, including 4 Limicolaria and
3 Thapsia, with 1 small Cyclophorus. Fresh-water genera are
abundant, and include most of the characteristic Ethiopian forms.

(b) The West African Province extends from Cape Palmas to
the mouth of the Congo, and is rich in Mollusca. The great
Achatina, largest of land snails, whose shell sometimes attains a
length of 64 in., Limicolaria, Perideris, and Pseudachatina are
the characteristic forms. The Agnatha are represented by Hnnea,
Streptaxis, and Streptostele. Rachis and Pachnodus, subgenera
of Luliminus, occur also on the east coast. A special feature is
the development of several peculiar slug-lke genera, e.g. Oopelta,
perhaps a form of Arion; Estria, a slug with an external shell,
akin to Parmacella; and Aspidelus, a form intermediate be-
tween Helicarion and Limazx. Claviger, a handsome group
akin to Cerithiwm, is peculiar to the estuaries of West African
rivers.

About sixteen species are known from the Cameroons District,
but no peculiar genera occur. The French Congo District has

330 CENTRAL AFRICAN SUB-REGION CHAP.

not yet been well explored. Tomostele, a genus alhed_ to
Streptostele, is peculiar, and Pseuvdachatina attains its maximun.

St. Thomas and Princes Is., in the Gulf of
Guinea, are well known. Princes I. has 22
species, 14 peculiar, and 2 common to St. Thomas
only, one of the latter being the great sinistral
Achatina bicarinata Chem. The remarkable
genus Columna (Fig. 217) is peculiar, and
Streptostele (4 sp.) attains its maximum. Peculiar
to St. Thomas are Pyrgina, a turreted form of
Stenogyra ; Thyrophorella, a sinistral form of
Zonites; and Atopocochlis, a large bulimoid
shell, whose true relationships are not yet known.
Homorus, a group of Achatina with an elongated
spire, occurring also in the Angola District and
on the east coast, has 4 species. No fresh-water
Fic. 217.—Columna species have as yet been discovered in either of

flammea_ Mull, the islands.

Princes I.

The Angola and Benguela District, extend-
ing from the Congo to the Cunene R., probably belongs to the
West African Sub-region, but until its fauna is better known
it is advisable to consider it apart. Achatina continues
abundant, but the other characteristic West African forms
(Pseudachatina, Streptostele, Perideris) diminish or are absent
altogether. No Helix and only 1 Cyclophorus occur.

Ovampo, Damara, and Great Namaqualand, lying between
the Cumene and Orange rivers, seem to form a_ transition
district between the West and South African faunas. Helis
reappears, while the characteristic West African genera are
alinost entirely wanting.

(c) The Hast African Province extends from about Delagoa
Bay to the Abyssinian shores of the Red Sea. In general out-
line the province consists of a flat marshy district, extending
inland for many miles from the sea; this is succeeded by rising
ground, which eventually becomes a high table-land, often
desolate and arid, whose line of slope lies parallel to the trend of
the coast. The Mollusca are little known, and have only been
studied in isolated districts, usually from the discoveries of
exploring expeditions.

The Mozambique District, from Delagoa Bay to Cape Delgado,

XI EASTERN AFRICA—-THE GREAT LAKES Bisel

includes no genus which does not occur on the west coast, except
Cyclostoma (2 sp.) Trochonanina (4 sp.), Urocyclus, a character-
istic African slug (2 sp.), Rachis (6 sp.), Pachnodus (2 sp.), and
Achatina (5 sp.), are the principal groups.

o FP

i {
—z |
!

. *

S Fic. 218.—Uvrocyclus comorensis
Fisch., Comoro Is. : G, Gen-
erative orifice; M, mucus
gland ; O, orifice leading to
internal shell ; P, pulmonary
orifice ; T, tentacles. (After
Fischer. )

The Zanzibar District, from Cape Delgado to the Somali
country, has the same general features. Meladomus, a large
sinistral Ampullaria, is characteristic, while Cyclostoma (5 sp.)
becomes more abundant. Helix is still absent, but the carnivor-
ous forms (Streptaxis 2 sp., Ennea 7 sp.) are rather numerous.

The Somali District is characterised by operculate groups of
the Otopoma type (Georgia, Rochebrunia, Revoilia) whose generic
value is rather doubtful. Petraeus, in an Arabian type, sup-
plants Rachis and Pachnodus. Achatina is nearly wanting,
but Limicolaria has 9 species. A few Helix, said to be of the
Pisana group, occur.

The District between the Great Lakes and the coast region 1s
fairly well known through recent explorations, especially those
associated with Emin Pasha. Streptavis (6 sp.) and Hnnea
(24 sp.) are numerous, Helix is wanting, and the Naninidae
are represented by Zrochonanina (7 sp.), and other forms at
present grouped under Vanina or Hyalinia. On the high ground
Buliminus, Cerastus, and Hapalus replace, to some extent, the
Achatina and Limicolaria of the marshy plains. Land oper-
culates (Cyclophorus 1, Cyclostoma 8) ave more numerous ; among
fresh-water genera we have Lanistes (5 sp.), Cleopatra (3 sp.),
Meladomus (1 sp.), and Leroya, a sinistral form with the facies
of a Littorina. The characteristic African bivalves (JJutela,
Spatha, etc.), are few in number.

(d) Province of the Great Lakes—The Mollusca of the four
great lakes of Eastern Central Africa—Lakes Albert Nyanza
(Luta Nzige, 2720 ft.), Victoria Nyanza (Oukéréwé, 3700 ft.),
Nyassa (1520 ft.), and Tanganyika (2800 ft.)—are well known,
and supply an interesting problem in distribution. Those of the

BOY THE GREAT LAKES CHAP.

three first mentioned lakes differ in no way from the rest of
tropical Africa, but the Mollusca of Tanganyika include, in
addition to the ordinary African element, a number of pecular
operculate genera, belonging principally to the Melaniidae and
Hydrobiidae. Several of these possess a solidity of form and com-
pactness of structure which is unusual in fresh-water genera, and
has led to the belief, among some authorities, that they are the
direct descendants of marine species, and that Tanganyika repre-
sents an ancient marine area. This view appears untenable.
The Victoria Nyanza and Nyassa are part of the same system as
Tanganyika, and it is not easy to see how, if Tanganyika were
once an arm of the sea, they were not equally so, especially as
they are several hundred miles nearer the Indian Ocean as at
present defined. Nor, as will be seen from the figures given
above, is there anything in the altitudes which would make us
expect anything exceptional in Tanganyika. The similar case of L.
Baikal must be compared (p. 290), where again a number of
specialised forms of Hydrobia occur.

Of the genera concerned, Paramelania and Nassopsis are
forms of Melanidae; Ziphobia (Fig. 219), which is allied to
Paludomus, is a compact shell with angulated spinose whorls ;
Lacunopsis, Ponsonbya, Limnotrochus, and Tanganyicia are prob-
ably forms of Lithoglyphus, some, as their names denote, being
of decidedly marine facies; Syrnolopsis and Turbonilla (2) look
lke Pyramidellidae, Horea and Reymondia like Rissoina ; Bowr-
guignatia appears to belong to Vivipara, with which has now
been merged the genus Veothawma. Recently discovered forms
from the adjacent L. Mweru are evidently of kindred origin.

(e) The Afro-Arabian Province includes Abyssinia, with S.
Arabia, the African shores of the Gulf of Aden, and Socotra.
The province contains a singular mixture of types. The high
ground of Abyssinia stands like a lofty European island in the
midst of a tropical plain, with Palaearctic genera flourishing hke
hardy northern plants on a mountain in low latitudes. Helia,
Vitrina, and Pupa abound, with a few Clausilia and even a
Inmaz. On the lower levels occur Limicolaria (3 sp.), Subulina
(7 sp.), Helicarion, and Homorus, but land operculates are entirely
wanting. Characteristic of the province as a whole are various
forms of buliminus, which in Socotra are represented by two
peculiar sub-genera, Achatinelloides and Passamaiella. In S.

>i SOUTHERN ARABIA—-SOUTH AFRICA 333

Arabia the mixture of types produces curious results: the Helix,
Clausilia, and Vitrina being Palaearctic, the Limicolaria and
all the operculates Ethiopian, while the single Zrochomorpha
is Indian. Indian influence, indeed, comes out unmistakably

Fie. 220. — Mollusea charac-
teristic of L. Tanganyika: A,
Nassopsis nassa Woodw. ;
B, Spekia zonata Woodw. ;

Fig. 219.—Tiphobia Horei BK. A. Smith, C, Syrnolopsis lacustris KE,
L. Tanganyika. . A. Smith.

throughout the province. Thus in Socotra there are two Cyclo-
topsis, in Abyssinia two Africarion (closely related to the Indian
Girasia), two Microcystis, and a Glessula, and in the Scioa dis-
trict there is a Sita/a. The fresh-water Mollusca of Socotra are
Indian forms.

(2) The South African Sub-region.—The principal charac-
teristic of the Mollusca of §. Africa is
the occurrence of numerous small species
of Helicidae, belonging chiefly to the
groups Pella, Phasis, Doreasia, and
Sculptaria, all of which are practically
peculiar. Carnivorous genera are also
prominent, Hnnew here attaming its
maximum. Rhytida (to which several
species still regarded as Pella belong) is
common only to the 8S. Pacific and Aus-
tralasia, and forms, with /sidora among
the fresh-water pulmonates, a remarkable
link of connexion. <Aerope, the largest
of all helicoid carnivorous genera, and

= B Fic. 221.—<Achatina zebra
Y q 09 , . ve . y a. ‘ A . ry -
Chlamydephorus, « carnivorous slug with Lam., 8. Africa, x }.

an internal shell, are pecuhar. Achatina
is still abundant, but Zimicolaria is wanting. Livinhacea, a

334 SOUTH AFRICA—ST. HELENA CHAP.

form with a continuous peristome, perhaps akin to Bulimus ;
Apera, a torm of slug; and Coeliaxis, a genus perhaps akin to
the Papuan and Queensland Perrieria, are all pecuhar. The
land operculates, which are not numerous, are of the East
African type.

Land Mollusca of the S. African Sub-region.

Chlamydephorus 1 Vitrina 7 Helix(ine.sed.) 4 Stenogyra. 4
Ennea . . . 31 Nanina 6 Rachis . . 1 Coeliaxis 1
Aerope 5 Conulus . 2 Pachnodus .. 3 Succinea 3
Rhytida . 3 Patula 2 Buliminus (?) 4 Vaginula . 2
Helicarion > “3 fella: 44 Pupa. . . 20. Cyclophorusmd
Trochonanina . 1 Doreasia . 8 Vertigo 2 Cyclostoma 7
Trochozonites . 1 Phasis 1 Achatina. . 18 Cyclotus(?) 1
Limax 1 Sculptaria 2 Livinhacea 1 Blanfordia. 1
Apera 1

St. Helena-—The Molluscan fauna of St. Helena is perhaps
the most puzzling, as regards its geographical affinities, of any in
the world. It consists of 29 peculiar species of land Mollusca
(fresh-water species being unknown), 19 of which are recently
extinct, partly owing to the destruction of the forest, but are
found in considerable abundance in a state of good preservation.!
The genera are-—

Hyalinia 1 Bulimulus 7 (5 extinct) Pupa . 2 (extinct)
Patula . 4 (8extinct) Pachyotus 1 (extinct) Succinea 3
Endodonta 10 (7 extinct) Tomigerus (?) 1 (extinct)

The 5 genera which concentrate our attention are Patula,
Endodonta, Pachyotus (Fig. 222), Tomigerus, and Bulimulus, all
of which appear utterly strange to an oceanic island in the middle
of the 8S. Atlantic. Patula and Hndodonta are essentially Poly-
nesian forms, occurring abundantly on all the island groups in
the Central Pacific. Pachyotus, Tomagerus (assuming its correct
identification), and Bulimulus are all 8. American forms, the two
former being especially characteristic of Brazil. How this mix-
ture of genera now confined to regions so widely distant, not only
from St. Helena itself, but from one another, became associated
here, is a problem obviously not easy of solution. The fauna
is probably a remnant of a very ancient type, possibly at one

1 Nine species have been introduced: 6 from Europe, 2 from the West Indies, 1
from the Western Isles.

XI MADAGASCAR ga

time much more widely distributed. Hndodonta (an essentially
insular form, like Omphalotropis) actually occurs on Fernando
Noronha, off the Brazil coast, and we shall see how an Indian
and even a Polynesian element is present off the eastern coasts
of Africa.

Ascension I—One indigenous species, a so-called Limaz, is all
that has ever been discovered.

(3) The Malagasy Sub-region includes Madagascar with its
attendant satellites Bourbon, Mauritius, and Rodriguez, and the
Seychelles and Comoro groups. No land Mollusca are known
from the Amirantes, the Chagos, or from Aldabra. The special
characteristics of the sub-region are the great development of the
carnivorous land Mollusca (Lannea, Gibbus), the occurrence of a
considerable number of true Helicidae of great size and beauty,
and the prominence of the genus Cyclostoma.

(a) Lhe Madagascan Province.—The land Mollusea of Mada-
gascar, although as yet imperfectly known, possess a striking
individuality. Two of the chief characteristics of the Ethiopian
region are the paucity of its land operculate and of its Helix
fauna ; Madagascar is especially distinguished by the rich develop-
ment of both these groups. For size, colouring, and beauty of
shape, the Helicidae of the two subgenera Ampelita and Helico-
phanta vival, if they do not surpass, any in the world. They
are quite peculiar to this sub-region, not a trace of them occur-
ring on the Mascarenes, Seychelles, or even on the Comoros.
Helicophanta is distinguished by the enormous size of its embry-
onic shell, which persists in the adult (Fig. 223), and in this
respect the group appears to be related to Acavus (Ceylon, Fig.
204) and Panda (N.E. Australia). As is usual when Helix is
well developed, Nanina (about 12 sp.) is proportionately scanty.

The African Bulimini (Pachnodus and Rachis) are repre-
sented by two species, but Achatina, so abundant on the main-
land, is scarce. Two other groups of Buliminus, Leucotaenia
and Clavator, are peculiar. The presence of a single Kaliella,
specifically identical with a common Indian form, is very
remarkable.

Cyclostoma proper, of which Madagascar is the metropolis,
is richly developed (54 sp.). Many of the species are of great
size and of striking beauty of ornamentation. Unlike its Heli-
cidae, this genus is not restricted to Madagascar; several species

336 MADAGASCAR CHAP.

occur on the mainland, 6 on the Comoros, one on the Seychelles,
and 16 in Mauritius. The sub-genera Acroptychia and Hainesia
are peculiar.

The fresh-water Mollusca of Madagascar contain further

Fic. 222.—Pachyotus. auris Fig. 223. — Helix (Helicophanta)
vulping Desh., St. Helena Souverbiana Fisch., Mada-
(sub-fossil). gascar, showing embryonic

shell, x 2.

traces of Indian relationship. Thus we find two species of
Paludomus, a genus whose metropolis is Ceylon, India, and
Further India, and which is barely represented on the Seychelles
and in the Somali district. Melanatria, which is peculiar to
Madagascar, has its nearest affinities in the Cingalese and Kast
Indian faunas. Several of the I/elania and the two bithynia
are of a type entirely wanting in Africa,
but common in the Indo-Malay sub-
region. Nota single one of the char-
acteristic African fresh-water bivalves
(Mutela, Spatha, Aetheria, Galatea, etc.)
has been found: in Madagascar. On
the other hand, certain African Gaster-
F1¢.224.—Cyclostoma campanu- opoda, such as Cleopatra and Jsidora,

TTT TE is, MIE IT occur, indicating, in common with the
land Mollusca, that an ultimate land connexion with Africa must
have taken place, but at an immeasurably remote period.

MADAGASCAR—THE MASCARENES

XI SIRs

Land and Fresh-water Mollusca of Madagascar.
Ennea . 9 Leucotaenia. 2 Melania . 7 Cyclostoma . 54
Urocyclus . 2 Clavator. . 2 Melanatria 4 Otopoma . 5
Helicarion (?). 1 Achatina. 3 Paludomus . 2 Lithidion. 1
Macrocyclis (?) 1 Opeas. 2 Vivipara. 1 Acroptychia. 3
Kaliella . . 1 Subulina. 3 Bithynia. 2 Hainesia . 3
Nanina(ine.sed.) 9 Vaginula. 4 Cleopatra 2 Unio 1
Ampelita . . 35 Limnaea. 2 <Ampullaria. 6 Corbicula. 2
Helicophanta. 17 Planorbis 3. Cyclophorus 2 Sphaerium 1
Pachnodus . 2 _ Isidora 3 Cyclotus (?). 1 Pisidium . 1
Bachises)\ .. 2

The Comoro

Islands.—This isolated group

possesses about

100 species, almost all of which are peculiar. The principal
feature is the rich development of Znnea (30 sp.) On the whole
the group shows more relationship to Madagascar than to the
mainland. Thus we have six species of true Cyclostoma, and
only one Achatina, while among the fresh-water genera is
Septaria, which is characteristic of the whole Malagasy Sub-
region, but is absent from the mainland. The Helicidae are all
of insignificant size. Peculiar to the group is the remarkable
genus Cyclosurus (Fig. 152, p. 247).

(b) The Mascarene Province (Mauritius, Bourbon, Rodriguez,
and the Seychelles)——The percentage of peculiar species, which
is very high, can only be paralleled in the case of some of the
West Indian islands, and sufficiently attests the extreme isola-
tion of the group from Madagascar. We have—

Fresh-water Peculiar to

Total sp. Land sp. sp. Peculiar. group.
Mauritius 2 kT3 104 9 78 102 (90 p.c.)
Bourbon 45 40 5 19 38 (84 p.c.)
Rodriguez . 23 19 4 15 21 (95 p.c.)
Seychelles . 34 27 7 24 30 (90 p.c.)

The Mollusca of the group exhibit three distinct elements,
the Indigenous, the Madagascan, and the Indian and Austra-
lasian.

The genus Pachystyla (Naninidae) is quite peculiar, forming
the main portion of the land snails proper. It attains its maxi-
mum in Mauritius (17 sp.), with 5 sp. in Bourbon and one
sub-fossil sp. in Rodriguez, while in the Seychelles it is absent.
But the principal feature of the Mascarene group is the extra-
ordinary development of the carnivorous genus Gibbus, which has

VOL. III Z

338 RELATION OF THE MASCARENES TO INDIA CHAP.

27 sp. in Mauritius, 8 in Bourbon, 4 in Rodriguez; in the
Seychelles it is replaced by Hdentulina and Streptostele. The
principal link with Madagascar is
found in a‘part of the operculate
land fauna. Cyclostoma is present
(with Otopoma) in several fine
living forms, and the number of
sub-fossil species is a clear indi-
cation that this group was, not
long ago, much more abundant,
for of the 16 Cyclostoma known

from Mauritius 10 are sub-fossil.
ue 225. — Characteristic Mauritian The operculates form a decided

and shells: A, Gibbus palanga Fer. ;

A’, young of same; B, Gibbus lyone- feature of the land fauna; thus

Hanes ol in Mauritius there are 32 species,
or more than 28 per cent of the whole.

Indian and Australasian affinities are unmistakably present.
Thus Omphalotropis, a genus characteristic of small islands, 1s
profusely represented, but it does not occur in Madagascar or
Africa. Two Helicina (Mauritius and Seychelles) and a single
Leptopoma (possibly a Leptopomoides) are also of eastern relation-
ship. Cyclotopsis, Cyathopoma, and Geostilbia are markedly
Indian genera. Microcystis, Patula, and Tornatellina are Poly-
nesian. Hyalimax—and this is a very striking fact—occurs
nowhere else but in the Andamans and Nicobars, and on the
Aracan coast. The nearest relation to the Seychelles Mariaella
appears to be the Cingalese Vennentia. Not a single repre-
sentative of these eleven genera has been found even in Mada-

gascar.

The fresh-water Mollusca (omitting the Neritidae) are:
Mauritius 9 species, Bourbon 5, Rodriguez 4, Seychelles 6, with
only 15 species in all. The one Planorbis and the Vivipara,
the Paludomus and two of the Melania are of Indian types. The
Lantzia (peculiar to Bourbon) is probably allied to the Indian
Camptonyx. Owing to the paucity of permanent streams, no
fresh-water bivalves occur. Among the Neritidae is a single
Septaria, a genus which, though occurring in Madagascar, is
entirely strange to Africa, and is abundant in the Oriental and
Australasian regions.

It would seem probable that when the closer connexion which

XI THE NEARCTIC REGION Boo

at one time undoubtedly existed between India and Eastern
Africa began to be less continuous,’ the Mascarene group was
first severed from what ultimately became Madagascar, while the
Seychelles, and perhaps the Comoros, still continued united to it.
The Comoros, which lack the great Helices, separated off from
Madagascar first, while thé Seychelles continued in more or less
direct union with that island sufficiently long to receive the pro-
genitors of Stylodonta (a peculiar group of Helia), but became
disunited at an exceedingly remote period.

E. The Nearctic Region

The southern boundary of this region may be regarded as
roughly corresponding to that of the United States, 7.e. Lower
California and Mexico are excluded. The southern portion of
Florida belongs to the Antillean sub-region.

The principal characteristic of the Nearctic Region is the
remarkable poverty of its land Mollusca. No district in the
world of equal extent 1s so poor in genera, while those which
occur are generally of small size, with scarcely anything re-
markable either in colouring or form. The elongated land shells
(Clausilia, Buliminus), so characteristic of Europe, are entirely
wanting, but a few Lulimulus, of Neotropical origin, penetrate
Texas, and from the same sources come a few species of Glandina
(as far north as 8. Carolina), Holospira (Texas), and Helicina.

The region falls into two well-marked sub-regions, the N.
American and the Californian, with the Rocky Mountain district
as a sort of debatable ground between them. The Californian
sub-region cousists of the narrow strip of country between the
Sierra Nevada, the Cascade Mountains and the coast-line, from
San Diego to Alaska; the N. American sub-region consists of the
remainder of the region.

(1) The N. American Sub-region.—The carnivorous genera
are represented solely by the few Glandina mentioned above,
and by the indigenous genus Selenites, a form mid-way between
Testacella and Limax, whose metropolis is on the Pacific slope,

1 It is by no means implied that wnabroken land communication between India
and Madagascar, across the Indian Ocean, ever existed. A series of great islands,
whose remains are attested by the Chagos and other banks, would be quite sufficient
to account for the results, as we find them. See especially Medlicott and Blanford,
Geology of India, vol. i. p. Ixviii.:

340 NORTH AMERICA CHAP.

but which spreads eastward into the Antilles. Among the
Limacidae, Limax is common to both sub-regions, but Zebenno-
phorus (4 sp. 3 of which belong to the genus Pallifera), a
genus found also in China and Siam, and Vitrinozonites do not
occur in the Californian. Hyalinia (Zonites) is fairly abundant,
especially in the groups JJesomphiz and Gastrodonta (peculiar
to this sub-region), and Hyalinia proper. Patula is well re-
presented. The Helicidae belong principally to the groups
Mesodon, Stenotrema, Triodopsis, Polygyra, and Strobila, only 6
of which, out of a total of 84, reach the Pacific slope. Land
operculates are conspicuous for their almost complete absence
(see Map, frontispiece).

The poverty of the land fauna is atoned for by the extra-
ordinary abundance and variety of the fresh-water genera. A
family of operculates, the Pleuroceridae, with 10 genera and

Fic. 226. — Characteristic
North American Mol-
lusca. A, Helix (Me-
sodon) palliata Say,
Ohio. B, Helix (Poly-
gyra) cereolus Mihlf.,
Texas. ©, Patula al-
ternuta Say, Tennessee.

about 450 species, is quite peculiar, a few stragglers only reach-
ing Central America and the Antilles. The nucleus of their
distribution is the Upper Tennessee River with its branches, and
the Coosa River. They appear to dislike the neighbourhood of
the sea, and are never found numerously within 100 miles
of it. They adhere to stones in rapid water, and differ from the
Melaniidae of the Old World and of 8S. America in the absence
of a fringe to the mantle and in being oviparous. They do not
oceur north of the St. Lawrence River, or north of U.S.
territory in the west, or in New England. Three-quarters of
all the known species inhabit the rough square formed by the
Tennessee River, the Mississippi, the Chattahoochee River, and
the Gulf of Mexico. The Mississippi is a formidable barrier to
their extension, and a whole section (7rypanostoma, with the
four genera Jo, Pleurocera, Angitrema, and Lithasia) does not
occur west of that river. The Viviparidae are also very largely
developed, the genera Melantho, Lioplax, and Tulotoma being
peculiar. The Pulmonata are also abundant, while the richness

XI NORTH AMERICA—CALIFORNIA 341

of the Unionidae may be gathered from the fact that Wetherby
states? that in 1874 no less than 832 species in all had been
described.

The entire Mississippi basin is inhabited by a common
assemblage of Unionidae, and a considerable number of the
species are distributed over the whole of this area, Texas, and
parts of E. Mexico. Some species have spread out of this area
into Michigan, Canada, the Red River, and Hudson’s Bay district,
and even into streams in New York which drain into the
Atlantic. An entirely different set of forms occupy the great
majority of the rivers falling into the Atlantic, the Appalachian
Mountains acting as an effective barrier between the two groups
of species, which appear to mingle below the southern end of the
range. In many cases Unionidae seem to have no difficulty in
migrating from river to river, if the distance is not extreme;
they probably are carried across overflowed districts in time of
flood?

(2) The Californian Sub-region is markedly distinct from
the rest of N. America. The characteristic sombre Helices
of the Eastern States are almost entirely
wanting, and are replaced by Arionta (20
sp.), a larger and more varied group, which
may have some affinity to Chinese forms.
Glyptostoma (1 sp.) is also peculiar. Se/e-
nites here has its metropolis, and Pristiloma
is a remarkable group of small Hyalinia
(Zonites), but the larger forms of the Eastern
States are wanting. Several remarkable p.. 997 — woe (Ane.

and quite peculiar forms of slug occur, onta) fidelis Gray,
Oregon.

namely, Ariolimaa (whose nearest relation is
Arion), Prophysaon, Hemphillia, and Binneya. There are no
land operculates.

Not more than 15 to 20 species of the Pleuroceridae (sect.
Goniobasis) occur west of the Rocky Mountains, and only a single
Unio, 5 Anodonta, and 1 Margaritana, which is common to
New England. Pompholyxz is a very remarkable ultra-dextral
form of ZLimnaea, apparently akin to the Choanomphalus of

1 Journ. Cine. Soc. Nat. Hist. iii. p. 317. The number is doubtless susceptible

of very considerable reduction, say by one-half at least.
2 Simpson, dmer. Nat. xxvii. 1893, p. 354.

342 THE NEOTROPICAL REGION CHAP.

L. Baikal. Lithynia, absent from the Kastern States, is repre-
sented by two species. The general indications are in favour of
the Californian fauna having migrated from an Old World source
after the upheaval of the Sierras; the American fauna, on the-
other hand, is purely indigenous, with no recent Old World
influence at all.

Land Mollusca of the Nearctic Region

Glandina 4 Pristiloma . 2 Praticola . 2 Strobila 2
Selenites 6 Tebennophorus 4 Glyptostoma 1 Pupa 18
Limax . 4 Arioimax . 6 Mesodon 27 Vertigo 8
Vitrina 4 Prophysaon. 2 Stenotrema . 11 Holospira 2
Vitrinozonites 1 Hemphillia. 1 Triodopsis 21 Cionella 1
Mesomphix 15 Binneya. . 1 Polygyra . 23 Bulimulus 6
Hyalinia . . 22 Patula . . 18 Polygyrella. 2 Macroceramus 1
Conulus 1 Punctum . 2 Gonostoma . 1 Succinea 21
Gastrodonta 9 Arionta . -. 20 Vallonia. 1 Vaginulus. 1

lsigheanie, . 5 2

F. The Neotropical Region

The land Mollusca of the Neotropical Region stand in com-
plete contrast to those of the Nearctic. Instead of being scanty,
they are exceedingly abundant; instead of being small and
obscure, they are among the largest in size, most brilliant in
colour, and most singular in shape that are known to exist. At
the same time they are, as a whole, isolated in type, and exhibit
but httle relation with the Mollusca of any other region.

The most marked feature is the predominance of the peculiar
genera Bulimus and Bulimulus, the centre of whose develop-
ment appears to he in Peru, Ecuador, and Bolivia, but which
diminish, both in numbers and variety of form, in the eastern
portion of the region. In the forests of Central America,
Venezuela, and Ecuador, and, to a lesser degree, in those of Peru
and Brazil, occurs the genus Orthalicus, whose tree-climbing
habits recall the Cochlostyla of the Philippines. These three
groups of bulimoid forms constitute, as far as the mainland is
concerned, the preponderating mass of the land Mollusca. Helix
proper 1s most strongly developed in the Greater Antilles, which
possess several peculiar groups of great beauty. In Central
America Heliz is comparatively scarce, but in the northern
portions of the continent several fine genera (Labyrinthus,

XI THE NEOTROPICAL REGION 343

Tsomeria, Solaropsis) oceur, which disappear altogether towards
the south.

Carnivorous land Mollusea are, so far as Central America is
concerned, more highly developed than in any other quarter of
the world, particularly in the genera Glandina and Streptostyla.
These genera also penetrate the northern portions of the con-
tinent, Glandina reaching as far as Ecuador, and Streptostyla as
far as Peru. The Greater Antilles have also characteristic forms
of these genera. Streptaxis is tolerably abundant all over
tropical South America, and is the one pulmonate genus which
shows any affinity with the African fauna.

The slugs are exceedingly scarce. Vaginula occurs through-
out, and is the only genus in any sense characteristic.

Clausilia, in the sub-genus Nenia, occurs along the Andean
chain from the extreme north (but
not in Central America) as far south
as Bolivia. It has in all probability
made its way into 8. America in
exceedingly remote ages from its head-
quarters in Eastern Asia. No species
survives in N. America, and a single
strageler is found in Porto Rico, They 7 ost Seite anenek
genera Macroceramus, Cylindrella, and Demerara. sh, Shell (shown
Strophia, are characteristic West eee) p.o, pulmonary
Indian forms, which are only shehtly
represented on the mainland. Homalonyx, a curious form akin
to Succinea, is peculiar to the region.

Land operculates attain a most extraordinary development in
the Greater Antilles, and constitute, in some cases, nearly one-
half of the whole Molluscan fauna. Several groups of the
Cyclostomatidae find their headquarters here, and some spread
no farther. On the mainland this prominence does not continue.
West Indian influence is felt in Central America and on the
northern coast district, and some Antillean genera make their
way as far as Ecuador. The whole group entirely disappears in
Chili and Argentina, becoming scarce even in Brazil.

Among the fresh-water operculates, Ampullaria is abundant,
and widely distributed. Vivipara, so characteristic of N.
America, is entirely absent. Chilina, a remarkable fresh-water
pulmonate, akin to Limnaea, is peculiar to Chil, Patagonia, and

344 ANTILLEAN SUB-REGION CHAP.

Southern Brazil, but is not found in the tropical portion of the
continent. Of the fresh-water Pelecypoda Mycetopus, Hyria,
Castalia, Leila, and Miilleria are peculiar forms, akin to the
Unionidae.

(1) The Antillean Sub-region surpasses all other districts in
the world in respect of (1) extraordinary abundance of species,
(2) sharp definition of limits as a whole, (3) extreme localisation
of the fauna of the separate islands. The sub-region includes the
whole of the half-circle of islands from the Bahamas to Grenada,
together with the extreme southern end of the peninsula of
Florida, which was once, no doubt, a number of small islands like
the Bahamas. Trinidad, and probably Tobago, although contain-
ing an Antillean element, belong to the mainland of 8. America,
from which they are only separated by very shallow water.’

The sub-region appears to fall into four provinces :—

(a) Cuba, the Bahamas, and 8. Florida; (0) Jamaica; (c)
San Domingo (Haiti), Porto Rico, and the Virgin Is., with the
Anguilla and St. Bartholomew group; (d) the islands from
Guadeloupe to Grenada. The first three provinces contain the
mass of the characteristic Antillean fauna, the primary feature
being the extraordinary development of the land operculates,
which here reaches a point unsurpassed in any other quarter
of the globe. The relative numbers are as follow :—

Cuba. Jamaica. San Domingo. Porto Rico.
Tnoperculate : 362 221 152 75
Operculate . ; 252 242 100 23

It appears, then, that the proportion of operculate to inoper-
culate species, while very high in Cuba (about 41 per cent of the
whole), reaches its maximum in Jamaica (where the operculates
are actually in a majority), begins to decline in San Domingo
(about 40 per cent), and continues to do so in Porto Rico, where
they are not more than 24 per cent of the whole. These oper-
culates almost all belong to the families Cyclostomatidae and
Helicinidae, only two genera (Aperostoma and Megalomastoma)
belonging to the Cyclophorus group. Comparatively few genera
are absolutely pecuhar to the islands, one or two species of most
of them occurring in Central or 8. America, but of the several
hundreds of operculate species which occur on the islands, not
two score are common to the mainland.

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Map to illustrate the
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2000 Thered. line marks the 700 fathom line |

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Map C . Between pages 344 and 345.

Map to illustrate the
GEOGRAPHICAL DISTRIBUTION
of the Land Mollusca of the
WEST INDIES.
Thered line marks the 100 fathom line.

Enghsh Miles
50 0 50 100 150 200 250
SS Ee ees

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eo! ANTILLEAN SUB-REGION 345

The next special feature of the sub-region is a remarkable
development of peculiar sub-genera of Heli. In this respect
the Antilles present a striking contrast to both Central and §.
America, where the prime feature of the land Pulmonata is the
profusion of Bulimus and Bulimulus, and Helia is relatively
obscured. No less than 14 sub-genera of Helix, some of which
contain species of almost unique beauty and size, are quite
peculiar to the Greater Antilles, and some are peculiar to in-
dividual islands.

Here, too, is the metropolis of Cylindrella (of which there are
130 species in Cuba alone), a genus which just reaches 8. America,
and has a few species along the eastern sea-board of the Gulf of
Mexico. Macroceramus and Strophia are quite peculiar; the
former, a genus allied to Cylindrella, which attains its maximum
in Cuba and San Domingo, is scarcely represented in Jamaica,
and disappears south of Anguilla; the latter, a singular form,
resembling a large Pupa in shape, which also attains its maxi-
mum in Cuba, is entirely wanting in Jamaica, and has its last
representative in S. Croix. One species irregularly occurs at
Curacao. .

The carnivorous group of land Mollusca are represented by
several peculiar forms of Glandina, which attain their maximum
in Jamaica and Cuba, but entirely disappear in the Lesser
Antilles.

A certain number of the characteristic N. American genera
are found in the Antillean Sub-region, indicating a former con-
nexion, more or less intimate, between the W. Indies and the
mainland. The genera are all of small size. The characteristic
N. American /yalinia are represented in Cuba, San Domingo,
and Porto Rico; among the Helicidae, Polygyra reaches Cuba, but
no farther, and Strobila Jamaica. The fresh-water Pulmonata are
of a N. American type, as far as the Greater Antilles are con-
cerned, but the occurrence of Gundlachia (Tasmania and Trinidad
only) in Cuba is an unexplained problem at present. Unionidae
significantly occur only at the two ends of the chain of islands,
not reaching farther than Cuba (Unio 3 sp.) at one end, and
‘Trinidad (which is 8. American) at the other.

A small amount of S. American influence is perceptible
throughout the Antilles, chiefly in the occurrence of a few species
of Bulimulus and Simpulopsis. The 8. American element may

346 CUBA " cuar.

have strayed into the sub-region by three distinct routes: (1)
by way of Trinidad, Tobago, and the islands northward; (2) by
a north-easterly extension of Honduras towards Jamaica, forming
a series of islands of which the Rosalind and Pedro banks are
perhaps the remains; (3) by a similar approximation of the
peninsula of Yucatan and the western extremity of Cuba.
Central America is essentially 8. American in its fauna, and the
characteristic genera of Antillean operculates which occur on its
eastern coasts are sufficient evidence of the previous existence of
a land connexion more or less intimate (see map).

(aw) Cuba is by far the richest of the Antilles in land Mollusca,
but it must be remembered that it is also much better explored
than San Domingo, the only island likely to rival it in point of
numbers. It contains in all 658 species, of which 620 are land
and 38 fresh-water, the land operculates alone amounting toe 252.

Carnivorous genera form but a small proportion of the whole.
There are 18 Glandina (which belong to the sections Varicella
and Boltenia) and 4 Streptostyla, the occurrence of this latter
genus being peculiar to Cuba and Haiti (1 sp.) among the
Antilles, and associating them closely with the mainland of
Central America, where Streptostyla is abundant. These two
genera alone represent the Agnatha throughout the sub-region.

There are no less than 84 species of Helix, belonging to 12
sub-genera. Only one of these (Polymita) is quite peculiar to
Cuba, but of 7 known species of Jeanerettia and 8 of Coryda, 6 and
7 respectively are Cuban. TZhelidomus has 15 species (Jamaica
3, Porto Rico 3); Polydontes has 3, the only other being from
Porto Rico; Hemitrochus has 12 (Jamaica 1, Bahamas 6); Cysti-
copsis 9 (Jamaica 6); Hurycampta 4 (Bahamas 1).

The Cylindrellidae find their maximum development in Cuba.
As many as 34 Macroceramus occur (two-thirds of the known
species), and 130 Cylindrella, some of the latter being most
remarkable in form (see Fig. 151, B, p. 2477).

The land operculates belong principally to the families
Cyclostomatidae and Helicinidae. Of the former, Cuba is the
metropolis of Ctenopoma and Chondropoma, the former of which
includes 30 Cuban species, as compared with 1 from San
Domingo and 2 from Jamaica. Megalomastoma (Cyclophoridae)
is also Haitian and Porto Rican, but not Jamaican. SBlaesospira,
Aenopoma, and Diplopoma are peculiar. The Helicinidae con-

*

ra CUBA

JAMAICA 347

sist mainly of Helicina proper (58 sp.), which here attains by
far its finest development in point of size and beauty, and of
Hutrochatella (21 sp.), which is pecuhar to the three creat islands
(Jamaica 6 sp., San Domingo 6 sp.)

The Lahamas, consisting in all of more than 700 islands, are
very imperfectly known, but appear to be related partly to Cuba,
partly to San Domingo, from each of which they are separated
by a narrow channel of very deep water. They are certainly
not rich in the characteristic groups of the Greater Antilles.
The principal forms of Helix are Plagioptycha (6 sp.), common
with San Domingo, and Hemitrochus (6 sp.),common with Cuba.

Fie. 229, — Characteristic
Cuban Helices. A, Poly-
dontes imperator Montf.
B, Caracolus rostrata
Pir. ©, Polymita mus-

carum Lea,

Strophia is exceedingly abundant, but Cylindrella, Macroceramus,
and Glandina have but few species. There are a few species of
Ctenopoma, Chondropoma, and Cistula, while a single Schasicheila
(absent from the rest of the sub-region) forms a link with
Mexico.

Southern Florida, with one or two species each of Hemitrochus,
Cylindrella, Macroceramus, Strophia, Ctenopoma, and Chondropoma,
belongs to this province.

(b) Jamaica.—The land Mollusca of Jamaica are, in point of
numbers and variety, quite unequalled in the world. There are
in all as many as 56 genera and more than 440 species, the
latter being nearly all peculiar. The principal features are the

348 JAMAICA CHAP.

Glandinae, the Helicidae, and the land operculates. The Glan-
dinae belong principally to the sub-genera Varicella, Melia, and
Volutaxis, Streptostyla being absent, although occurring in Cuba
and San Domingo. There are 10 genera of Helix, of which
Pleurodonta is quite peculiar, while Sagda (13 sp.) is common
only with 8.W. San Domingo (2 sp.), and Leptoloma (8 sp.) only
with Cuba (1 sp.) The single Strobila seems to be a straggler
from a N. American source. MJacroceramus has only 2 species as
against 34 in Cuba, and of Cylindrella, in which Cuba (130 sp.)
is so rich, only 36 species occur. The genus Leia, however (14
sp.), is all but peculiar, occurring elsewhere only in the neighbour-
ing angle of San Domingo, which is so closely allied with Jamaica.
The complete absence of Strophia is remarkable.

Fic. 230.—Characteristic Jamai-
can and Haitian Mollusea:
A, Sagda epistylium Miill.,
Jamaica; B, Chondropoma
salleanum Pfr., San Domingo ;
C, Eutrochatella Tankervillet
Gray, Jamaica; D, Cylin-
drella agnesiana C. B, Ad.,
Jamaica.

The land opereulates form the bulk of the land fauna, there
being actually 242 species, as against 221 of land Pulmonata, a
proportion never again approached in any part of the world.
As many as 80 of these belong to the curious little genus Stoa-
stoma, which is all but peculiar to the island, one species having
been found in San Domingo, and one in Porto Rico. Geomelania
and Chittya,two singular inland forms akin to 7'runeatella, are quite
peculiar. Alcadia reaches its maximum of 14 species, as against
4 species in San Domingo and 9 species in Cuba, and Lucidella
is common to San Domingo only; but, if Stoastoma be omitted,
the Helicinidae generally are not represented by so many or by
so striking forms as in Cuba, which has 90 species, as against
Jamaica 44, and San Domingo 35.

XI SAN DOMINGO 349

(c) San Domingo, although not characterised by the extra-
ordinary richness of Cuba and Jamaica, possesses many specially
remarkable forms of land Mollusca, to which a thorough explora-
tion, when circumstances permit, will no doubt make important
additions. From its geographical position, impinging as it does
on all the islands of the Greater Antilles, it would be expected
that the fauna of San Domingo would not exhibit equal signs of
isolation, but would appear to be influenced by them severally.
This is exactly what occurs, and San Domingo is consequently,
although very rich in peculiar species, not equally so in peculiar
genera. The south-west district shows distinct relations with
Jamaica, the Jamaican genera Leia, Stoastoma, Lucidella, and the
Thaumasia section of Cylindrella occurring here only. The
north and north-west districts are related to Cuba, while the
central district, consisting of the long band of mountainous
country which traverses the island, contains the more char-
acteristic Haitian forms.

The Helicide are the most noteworthy of the San Domingo
land Mollusca. The group Hurycratera, which contains some
of the finest existing land snails, is quite peculiar, while Par-
thena, Cepolis. Plagioptycha, and Caracolus here reach their
maximum. The Cylindrellidae are very abundant, but no
section is peculiar. Land operculates do not bear quite the same
proportion to the Pulmonata as in Cuba and Jamaica, but they
are well represented (100 to 152); £olleta is the only peculiar
genus.

The relations of San Domingo to the neighbouring islands
are considerably obscured by the fact that they are well known,
while San Domingo is comparatively little explored. To this
may perhaps be due the curious fact that there are actually more
species common to Cuba and Porto Rico (26) than to Porto Rico
and San Domingo. Cuba shares with San Domingo its small-
sized Caracolus and also Liguus, but the great Hurycratera, Par-
thena, and Plagioptycha are wholly wanting in Cuba. The land
operculates are partly related to Cuba, partly to Jamaica, thus
Choanopoma, Ctenopoma, Cistula, Tudora, and many others, are
represented on all these islands, while the Jamaican Stoastoma
occurs on San Domingo and Porto Rico, but not on Cuba, and
Lucidella is common to San Domingo and Jamaica alone. An
especial link between Jamaica and San Domingo is the occurrence

,

350 PORTO RICO CHAP,

in the south-west district of the latter island of Sagda (2. sp.).
The relative numbers of the genera Strophia, Macroceramus, and
Helicina, as given below (p. 351), are of interest in this con-
Hexion,

Porto Rico, with Vietque, is practically a fragment of San
Domingo. The points of close relationship are the occurrence of
Curacolus, Cepolis, and Parthena among the Helicidae, and of Sim-
pulopsis, Pseudobalea, and Stoastoma. Cylindrella and Macroceramus
are but poorly represented, but Strophia still occurs. The land

Itc. 231.—EHxamples of West
Indian Helices: A, J/elia
(Parthena) angulata Wer.,
Porto Rico; B, Melia (The-
lidomus) lima Feér., Vieque ;
C, Helix (Dentellaria) nue
denticulata Chem., Martin-
ique.

operculates (see the Table) show equal signs of removal from the
headquarters of development. JZegalomastoma, however, has some
striking forms. The appearance of a single Clausilia, whose
nearest relations are im the northern Andes, is very remarkable.
Gacotis, Which is allied to Peltella (ecuador only), is peculiar.

x1 GREATER ANTILLES 25a

Land Mollusca of the Greater Antilles.

I gS es a 2 ~

awa ees Sta e e

1S) es mn Pa o Lr) v2) 4
Glandina 18 24 1b 8 | Opeas See Ga) 4 6
Streptostyla brie: ae ee 2 Subulina —. 6) lA 2 2
Volutaxis. Se teeny L(t) al Glandinella . ] sh
Selenites Oe ae Spiraxis 2 (2) 2 i
Hyalinia etal 5 6 | Melaniella 7 ae
Patula a Mis) 1 ... «» | Geostilbia 1 1
Sagda . : Se eri Bey} 2 Cionella oe aie Maas ee et
Microphysa . es, eels 8 3 | Leptinaria . ae 1 aC 3
Cysticopsis . an 9 6 oe Obeliscus . tA an, ow Wes 1 2
Hygromia (¢) : 3 Pupa . 5 ee a 7 3 2
Leptaxis (?) . ae 1 Vertigo : spe eae one Sree ae
Polygyra 2 .. | Strophia . se HS are 3 2
Jeanerettia . 6 1 | Clausilia He Jc ™ 1
Euclasta . Se eco weeOoL ah 4|Succinea. Sg! 2 5 3
Plagioptycha +) coc ee 14 2] Vaginula 5 2 2 ]
Strobila : a ph 1 ... «| Megalomastoma . 13... ] 3
Dialeuca ay oo il .. . | Neocyclotus Be EWA
Leptoloma . ee 8 roa pn || AL atehye) ee! re 3
Kurycampta i ke aes .. «. | Jamaicia a 2 ne
Coryda a Tite aor ws... | Crocidopoma are 1 3
Thelidomus i US 3 ir 3 | Rolleia ; By ae neice 1
Kurycratera 7... | Choanopoma 2) 12 19 3
Parthena 2 2} Ctenopoma . 30 2 Fae
Cepolis eae 3 1 | Cistula 15 3 3 3
Caracolus — . 5 6 2 | Chondropoma 57 (2) If 4
Polydontes . ee BS Ba : 1 | Tudora ff Aly 5
Hemitrochus ee 2 1 ... .» | Adamsiella . ee
Polymita . oN 8 cee ... .. | Blaesospira . 1
Pleurodonta ev eeen ioe .», oe. | NCNOpoMa 1 ss
Ine. sed. . BBE goer oe ene | WIStilel 15 e 3
Simpulopsis oh DOR 1 1 | Colobostylus 4 13 5
3ulimulus . 2 3 6 7 | Diplopoma . AW Sac
Orthalicus . a © gi il .. «. | Geomelania Pua ll
Liguus : eeOs | ees 1... | Chittya ; a nc 1 eh
‘Gaeotis : no DG a ME =i 3 | Blandiella . a eo Ie.
Pineria : es com 1 | Stoastoma . wee 2700) 1 ]
Macroceramus . 354 2 14 3| Eutrochatella . 21 6 6
Leia . ; 4 ne, we 2 ... | Lueidella . eens 4 1
Cylindrella . sles 36 35 3 | Aleadia F . 9 14 AP a
Pseudobalea 7 ane 1 1 | Helicina . 7) pe wo 24 9
Stenogyra . a) 7 (?) ... | Proserpina . re 4

The Virgin Is. with St. Croix, Anguilla, and the St. Bar-
tholomew group (all of which are non-volcanic islands), are
related to Porto Rico, while Guadeloupe and all the islands to the
south, up to Grenada (all of which are volcanic), show marked
traces of S. American influence. St. Kitt’s, Antigua, and
Montserrat may be regarded as intermediate between the two
groups. St. Thomas, St. John, and Tortola have each one
Plagioptycha and one Thelidomus, while St. Croix has two sub-

352 LESSER ANTILLES CHAP.

fossil Caracolus which are now living in Porto Rico, together with
one Plagioptycha and one Thelidomus (sub-fossil). The gradual
disappearance of some of the characteristic greater Antillean
forms, and the appearance of S. American forms in the Lesser
Antilles, is shown by the following table :—

|

g| 8 Miles Saale een te

Aislalelaleizislsisizisleleiais

OF} Ssiiliss las 17S eet | as eee | ise sii ics 1 Sse lene

HAi/Nl/ninilAal/aAl/al/dl/oj/Alalal/Alsalisia
Bulimulus CE a AEP ae Pe I Sh sh I) by | 6 | 2] 4
Cylindrella Ba Peal Wal | late W yhece ff ab al jpeal il
Macroceramus FP Daal lose dl af at raelleaceulteee [sacs oe
Cyclostomatidae, ete.|23 | 4|1/5]1]1)11|...| 4}... se 1
Dentellaria. =p lassen] echea| eseal eeteonl -csiee lire ley [Amen elean | eG rem Lele rea eam tal
Cyclophorus . Bs Nene heater eCileet ela: Dalene Sah
Amphibulimus | 2)3)1
Homalonyx | Ta een

(d) In Guadeloupe we find Cyclophorus, Amphibulimus, Homal-
onyx, and Pellicula, which are characteristic of S. America, and
nearly all recur in Dominica and Martinique. These islands are
the metropolis of Dentellaria, a group of Helix, evidently related to
some of the forms developed in the Greater Antilles. Stragglers
occur as far north as St. Kitt’s and Antigua, and there are several
on the mainland as far south as Cayenne. Traces of the great
Bulimus, so characteristic of 8. America, occur as far north as S.
Lucia, where also is found a Parthena (San Domingo and
Porto Rico). Trinidad is markedly S$. American; 55 species in
all are known, of which 22 are peculiar, 28 are common to S.
America (8 of these reach no farther north along the islands),
and only 5 are common to the Antilles, but not to 8. America.
The occurrence of Gundlachia in Trinidad has already been
mentioned.

The Bermudas show no very marked relationship either to
the N. American or to the West Indian fauna. In common
with the former they possess a Polygyra, with the latter (intro-
duced species being excluded) one species each of Hyalosagda,
Subulina, Vaginula, and Helicina, so that, on the whole, they
may be called West Indian. ‘The only peculiar group is Poecilo-
zonites, a rather large and depressed shell of the Hyalinia type.

(2) The Central American Sub-region may be regarded as

< CENTRAL AMERICA 33.3

extending from the political boundary of Mexico in the north
to the isthmus of Panama in the south. It thus impinges on
three important districts—the N. American, West Indian, and 5.
American; and it appears, as we should perhaps expect, that the
two latter of these regions have considerably more influence
upon its fauna than the former. Of the N. American Helicidae,
Polygyra is abundant in Mexico only, and two species of Strobila
reach N. Guatemala, while the Californian Arionta occurs in
Mexico. 8S. American Helicidae, in the sub-genera Solaropsis
and Labyrinthus, occur no farther north than Costa Rica. Not
a single representative of any of the characteristic West Indian
Helicidae occurs. Bulimulus and Otostomus, which form so large
a proportion of the Mollusca of Venezuela, Colombia, Ecuador, and
Peru, together with Orthalicus, are abundant all over the region.
Again, Cylindrella, Macroceramus, and some of the characteristic
Antillean operculates, are represented, their occurrence being in
most cases limited to the eastern coast-line and eastern slope of
the central range.

Besides these external elements, the region is rich in indigenous
genera. Central America is remarkable
for an immense number of large carni-
vorous Mollusca possessing shells. There
are 49 species of Glandina, the bulk of
which occur in eastern and southern
Mexico; 36 of Streptostyla (S.E. Mexico
and Guatemala, only 1 species reaching
Venezuela and another Peru); 5 of Sala-
siella, 2 of Petenia, and 1 of Strebelia ; the
last three genera being peculiar. Strept-
axis, fairly common in §. America, does
not occur. Velifera and Cryptostracon,
two remarkable slug-like forms, each with
a single species, are pecular to Costa Rica.
Among the especial peculiarities of the pre, 232. —Examples of

region are the giant forms belonging to the — characteristic Mexican

vere : - Mollusca: A, Coelocen-

Cylindrellidae, which are known as Holo- trum turris Pfr.; -B,

spira, Eucalodium, and Coelocentrum (Fig. Sora? Delatirer
= r.

232). They are almost entirely peculiar
to Mexico, only 7 out of a total of 33 reaching south of that
district, and only 1 not occurring in it at all.

VOL. III 2A

354 CENTRAL AMERICA CHAP.

The land operculates are but scanty. Zomocyclus and Amphi-
cyclotus are peculiar, and Schasicheila, a form of Helicina, occurs
elsewhere only in the Bahamas. Ceres (see Fig. 18, C, p. 21) and
Proserpinella, two remarkable forms of non-operculate Helicinidae
(compare the Chinese Heudeia), are quite peculiar. Pachychilus,
one of the characteristic fresh-water genera, belongs to the S.
American (Melaniidae) type, not to the N. American (Pleuro-
ceridae). Among the fresh-water Pulmonata, the Aplecta are
remarkable for their great size and beauty. In the accompany-
ing table “Mexico” is to be taken as including the region from
the United States border up to and including the isthmus of
Tehuantepec, and “ Central America” as the whole region south
of that point.

Land Mollusca of Central America

ay 2 = 9
ee 6 eee
|) fe. Gee c. 6s. ee
EN srcieae Ee g “E22. 34
a3 o468 io2 =: $468 3
Strebelia 1 nS ... | Berendtia 1 ee
Glandina 33 13 3 | Orthalicus 6 3 3
Salasiella ‘ 1 4 1 | Pupa il 1
Streptostyla . 18 12 6 | Vertigo. 1
Petenia . it 1 | Holospira 12
Limax 1 Coelocentrum 6 1 il
Velifera si 1 ... | Eucalodium 15 wae 5
Omphalina 10 1 1 | Cylindrella 6 4
Hyalinia 2 5 3 | Macroceramus 2 1
Guppya : cae meer 8 3 | Simpulopsis . 2 1
Pseudohyalina —. 2 Ba; 2 | Caecilianella . 1 a sis
Tebennophorus. 1 A Opeas 1 2 3
Cry ptostracon she 1 ... | Spiraxis 8 2 il
Xanthonyx . E 4 a ... | Leptinaria ae 2
Patula . : ‘ € ee 4 Subulina 2 3 4
Acanthinula . ; 1 2 2 | Succinea 11 3 1
Vallonia : Seek i! ... | Vaginula 1 ae ie
Trichodiscus . 2 2 3 | Aperostoma . aaa 4 1
Praticolella i il cee 1 | Amphicyelotus 2 1 2
Arionta 3 : 3 Se ... | Cystopoma : 2 ve och
Lysinoe 1 1 1 Tomocyelus . yy eee 1 2
Oxychona 2 5 | Choanopoma . 2 2
Solaropsis Pee 2 ... | Chondropoma 2 11 50
Polygyra : =. ala il 2 | Helicina 13 10 6
Strobila : : 1 il Schasicheila . 2 1
Labyrinthus . ae. Mt 5 ». | Ceres : 2
Otostomus. 7 23 20 7 | Proserpinella 1
Sulimulus. F 6 5 2

(5) The Colombian Sub-region includes Colombia, New
Grenada, Venezuela, Guiana, Ecuador, Peru, and Bolivia. It has

or COLOMBIA AND VENEZUELA 3

unr
in

been usual to separate off the two latter countries as forming a dis-
tinct “Peruvian” sub-region; but there is, as will be seen, absolutely
no line to be drawn between the Mollusca of Peru and those of
Keuador; nor would one, on geographical considerations, expect
to be able to draw such a line. A better method of subdivision,
so far as the species of the whole eastern portion of the region
are concerned, would be to group the Mollusca according to the
altitude at which they occur, were it not that the evidence on
this pomt is at present but fragmentary. We know, however,
that all along the line of the Andes certain species, more parti-
cularly of Bulimulus, occupy their own zones of elevation, some
ascending as high as 10,000 feet above the sea, and never occur-
ring on the plains.

In the northern portions of this sub-region, Central American
and West Indian influence is felt to a certain extent. Thus there

Fic. 238.—A, Orthalicus
Deburghiue Reeve,
Eeuador ; B, Bulimius
(Pachyotus) egregius
Jay, Brazil.

B

are eight Glandina and one Streptostyla in Venezuela and Colombia
together with one or two species of Cistula, Chondropoma, Pro-
serpina, and Cylindrella, while a single Strophia (decidedly a
straggler) occurs at Curacao. In Demerara and Cayeune there
are three or four species of Dentellaria. In Ecuador, however,
Glandina diminishes to three species, and in Peru isappears
altogether, although one Streptostyla oceurs. Sunilarly the West
Indian operculates are reduced to one Chondropoma (Ecuador),
and disappear entirely in Peru. ;

356 ECUADOR, PERU, AND BOLIVIA CHAP.

The Helicidae are most abundant in the north and west, and
are represented by several very striking sub-genera, some of which
possess remarkably toothed apertures, and perhaps betray an
ancestry common to some of the West Indian genera. Of these,
Labyrinthus has 12 species in Venezuela and Colombia, 5 in
Ecuador, and 3 in Peru and Bolivia; /someria 12 in Venezuela
and Colombia, 20 in Ecuador, and 2 in Peru and Bolivia;
Solaropsis is represented in these countries by 6, 3, and 7 species,
and Systrophia by 4, 5, and 8 species respectively.

Clausilia—in the group Nenia—appears in some numbers
along the Andes chain, the only other representative in the New
World being the solitary species occurring at Porto Rico. There
have been described, from Venezuela and Colombia 10 species,
from Ecuador 5, and from Peru and Bolivia 12.

Another marked feature of the region is the occurrence of the
Orthalicidae, in the two genera Orthalicus and Porphyrobaphe.
The latter of these magnificent forms is peculiar, while the
former reaches Mexico, the West Indies, and Brazil. Ecuador,
which contains 23 species, seems the metropolis. of the
eroup.

Bulimus and Bulimulus, the former genus being peculiar to
S. America and the adjacent islands, are largely
represented, the former in the three groups
Borus, Dryptus, and Orphnus. These attain
their maximum in Peru, with 25 species, but
Venezuela and Colombia have as many as 17.
Bulimulus has been subdivided into a number
of groups, eg. Drymacus, Mesembrinus, Thau-
mastus, Mormus, Scutalus, with many others,
—the exact scientific limits of which are not
easily discernible. It must suffice here to
state that Peru seems to be the head-quarters
of the group with about 190 species (which
probably may well be reduced), Ecuador having
about 70, and Venezuela and Colombia between
80 and 90.

Fic, 234. — Rhodea Two very remarkable forms belonging to the
ST ec Pupidae, Anostoma (Fig. 154, p. 248) and Zomi-
gerus, occur in Venezuela,the metropolis. Rhodea,

another very peculiar shell (Fig. 234), whose exact family position

XI THE GALAPAGOS—BRAZIL Ae Fi

is uncertain, is peculiar to New Grenada. The land operculates
are few in number, and in Bolivia almost disappear. They
belong principally to Neocyclotus (of which 11 species occur in
Venezuela and Colombia) and Helicina (10 species in the same
district), besides the stragglers already mentioned from West
Indian sources, and a few Cyclophorus. Bourcieria is a form of
Helicina peculiar to Ecuador. Ampullaria, with Ceratodes, a
peculiar planorbiform sub-genus, and Hemisinus, form the
bulk of the fresh-water operculates.

The Galapagos. — Thirty-four species of land Mollusca, all
peculiar, are known from these islands; 25 of these are forms
of Bulimulus. There are no Helicidae, one each of Hyalinia,
Leptinaria, and Helicina, and two Pupa. The Bulimulus are
mostly of the group WVesiotis, and in their brown colour bear
some outward resemblance to the dark Achatinella of the Sand-
wich Is., living as they do mostly under scoriae on the ground,
and not on trees. In type, however, they appear to be derived
from Chili and Peru, rather than from the parts of 8. America
immediately contiguous. Another section (Pleuropyrgus 2. sp.)
closely resembles a marine Chemnitzia. The islands are all
volcanic, and are probably not the result of subsidence; thus the
existing species are not to be regarded as the relics of a more
widespread fauna, but as a new set of inhabitants.

(4) The Brazilian Sub-region.— This immense district is very
little known, except in the south, and it is consequently im-
possible to give any satisfactory account of its Mollusca. It is
possible that eventually it will be found that it falls into
provinces which correspond more or less to (@) the Amazon basin ;
(>) the mountainous district in the east, drained by the Tocantins
and the San Francisco; (¢) the Parana basin in the south central
district ; and (@) the Argentine or Pampas district in the extreme
south. But at present the data are insufficient to establish any
such subdivisions, whose existence, if proved, would have an
important bearing on the problem of the coalescence of S.
America into its present form.!

The Agnatha are represented by Streptaxis alone (17 sp.). Helia
is rare, but includes the peculiar Polygyratia (Fig. 150, A, p. 246),
while Labyrinthus (2 sp.), Solaropsis (5 sp.), and Systrophia are

' Compare von Martens, Jalak. Lldtt. 1868, p. 169 ; von Ihering, Nachr. Deutsch.
Malak, Gesell. 1891, p. 93.

358 ARGENTINA-—CHILI CHAP.

common with the Colombian sub-region, and Oxychona (4 sp.)
with the Central American. Sulimus has
in all 56 species, the sub-genera Pachyotus
(Fig. 235) and Strophoehilus being peculiar.
Bulimulus, though not so abundant as in Peru
and Ecuador, has about 60 species, of which
Fic. 285. — Bulimulus Novicula (Fig. 235) is the most remarkable
(Navicula) navies group. Megaspira is peculiar. Orthalicus has
Wagn., Brazil. : : é
only 4 species, while Zomigerus (4 sp.) and
Anostoma (3 sp.) are common with Venezuela. Land opercu-
lates are scarce, and appear to include only MNeocyclotus, Cyclo-
phorus, and Helicina.

In Argentina, which may probably rank as a separate pro-
vince, the tropical forms greatly decrease,
Streptaxis being reduced to 2 species, and
Bulimus and Bulimulus together to 40, while
Orthalicus, the great Helices, and the land
operculates disappear altogether. = Odonto-
stomus (Fig. 236), a genus of the Pupidae, is
abundant in the northern part of the province.
Two or three species of Chilina occur.

(5) The Chilian Sub-region.—The greater
part of Chili, from its arid and rainless climate, is

Fic. 236. — Odonto-
“ : stomus pantagru-
unfavourable to the existence of land Mollusca. elinus Moric., 8.

Bulimus(Borus) still has 3 or 4 species,and Buli- — ®™"- * »
mulus (Plectostylus 11, Scutalus 9, Peronaeus 7) is fairly abundant,
but the profusion of the tropics is wanting. There are no car-
nivorous genera, and only two land operculates. A remarkable
form of Helix (Macrocyelis, Fig. 237) is quite peculiar, but the
majority of the species belong to two rather obscure groups,
Stepsanoda and Amphidoxa. Chilina, a singularly solid form of
Limnaea (of which 8 sp., with a sub-genus Pseudochilina, occur Mm
Chili), is peculiar to Chili, 8. Brazil, and Patagonia. From the
two islands of Juan Fernandez and Masafuera, are known several
Helix, of Chilian affinity, several curious Succinea, a Homalonyz,
Leptinaria, and Nothus, and three species of Vornatellina, with
the almost universal Limax gagates.

The question of the existence at some remote period of a
Neantarctic continent, which formed a communication between
the three great southern peninsulas of the world, is one on

XI QUESTION OF A NEANTARCTIC CONTINENT 359

which the Mollusca may offer evidence. Von Ihering holds that
an essential difference can be observed between certain of the
Unionidae which inhabit S. America, Africa, and Australia with
New Zealand, and those which inhabit Europe, Asia, and N.
America, but the point can hardly be regarded as definitely
established at present. Something perhaps may be made of the
distribution of Bulimus and Bulimulus. It seems difficult to
explain the occurrence of sub-fossil Budimus on St. Helena except
on some such lines as have been recently adduced to account for
the presence of struthious birds in the Mascarenes, and possibly
the form Livinhacea may be a trace of the same element in 8.
Africa. Again, the Liparus of S. and W. Australia, with the
Caryodes of Tasmania, and the Leucotaenia and Clavator of
Madagascar (which all may be related to Bul/imus), together with
the Placostylus of New Caledonia and the adjacent islands,

SS

Fia. 237.—Macrocyclis
laxata Fér,, Chili.

reaching even to New Zealand, and perhaps even the Amphidromus
of Malaysia (which are more akin to Lulimulus), may be thought
to exhibit, in some remote degree, traces of a common ancestry.

The land operculates give no help, and, of the carnivorous
genera, Rhytida is a marked lnk between Africa and Australia,
while Streptaxis is equally so between 8. America and Africa.
As regards fresh-water Gasteropoda, Ampullaria is common to 8.
America and Africa, while /sidora is common to Africa, Australia,
and New Zealand, but is altogether absent from S. America.
Gundlachia ocews in Florida, Trinidad, and Tasmania, but has
not been detected in Africa. It must be concluded, therefore,
that the present state of the evidence which the Mollusca can
afford, while exhibiting certain curious points of relationship be-
tween the three regions in question, is insufficient to warrant
any decided conclusion.

CHAPTER XIl

DISTRIBUTION OF MARINE MOLLUSCA——DEEP-SEA MOLLUSCA AND
THEIR CHARACTERISTICS

MARINE Mollusca may be divided roughly into Pelagic and non-
Pelagic genera. To the former division belong all Pteropoda and
Heteropoda, and a large number of Cephalopoda, together with
a very few specialised forms of Gasteropoda (Janthina, Litiopa,
Phyllirrhoe, ete.). Pelagic Mollusca appear, as a rule, to live at
varying depths below the surface during the day, and to rise to
the top only at night. The majority inhabit warm or tropical
seas, though some are exceedingly abundant in the Arctic
regions; Clione and Limacina have been noticed as far north
as 72°?

The vertical range of Pelagic Mollusca has received attention
from Dr. Murray of the Challenger, Professor Agassiz of the Blake
and Albatross, and others. Agassiz appears to have established
the fact that the surface fauna of the sea is limited to a com-
paratively narrow belt of depth, and that there is no inter-
mediate belt of animal life between creatures which live on or
near the bottom and the surface fauna. Pelagic forms sink, to
avoid disturbances of various kinds, to depths not much exceed-
ing 150 to 200 fathoms, except in closed seas like the Gulf of
California and the Mediterranean, where the bathymetrical range
appears to be much greater.”

Non- Pelagic Mollusca are, from one point of view, con-
veniently classified according to the different zones of depth at

1 The distribution of some Pteropoda has been worked out by Munthe, ih.
Svensk. Ak. Handl. XII. iv. 2, by Pelseneer ‘‘ Challenger” Rep., Zool., xxiii., and by
Boas, Spolia Atlantica.

2 Bull. Mus. C. Z. Harv. xiv. p. 202 ; xxiii. p. 34 f.

XII PHENOMENA OF DISTRIBUTION 361

which they occur. Thus we are enabled to distinguish Mollusca
of (a) the littoral, (b) the laminarian, (c) the nullipore or
coralline, and (d@) the abyssal zones. It must be borne in mind,
however, that these zones cannot be exactly defined, and that
while the littoral zone may be understood to imply the area
between tide-marks, and the abyssal zone a depth of 500
fathoms and upwards, the hmits between the laminarian and the
coralline, and between the coralline and abyssal zones can only
be fixed approximately.

The difficulty of assigning special genera or species to special
‘zones of depth’ is increased by two important facts in the
phenomena of distribution. In the first place, it is found that
species which occur in shallow water in northern seas often
extend to very deep water in much lower latitudes. This in-
teresting fact, which shows the importance of temperature in
determining distribution, was first established by the dredgings
of the Lightning and Porcupine off the western coasts of Europe.
In the second place, a certain number of species seem equally at
home in shallow and in abyssal waters, in cases where a great
difference of latitude does not occur to equalise the temperature.
Thus the Challenger found Venus mesodesma living on the beach
(New Zealand) and at 1000 fath. (Tristan da Cunha); Lima
multicostata in ‘shallow water’ (Tonga and Port Jackson) and
at 1075 fath. (Bermuda); Scalaria acus from 49 to 1254 fath.
(N. Atlantic); and S. hellenica from 40 to 1260 fath. (Canaries).
The Lightning and Porcupine found, or record as found,’ Anomia
ephippium at 0 to 1450 fath., Pecten groenlandicus at 5 to 1785
fath., Lima subauriculata at 10 to 1785 fath., Modiolaria discors
at 0 to 1785 fath., Crenella decussata at 0 to 1750 fath.,
Dacrydium vitreum at 30 to 2750 fath., Arca glacialis at 25
to 1620 fath., Astarte compressa at 3 to 2000 fath., and Sero-
bicularia longicallus at 20 to 2435 fath. Puncturella noachina
has been found at 20 to 1095 fath., Natiea groenlandica at 2 to
1290 fath., Rissow tenuisculpta at 25 to 1095 fath. In many
of these cases we are assured that no appreciable difference can
be detected between specimens from the two extremes of
depth.

In spite, however, of these remarkable vagaries on the part
of certain species, we are enabled roughly to distinguish a large

1 See papers in P. Z. S. 1878-85.

362 RECENT EXPLORING EXPEDITIONS CHAP.

number of genera as ‘shallow-water’ and ‘deep-water’ respec-
tively, while a still larger number occupy an intermediate
position. Among shallow-water genera may be named Patella,
Littorina, Nassa, Purpura, Strombus, Haliotis, Mytilus, Cardium,
Solen ; while among deep-water. genera are Plewrotoma, Scissu-
rella, Sequenzia, Dentalium, Cadulus, Limopsis, Nucula, Leda,
Lima, and Axinus.

Theories on the geographical distribution of marie Mollusca
have been revolutionised by the discoveries of recent exploring
expeditions. The principal have been those of Torell (Swedish)
(1859-61) on the coasts of Greenland and Spitzbergen; of the
Lightning and Porcupine (British) in 1868-70, in the N.E.
Atlantic, off the Scotch, Irish, French, and Portuguese coasts,
and in the Mediterranean; of the Challenger (British), under
Sir C. Wyville Thomson, in 1873-76, in which all the great
ocean basins were dredged or sounded; of the Blake (American),
under Alexander Agassiz, in 1877-80, in the West Atlantic,
Gult of Mexico, and Caribbean Sea; of the Zravailleur (French)
in 1880-85, off the west coasts of France, Portugal, and Morocco,
Madeira, the Canaries, and the Golfe du Lion; of the Yalisman
(French) in 1882, off the west coast of Africa from Tangier to
Senegal, the Atlantic Islands, and the Sargasso Sea; of the
Albatross (American) in 1891, off the west coast of tropical
America; of several other vessels belonging to the U.S. Fish
Commission and Coast Survey, off east American shores; and
of the Prince of Monaco in the WHirondelle and Princesse
Alice at the present time, in the N. Atlantic and Medi-
terranean.

The general result of these explorations has been to show
that the marine fauna of very deep water is much the same all
the world over, and that identical species occur at points as far
removed as possible from one another. The ocean floor, in fact,
with its uniform similarity of temperature, food, station, and
general conditions of life, contains no effectual barrier to the
almost indefinite spread of species." To give a few instances.
The Challenger dredged Silenia Sarsii in 1950 fath., 1100

‘ A break in this uniformity may be found underneath the course of a great
oceanic current like the Gulf Stream, which rains upon the bottom a large amount
of food. <A. Agassiz (Bull. Mus. C. Z. Harv. xxi. p. 185 f.) explains in this way the

richness of the fauna of the Gulf of Mexico as compared with that of the west coast
of tropical America.

XI WIDE DISTRIBUTION OF DEEP WATER FORMS 363

miles south-west of Australia, and also in 2650 fath. off the mouth
of the Rio de la Plata; Semele profundorum in 1125 fath.
near the Canaries, and in 2900 fath. mid N. Pacific; Verti-
cordia deshayesiana in 155 fath. near Cape York, and in 350
fath. off Pernambuco; Arca pteroessa in 2050 fath. mid N.
Pacific, in 1000-1675 fath. west of the Azores, and in 390 fath.
off the West Indies; Area corpulenta in 1400 fath. off N.E.
Australia, in 2425 fath. mid-Pacific, and in 1375 fath. near
Juan Fernandez; Lima goliath in 775 fath. off S. Japan, and
in 245 fath. off S. Patagonia; Plewrotoma engonia in 700 tath.
north-east of New Zealand, and in 345 fath. off Inoshima. <A
surprising range was occasionally found even in shallow-water
species; thus Petricolw lapicida was discovered by the same
expedition in the West Indies and N. Australia, Cerdita calycu-
lata off Teneriffe and in Bass Strait, Arca imbricata off Cape
York and in the West Indies, Modiolaria cuneata at Port Jack-
son and Cape of Good Hope, Zima squamosa at Teneriffe and the
Philippines. In these latter cases it is not improbable that the
species lives in deep water as well, from which it has not yet
been dredged.

It follows from these considerations that any attempt to
classify marine Mollusca under Regions and Provinces can only
apply to Mollusca which occur at moderate depths. The most
important factor in the environment, as determining distribution,
is the temperature of the water, which is probably to be regarded
as affecting not so much the adult Mollusca as their ova; for
the adult might possibly support life under conditions in which
the ova would perish. It appears that a sudden change of tem-
perature is the most effective barrier to distribution,’ and may
bring the range of a species to an almost instantaneous stop,
while a very gradual change will allow it to extend its range
very widely.

1 On the western coasts of Europe and America, where the change in surface
temperature is very gradual, Purpura lapillus (the west American ‘species’ are
at best only derivatives) is able to creep as far south as lat. 32° (Mogador) in the
former case, and lat. 24° (Margarita Bay) in the latter, the mean annual tempera-
ture of the surface water being 66° off Mogador, with an extreme range of only 8’,
and that of Margarita Bay 73°, with an extreme range of only 5°. On the eastern
coasts, where the Pacific and Atlantic gulf-streams cause a sudden change of tem-
perature, the Purpura is barred back at points many degrees farther north, viz. at
lat. 41° (Hakodadi), surface temperature 52°, extreme range 25°; and at lat. 42°
(Newhaven), surface temperature 52°, extreme range 30°.

364 ATLANTIC REGION CHAP.

It has been usual to classify marine Mollusca from moderate
depths under the following regions and sub-regions :—

Regions. Sub-regions. Regions. Sub-regions.
1, Arctic. » (1: Australian:
2. Boreal. C. Australian ) 5 Neozealanian.
A. Atlantic and } 3. Celtic. 1. Aleutian.
Circumpolar | 4. Lusitanian. 2. Californian.
5. West African. 3. Panamic.
6. South African. 3 4, Peruvian.
rican D; American er ae
: fi. Indo-Pacific. 5. Magellanic.
B. Indo-Pacific naa
(2. Japanese. 6. Argentinian.
7. Caribbean.
8. Transatlantic.

A. The Atlantic Region

includes the whole of the eastern shores of the Atlantic, from
the extreme north to the Cape of Good Hope, together with the
circumpolar seas, which may be regarded as roughly bounded
by the Aleutian Islands and the coasts of Newfoundland.

(1) Lhe Arctic Sub-region includes the circumpolar seas, and
‘is bounded in the N. Pacific by a line drawn between Cape
Avinoff in Alaska, and Cape Lopatka in Kamschatka, so as to ex-
clude the Aleutian Islands. On the western shores of the Atlantic
the cold Labrador current brings it as far south as the coast of
Newfoundland, but on the eastern shores the influence of the
Gulf Stream has the contrary effect, so that the North Cape may
be taken as its southern limit.

The principal genera (many species of which are common to
the whole sub-region) are Volutomitra, Buecinum, Buccinopsis,
Neptunea, Trophon, Bela, Admete, Velutina, Trichotropis, Lacuna,
Margarita, Philine, Pecten, Leda, Yoldia, Astarte, and Mya. The
shells are generally unicoloured, and of a dead white or rather
sombre tint.

(2) The Boreal Sub-region may be subdivided into two
provinces—the European and the American. The former includes
the entire coast-line of Norway, the Fiiroe Islands, and Iceland
(except perhaps the northern coast), and possibly the Shetland
Islands; the latter the American coasts from the Gulf of St.
Lawrence to Cape Cod (lat. 42°). Thus the Boreal American
province does not extend nearly so far south as the Boreal

XII BOREAL AND CELTIC SUB-REGIONS 365

European, the reason being that on the American coasts the cold
Labrador current, which hues the land, bars back the advance of
southern genera, but allows boreal genera to spread southwards,
while on the European side the warmer conditions produced by
the Gulf Stream keep the boreal species back, and allow more
southern forms to spread northwards.

Many of the Boreal species occur on both sides of the Atlantic,
and thus support the theory of a more continuous fringe of con-
tinental land once existing along the north of the Atlantic.
Among the prominent genera, besides several of those mentioned
under the Arctic Sub-region, are Purpura, Chenopus, Littorina,
Gibbula, Natica, Patella, Tectura, Chiton, Doris, Aeolis, Tellina,
Thracia.

(3) Lhe Celtic Sub-region includes the British Islands (except-
ing perhaps the Shetland Islands), the coasts of the North Sea
and the Baltic, with N. France to Cape Ushant. The absence
of any cold or warm current exerting direct influence upon the
coast-line of this sub-region causes a very gradual change in the
conditions of life as we move either southward or northward.
The fauna of the British seas contains a decided mixture of
northern and southern forms. The following are among the
common boreal species which attain their southward range on
our coasts: Tectura testudinalis Mill. (to Dublin Bay and
Scarborough), Zrichotropis borealis Brod. (to the Dogger Bank),
Margarita helicina Fabr. (to Yorkshire and Dublin Bay), JZ
groenlandica Chem. (western Scotland), Natica montacuti Forb.
(to Cornwall), Trophon truncatus Str. (to Tenby), Chiton mar-
moreus Fabr. (to Dublin Bay and Scarborough). Buccinwm
undatum and Littorina littorea become very scarce on our extreme
south-western coasts. Among Lusitanian species which reach our
coasts are Gibbula magus L. (to Orkney and Shetland Islands),
Phasianella pullus L. (to Caithness), Galerus chinensis L. (to
Milford Haven), Galeomma Turtoni Turt. (to Weymouth), Car-
dium aculeatum L. (to Isle of Man), Solen vagina L. (to north
Ireland).

It appears from the Mollusca of our Crag formations that at
the time of their deposition the temperature of our seas must
have been considerably warmer than it is now. Thus in the
Crag we find many species and even genera (e.g. Mitra, Fossarus,
Triton, Vermetus, Ringicula, Chama) which now occur no farther

366 LUSITANIAN SUB-REGION CHAP.

north than the southern coasts of the Channel, the west of
France, and the Mediterranean.

The Baltic, a sea specially lable to violent changes of tem-
perature, with a large admixture of fresh water at its eastern
end, appears to possess only about 65 species in all. More than
50 genera occurring on the western coasts of Denmark do not
enter the Sound. In the eastern portion of the Baltic marine
and fresh-water species live together (p. 12).

(4) The Lusitanian Sub-region extends from Cape Ushant
in the north to Cape Juby (lat. 28°) in the south, and includes
the whole of the Mediterranean, as well as the Azores, Canaries,
and Madeira groups.

The English Channel acts as an effectual barrier to the
northward extension of many species; as many as 81 species
which occur in western France do not reach British coasts
(P. Fischer). At the same time, the western coasts of France
are rather intermediate between the two sub-regions than
distinctly Lusitanian, for between 50 and 60 Mediterranean
genera do not occur on those coasts.

The Mediterranean itself is exceedingly rich in species, about
1200 in all QGncluding deep-water species) being known. <A
certain number of these belong to tropical genera which here
find their northern limit, e.g. Fasciolaria, Cancellaria, Sigaretus,
Siliquaria, Chama, Spondylus. Here too occur Carinaria,
Lobiger, Oxynoe, Pedicularia, Cypraea, Marginella, Mitra, Dolium,
Cassis, Cassidaria, Pisania, Huthria, Vermetus, Argonauta, and
many others. A few Celtic and even Boreal species, which occur
on the western coasts of Morocco, do not enter the Mediterranean.
Among these are Purpura lapillus, Helcion pellucidum, and
Tellina balthica. Halia, a rare West African genus akin to
Pleurotoma, is found in Cadiz Bay, and the West African Cym-
bium occurs on the Spanish coasts as far as Malaga.

The Black Sea, whose northern and western coasts are
exceedingly cold, 1s comparatively poor in species. The Sea of
Azot is chiefly characterised by forms of Cardium.

(5) The West African Sub-region extends from Cape Juby to
a point probably not very far south of lat. 30° 8., the cold cur-
rent which sweeps up from the Pole probably limiting the south-
ward extension of tropical species on this side of Africa, while
the warm Mozambique current on the eastern side permits the

XII WEST AND SOUTH AFRICAN SUB-REGIONS 367

spread of many Indo-Pacific species almost as far south as the Cape.
Owing to its extreme unhealthiness, and the absence of harbours,
the sub-region is very little known.

The principal genera are Cymbium, Pleuwrotoma, Marginella,
Terebra, Mitra, Agaronia, Murex, Cancellaria, Purpura, Pseud-
oliva, Natica, Tellina, Lucina, Tugonia, Schizodesma, and Arca.
Studer has enumerated as many as 55 species common to West
Africa and the opposite American shores. The north and south
equatorial currents, which circulate in this part of the Atlantic,
probably transport the larvae from one coast to the other. Pur-
pura coronata Lam., a characteristic West African species, is
represented by a well-marked variety 11 Demerara.

The Mollusca of St. Helena (178 known species) most
resemble those of the West Indies, 50 per cent being common,
while 50 per cent are common to the Mediterranean. From
Ascension Island only 83 species are known, which in their
general relations resemble those of St. Helena.!

(6) The South African Sub-region extends along the coast
from about lat. 30° on the west, to about East London on the
east. Mr. G. B. Sowerby enumerates 740 species from ‘South
Africa,’ but includes in this list Natal species, which more properly
belong to the Indo-Pacific fauna. Of these 740, 323 are
pecuhar, while 67 also occur in European seas, some being
familiar on our own shores. It is remarkable to find in a sub-
region separated from ourselves by the whole width of the tropics,
such well-known forms as Mangilia costata Don., I. septangularis
Mont., Cylichna cylindracea Penn., Pholas dactylus 1, Solen
marginatus Pult., Cultellus pellucidus Penn., Ceratisolen lequmen
L., Lutraria oblonga Chem., Tellina fabula Gmwnel., 7. tenuis Da C.,
Modiolaria discors L., and many others.

The leading genera are Huthria, Triton, Cominella, Bullia,
Nassa, Cypraeovula, Oxystele, Fissurella, Fissurellidaea, Patella,
and Chiton.

The Mollusca of Kerguelen Island and the Marion and
Crozets groups show relationship partly with South America,
partly with the Cape, and partly with South Australia and New
Zealand, thus showing some trace of a circumpolar antarctic fauna
corresponding to, but not nearly so well marked as that of the
circumpolar arctic sub-region. Among the remarkable forms

1 E. A. Smith, P. Z S. 1890, pp. 247, 317.

308 INDO-PACIFIC REGION CHAP.

discovered off Kerguelen are Neobuccinwm and a sub-genus of
Struthiolaria (Perissodonta).

B. The Indo-Pacific Region

includes the whole of the coast-line of the Indian and western
Pacific oceans, from about East London in South Africa to the
north of Niphon (lat. 42°) in Japan, with the Red Sea and
Persian Gulf, the whole of the Indo-Malay Archipelago, Polynesia
to the Sandwich Islands in the north-east, and Easter Island in
the south-east, and Australia to Swan River in the west, and to
Sandy Cape and Lord Howe’s Island in the east. It is especially
the region of coral reefs, which furnish so favourite a home of the
Mollusca, and which are entirely absent from the Atlantic
Region.

(1) Lhe Indo-Pacific Sub-region proper (which includes the
whole of this region except that part defined below as the
Japanese Sub-region) is by far the richest in the world. The
marine Mollusca of the Philippines alone (in some respects the
nucleus of the whole region) have been estimated at between
5000 and 6000 species, and Jousseaume estimates Red Sea
species at about 1000. Some prominent genera are very rich in
species. Garrett enumerates from Polynesia 81 species of Conus,
60 of which occur on the Viti Is, 21 on the Sandwich Is., and
only 14 on the Marquesas, where coral reefs are almost absent ;
82 species of Cypraca, Viti Is. 44, Sandwich Is. 31, Marquesas
only 13; 167 species of Mitra (besides 29 recorded by others),
Viti Is. 120, Sandwich Is. 36, Marquesas 7. Of 50 existing
species of Strombus, 39 occur in this region, and 10 out of 1
EHburna.

The following important genera are quite peculiar to the
region: Nautilus, several forms of Purpuridae, eg. apana,
Magilus, Rapa, Melapium, and Ricinula ; Tudicla, several forms
of Strombidae, e.g. Rostellaria, Terebellum, Pteroceras, and Rimella ;
Cithara, Melo, Neritopsis, Stomatia, Malleus, Vulsella, Cucullaea,
Tridacna, Hippopus, Libitina, Glaucomya, Anatina, Aspergilum,
and many others.

The number of species common to the Red Sea and
Mediterranean is exceedingly small, some authorities even deny-
ing the existence of a single common species. The present

XII JAPANESE SUB-REGION—-AUSTRALIAN REGION 369

author, from an examination of the shells dredged by Mac-
Andrew at Suez, regarded 17 species as common, and Mr. E. A.
Smith has confirmed this view with regard to 8 of the species in
question.t The Mollusca occurring in Post-pliocene beds at Suez
show that Mediterranean species lived there in comparatively
recent geological times.

The opening of the Suez Canal appears to have already
induced several species to start on their travels from the Mediter-
ranean to the Red Sea and vice versd. Two Red Sea species
(Mactra olorina Phil., Mytilus variabilis Kr.) had in 1882 estab-
lished themselves at Port Said, while two Mediterranean species
(Pholas dactylus L., Solen vagina L.) had reached Ismailia.”

(2) The Japanese Sub-region consists of the Japanese Islands to
Niphon, together with Corea and a stretch of adjacent mainland
coast of unknown extent. The warm Kuro Siwo current, sweep-
ing up between Luzon and Formosa, permits tropical species to
extend much farther north than on the opposite shores of America,
where a cold polar current keeps them back. A certain number
of species, however, are common to the two shores of the Pacific,
and a few circumpolar species occurring on our own coasts reach
Japan, e.g. Trophon clathratus, Puncturella noachina, Mya arenaria,
Modiola modiolus, Lasaea rubra, and Nucula tenuis.

Among the characteristic genera are Fusus, Siphonalia, Colum-
barium, Hemifusus, Rapana, Chlorostoma, Pleurotomaria, Haliotis,
and Cyclina.

C. The Australian Region

includes the Australian coast-lhne from about Swan R. (lat.
32° S.) to Sandy Cape (lat. 25° S.), Tasmania, New Zealand, and
the adjacent islands (except Lord Howe’s I.).

(1) The Australian Sub-region proper (which consists of the

1 A. H. Cooke, Ann. Mag. Nat. Hist. (5) xviii. (1886) p. 880 f; E. A. Smith,
P. Z. S. 1891, p. 391 f.

2 C. Keller, Newe Denksch. Schw. Gesell. xxviii. 1883, pt. 3.

® According to Tate (Zrans. Roy. Soc. S. Austr. 1887-88, p. 70), ‘ Australian’
species predominate at Freemantle (32°), but Tenison-Woods (J. Roy. Soc. N. S. Wales,
xxii. p. 106) holds that the tropical fauna extends as far south as Cape Leeuwin (34°),
and that the Australian forms are not predominant until the extreme south.
Tenison-Woods regards Cape Byron (31°) as the limit of the tropical fauna on the
east coast, while some characteristic tropical genera reach Port Jackson, and a few
(e.g. Cypraea annulus) Tasmania.

VOL. III 2B

370 AUSTRALIAN REGION CHAP.

whole of the region excepting New Zealand and the adjacent
islands) is determined by the influence of the Antarctic Drift,
which washes the whole of the southern coasts of Australia, and
runs strongly northward between Australia and New Zealand.
The E. Australian warm current from the north is checked at
Sandy Cape by this cold current, and flows off to New Zealand,
the western shores of which island are consequently much warmer
than the eastern. On the western coast of Australia the
Antarctic Drift has less force, and tropical genera accordingly
range some 7 degrees farther south on the western than on the
eastern coasts.

The characteristic genera are Voluta (of which half the known
species occur on Australian coasts’), Cominella, Siphonalia,
Struthiolaria, Risella, Phasianella, a number of genera belonging
to the Trochidae, eg. Liotia, Clanculus, Huchelus, Thalotia,
Hlenchus, Trochocochlea, Zizyphinus, Bankivia; Trigonia, Myodora,
Myochama, Solenomya, Ephippodonta, Anapa, Mylitta, Mesodesma,
and Chamostrea. Trigonia, originally discovered as a recent
form in Sydney Harbour (p. 65), is not peculiar to that locality,
occurring also off Cape York, West Australia, and Tasmania.

(2) The Neozealanian Sub-region includes New Zealand, with
the outlying islands (Chatham, Auckland, and Campbell Is.).

As many as 455 species (Cephalopoda, 8; Gasteropoda, 311;
Scaphopoda, 2; Pelecypoda, 154) have been enumerated by Professor
F. W. Hutton as occurring within the sub-region, of which only
64 are found elsewhere, the proportion of peculiar species being
thus nearly 86 per cent. New Zealand therefore is, in its marine,
no less than its land Mollusca, greatly isolated.

The characteristic genera are Anthora, Cryptoconchus, and
Vanganella, which appear to be quite peculiar, 7Zrophon, Cominella,
Euthria, most of the Trochidae also characteristic of S. Australia,
Haliotis, Patella; Taria, Mesodesma, Mylitta, Zenatia, Standella,
and Myodora.

D. The American Region
includes the entire coasts of North and South America with the
adjacent islands, south of Cape Avinoff on the western, and south

1 A full account of the distribution of Voluta is given by Crosse, Journ. de Conchy!.
(3) xix. p. 263.

XII ALEUTIAN, CALIFORNIAN, PANAMIC SUB-REGIONS 27 1

of Cape Cod on the eastern coast, the portions north of these
points belonging to the Arctic Sub-region.

(1) The Aleutian Sub-region consists of the islands of Yesso and
Saghalien, with the adjacent shores of the Sea of Okhotsk to Cape
Lopatka, the Aleutian Is., and the west American coast from about
Cape Avinoff (lat. 60° N.) to St. Jean de Fuca Straits.

A certain number of species, probably of arctic origin, are
common with British and also with East American shores, the
former being the more numerous. Species as familiar to us as
Lacuna divaricata Fabr., Trichotropis borealis Brod., Pholas
crispata L., Mya truncata L., MW. arenaria L., Mytilus edulis L.,
and Modiolaria nigra Gray, occur. The more characteristic
genera are Chrysodomus, Volutharpa, Buccinum, Tectura, Scurria,
Chiton, Cryptochiton (Cr. Stelleri Midd. is by far the largest
known of the Chitonidae, 6 inches long), Zellina, and Pecten.

(2) The Californian Sub-region extends from St. Jean de Fuca
Straits (lat. 48° N.) to Cape St. Lucas, the Gulf of California
belonging to the Panamic sub-region. The northern polar current,
which washes the shores of this sub-region throughout their whole
extent, prolongs the southward range of the more northern genera,
and keeps back those more markedly tropical, the latter, however,
creeping northward in the warmer waters of the Gulf of California.
Some authorities subdivide this immense stretch of coast-line, as
characterised by sub-temperate, temperate, and sub - tropical
genera, into the Oregonian, Californian, and Lower Californian
provinces.

The characteristic genera are—ain the north, Argobuccinum,
Zizyphinus, Chlorostoma, Tectura, Scurria, Chiton (Katharina,
Mopalia, Tonicia), Cryptochiton, Placunanomia, and Mytilimeria ;
in the centre, Purpura, Monoceros, Amphissa, Norrisia, Platyodon,
Tapes, and Macoma; and, towards the south, Olivella, Chorus,
Macron, Pseudoliva, Trivia, and Haliotis.

(3) The Panamice Sub-region extends from the head of the
Gulf of California to Payta in Peru (lat. 5°S.). It is exceed-
ingly rich in species, about 1500 having been described. The
Mollusca are entirely distinct from those of the Indo-Pacific
Region, which, although extending from Natal to the Sandwich
Islands, are unable to pass the enormous extent of sea which
separates the nearest Polynesian island from the American coast.

On the two sides of the isthmus of Panama there occur certain

372 PANAMIC, PERUVIAN, AND MAGELLANIC SUB-REGIONS cuap.

pairs of species, which, while specifically distant, are evidently
closely related to one another. Amongst these are, on the
Panamic side, Purpura speciosa, Cypraea cervinetta, Cassis ab-
breviata, Natica Chemnitzii, and Strombus gracilior, correspond-
ing to Purpura deltoidea, Cypraea exanthema, Cassis inflata,
Natica marocecana, and Strombus pugilis, on the Caribbean. It is
reasonable to conclude that these “analogous species” are
descendants of a stock which was common to both seas when the
isthmus was open (probably not later than Miocene times), and
which have, since the closing of the isthmus, become modified,
some species considerably more than others.

Among the characteristic genera (compare p. 3) are Conus,
Pleurotoma, Terebra, Murex, Purpura, Oliva, Northia, Cantharus,
Columbella, Anachis, Cypraea, Strombus, Cerithium, Coecum,
Crepidula, Crucibulum, Vitrinella; Tellina, Semele, Tellidora ;
and Arca.

(4) The Peruvian Sub-region extends from Payta in Peru to
about the latitude of Conception in 8. Chili (37° S.), being
checked from further extension southward by the cold Humboldt
current, whose force is distinctly felt as far north as Callao. This
cold current thus produces the same results as the similar current
which impinges on 8. Africa, but has even more effect in decisively
separating the fauna on the two sides of the great peninsula,
scarcely a single species being common to the western and eastern
coasts of 8. America. The characteristics of the coast-lines them-
selves contribute to this result. The Chilian coast is rocky, and
descends abruptly to a great depth, while that of Patagonia and
Argentina is sandy and very shallow to a great distance from
land.

The characteristic genera are Cancellaria, Columbella, Monoceros,
Concholepas, Trochita, Fissurella, Chiton ; Ceronia, Malletia, and
Cumingia. Some of the Californian genera, absent or poorly
represented in the Panamic Sub-region, reappear in Chih, eg.
Scurria, Tectura, and Chlorostoma.

(5) The Magellanic Sub-region includes the coast-line and
adjacent islands (with the Falklands) from Conception in
S. Chili to about Port Melo in Eastern Patagonia (lat. 45° S.).

The principal genera (many of which find a habitat on the
gigantic Macrocystis which grows on every rock at low water) are
Huthria, Voluta (6 species, one, V. magellanica, the largest known),

XII ARGENTINIAN AND CARIBBEAN SUB-REGIONS 373

Monoceros, Photinula, Patella, Chiton ; Modiolarca, Malletia, and
Mulinia. Several genera, characteristic of the Boreal and Arctic
sub-regions, recur, e.g. Trophon, Admete, Margarita, Puncturella,
Cyamium, and Astarte.

(6) The Argentinian’ Sub-region extends from about Cape
Melo in Patagonia to the neighbourhood of 8. Caterina I. in
South Brazil (lat. 28° S.). The sub-region stands in the same
relation to the Magellanic, on the east coast, as the Peruvian sub-
region on the west, but, owing to the influence of the warm
Brazil current, which overpowers the colder water of the Falkland
branch of the Cape Horn current, it reaches a point much farther
south.

The Mollusca are not well known. The prevailing genera
appear to be Oliva, Olivancillaria, Voluta, Bullia, Crepidula ;
Periploma, and Lyonsia.

(7) The Caribbean Sub-region extends from 8. Caterina I. in
the south to Florida in the north, and includes the shores of the
Gulf of Mexico and the whole of the West Indies. The influence
of the warm Brazil current (a branch of the South Equatorial)
carries the range of the purely tropical species to a point much
farther south than is reached by the tropical species on the west
coast.

The sub-region is very rich in species, especially on the coral
reefs of the Bahamas and N. Cuba, but the exceedingly small
tide-fall makes shore collecting somewhat difficult beyond a certain
point. The leading genera are Murex, Purpura, Melongena,
Latirus, Marginella, Strombus, Triton, Cerithium, Littorina,
Nerita, Scalaria ; Tellina, Strigilla, Lucina, and Venus. Plewro-
tomaria, a genus long regarded as extinct, has been dredged alive
off Tobago.

As compared with the tropical fauna of the Old World, that
of the New World is poor in peculiar genera (compare p. 368).
The relations of this sub-region to the West African and the
Panamic have been already dealt with (pp. 367 and 372).

(8) The Transatlantic Sub-region extends from Florida to Cape
Cod (see p. 364). In the north the limits of the sub-region are
distinctly marked, in the south Caribbean species intermingle.

1 Usually known as ‘ Patagonian,’ but since the Magellanic Sub-region includes
a considerable part of Patagonia, and since the greater part of sub-region (6) lies out
of Patagonia, it has been thought advisable to change the name.

374 TRANSATLANTIC SUB-REGION—-ABYSSAL MOLLUSCA cuap.

Gould and Binney,in their Jnvertebrata of Massachusetts, enumerate
2175 species (Cephalopoda, 6; Gasteropoda, 159 ; Scaphopoda, 2 ;
Pelecypoda, 108), of which 59 (Gasteropoda, 37; Pelecypoda,
22) are British.

Among the characteristic genera are Urosalpinz, Hupleura,
Fulgur, Ptychatractus, Nassa, Crepidula; Solenomya, Mactra,
Cypricia, Raéta, Astarte, and Yoldia. Our common Littorina
littorea appears to have been introduced into Nova Scotian
waters in about 1857, no previous trace of it occurring either in
literature or shell-heaps. Since then it has spread rapidly into
the Gulf of St. Lawrence, and also as far south as Newhaven, and
is said to be driving out the indigenous ZL. palliata from New
England shores.'_ The debt has been repaid by the introduction
into British waters of the American clam (Venus mercenaria L.),
which, according to the Manchester City News of 23rd March
1889, was first observed in the Humber in 1864, and has
steadily increased up to the present time, when it bids fair to
compete, in those waters, with the familiar Cardiwm edule.

Characteristics of Abyssal Mollusca.—Large shells appear
to be rare in the great ocean depths, and are usually very fragile ;
even moderately-sized specimens are far from common. ‘The
only group in which species occur larger than the usual size is
the Nudibranchs, which are represented by at least one form
larger than an orange.

It would seem that abyssal molluscs are much less active and
energetic than their brethren on the shores. This view is
favoured by the looseness of their tissues, which seem ill adapted
for prompt and vigorous action. The tenacious character of the
mud on the ocean floor must make rapid motion very difficult.
The shell itself is usually fragile and delicate, the upper layers
of arragonite being thin as compared with shallow-water species,
which makes the nacreous layer, when present, appear unusually
conspicuous; in many cases the surface is characterised by a
peculiar iridescence or sheen. The colour in the shell of deep-sea
Mollusca is never very pronounced, and is often absent altogether.
Light pink and salmon, pale yellow and brown, are not uncommon.
If the colour is in pattern, it is usually in the form of necklaces
of spots, which sometimes coalesce into bands. With regard to
sculpture, stout knobs and powerfully buttressed varices, such as

1 Amer. Nat. xx. p. 9381.

XII CHARACTERISTICS OF ABYSSAL MOLLUSCA 375

occur in the tropical Murex and Purpura, are not found in deep-
sea species. But the ornamentation is frequently elaborate, and
the sculpture rich and varied. There is an especial tendency
towards strings of bead-like knobs, revolving striae, and delicate
transverse waves, the sculpture being in many cases of a
character which tends to strengthen the structure of the shell,
like the ridges in corrugated iron.

A remarkable feature in some deep-sea Mollusca is their
singular resemblance, in shape, and particularly in the possession
of a strong green periostracum, to some of our common fresh-water
species. According to Dr. Dall, the cause of this phenomenon
is the same in both cases. The fresh-water Mollusca secrete a
strong periostracum, in order to protect the shell against the
corrosive influence of the carbonic acid gas with which the water
is surcharged. The shells of deep-sea Mollusca, living, as they
do in water probably undisturbed by currents of any kind, have
to protect themselves against the same eroding influence, and do
so in the same way.'

Mollusca which live exclusively on algae and other forms of
plant life are almost entirely wanting in the great depths, where
vegetation is probably unknown. ‘The struggle for, existence
must be much less keen than in the thickly populated shallows,
where vicissitudes of every kind occur. The absence of rapid
motion of water must obliterate many of those mechanical effects
which tend to produce modifying influences upon the animals
affected. In the absence of circumstances tending to cause varia-
tion, in the unbroken monotony of their surroundings, species
must, one would think, preserve a marked uniformity over an
exceedingly wide area of range.

Vegetable food being wanting, those genera which in shal-
lower waters never taste flesh, are compelled to become carnivor-
ous. Characteristic of the great depths are very remarkable forms
of Trochidae, in whose stomachs have been found the remains
of Corallines and Foraminifera. According to Dr. Dall, the
results of this diet show themselves in the greatly increased space
occupied by the intestine, in the diminution, as regards size, of
the masticatory organs, the teeth and jaws, and also in the pro-
longation of the anal end of the intestine into a free tube, which
carries away the excreta in such a way that they do not foul the

1 W. H. Dall, Proc. Biol. Soc. Washington, v. p. 1 f.

376 CHARACTERISTICS OF ABYSSAL MOLLUSCA CHAP.

water taken into the gills) The amount of nutriment contained
in the bodies of dead Foraminifera is so small that a compara-
tively large quantity must be swallowed to keep the vital
energies active, and therefore the amount evacuated must be pro-
portionately larger also. The abyssal Trochidae, then, and many
other genera, sustain themselves by feeding on the ‘rain’ of dead
animal matter which falls upon the ocean floor, not so much
hunting their prey as opening their mouths and eating what-
ever happens to fall into them. Genera which are normally
carnivorous would appear to do the same. The Pleurotomidae,
for instance, are a family markedly characteristic of very deep
water. Representatives of the genus which occur in shallower
water are known to secure their prey while in the living state.
But, according to Dr. Dall, a singularly small proportion of deep-
sea Mollusca, as compared with those from the littoral region,
show signs of having been drilled or attacked by other Mollusca.
This could hardly be the case if the Pleurotomidae retained their
predatory habits, since they are more numerous in the great
depths than any six other families taken together. It has
already been mentioned (p. 186) that a large proportion of deep-
sea Mollusca are perfectly blind.

Amongst other remarkable forms from the great depths may
be mentioned Plewrotomaria, with its singular anal slit (Fig. 269,
p. 407) extending in some cases half-way round the last whorl.
Three or four species of this genus, so characteristic of almost all
fossiliferous strata down to the Cambrian, have been obtained in
very limited numbers off the West Indies and Japan. Dentaliidae,
especially the sub-genus Cadulus, find a congenial home in the
slimy ocean mud. One of the greatest molluscan treasures procured
by the Challenger was Guivillea alabastrina Wats., a magnificent
Volute as white as alabaster, 65 inches long, which was dredged
from 1600 fath. in the South Atlantic, between Marion Island
and the Crozets. Another very curious form, belonging to the
same family, is Provocator pulcher Wats., a shell about half the
size of Guivillea, of stouter proportions, and with an angulated
and patulous mouth. This shell was dredged by the Challenger
in comparatively shallow water (105-150 fath.) off Kerguelen
Island. Among the Trochidae are the fine new genera Lasilissa,
Bembia, and Gaza. The exploring voyages of the American sur-
veying steamer Blake, in the Gulf of Mexico and the Caribbean

XII REMARKABLE ABYSSAL MOLLUSCA BY:

Sea, have given us the remarkable new forms Benthobia (possibly
akin to Admete), Mesorhytis (a sub-genus of Fasciolaria hitherto
only known from the Cretaceous of North America), and Bentho-
dolium (possibly = Oocorys), a genus akin to Cassis.

In his report on the Pelecypoda obtained by the Challenger,
Mr. E. A. Smith remarks that as a rule “very deep-water
‘benthal’ species certainly have a tendency to be without
colour and of thin structure, facts no doubt resulting from the
absence of light, the difficulty of secreting lime, the scarcity of
food, and other unfavourable conditions of existence.” At the
same time, he notices that most of the species obtained belong to
genera which, even when occurring in shallow water, are thin and
colourless, e.g. Neaera, Lima, Cryptodon, Abra, Verticordia, ete.
Deep-water species of such genera as have a decided periostracum
(Malletia, Limopsis, Leda, Nucula, Arca) retain it with little if
any modification. The deep-water Pelecypoda of the Atlantic
and Pacific Oceans present no special features of interest. The
species are few in number, and the genera are not remarkable
either for novelty or peculiarity of form.

The greatest depth at waich Pelecypoda have been obtained
is 2900 fath. mid North Pacific (Callocardia pacifica Sm., Abra
profundorum Sm.); the greatest depth at which Gasteropoda have
been obtained is 2650 fath. South Atlantic (Stylifer brychius
Wats.), both by the Challenger. The deepest Challenger Nudi-
branch came from 2425 fath., and the deepest Chiton from 2300
fath. The greatest depth ever dredged is 4575 fath. off the east
coast of Japan.

CHAPTER XIII
CLASS CEPHALOPODA

THE Cephalopoda present a complete contrast to the majority of
the Mollusca in habits and in many points of organisation. In
their power of rapid movement and their means of progression,
their extreme ferocity and carnivorous habits, their loss, in so
many cases, of a shell, and in its constitution when present, in
the general symmetry of their parts, in their reproductive and
nervous system, they stand in a position of extreme isolation
with nothing to connect them with the rest of the phylum.

Professor A. E. Verrill has collected many interesting details
with regard to gigantic Cephalopoda occurring on the north-
eastern coasts of America. From these it appears that the
tentacular arms of some species of Architeuthis measure as much
as 32, 33, 35, and 42 feet in length, while the total length,
including the body, sometimes exceeds 50 feet. Even off the
Irish coast a specimen was once captured whose tentacular arms
were 30 feet long, the mandibles 4 inches across, and the eyes
about 15 inches in diameter.1. The strength of these giant
Cephalopods, aided as they are by formidable rows of suckers and
other means of securing a grip, is almost incredible. Cases are
not uncommon, in which persons diving or bathing have been
attacked, and have with difficulty made their escape.

Great damage is frequently inflicted by Cephalopoda upon
shoals of fish on our own coasts. Off Lybster (Caithness) Loligo
and Ommastrephes devour the herring, large numbers of which are
cut up and bitten on the back of the neck by these creatures.
On the American coasts the mackerel fisheries are sometimes
entirely spoiled by the immense schools of squid which infest the

1 Trans. Connect. Acad. v. p. 177 ; Zoologist, 1875, p. 4502.

CHAP. XIII CEPHALOPODA 379

Bay of St. Lawrence.’ When excited in the pursuit of fish
Cephalopoda leap high out of the sea. Dr. W. H. Rush? relates
that when about 300 miles off the coast of Brazil, a swarm of
hundreds of decapods flew from the water and landed on the
deck of the ship, which was 12 feet above the surface level, and
they had to go over the hammock nettings to reach it.

The common Octopus vulgaris Lam., of our own and the south
European coasts, inhabits some rocky hole, the approaches to
which, like the den of a fabled giant, are strewn with the bones
of his victims. Homer himself knew how hard it is to drag the
polypus out of his hole, and how the stones cling fast to his

Fic. 238.—Octopus
vulgaris Laim.,
Naples: A, At
rest ; B, in mo-
tion ; 7, funnel,
the arrow show-
ing the direc-
tion of the pro-
pelling current
of water. (After
Merculiano. )

sa fee es =e GOON
\ NY : = Re ert = ay =
a = y! i (dat STN EH) NO ith.
Hitt Wil facet . Sle

suckers. The colour-changes, which flit across the skin of the
Octopus, appear, to some extent, expressive of the different emotions
of the animal. They are also undoubtedly protective, enabling it
to assimilate itself in colour to its environment. Mr. J. Hornell *
has noticed an Octopus, while crawling over the rock-work in his
tank, suddenly change the colour of the whole right or left side
of its body, and of the four arms on the same side, to a snowy
whiteness. They have also been seen to change colour, as if
involuntarily, according to the material on which they crawl.
1 Rep. Scotch Fish. iii. 1885, App. F, p. 67.
2 Nautilus, vi. 1892, p. 82. 3 Journ. Mar. Zool. i. pp. 3, 9.

380 CEPHALOPODA—DIBRANCHIATA CHAP.

The nerve-centres which control the chromatophores or pigment
cells, causing them to expand or contract, are found to connect
with the optic ganglia; hence the changes of colour may be
regarded as a reflex result of the creature’s visual perception of
its surroundings.

Order Dibranchiata

Cephalopoda with two symmetrical branchiae, funnel com-
pletely tubular, mouth surrounded by 8 or 10 arms furnished
with suckers or hooks, ink-sac and fins usually present, eyes with
a lens; shell internal or absent.

The Dibranchiata are not known from Palaeozoic strata, and
first appear (Belemnites, Belemnoteuthis) in the Trias. Whether
they are to be regarded as derived from some form of Tetra-
branchiata, e.g. Orthoceras, or as possessing an independent origin
from some common stock, cannot at present be decided. They
attain their highest development at the present time. The
earhest representatives of the Order (the Phragmophora) possessed
a shell chambered like that of the Tetrabranchiata. These
chambered Dibranchiates rapidly reached their maximum in the
upper Lias and as rapidly declined, until at the close of the
Cretaceous epoch they were comparatively scarce, only a few genera
(Beloptera, Spirulirostra) surviving into Tertiary times.

The ordinary Dibranchiate Cephalopod may be regarded as
consisting of two parts—(a) the head, in which are situated the
organs of sense, and to which are appended the prehensile organs
and the principal organs of locomotion; (6) a trunk or visceral
sac, enclosed in a muscular mantle and containing the respir-
atory, generative, and digestive organs. The visceral sac is often
strengthened, and the viscera protected, by an internal non-spiral
shell. The ‘arms’ which surround the mouth are modifications
of the molluscan foot (p. 200), and are either eight or ten in
number. In the former case (Octopoda) the arms, which are
termed ‘sessile, are all of similar formation, in the latter
(Decapoda), besides the eight sessile arms there are two much
longer ‘ tentacular’ arms, which widen at their tips into ‘clubs’
covered with suckers.

Remarks have already been made on the generative organs
of Cephalopoda (p. 136 f.), the branchiae (p. 170), the nervous

XIII CEPHALOPODA—DIBRANCHIATA 381

system (p. 206), the eye (p. 182), the radula (p. 236), and the
ink-sac (p. 241).

One of the most characteristic features of the Dibranchiata
are the acetabula, or suckers, with which the
arms are furnished. They are usually disposed
on the sessile arms in rows (of which there are
four in most Sepia, two in Octopus, and one in
Eledone), and become more numerous and smaller
at the tip of the arm. They are massed together
in large numbers of unequal size on the ‘clubs’
in the Decapoda, particularly in Loligo. | In most
Octopoda their base is flush with the surface of
the arm, but in Decapoda the acetabula are ped-
unculate, or raised on short stalks. In Octopoda
again, the acetabula are fleshy throughout, but
in the Decapoda they are strengthened by a
corneous rim with a smooth or denticulate edge
(Ommastrephes, Architeuthis). Many of the J
acetabula on the tentacular and sometimes on Fre. 239,—‘Club’
the sessile arms of the Onychoteuthidae enclose lige bul

: ; garis L., show-
a powerful hook, which is retractile lke the ing the crowded
slewvs Of a. cat pedunculate ace-
eee un eeeLe tabula, x4.
In mechanical structure the acetabula consist
of a disc with a slightly swollen margin, from which a series of
muscular folds converge towards the centre of the
disc, where a round aperture leads to a gradually
widening cavity. Within this cavity is a sort of
button, the caruwnele, which can be elevated or
depressed like the piston of a syringe; thus when
the sucker is applied the piston is withdrawn and
— a vacuum created (Owen).
Fie. 240. — One
Ot theunackers In many Octopoda the arms are connected by
of Architeuthis » web (the wmbrella), which sometimes extends up
duaz Stp.,show- : z ;
ing the denti- the greater part of the arms (Cirrhoteuthis, some
culate margin P/edone), at others occurs only at the base. The
and corneous : : : .
ring; p, ped- use of the umbrella is perhaps to assist in loco-
mae. motion, by alternate contraction and expansion..
A cartilaginous skeleton is well developed, especially in the
Decapoda. In Sepia a cephalic cartilage forms a complete ring
round the oesophagus, the eyes being situated in lateral prolonga-

3 82 OCTOPODA CHAP.

tions of the same. In front of the cephalic cartilage occurs a
piece like an inverted T, which supports the base of the anterior
arms. The Decapoda have also a ‘nuchal’ cartilage, connecting
the head with the anterior dorsal portion of the mantle, while
cartilaginous knobs on the ventral mantle button into correspond-
ing sockets on the funnel.

Sub-order I.—Octopoda.—Body round or bag-like, generally

Fic. 241.—Cirrhoteuthis magna Hoyle, 8. Atlantic. Two of the left arms and their
web have been removed : f, funnel ; fi, ji, fins ; m, mouth. (After Hoyle, x 5's.)

without fins, arms eight, suckers fleshy, usually sessile, oviducts
paired, no nidamental glands, shell absent.

Fam. 1. Cirrhoteuthidae.— Body with two prominent. fins ;
arms in great part united by a web; one row of small suckers,
with cirrhi on each side—Atlantic and Pacific Oceans, deep
water (Fig. 241).

Fam. 2. Amphitretidae——Body gelatinous, mantle fused with

XIII OCTOPODA

383

the funnel in the median line, forming two openings into the
branchial cavity; arms with one row of suckers; umbrella
extending more than two-thirds up the arms——South Pacific

(Fig. 242).

The two pocket-like openings into
the branchial cavity are unique among
Cephalopoda (Hoyle).

Fam. 3. <Argonautidae. — Female
furnished with a symmetrical, unilo-
cular shell, spiral in one plane, secreted
by thin terminal expansions (the vela)
of the two dorsal arms, no attach-
ment muscle; suckers in two rows,
pedunculate ; male very small, without
veligerous arms or shell.— All warm
seas (Fig. 243). Pliocene

The shell consists of three layers,
the two external being prismatic, the
middle fibrous. Its secretion by the
arms and not by the mantle edge is

Fic. 242. — Amphitretus pela-
gicus Hoyle, off Kermadec
Is.: e, eyes; f, funnel; yp,
right mantle-pocket. (After
Hoyle. )

unique, and shows that it is not homologous with the ordinary

mollusean shell.

The great controversy on the Argonauta, which once raged
with so much fierceness, is now matter of ancient history. It

Fic. 245.—Argonauta argo
L., the position assumed
by a specimen kept in
captivity, the arrow show-
ing the direction of move-
ment: 7, funnel ; m, mouth,
with jaws projecting ; sh,
shell, with arms as seen
through it; wa, webbed
arm clasping shell. (After
Lacaze-Duthiers. )

seems scarcely credible that between fifty and sixty years ago,
two of the leading zoologists of the day, Mr. Gray and M. de

384 OCTOPODA CHAP.

Blainville maintained that the animal which inhabits the
Argonaut shell is a parasite, without any means of depositing
or forming a shell of its own, but which possesses itself of the
Argonaut shell, either by expelling or succeeding the original
inhabitant, a supposed nucleo-branchiate (Heteropod) molluse akin
to Carinaria. The final blow to this strange hypothesis—which
was urged by the most ingenious series of arguments—was given
by Professor Owen, who in 1839 brought before the Zoological
Society of London the admirable observations of Madame
Jeannette Power, who made a continuous study of a number of
specimens of Argonauta in her vivarium at Messina. The
result of these observations tended to show that the young
Argonauta when first excluded from the egg is naked, but that
in ten or twelve days the shell begins to form; that the
principal agents in the deposition of shell are the two velated or
web-like arms; and that portions of the shell, if broken away,
are repaired by a deposition of calcareous matter.t

Fam. 4. Philonexidae.—Mantle supported by two ridges
placed on the funnel; large ‘aquiferous’ pores (supposed to
introduce water into the tissues) near the head or funnel; suckers
in two rows, pedunculate-—Atlantic and Mediterranean.

Genera: Ocythoe, arms of unequal size, no intervening mem-
brane, third arm on the right hectocotylised (see Fig, 51 p. 138),
two aquiferous pores at the base of the siphon; male very small;
Tremoctopus, two aquiferous pores between the eyes, two on the
ventral side of the head.

Fam. 5. Alloposidae—Mantle edge united to the head by
three commissures; arms extensively webbed, acetabula sessile.
Hectocotylised arm developed in a cavity in front of the right
eye.—N. Atlantic.

Fam. 6. Octopodidae—Head very large, arms elongated,
similar, more or less webbed, acetabula usually in two rows, sessile ;
mantle supported by fleshy bands, no cephalic aquiferous pores.

In Octopus proper the web is usually confined to the lower
part of the arms; Fischer separates off as Pteroctopus a form in
which it reaches almost to their extremity. The third right
arm (Fig. 52, p. 140) is hectocotylised, the modified extremity
being, according to Hoyle, sometimes minute, sometimes spoon-
shaped, with a tendency to transverse ridges, rarely slender and

1 Rep. Brit. Assoc. 1844, Transactions p. 74; P. Z. S. 1839, p. 35.

XII DECAPODA 385

very long. The relative length of the pairs of arms varies in
different species. Two cartilaginous stylets, imbedded in the
dorsal mantle, are said by Owen to represent the shell.

Other genera ; Pinnoctopus, body furnished with broad lateral
wings which meet at the posterior end; Cistopus, a large web
prolonged along the sides of
the arms, fitted with oval
aquiferous pouches, with pores
at their base, between each
pair of arms; ledone (Fig.
244), one row of acetabula ;
Tritaxeopus, Lapetella.

Sub-order II—Decapodu.
— Body oblong, mouth sur-
rounded by four pairs of sessile
andone pair of tentacular arms, Nes
the latter terminated by a ;
‘elub’; acetabula pedunculate \ |

and furnished with a corneous Fic. 244.—Hledone Aldrovandi Delle Chiaje,
Naples, from ventral side. x 43.

marein ; mantle margin locked
to the base of the funnel by a cartilaginous apparatus; head and
anterior part of body furnished with aquiferous pores; fins
present ; mandibles corneous ; oviduct single, large nidamental
glands in the female; shell internal.

The tentacular arms, which are the principal external feature
of the Decapoda, are not derived from the same muscular ring as
the sessile arms, but arise from the cephalic cartilage, and emerge
between the third and fourth arm on each side. In Sepia they
can be entirely retracted into a kind of pocket behind the eyes,
while in Loligo they are simply folded over one another. In
Chiroteuthis the arms are six times as long as the body, and the
clubs have four rows of denticulate suckers.

The anterior ventral! portion of the mantle is furnished with
a singular contrivance for locking it to the funnel, and so render-
ing the whole animal more capable of resisting the impact of any
force. This contrivance generally consists of a series of ridges
or buttons which fit into grooves or button-holes, the ridges being
on the interior face of the mantle and the corresponding grooves

1 It is convenient, but not morphologically correct, to apply the terms ‘ ventral’

and ‘dorsal’ in this sense.
VOL. II aC

386 DECAPODA CHAP.

on the funnel, or vice versd. This ‘resisting apparatus’ is most
elaborate in the pelagic genera, and least so in the more slugeish
littoral forms. A similar, but not so complex, arrangement
occurs also in the Octopoda.

The different forms of the shell appear to indicate successive
stages in a regular course of development. We have in Spirula
(Fig. 247) a chambered shell of the Tetrabranchiate type, but of
considerably diminished size, which has ceased to
contain the animal in its last chamber, and has
become almost entirely enveloped in reflected folds
of the mantle. These folds gradually concresce to
form a definite shell-sac, by the walls of which are
secreted additional laminae of calcareous shell -
substance. These laminae invest the original
shell, which gradually (Spirulirostra, Belosepia)
loses the spiral form and becomes straight, eventu-
ally disappearing, while the calcareous laminae
alone remain (Sepia). These in their turn dis-
appear, leaving only the plate or ‘pen’ upon which
they were deposited (Loligo), which itself also,
with the shell-sac, finally disappears, surviving
only in the early stages of Octopus (Lankester).

The Decapoda are divided, according to the
character of the shell, into Phragmophora, Sepio-
phora, and Chondrophora.'

A. PHRAGMOPHORA.— Arms furnished with
hooks or acetabula; shell consisting of a phrag-

Fic. 245.—‘ Club’ : :
of Onychotev- nvocone or chambered sac enclosed in a thin wall
this sp., show- (the conotheca), septa pierced by a siphuncle near
ing the hooks ; ¢ oe :
and clusters of the ventral margin (in Spirula alone this cham-

ixing cushions Hered sac forms the whole of the shell). The
and acetabula

below them. apex of the cone hes towards the posterior end of

ce the body, and is usually enveloped in a calcareous
guard or rostrum. Beyond the anterior end of the rostrum the
conotheca is extended forward dorsally by a pro-ostracum or
anterior shell, which may be shelly or horny, and corresponds to
the gladius of the Chondrophora. The rostrum consists of
calcareous fibres arranged perpendicularly to the planes of the
laminae of growth, and radiating from an axis, the so-called

1 dpayuos, partition ; o7mov, cuttle-bone ; xdvdpos, long cartilage.

XIII DECAPODA 387

apical line, which extends from the extremity of the phragmocone
to that of the rostrum. Distribution, see p. 380.

Fam. 1. Spirulidae—Arms with acetabula, shell a loose
spiral, without rostrum or pro-ostracum, partially external,
enclosed in two lobes of the mantle (Figs. 247 and 248).

The single species of the single genus (S. Peronii Lam. = laevis
Gray) has not yet been thoroughly investigated, although the
shell occurs in thousands on many tropical beaches, and is some-
times drifted on our own shores. The animal appears to have
the power of adhesion to the rocks by means of a terminal sucker
or pore. The protoconch is present,
and contains a prosiphon, which does
not connect with the siphuncle. The
septal necks are continuous, not broken
as in Nautilus. The siphuncle is on
the ventral margin of the shell, the
last whorl of which projects shghtly on
the dorsal and ventral sides, but 1s
even there covered by a thin fold of
the mantle. The retractor muscles of
the funnel and of the head find their
point @appur on the shell, the last
chamber of which contains the pos-
terior part of the liver, with which the
membranous siphuncle is connected.

Fam. 2. Belemnitidae—Arms hooked
as in Onychoteuthis, fins large; phrag-
mocone straight, initial chamber globu-
lar, larger than the second, rostrum

~ IK

often very long, investing the phrag- NI

mocone, pro-ostracum sword- or leaf- Fie. 246.—Sepia officinalis L.,
with mantle cut away to

show position of internal

served, ink-sac present—Lower Lias shell. x4. (The ends of the
tentacular arms are cut off.)

shaped, rounded in front, seldom pre-

to Cretaceous.

The Belemnitidae are believed to have been gregarious, and to
have lived in shallow water on a muddy bottom. Specimens are
sometimes found in which even the ink-sac can be recognised 7
situ. The relative proportions of rostrum and phragmocone vary
greatly in different groups, the rostrum being in some cases
two feet long, in others only just enclosing the phragmocone.

388 DECAPODA CHAP.

As a rule the rostrum is the only portion which has been
preserved.

Fam. 3. Belosepiidae.—Phragmocone short, slightly curved,
chambers small, placed at the posterior end of a sepion, rostrum
solid, obtuse-—Kocene (Paris, Bracklesham, ete).

Fam. 4. Belopteridae.—Sepion not known; phragmocone
curved, siphuncle on the ventral margin, rostrum well developed,
pointed. Principal genus, Spirulirostra.mMiocene of Turin.

These two families, with their small, curved
phragmocone and (in the case of the Belose-
plidae) large sepion, are clearly intermediate

Fia. 248.—Spirula Per-
onii Lam.: d, ter-
minal sucker ; /,
funnel ; 5), Sa, pro-
jecting portions of

Fic. 247.—Shell of Spirula Peronii Lam A, Outside view ; B, shell, the internal

showing last chamber and position of siphuncle ; C, in section, part of which is
showing the septa and course of siphuncle ; D, shell broken dotted in. (From
to show the convexity of the inner side of the septa; E, por- Owenand A. Adams
tion of a septal neck. combined. )

between the Phragmophora and Sepiophora. Some authorities
place them with the latter group.

B. SEplopHorA.—Shell internal, consisting usually of (@) an
anterior cancellated portion, (4) a posterior laminated portion,
the laminae enclosing air. It terminates in a very rudimentary
phragmocone and a rostrum, but there is no siphuncle.

Fam. Sepiidae.—Kyes with cornea complete, body oval, fins
narrow, lateral, as long as the body, generally united behind ;
sessile arms short, tentacular arms long, acetabula generally in

XIII DECAPODA 389

four rows, fourth left arm in the male hectocotylised near the
base (Fig. 249).—World-wide.

The sepion or ‘cuttle-bone’ runs the whole length and width
of the body. In Sepia it is very thick in front, while the
posterior ventral end is concave and terminated by a prominent
spine, the rostrum or mucro, which points downwards. The
whole shell is surrounded by a thin
chitinous margin, which forms a
lateral expansion. Other genera are
Sepiella, Hemisepius, and Trachyteu-
this (fossil only).

C. CHONDROPHORA.— Shell (gladius
or pen) long, chitinous.

oO?
a) Myopsidae:' cornea entire tos
( ) Myops ? ‘Fig, 249, —Hectocotylised arm (h.a)
specres mostly sub-littoral. of Sepia officinalis L., shown in

Fam. 1. Sepiolidae—Fins large, eae aioe es is) Poonay
dorso-lateral ; tentacular arms retrac- pocket itd arimonetiel tentacle
tile; two first dorsal arms in the %™ 3s retracted.
male hectocotylised ; gladius narrow, half as long as the body.—
World-wide.

Principal genera: Sepiola, dorsal mantle connected with the
head by a broad cervical band, ventral mantle with the funnel by
a ridge fitting into a groove; Sossia, dorsal mantle supported
by a ridge, arms with never more than four rows of acetabula ;
Inioteuthis, Stoloteuthis, Nectoteuthis, and Promachoteuthis.

Fam. 2. Sepiadariidae.—F ins not as long as the body, mantle
united to the head on the dorsal side, fourth left arm in the
male hectocotylsed ; no gladius. Principal genera, Sepiadarium,
Sepioloidea.—Chiefly Pacific Ocean.

Fam. 3. Idiosepiidae—Fins very small, terminal; fourth
pair of arms in the male hectocotylised, bare of suckers.

The only genus, /diosepion, with a single species (ZL pyg-
macum Stp.) 18 from the Indian ocean, and is the smallest
known Cephalopod, measuring only about 15 mm. in length.

Fam. 4. Loliginidae.—Body rather long, fins varying in size,
tentacular arms partially retractile, gladius as long as the back,
pointed in front, shaft keeled on the ventral side— World-wide.

Loligo proper has a pointed body with triangular posterior
fins united behind; sessile arms with two rows of acetabula,

1 uvéw, close the eyes ; dys, sight ; contrasted with Oigopsidae (olyw, open).

390 DECAPODA CHAP.

tentacular arms with four; fourth left arm hectocotylised at the
tip; funnel attached to the head. Other genera are Loliguncula,
Sepioteuthis, and Loliolus. Belemnosepia, Beloteuthis, Leptoteu-
this, and Phylloteuthis are fossil genera only, differme in the
shape of the gladius.

(b) Oigopsidae: cornea more or less open ; species pelagic.

Fam. 5. Ommastrephidae.—Body cylindrical, fins generally
terminal, united together, regularly rhomboidal, sessile arms with
varying number of rows of acetabula, mantle connexions elabo-
rate; gladius horny, narrow lanceolate, with a hollow cone at
the posterior end.— World-wide.

Ommastrephes proper has a natatory web on the sessile arms ;
the wrist of each club has a series of acetabula with correspond-
ing cushions on the other wrist. In Zhysanoteuthis (often made
a separate family) the sessile arms have two rows of cirrhi, with
lateral expansions of the skin; fins as long as the body. In

fe

Fic, 250.—Architeuthis princeps, Verr., E. America: f, Right fin; fu, funnel; fic,
fixing cushions and acetabula on the tentacular arms (¢, ¢). (After Verrill. x jy.)
Architeuthis, to which belong the largest Cephalopoda known,
the fins together are shaped like a broad arrow-head; acetabula
of sessile arms strongly denticulate; tentacular arms very long,
with equidistant pairs of acetabula and fixing cushions through-
out their entire length, and a group of the same at the base of
the club, The acetabula and cushions correspond on the oppos-
ing tentacles, and enable them to pull together. Other genera
are Dosidicus, Todarodes, Illex, Bathyteuthis and Mastigoteuthis.

Fam. 6. Onychoteuthidae.—Body cylindrical, fins terminal or
lateral, mantle-locking apparatus elaborate, tentacular arms very
long, sessile or tentacular arms furnished with retractile hooks,
gladius lanceolate, with a terminal cone.— World-wide.

The prehensile apparatus of Cephalopoda reaches its maximum
of power and singularity in this family. In Onychia, Onycho-

XII DECAPODA 391

teuthis, and Ancistroteuthis, the sessile arms have acetabula only,
in Gonatus and <Abralia they have hooks as well, while in
Verania, Ancistrochirus and Enoploteuthis, the sessile arms have
hooks only. The number of rows of hooks or acetabula varies
with the different genera.

Fam. 7. Chiroteuthidae.—Head nearly as large as the body ;
fins terminal, tentacular arms very long,
sessile arms slightly webbed, acetabula
denticulated; mantle-supports consisting
of cartilaginous ridges on the mantle,
which fit into corresponding depressions
on the funnel, gladius expanded at each
end.—Atlantic Ocean.

The six dorsal arms in Histioteuthis
are united by a broad web, while in
Histiopsis the web only reaches half
way up the arm. In Chiroteuthis the
tentacular arms have scattered sessile
suckers throughout their whole length,
and four rows of very long peduncu-
late suckers on the clubs.

Fam. 8. Cranchiidae.—Head small,
body rounded, barrel-shaped, fins termi-
nal, eyes often very large, sessile arms
short, tentacular arms long, thread-like.
—W orld-wide.

Cranchia proper has the tentacular
clubs finned, with eight rows of suckers,
body sometimes covered with warty
tubercles. Loligopsis has a very attenu-
ated body, with fins terminally united : ¢
some species are spotted with colour, Pe ee Haren ee
or have rows of tubercles on the ventral Jf, f, fins; ¢, ¢, tentacular
side. Taonius (Fig. 251) is doubtfully =“ etter Hoyle; * 4):

distinct from Loligopsis.

Order Tetrabranchiata

Cephalopoda with four branchiae and four kidneys; animal
inhabiting the last chamber of an external multilocular shell ;

392 CEPHALOPODA——_TETRABRANCHIATA CHAP.

funnel consisting of two separate lobes; tentacles numerous,
without suckers or hooks; no ink-sae.

The shell consists of two layers, the outer being porcellanous,
and the inner, as well as the walls of the chambers or septa
nacreous. The septa vary greatly in shape. In most of the
Nautiloidea they are regularly curved, as in Nautilus, or
straight, as in Orthoceras, but in the Ammonoidea they are often
exceedingly complex. The edge of the septum, where it unites
with the shell-wall, is called the suture, and the sutural line,
which is not seen until the porcellanous layer is removed, varies
in shape with the septum.

The septa are traversed by a membranous tube known as the
siphunele, which in Nautilus is said by Owen to connect ulti-
mately with the pericardium. The septal necks, or short tubular

Fic. 252.—Nautilus pompilius L., in section, showing the septa (s, s), the septal necks
(s.m, 8.2), the siphuncle dotted in (sz), and the large body chamber (ch).
prolongations of the septa where they are perforated by the
siphuncle, are in the great majority of the Nautiloidea directed
backwards (Fig. 252), 7.e., they project from the front wall of
each chamber, while in nearly all Ammonoidea they are directed
forwards. When the siphuncle is narrow, as in the Ammon-
oidea, it is simple, but when wide, as in many of the Nautiloidea,

eit NAUTILOIDEA 395

its walls are often thickened by the deposition of masses of cal-
careous matter, or by rings and radiating lamellae of the same
material. In position, the siphuncle is sometimes central, some-
times sub-central, sometimes (Ammonoidea)
marginal. In some cases its position is
believed to change during the growth of
the individual. The precise object served
by the siphuncle is at present unknown.
Some hold that it preserves the vitality of
the unoccupied chambers, by connecting
them with the soft parts of the animal ; Fite. 253 —Ammonites (Ca-

: doceras) sublaevis Sowb. ,
others have regarded it as a means for Kellaway’s Rock, show-
lightening the shell by the passage of some ae aoe anaes
gas into the chambers.

The initial chamber in Nautiloidea consists of an obtuse
incurved cone, marked on the outer surface of its posterior wall
by a small scar known as the eieatriz, which may be slit-like,
round, oval, or cruciform in shape. It has been held that the
cicatrix originally communicated with the protoconch or larval
shell, which probably dropped off as development proceeded. In
the Ammonoidea, on the other hand, there is no cicatrix, and the
initial chamber probably represents the protoconch, as seen in the
nucleus of many Gasteropoda.

Sub-order 1. Vauwtiloidea—Shell straight, bent, or coiled,
aperture simple or contracted; siphuncle often narrowed by
internal deposits, position variable; septal necks short, usually
directed backwards; septa concave towards the aperture; initial
chamber conical, with a cicatrix on the posterior wall.

The Nautiloidea, of which Nautilus is the sole living repre-
sentative, date back to the Cambrian epoch, and attain their
maximum in the Silurian and Devonian. At the close of the
Palaeozoic era, every family, with the sole exceptions of the
Orthoceratidae and Nautilidae, appears to have become extinct.
The former disappear with the Trias, and after the lapse of the
whole Secondary era, Aturia, a form closely related to Nautilus,
makes its appearance.

(a) Retrosiphonata : septal necks directed bachwards.
Fam. 1. Orthoceratidae.'—Shell straight or slightly curved,
aperture simple, body-chamber large; siphuncle cylindrical,

1 The classification is that of Foord, Catal. Fossil Cephal. Brit. Mus., 1888.

394 NAUTILOIDEA CHAP.

position variable. Single genus, Orthoceras (Fig. 254)—\Cam-
brian to Trias.

Fam. 2. Hndoceratidae—Shell straight, siphuncle wide, mar-
ginal, septal necks produced into tubes fitting into one another.
Principal genera : Hndoceras (specimens of which occur six feet

long), and Piloceras.— Ordovician.
Fam. 3. <Actinoceratidae.

Shell straight or shghtly curved,
siphuncle wide, contracted at
the septa by obstruction-rings.
Principal genera: Actinoceras,
Discosorus, Huronia, Sactoceras.
—Ordovician to Carboniferous.

Fam. 4. Gomphoceratidae.—
Shell globular, straight or con-
siderably curved, aperture nar-
rowed, T-shaped, body-chamber
large, siphuncle variable in posi-
tion. The aperture is in some
cases so narrow that probably

only the arms could be pro-

Ita. 254.—A, Section of Orthoceras, a) ieede i
showing the septa (s, s), and siphuncle truded. Principal genus, Gom-
(si, si); B, portion of the exterior of mhoceras (Fig. 255).—Silurian.

Orthoceras annulatum Sowb., x4. =e Oy ;

(Woodwardian Museum, Cambridge. ) Fam. 5. Ascoceratidae.—Shell

sac-like or flask-shaped, apex
truncated, unknown, body-chamber occupying nearly the whole
of the shell on the ventral side, contracting at the aperture, last
few septa coalescing on the dorsal side and encroaching upon the
body chamber. The young form has a symmetrical shell like

Orthoceras, attached to the sac-like shell above deseribed; as

growth proceeds the former portion is thrown off. Principal

genera : Ascoceras, Glossoceras.—Ordovician and Silurian.

Fam. 6. Poterioceratidae—Shell fusiform, contracted at both
ends, aperture simple, siphuncle variable in position, inflated
between the septa. The form generally resembles Gomphoceras,
except for the simple aperture and fusiform shape.—Ordovician
to Carboniferous.

Fam. 7. Cyrtoceratidae.—Shell conical or sub-cylindrical,
slightly curved, body-chamber large, siphuncle variable in posi-
tion. Single genus, Cyrtoceras.—Cambrian to Carboniferous.

Fam. 8. Lituwitidae.—Shell coiled in a flat, sometimes loose

XII NAUTILOIDEA 395

spiral, last whorl straight, containing the body-chamber, often
greatly prolonged. Principal genera: Litwites, Ophidioceras.—
Ordovician and Silurian.

Fam. 9. Tvochoceratidae—Shell .helicoid, with seldom more
than two whorls, dextral or sinistral, last whorl sometimes
partly uncoiled. Principal genera: Trochoceras, Adelphoceras—
Ordovician to Devonian.

Fam. 10. Nautilidae—Shell with few whorls more or less
overlapping, septa simple, siphuncle central
or sub-central, aperture not contracted.

The ‘ tentacles’ are about 90 in number,
and consist of four groups each of 12 or 13
labial tentacles surrounding the mouth, two “PD -- aR
groups each of 17 larger (brachial) tentacles
on each side of the head, two thicker tenta-
eles which combine to form the ‘hood, and
two small tentacles on each side of the eye. s-
When the animal swims, the tentacles are
extended radially from the head, somewhat
hike those of a sea-anemone. The direction of a
the many pairs of tentacles at constant but pet aoe

different angles from the head is the most Silurian: B, aperture
: (ap) of same; s, s,

striking feature in the living Nautilus, and septa; si, position of
accounts for its beimg described, when seen Ae (After
ake,

on the surface, as ‘a shell with something like
a cauliflower sticking out of it. * The funnel is not a complete tube,
but is formed by the overlapping of the margins of two thin fleshy
lobes (which are probably morphologically epipodia), so that when
the two lobes are parted, a broad canal appears, leading to the bran-
chial cavity. The head is conical, and the mouth and its appendages
can be retracted into a sort of sheath, over which fits the ‘ hood.’

Other genera are Z'rocholites, Gyroceras, Hercoceras, Discites,
Aturia.—Ordovician to present time.

Fam. 11. Sactritidae.— Shell straight, conical, siphuncle
small, marginal, septal necks long, funnel-shaped, sutures undu-
lating, with a sinus corresponding to the siphuncle. This family,
from the form of its sutures, appears to constitute a passage to the
Ammonoidea. Single genus, Bactrites—Silurian and Devonian.

(1) Prosiphonata.—Septal necks directed forwards.

1 Saville Kent, Proc. Roy. Soc. Queensland, vi. p. 229.

396 AMMONOIDEA CHAP.

The two genera are Bathmoceras (Ordovician), shell straight,
conical, always truncated, siphon marginal; and WNothoceras
(Silurian), shell nautiloid with simple sutures.

Sub-order 2. Ammonoidea,— Shell multiform, straight,
curved, flat spiral, or turretted, sutural line more or less complex,
siphunele simple.

Some authorities hold that the members of this great sub-
order, now totally extinct, belong to the Dibranchiata, on the
ground that the protoconch resembles that of Spirula rather
than that of the Nautiloidea. Others again regard the Am-
monoidea as a third, and distinct Order of Cephalopoda. Their
distribution extends from the Silurian to (possibly) the early
Tertiary. No trace has ever been found of an ink-sac, mandible,
or hooks on the arms; the shell was undoubtedly external.

The sutural line, which indicates the septa, and is generally
concealed beneath the outer layer of shell, consists of a number
ot lobes or depressions, the concave part of which is directed
towards the aperture. Between these lobes lie corresponding
elevations, or saddles, the convex part of which is directed

SOM Sit, (Si ust Sv esis

f Fic. 256.—Diagram of the sutures of
Ammonites: A, an elaborate suture
(Phylloceras); B, a simple suture
(Ceratites) ; s.s, siphonal, s.v, ven-
tral, s./, first lateral, s./’, second
lateral saddles; s.a, s.a, auxiliary
saddles ; 7.v, ventral, /, first lat-
eral, 1’, second lateral lobe; Z.a,
l.a, auxiliary lobes. The arrow
points towards the aperture. (From
Woodward.) Compare Fig. 258.

'
1
'
'
1
‘

towards the aperture. There are six principal lobes (Fig. 256)
the siphonal or ventral, which is traversed by the siphuncle, the
dorsal, and a superior and inferior lateral on each side; smaller
auxilary lobes may.succeed these latter. The adjacent saddles
have received corresponding names. As a rule the sutural line
is very complex, but in some cases (Goniatites, Lobites) it is
simple (Fig. 258, A). The first saddle of a large number of genera
serves aS a means of classification, according as it 1s broad or
narrow. Some authorities reverse the terms ventral and dorsal,

XIII AMMONOIDEA 397

as applied above. It is probable, however, that the position of
the animal of Ammonites in its shell resembled that of Nautilus.
The siphuncle is dorsal (internal) in
Clymenia only, ventral (external) in all
other genera.

The aptychus of Ammonoidea is a
corneous or calcareous valve-like body,
generally formed of two symmetrical
parts (Fig. 257). It has been regarded
by some as the covering of the nida-
mental gland, and hence as occurring Fié. 257,—Aptychus of Ammonite
only in the female, by others, with more ees oe 1 a

g jHllys | ae
probability, as an operculum, covering
or imbedded in a hood formed, as in Nawtilus, of modified arms.
Sometimes the Aptychus is in a single piece (Anaptychus), some-
times the two pieces are united on the median line (Synaptychus).

The Ammonoidea are thus classified by Dr. P. Fischer :—

(a) Retrosiphonata . : : : Goniatitidae.
First saddle, f Arcestidae, Tropitidae,
No Aptychus or wide \ Ceratitidae, Clydonitidae.
Anaptychus | Pinacoceratidae, Amal-
(b) Prosiphonata corneous, First saddle,, theidae, Ammonitidae,
single | narrow | Lytoceratidae.
Aptychus calcareous, valves ( Harpoceratidae, Stephano-
double or united ( ceratidae.

(a) Retrosiphonata. FAM. 1. Goniatitidae—Shell nautiloid,
whorls sometimes disjoined, siphuncle ventral or dorsal, sutures
simple. Principal genera: Clymenia, Goniatites, (Fig. 258, A).
—Devonian to Carboniferous.

(b) Prosiphonata. FAM, 2. Arcestidae.
or striated and rayed, body-chamber very long, aperture often
with a projecting hood, umbilicus closed by a callosity, lobes
numerous, foliaceous, aptychus present. Principal genera: Arcestes,
Lobites—Principally Trias.

Fam. 3. Tropitidae.—Differs from Arcestidae mainly in the
more highly ornamented surface, which is decorated with ribs
which become granular at the periphery. Principal genus,
Tropites—tTrias and Lias.

Fam. 4. Ceratitidae——Shell ribbed and tuberculated, body
chamber short, lobes denticulated, saddles simple. — Principal
genera: Ceratites (Fig. 258, B), Zrachyceras.—Principally Trias.

Shell globular, smooth

398 AMMONOIDEA CHAP.

Fam. 5. Clydonitidae.—Shell variable in form, body-chamber
short, sutural line undulated, simple. Principal genera: Clydonites,
Choristoceras, Rhabdoceras, Cochloceras.—Trias.

Fam. 6. Pinacoceratidae-—Shell discoidal, usually smooth,
body-chamber short, sutural line very complex, lobes numerous.
Principal genera: Pinacoceras, Sageceras. Carboniferous to Trias.

Fam. 7. Amaltheidae-—Shell broad, keeled, last whorl con-
cealing most of the spire, sutures with auxiliary lobes, incised.
—Principal genera: Amaltheus, Schloenbacia, Sphenodiscus.—
Trias, Cretaceous.

Fam. 8. Ammonitidac.—Body-chamber long, whorls narrow,

Fig. 258.—Various forms of Ammonoidea: A, Goniatites crenistria J. Phil., Carb.
Limestone ; B, Ceratites nodosus de Hann., Muschelkalk ; C, Ammonites (Parkin-
sonia) Parkinsoni Sowb., Inf. Oolite ; D, Phylloceras heterophyllum Sowb., Upper
Lias ; s, s, sutural lines.

uncovered, more or less ribbed, aperture simple, sutural line

normal, aptychus single, corneous. Principal genera : Ammonites,

Aegoceras.—Principally Lias.

Fam. 9. Lytoceratidae——Shell discoidal, body-chamber short,
aperture simple, no aptychus. Principal genera: Lytoceras,
Phylloceras (Fig. 258, D).—Trias to Cretaceous.

Fam. 10. Harpoceratidae.— Shell discoidal, compressed,
margin keeled, surface with straight or arched ribs, aperture

tin AMMONOIDEA 309

with lateral projections, suture with accessory lobes, aptychus in
two pieces. Principal genera: Harpoceras, Oppelia, Lissoceras.
—Jurassic to Cretaceous.

Fam. 11. Stephanoceratidae.— Shell discoidal, helicoid or
straight, whorls sometimes disunited, surface often with bitur-
cating ribs, which are tubercled,
aperture often with lateral pro-
jections, sutural line incised,
aptychus im two pieces, some-
times united.

In the discoidal group, Ste-
phanoceras is strongly ribbed,
tubercled at the point of bifur-
cation, Cosmoceras has long
lateral projections of the aper-
ture when young, Perisphinctes
has a large body chamber and
numerous smooth ribs. Other
genera are <Acanthoceras, Pelto-
CORES: Aspidoceras, and Hoplites. Fig. 259.—A, Turrilites catenulatus VOrb,
Among the loosely whorled Gault ; B, Macroscaphites Iranii @ Orb,
genera, Scaph ites (Fig. 260, A) Upper Neocomian. (From Zittel.)
has the last whorl produced and bent back again in horse-shoe
form, while the early whorls are concealed; Hamites, Hamulina,
and Ptychoceras have a shell shaped like a single or double hook,
the sides of which
may or may not be
united; = Crioceras
(Fig. 260, B) in form
of whorls resembles a
Spirula, Aneyloceras
a Scaphites with
the first whorls dis-
united. Macrosea-
phites (Fig. 259, B)
is similar, but with

Fic. 260.—A, Scaphites aequalis Sowb., Cretaceous; B, the first whorls
Crioceras bifurcatum Quenst., Cretaceous. (From Zittel. )

united and not con-
cealed. Turrilites (Fig. 259, A) is turretted and sinistral, while
Laculites is quite straight, with a long body-chamber.

CHAPTER XIV

CLASS GASTEROPODA——AMPHINEURA AND PROSOBRANCHIATA

Order I. Amphineura

BILATERALLY symmetrical Mollusca, anus at the terminal end of
the body, dorsal tegument more or less furnished with spicules.

Sub-Order 1. Polyplacophora (Chitous).—Foot co-extensive
with ventral surface of the body, dorsum with eight transverse
plates, articulated (except in Chitonellus), a row of ctenidia on
each side between the mantle and the foot. Silurian

The Chitons are found in all parts of the world, ranging in
size from a length of about half an inch to six inches or more in
the giant Cryptochiton. Although in the main sub-httoral, they
occur at very great depths; the Challenger dredged Leptochiton
benthus Hadd. at 2300 fathoms. Chiton Polw exceptionally
occurs at Malta—teste MacAndrew—above sea margin, but
within reach of the ripple. As a rule, the Chitons live in con-
cealment, on the under surface of stones or in deep and narrow
fissures in the rocks.) When the stone to which they are
attached is turned over, they crawl slowly to the side which is
not exposed, as if disliking the light. An undescribed species,
however, which I took at Panama, crawled quite as fast as an
ordinary snail. Chiton fulvus Wood, apparently is accustomed
to crawl with some rapidity. MacAndrew took it in abundance
on his anchor chain in Vigo Bay every time his yacht was got
under weigh. He also found it crawling in sand on the shore, to
which habit is no doubt due its extreme cleanness and freedom
from the foreign growths which are so characteristic of many of
the species. When detached a Chiton contracts the muscles of
the whole body, and rolls up into a ball like a wood-louse.

—————

XIV

POLYPLACOPHORA 401

The Polyplacophora are characterised, externally, by their
usually articulated shell of eight plates or valves, which is
surrounded and partly kept in position

by a muscular girdle. These plates over-
lap like tiles on a roof in such a way
that the posterior edge of the first, ceph-
alic, or anterior valve projects over the

anterior edge of

which in its turn overlaps the next, and so

Fic. 262. — Valves of
Chitonellus separated
out (anterior valve
uppermost) : #, a, ar-
ticulamentum ; ¢, ¢,
tegmentum. x2.

the succeeding valve,

on throughout. Seven-
valved monstrosities
very rarely occur.

A certain portion
of each valve is covered
either by the girdle or
by the valve next an-
terior to it. This por-
tion, which is whitish
in colour and non-
porous in structure,
forms part of an inner

2 ; Fic. 261.—Valves of a Chiton
layer which underlies separated to show the vari-
the rest of the sub- ous parts (anterior valve

uppermost): @, a, articu-
stance of the valve, lamentum; 6, beak ; /,
and is called the arti-. Jugum; pl, pl, pleura;

t, ¢, tegmentum.
culamentum. The ex-
ternal portion of the valves, or tegmentum, 18
generally more or less sculptured, and is largely
composed of chitin, impregnated with salts of
lime, thus answering more to a cuticle than
to a shell proper. It is very porous, being
pierced by a quantity of minute holes of two
sizes, known as megalopores and micropores,
which are connected together by minute
canals containing what is probably fibrous
or nerve tissue, the mouths of the pores being
occupied by sense organs connected with these
nerves. The tegmentum of the six inter-
mediate valves is generally divided into three

triangular areas by two more or less prominent ribs, which

VOL. III

ABT

402 POLYPLACOPHORA CHAP.

diverge from the neighbourhood of the median beak or umbo.
The space enclosed between these ribs is known as the median
area or jgugum, the other two
spaces as the Jateral areas or
pleura. The ribs terminate with
the edge of the tegmentum, and
are not found on the articula-
mentum. In certain genera these
areas are either non-existent, or
are not distinctly marked. The
sculpture of the lateral areas (which
is, aS a rule, much stronger than
that of the median area) will
generally be found to resemble
that of the anterior valve, which
has no proper median area. In
the posterior valve the median
Fic. 263.—First, fourth, and eighth area 18 very small, while the sculp-

valves of a Chiton, showing J.7, ture of the rest of the valve cor-

ee wears a aa responds to that of the lateral

areas generally (see Fig. 261).

The articulamentum of the intermediate valves is divided into
two equal parts in the middle of the anterior edge, opposite to
the beak, by a sinus. Each of the portions thus formed is again
divided by a notch or suture into two unequal parts, the anterior
of which is known as the sutural lamina, and is more or less
concealed by the valve in front of it, while the lateral part, or
lamina of insertion, is entirely concealed by the girdle. The
articulamenta of the anterior and posterior valves are either
simple or pierced by a series of notches (Fig. 263).

The girdle of the Chitonidae varies considerably in character.
Sometimes its upper surface is simply corneous or cartilaginoid,
with no other sculpture than fine striae, at others it is densely
beset with spines or bristles, or tufted at intervals with bunches
of deciduous hairs; again it is marbled like shagreen or mossy
down, or covered with serpent-like scales. The width of the
girdle varies greatly, being sometimes very narrow, sometimes
entirely covering all the valves (Cryptochiton). As a rule, its
outer edge is continuous, but in Schizochiton it is sharply notched
over the anus.

XIV POLYPLACOPHORA 403

A description has already been given of the dorsal eyes in
Chiton (p. 187), the nervous system (p. 202), the branchiae (p.
154), the radula (p. 228), and the generative system (p. 126).

The recent Chitons are thus classified by Dr. W. H. Dall :—

SecTION I. CHITONES REGULARES.—Anterior and posterior

valves of similar character,

A. Leptoidea. — Insertion plates obsolete, or, if present,
unslit ; Leptochiton, Hanleyia, Hemiarthrum, Microplax.
B. Ischnoidea. — Insertion plates sharp, smooth, fissured ;

with eaves; Vrachydermon, Callochiton, Tonicella, Schizo-
plax, Leptoplax, Chaetopleura, Spongiochiton, Ischnochiton,
Callistochiton.

C. Lophyroidea.—Insertion plates broad, pectinated, project-

Fic. 264.—Girdles of
various Chitonidae.
A, Radsia sulcata
Woody) 1 x<.20- Bs
Maugeria = granu-
lata Gmel., x 3;
C, Enoplochiton
niger Barnes, x3;
D, <Acanthochiton
fascicularis Li, x
4; E, Tonicia fas-
tigiata Sowb., x 4.

ing backward; Chiton, Tonicia, Hudoxochiton, Craspedo-
chiton.

D. Acanthoidea.—Insertion plates thrown forward; Sclero-
chiton, Acanthopleura, Dinoplax, Middendorfia, Nuttallina,
Arthuria, Phacellopleura.

Section II. CHITONES IJRREGULARES. — Posterior valve
abnormal, or with a sinus behind.

E. Schizoidea.—Posterior valve fissured; Lorica, Schizochiton.

F. Placiphoroidea.—Posterior valve unslit, internally ridged,
umbo nearly terminal; Hnoplochiton, Ornithochiton,
Plaxiphora.

G. Mopaloidea—Posterior valve with posterior sinus and one
slit on each side; Mopalia, Katherina, Acanthochiton,
Notoplaxz.

404

APLACOPHORA CHAP.

H. Cryptoidea.—With double sutural laminae; Cryptoconchus,
Amicula, Cryptochiton.

Fic. 265.—Chitonellus fasciatus Quoy ; ant, anterior end.

I. Chitonelloidea.—Posterior valve funnel shaped; laminae
thrown forward; Chitonellus, Choneplazx.
Sub-order II. Aplacophora.—Animal vermiform, foot absent,

Fic. 266. — Neomenia

or a mere groove, cuticle more or less covered
with spicules.

According to Marion, one of the principal
authorities on the group, the Aplacophora
are perhaps Amphineura whose development
has been arrested at an early stage, their

carinata Tullb.: a, worm-like exterior being

een i pai due to adaptation to sur-

roundings. They have
hitherto been found chiefly in the N. Atlantic
and Mediterranean, generally at considerable
depths, and often associated with certain
polyps in a way which suggests a kind of
commensalism.

Fam. 1. Meomeniidae. — Foot a narrow
eroove, intestinal tube without differentiated
liver, kidneys with common exterior orifice,
sexes united, ctenidia present or absent.
Genera: Neomenia (Fig. 266), Paramenia,
Proneomenia, Ismenia, Lepidomenia, Don-
dersia.

Fic. 267.—Chaetoderma -
nitidulum Loy.: a,
anus ; m, mouth.
x3.

Fam 2. Chaetodermatidae.— Body cylindrical, no ventral
groove, liver a single sac, kidneys with separate orifices into the
branchial cloaca, two bipectinate ctenidia. Single genus, Chaeto-

derma (Fig. 267).

Order II. Prosobranchiata.

Visceral loop twisted into a figure of 8 (streptoneurous), right

XIV DIOTOCARDIA—RHIPIDOGLOSSA 405

half supra-intestinal, left half infra-intestinal; branchia (cteni-
dium) generally single, usually in front of the heart; head with
a single pair of tentacles; animal dioecious, usually marine,
more or less contained within a shell, operculum generally
present. Cambrian to present time.

Sub-order 1. Diotocardia.— Heart with two auricles (except
in the Docoglossa and Helicinidae), branchiae bipectinate, front
end free; two kidneys, the genital gland opening into the right
(except in Neritidae); nervous system not concentrated; no
proboscis or siphon, penis usually absent.

(a) DocoaLossa (p. 227).—Heart with a single auricle,
ventricle not traversed by the rectum, visceral sac not spiral,
shell widely conical, non-spiral, no operculum; radula very long,
with few hooked teeth in each row.

Fam. 1. Acmaeidae.—Left ctenidium alone occurring, free on
a long stalk. Cretaceous Principal genera: Pectinodonta,
front part of head much produced, radula 0 (1. 0. 1.) 0; Acmaea
(=Tectura), with sub-genera Collisella and Collisellina, no
accessory branchial ring, shell closely resembling that of Patedla,
but generally with a distinct internal border; Scurria, accessory
branchial ring on the mantle.

Fam. 2. Lepetidae.—No ctenidia or accessory branchiae,
animal generally blind. Pliocene Principal genera :
Lepeta ; Propilidium, apex with internal septum; Lepetella.

Fam. 3. Patellidae—No ctenidia, the osphradial patch at the
base of each alone surviving, a circlet of secondary branchiae
between the mantle and sides of the foot. Ordovician
Gi.) Patellinae—Three lateral teeth on each side, two of them
anterior. Principal genera: Patella, branchial circlet complete ;
chief sections Patella proper, Scutellastra, Ancistromesus (A.
mexicana Brod., measures 8-14 in. long); Helcion, branchial
circlet interrupted in front; Zryblidiwm (Ordovician).—(i1.)
Nacellinae—Two developed laterals on each side, one anterior.
Genera: Nacella, branchial circlet complete; Helcioniscus, bran-
chial circlet interrupted in front.

(b) RHIPIDOGLOSSA (p. 225).—Ventricle of the heart traversed
by the rectum (except in Helicinidae), one or two ctenidia; jaw
in two pieces, radula long, marginals multiplied, rows curved.

Of all the Gasteropoda, this section of the Diotocardia approach
nearest to the Pelecypoda, particularly in the least specialised

406 DIOTOCARDIA—RHIPIDOGLOSSA CHAP.

forms. The auricle, the branchiae, and the kidneys are in many
‘ases paired, and more or less symmetrical. The ventricle is
generally traversed by the rectum, there is a long labial com-
missure between the cerebral ganglia, special copulative organs
are usually absent, while the shell is often nacreous, like those
of Pelecypoda of a primitive type.

SECTION I. ZYGOBRANCHIATA.—Two ctenidia, shell with apical
or marginal slit or holes, corresponding to an anal tube in the
mantle (p. 265).

Pam. 1. Fissurellidae—Two symmetrical ctenidia and kidneys,
visceral mass conical, shell conical, elevated or depressed, with
a single anterior or apical slit or impression; no operculum.
J urassic-——. G.) Fisswrellinae. Shell wholly external, apex
entirely removed by perforation, apical
‘allus not truncated posteriorly ; cen-
tral tooth narrow. Genera: Fissurella
(Figs. 171, p. 261; 178, p. 265), Hs-
suridea, Clypidella. (i1.) Fissurelli-
dinae. Shell partly internal, otherwise
as in (i.); central tooth broad, mantle
more or less reflected over the shell,
apical hole very wide. Genera: F%s-
surellidaca, Pupillaea, Lucapina, Mega-
tebennus, Macroschisma, Lucapinella.
Gil.) HLmarginulinae. Shell usually
Fic. 268.—Scutus australis Lam., Wholly external, apex usually not re-

Soe ke , m, m, mantle ; shy moved by perforation, sometimes with in-

ng l ternal septum, anal tube ina narrow slit
or sinus. Genera: Glyphis, externals of Fissurella, but hole-callus
truncated behind; Puncturella (sub-genera Cranopsis and Fissuri-
septa),slit just anterior to the apex,a small internal septum; Zeidora,
large internal septum as in Crepidula: Hmarginula, shell elevated,
slit very narrow, on the anterior margin (in subg. Rimula, it is
between the apex and the margin), radula bilaterally asymmetrical ;
Subemarginwa, margin indented by a shallow groove; Scutus
(= Parmophorus) shell oblong, depressed, nicked in front, largely
covered by the mantle.

Fam. 2. Haliotidae—Right ctenidium the smaller, epipodial
line broad, profusely lobed; shell rather flattened, spire short, last
whorl very large, with a row of perforations on the left side,

XIV DIOTOCARDIA—RHIPIDOGLOSSA 407

which become successively obliterated ; through these holes, the
posterior of which is anal, pass tentacular appendages of the
mantle ; no operculum. Cretaceous——. Single genus, Haliotis ;
principal sub-genera Padollus, Teinoiis.

Fam. 3. Pleurotomariidae—Central tooth single, narrow,
about 26 laterals, 60 to 70 uncini. Shell generally variously
trochiform, nacreous, operculate, with a rather broad marginal

sinus in the last whorl; as this sinus closes up 1t forms an “ anal
fasciole”” or “sinus band.” Cambrian-

Principal genera :
Scissurella, epipodial line with several long ciliated appendages at
each side, shell very small, sht open, sinus band extending nearly
to apex; Schismope, anal slit closed in the adult into an oblong
perforation; JMurchisonia (Palaeozoic only), shell long, turretted,
whorls angulate or keeled with a sinus band; Odontomaria
(Palaeozoic only), — shell
tubular, curved; Polytre-
maria (Carboniferous),
shell turbinate, slit a series
of small holes connected
by a passage; Z'rochotoma,
shell trochiform, perfora-
tion consisting of two nar-
row holes united by a sht ;
Pleurotomaria, branchiae
almost symmetrical, radula
as above, shell variously
spiral.

In Pleurotomaria we

have the case of a genus
Fic. 269.—Pleurotomaria adansoniana Cr. and F.,

lone supposed to be extinct.
B PUPRes Tobago. x.

More than 1100 fossil

species have been described, and within the last 38 years about
20 specimens, belonging to 5 species, have been discovered in a
living state.

Fam. 4. Bellerophontidae.—Shell nautiloid, spire generally
concealed, aperture large, sinus or perforations central (Fig. 179,
p. 266). Ordovician — Trias. Genera: Bellerophon, Trema-
tonotus, Cyrtolites.

SEction II—AzyYGOBRANCHIATA.—One ctenidium (the left)
present.

408 DIOTOCARDIA—RHIPIDOGLOSSA CHAP.

Fam. 1. Cocculinidae-——A single cervical ctenidium, foot
broad, no eyes, shell patelliform, with caducous spire. Single
genus, Cocculina. Deep water.

Fam. 2. Stomatellidae.—A single (left) ctenidium, front third
free, shell nacreous, spiral or patelliform, depressed, last whorl
large. Jurassic Genera: Stomatella (subg. Synaptocochlea,
Niphonia), shell depressed, spirally ribbed, spire short, operculum
present; Phaneta, fluviatile only, shell trochiform, imperforate,
last whorl keeled, sinuate in front ; Stomatia, spire short, surface
tubercled or keeled, no operculum: Gena, shell haliotis-shaped,
surface smooth, aperture very large: Broderipia, shell patelliform,
spiral apex often lost.

Fam. 3. Cyclostrematidae.—Tentacles ciliated, thread-like,
snout bilobed, foot truncated in front, angles produced into a
filament, shell depressed, umbuilicated, not nacreous. Eocene
Principal genera: Cyclostrema, Teinostoma, Vitrinella.

Fam. 4. Liotiidae—FEpipodial line with a lobe behind each
eye-peduncle, shell solid, trochiform, longitudinally ribbed or
trellised, aperture round, operculum multispiral, hispid, corneous,
with a calcareous layer. Silurian —, Principal genera :
Liotia, Craspedostoma (Silurian), Crossostoma (Jurassic).

Fam. 5. Z'vrochidae—Snout short, broad, frontal lobes often
present, epipodial line furnished with cirrhi; shell nacreous,
variously spiral, operculum corneous, multispiral, nucleus central
(Fig. 182, p. 268). Silurian
a.) Zrochinae.—Frontal lobes present,
lateral teeth ( = side centrals) 5 only,
no jaws, peristome incomplete. Prin-
cipal genera: Trochus (subg. Cardi-
nalia, Tectus, Infundibulum, Clan-
culus), Monodonta (subg. Diloma),
Fig. 270.— Monodonta canalifera Cantharidus (subg. Bankivia, Tha-

eee (After Quoy [otia), Gaza (subg. Microgaza),

Callogaza, Bembix, Chlorostoma. (ii.)
Gibbulinae.—Frontal lobes and jaws present, laterals often
more than 5, peristome incomplete. Principal genera: (ib-
bula (subg. Monilia, Aphanotrochus, Enida), Minolia, Circulus,
Trochiscus, Livona, Photinula, Margarita, Solariella, Calli-
ostoma, Turcica, Basilissa, Huchelus (subg. Olivia, Perrinia).
(iul.) Delphinulinae.-—No frontal lobes, jaws present ; shell solid,

XIV DIOTOCARDIA——RHIPIDOGLOSSA 409

surface spirauy lirate, scaly, spinose, umbilicate, peristome con-
tinuous. Single genus, Delphinula. (iv.) Umboniinae—Eyes
pedunculate, left tentacle attached to a frontal appendage, mantle
reflected over edge of aperture, lateral teeth 6 on each side;
shell polished, peristome incomplete, umbilicus generally closed
by a callosity. Principal genera: Umboniwm, Ethalia, Isanda,
Camitia, Umbonella, Chrysostoma.

Fam. 6. Zurbinidae—Epipodial line with slender cirrhi, snout
broad, short, eyes pedunculate at outer base of tentacles, a frontal
veil between tentacles ; shell turbinate, solid, aperture continuous,
operculum solid, calcareous, usually paucispiral, convex exteriorly
(Fig. 182, p. 268) Silurian——. G.) Phasianellinae.—Shell
bulimoid,polished,not nacreous, coloured in patterns, aperture oval.
Single genus, Phasianella (Fig. 271). (a1.) Turbininae.—Shell very
solid, nacreous within, aperture circular or long oval. Principal
genera, Z'urbo, whorls rounded above and below, spines, if present,
becoming more prominent with age, operculum smooth or granu-
lose, nucleus sub-central ; subg. Callopoma, Ninella, Marmorostoma,
Sarmaticus, Prisogaster ; -Astralium, whorls flattened above and
below, spines, if present, becoming less prominent with age,
operculum oblong, often excavated at centre, last whorl large,
nucleus marginal or sub-marginal; subg. Lithopoma, Imperator,
Guildfordia, Bolma, Cyclocantha, Uvanilla,
Cookia, Pomaulax, Pachypoma. (iu.) Cyclo-
nematinae.—Shell nacreous, wnbilicate, oper-
culum conical outside, whorls scalariform.
Principal genera; Cyclonema, Horiostoma,
(?) Amberleya (Silurian to Lias). (iv.) Lepto-
thyrinae. — Shell small, solid, depressed,
operculum nearly flat, nucleus sub-central.
Genera ; Leptothyra, Collonia (?).

Fam. 7. Neritopsidae.—Tentacles wide
apart, long, eyes on short peduncles at the
outer base; shell solid, neritiform or naticoid,
aperture semi-lunar or oval; operculum
(Fig. 183, p. 269) thick, calcareous, non- M

Wes ; : a Fic. 271.—Phasianella aus-
spiral, exterior face smooth, interior face ~ ¢7is Gmel., Australia.
divided into two unequal parts, with a broad
median appendage. Devonian——. Principal genera: Veri-
topsis (one recent species), Naticopsis (Devonian to Miocene).

ALO DIOTOCARDIA—-RHIPIDOGLOSSA CHAP.

Fam. 8. Macluritidae.—Shell discoidal, whorls few, longi-
tudinally grooved behind, right side convex, deeply umbilicated,
left side flat ; operculum very thick, nucleus excentrical, internal
face with two apophyses, one very large. The general appearance
is more that of an inequivalve bivalve, such as Requienia, than of
a spiral gasteropod. Palaeozoic Single genus, Maclurea.

Fam. 9. Neritidae—Snout short, tentacles long, eyes pedun-
culate at their outer base, branchia triangular, free at the front
end, epipodium without cirrhi, penis near the right tentacle ;
shell solid, imperforate, turbinate to almost patelliform, spire
short, internal partitions absorbed (p.168), columellar region broad,
edge simple or dentate, operculum calcareous, spiral or non-spiral,
with prominent apophyses on the interior face, one of which locks
behind the columellar lip. — Jurassic———. Principal genera :
Nerita (Fig. 13, p. 17); Neritina (chiefly brackish water and
fluviatile), sub- genus Clithon, usually coronated with spines;
Velates (Tertiary), Neritoma (Jurassic), Devanira (Cretaceous),
Septaria (= Navicella), shell more or less narrowly patelliform,
with terminal apex, aperture very large, with a broad columellar
septum, operculum too small for the aperture, more or less
covered by the integument of the foot; fluviatile only ; P¢leolus
Jurassic to Cretaceous).

Fam. 10. Hydrocenidae—Byranchia replaced by a pulmonary
chamber, eyes at the outer base of the tentacles, marginals of
the radula very oblique, centrals often wanting; shell small,
conical, whorls convex, operculum calcareous, with a prominent
apophysis. Recent. Principal genera; Hydrocena, Georissa.

Fam. 11. Helicinidae.—Branchia replaced by a pulmonary
chamber, heart with one auricle; shell globular, with a short
spire, internal partitions absorbed ; operculum without apophysis.
Carboniferous- Principal genera: Helicina (Fig. 18, B, p.
21; sube. Aleadia, Schasicheila, Heudeia, Calybium), Eutrochatella
(subg. Lucidella), Stoastoma, Bourcieria, Dawsonella (Carboniferous).

Fam. 12. Proserpinidae. Branchia replaced by a pulmonary
chamber, mantle partly reflected over the shell, eyes sessile ; shell
depressed, discoidal, columella folded or truncated at the base,
whorls with one or more internal plicae, internal partitions
absorbed, no operculum. Eocene- Single genus; Proser-
pina, subg. Proserpinella, Cyane, Dimorphoptychia (Eocene), and
Ceres (Fig. 18, C, p. 21).

XIV MONOTOCARDIA——-TAENIOGLOSSA ALE

Sub-order II. Monotocardia.—Heart with one auricle, one
ctenidium (the left), monopectinate, fused with the mantle
(except in Valvata), one kidney, not receiving the genital
products, nervous system somewhat concentrated, proboscis and
penis usually present.

(a) PreNoGcLossA.—Radula with formula o.°o.0, teeth
similar throughout, outermost largest (p. 224).

Fam. 1. Janthinidae—Snout prominent, blunt, no eyes, shell
helicoid, fragile, bluish, no operculum ; eggs carried on a raft of
vesicles attached to the foot (Fig. 42, p. 126). Pelagic only.
Pliocene Genera: lanthina, Recluzia.

Fam. 2. Scalariidae—Shell long, turriculate, whorls often
partly uncoiled, with longitudinal ribs and prominent lamellae,
aperture circular, operculum spiral, corneous, animal carnivorous.
Ordovician Principal genera; Scalaria, Eglisia, Elas-
moneura (Silurian), Holopella (Silurian to Trias), Aelis.

(b) TAENIOGLOSSA.—Radula with normal formula 2.1.1.1.2,
marginals sometimes multiplied (p. 225).

SECTION I. PLatypopa.—F oot more or less flattened ventrally.

Fam. 1. Naticidae-—Foot very large, produced before and
behind, propodium reflected upon the head, eyes absent or buried
in the integument, central and lateral tooth of the radula tri-
cuspid, middle cusp strong; shell globular or auriform, outer lip
simple, operculum corneous or calcareous, nucleus excentrical.
Carboniferous Principal genera; Natica, with many
sub-genera; Ampullina (Tertiary); Amaura; Deshayesia (Ter-
tiary) ; Sigaretus (Fig. 91, p. 186), shell auriform, last whorl very
large, operculum much too small for the aperture.

Fam. 2. Lamellariidae—RMantle reflected over more or less
of the shell, shell delicate, no operculum. Eocene Prin-
cipal genera: Lamellaria, shell completely internal, transparent,
auriform ; some species deposit their eggs on compound Ascidians
(p. 74); Velutina, shell almost entirely external, paucispiral,
with a thick periostracum; Marsenina, shell auriform, partly
internal ; Onchidiopsis, shell a membranous plate, internal.

Fam. 3. Tvrichotropidae-—Branchial siphon short, eyes on
the outer side of the tentacles; radula closely allied to that of
Velutina; shell conical, last whorl rather large, periostracum
thick and hairy, operculum blunt claw-shaped, nucleus terminal.
Cretaceous : Genera: T'richotropis, Torellia.

412 MONOTOCARDIA—TAENIOGLOSSA CHAP.

Fam. 4. Naricidae—Tentacles broad in the middle, with
sessile eyes at the exterior base, propodium narrow, quadrangular,
a large epipodial veil on each side of the foot; shell naticoid,
cancellated, with velvety periostracum. Jurassic Single
genus ; Varied.

Fam. 5. Xenophoridae—Foot divided by a groove, anterior
portion the larger ; central tooth heart-shaped, with blunt cusps,
lateral large, roughly triangular, marginals long, falciform ; shell
trochiform, somewhat flattened, attaching various fragments
externally. Devonian Single genus, Venophora (Figs.
25, 26, p. 64).

Fam. 6. Capulidae.-—Ctenidium deeply and finely pectinate,
visceral sac scarcely spiral, penis long, behind the right tentacle ;
shell roughly patelliform, with scarcely any spire, interior
polished, usually with a septum or internal plate of variable form,
no operculum. Devonian Principal genera (Fig. 155,
p- 248); Capulus, shell cap-shaped, no internal plate; Platyceras
(Palaeozoic, see p. 76), Diaphorostoma (Palaeozoic), Addisonia
(2); Crucibulum, internal appendage funnel-shaped; Crepidula,
Gneluding Orepipatella and Ergaea), shell
slipper -shaped, with a large septum ;
Calyptraea (including Galerus and Tro-
chita), internal lamina semi-spiral.

Fam. 7. Hipponycidae-—Foot aborted,
animal sedentary, adductor-muscle shaped
like a horse’s hoof, fastened on the ven-
tral side to the region of attachment, or
Fra, 272.—Two specimens of t0 @ thin calcareous plate which closes

Crepidula (marked a and the aperture like a valve; ventral side of

6) on an old shell of :

ears rie Canals the body surrounded by a mantle with

papillose border, which corresponds mor-
phologically to the epipodia, head emerging between the dorsal
and ventral mantles. Shell thick, bluntly conical, surface rugose.
Eocene yenera: Hipponyx ; Mitrularia, a narrow halt
funnel-shaped appendage within the shell.

Fam. 8. Solariidae.—Foot large, eyes sessile, near the outer
base of the tentacles, radula abnormal (p. 224); shell more or less
depressed, lip simple, umbilicus wide, margins often crenulated,
operculum variable. The proper position of the family is quite
uncertain. Ordovician -. (i.) Solariinae. Genera: Sola-

XIV MONOTOCARDIA—-TAENIOGLOSSA 413

rium, shell depressed, highly finished, angular at periphery,
operculum corneous, central tooth
absent, laterals and marginals num-
erous, long, and narrow; Platyschisma
(Silurian). (ii.) Zoriniinae. Genera :
Torinia, whorls usually rounded,
operculum (Fig. 183) conically ele-
vated, spiral externally, central tooth
present, marginals few, edge pecti-
nated; Omalaaxis. (ii1.) Huompha-
linae, shell planorbiform, whorls
rounded. Genera: Huomphalus, Opht- rq, 973, Solarium perspectivum
leta, Schizostoma, Lecyliomphalus Lam., Eastern Seas.

(all Palaeozoic).

Fam. 9. Homalogyridae.—Tentacles absent, eyes sessile,
central tooth unicuspid on a quadrangular base, laterals and
marginals replaced by an oblong plate; shell very small, planor-
biform. Recent. Single genus: Homalogyra, whose true position
is uncertain.

Fam. 10. Littorinidae.—Proboseis short, broad, tentacles
long, eyes at their outer bases, penis behind the right tentacle ;
Tenroauetion oviparous or ovoviviparous, radula very long; shell
turbinate, solid, columella thickened, lip simple, operculum corne-
ous, nucleus excentrical. Jurassic : Principal genera :
Littorina (radula, Fig. 16, p. 20), Cremnoconchus (p. 16), Fos-
sarina; Tectarius, shell tubercled or spinose ; Lisella, base slightly
concave ; Lacuna, shell thin, grooved behind the columellar lip.

Fam. 11. Fossaridae.—Shell turbinate, solid, small, white,
spirally ribbed, outer lp simple. Miocene
genus, Hossarus.

Fam. 12. Cyclophoridae—Ctenidium replaced by a pulmon-
ary sac, tentacles long, thread-like (radula, Fig. 17, p. 21);
shell variously spiral, peristome round, often reflected, operculum
circular. Terrestrial only. Cretaceous———. _(i.) Pomatiasinae,
shell high, conical, longitudinally striated, operculum consisting
of two Jaminae united together. Single genus, Pomatias. (i.)
Diplommatininae, shell more or less pupiform, peristome thick-
ened or reflected, often double. Genera ; Diplommatina (subg.,
Nicida, Palaina, Paxillus, Arinia), shell dextral or sinistral,
small, columella often denticulated ; Opisthostoma (Fig. 208, p.

Ze.
See
“ = =n

Sa O'% “
mie he he
yi by \® 4 .

x

Principal

A14 MONOTOCARDIA—TAENIOGLOSSA CHAP.

309), last whorl disconnected, often reflected back upon the
spire. (ail.) Pupininae, shell more or less lustrous, bluntly
conical, lp with a channel above or below. Genera: Pupina
(subg. Registoma, Callia, Streptaulus, Pupinella, Anaulus), Hybo-
cystis (Fig. 205, p. 305), Cataulus, Coptochilus, Megalomastoma.
(iv.) Cyclophorinae, shell turbinate or depressed, operculum corne-
ous or calcareous. Genera: Alycaeus, Craspedopoma, Leptopoma,
Lagochilus, Cyclophorus (Fig. 206, p. 306; including Diadema,
Aulopoma, Ditropis, and others), Aperostoma (including Cyrtotoma
and others), Cyathopoma, Pterocyclus (subg., Myxostoma, Spira-
culum, Opisthoporus, and Rhiostoma (Fig. 180, p. 266), Cyclotus,
Cyclosurus, and Strophostoma.,

Fam. 13. Cyclostomatidae—Ctenidium replaced by a pul-
monary sac, tentacles obtuse, foot with a deep longitudinal median
groove; central tooth, lateral, and first marginal more or less
bluntly cusped, second marginal large, edge pectinate; shell
variously spiral, spire usually elevated,
aperture not quite circular; operculum
generally with an external calcareous and
an internal cartilaginoid lamina, rarely
corneous. Terrestrial only. Cretaceous
Genera : Cyclostoma (sube.,
Leonia, Tropidophora, Rochebrunia,
Fic. 274.—Cyclostoma cam- Georgia, Otopoma, Lnthidion, Revoilia),

eg ae Pir, Mada- Cyelotopsis, Choanopoma (subg., Licina,

Jamaicia, Clenopoma, Diplopoma, Adam-

siella), Cistula (subg., Chondropoma, Tudora), Omphalotropis (subg.,
Realia, Cyclomorpha), Hainesia, Acroptychia.

Fam. 14. Aciculidae.—Ctenidiam replaced by a pulmonary
sac, tentacles cylindrical, pointed at the end, eyes behind their base,
foot long and narrow; central tooth and lateral very similar,pinched

in at the sides, external marginal broad, edge finely pectinate ;
shell small, acuminate, with a blunt spire, operculum corneous.
Terrestrial only. Tertiary Genus, Acicula (= Acme).

Fam. 15. Zruncatellidae.—Ctenidium replaced by a pulmonary
sac, proboscis very long, eyes sessile, behind the base of the
tentacles, shell small, evenly cylindrical, apex truncated in the
adult. Eocene Genera: Truncatella (subg., Taheitia,
Blanfordia, and Tomichia), Geomelania (sube., Chittya and
Blandiella), Cecina (?).

XIV MONOTOCARDIA—-TAENIOGLOSSA A415

Fam. 16. Rissoidae.— Eyes at the external base of the
tentacles, epipodium with filaments, operculigerous lobe with
appendages; central tooth pleated at the basal angles, lateral
large, bluntly multicuspid, marginals long, narrow, denticulate at
the edge; shell small, acuminate, often elaborately sculptured,
mouth entire or with a shallow canal, operculum corneous.
Marine or brackish water. Jurassic———. Principal genera :
Rissoa (subg., Kolinia, Onoba, Alvania, Cingula, Nodulus, Anaba-
thron, Fenella, Iravadia, and others), Scaliola (shell agglutinating
fragments of sand, ete.), Aissoina (lip thickened, operculum with
an apophysis as in Nerita), Barleeia, Paryphostoma (Kocene).

Fam. 17. Hydrobudae.—Eyes at the outer base of the
tentacles, penis behind the right tentacle, prominent, operculi-
gerous lobe without filaments; radula rissoidan, central tooth
often with basal denticulations; shell more or less acuminate,
small, aperture entire, operculum corneous or calcareous. Brackish
or fresh water. Jurassic Principal genera: Baicalia, with
its various sub-genera (p. 290); Pomatiopsis, Hydrobia, Bithynella,
Micropyrgus (Tertiary), Pyrgula, Emmericia, Benedictia, Litho-
glyphus, Tanganyicia, Limnotrochus (?), Jullienia, Pachydrobia,
Potamopyrgus, Littorinida, Amnicola, Fluminiecola (subg., Gillia,
Somatogyrus), Bithynia, Fossarulus (Tertiary), Stenothyra.

Fam. 18. Assimineidae—Ctenidium replaced by a pulmonary
sac, no true tentacles, eye-peduncles long, retractile; radula that
of Hydrobia ; shell small, conoidal, operculum corneous, nucleus
sub-lateral. Eocene Genera: Assiminea, Acmella.

Fam. 19. Skeneidae.—Radula resembling that of Hydrobia,
shell very small, depressed, widely umbilicated, operculum
corneous. Pleistocene—. Single genus, Skenea.

Fam. 20. Jeffreysiidae——Mantle with two pointed ciliated
appendages in front, tentacles ciliated, eyes sessile, far behind
the base of the tentacles; marginal teeth sometimes absent ;
shell small, thin, pellucid, whorls rather swollen, operculum with
marginal nucleus, divided by a rib on the inner face. Recent.
Genera: Jeffreysia, Dardania. Marine, living on algae.

Fam. 21. Litiopidae—Epipodium with cirrhi on each side,
operculigerous lobe with appendages; radula rissoidan; shell
small, conical, columella truncated, operculum corneous. Eocene
Genera: Litiopa, living on the Sargasso weed, suspended
by a long filament; Alaba, Diala.

416 MONOTOCARDIA—TAENIOGLOSSA CHAP.

Fam. 22. Adeorbidae. Radula essentially rissoidan; shell
depressed, circular or auriform, widely umbilicated, operculum
corneous, paucispiral, nucleus excentrical. Plocene
Principal genera: Adeorbis, Stenotis, Megalomphalus.

Fam. 23. Viviparidae—sSnout blunt, tentacles long, right
tentacle in the male deformed, pierced with a hole corresponding
to the aperture of the penis, two cervical lobes, the right being
siphonal, foot with an anterior transverse groove; teeth broad,
shallowly pectinate at the ends; shell turbinate, whorls more or
less rounded, aperture continuous, operculum corneous, nucleus
sub-lateral, with a false sub-central nucleus on the external face.
Animal ovoviviparous. Fresh water. Cretaceous Genera:
Vivipara (= Paludina), subg., Cleopatra, Melantho, Tulotoma ;
Tylopoma (Tertiary), and Lvoplax.

Fam. 24. Valvatidae.—Branchia exserted, bipectinate, carried
on the back of the neck, a filiform appendage (Fig. 66, p. 159) on
the right of the neck, penis under the right tentacle, prominent,
eyes sessile, behind the tentacles; radula like that of Vivipara ;
shell small, turbinate or flattened, operculum corneous, nucleus
central. Fresh water. Jurassic Single genus, Valvata.

Fam. 25. Ampullariidae.—Snout with two tentacles, tentacles
proper very long, tapering, eyes prominently pedunculate, two
cervical lobes, the left siphonal, respiratory cavity divided by a
partition, a large branchia in the right chamber, the left func-
tioning as a pulmonary sac (Fig. 65, p. 158); radula large,
central tooth multicuspid, base broad, lateral and marginals falci-
form, simple or bicuspid; shell large, turbinate or flattened, spire
small, whorls rounded; operculum generally corneous, nucleus
sub-lateral, false nucleus as in Vivipara. Fresh water. Creta-
ceous Single genus Ampullaria (subg., Ceratodes, Pachy-
labra, Asolene, Lanistes, and Meladomus).

Fam. 26. Cerithiidae.—Branchial siphon present, short, eyes
variable in position; central tooth small, evenly cusped, lateral
hollowed at base, multicuspid, marginals narrow; shell long,
turriculate, whorls many, generally tuberculate, varicose or spiny,
aperture sometimes strongly channelled; operculum corneous,
sub-circular, nucleus nearly central. Marine or brackish water.
Trias Principal genera: Zvriforis, shell small, generally
sinistral; Fustigiella, Cerithium (Fig. 12, p. 16), Bittiwm, Pota-
mides (subg., Tympanotomus,. Pyrazus, Pirenella, Telescopvum,

XIV MONOTOCARDIA—-TAENIOGLOSSA Ane

Cerithidea, Lampania, all brackish water), Diastoma (Kocene),
Cerithiopsis ; Ceritella (Jurassic), Brachytrema (Jurassic), and
Planaxis (subg., Quoyia and Holcostoma).

Fam. 27. Modulidae—No siphon, radula of Cerithiwm ; shell
with short spire, columella strongly toothed at the base, aperture
nearly circular. Recent. Single genus, Modulus.

Fam. 28. Nerineidae.—Shell solid, long sub-cylindrical, aper-
ture channelled, columella and interior of whorls with continuous
ridges, extending up the spire. Genera: Nerinea (Trias to
@reticeous), Tivo (Jurassic).

Fam. 29. Melaniidae.—Border of mantle fejooucdl foot broad,
with an anterior groove, penis present ; radula closely resembling
that of Cerithium ; shell long, spiral, with a thick periostracum,
surface with tubercles, ribs, or striae, suture shallow; operculum
corneous, paucispiral, nucleus excentrical. Animal
ovoviviparous. Fresh water. Cretaceous
Principal genera: JMJelania (with many sections or
sub-genera), Pachychilus, Claviger (= Vibex), Hemi-
sinus, Pirena, Melanopsis, Tiphobia, Paludomus
(sube., Philopotamis, Tanalia, Stomatodon), Hant-
kenia (Eocene), Larina (?).

Fam. 30. Pleuroceridae. — Mantle edge not
festooned, no copulatory organ, otherwise like
Melaniidae ; operculum with nucleus sub-marginal.
Animal oviparous. Fresh water. Cretaceous : “Bree: O75 Me:
Genera: Pleurocera (including Jo, Fig. 12, p. 16, ania __con-
Angitrema, Lithasia, Strephobasis), Goniobasis, Ancu- ae a
lotus, Gyrotoma.

Fam. 31. Pseudomelaniidae. — Shell resembling that of
Melaniidae, but marine. Genera: Pseudomelania, Loxonema,
Bourguetia, Macrochilus. Palaeozoic to Tertiary strata.

Fam. 32. Turritellidae—Mantle with a siphonal fold on the
right side; radula variable (p. 224); shell long, whorls many,
slowly increasing in size, tranversely ribbed or striated, aper-
ture small; operculum corneous, nucleus central. Jurassic
Principal genera: Turritella, Mesalia, Protoma, Mathilda (?).

FAM. 35. Coecidae.—Tentacles long, eyes sessile at their base ;
shell small, spiral in the young form, spire generally lost in the
adult, the shell becoming simply a straight or curved cylinder; oper-
culum corneous, multispiral. Eoce Single genus, Coecwm.

VOU 25

a

418 MONOTOCARDIA—TAENIOGLOSSA CHAP.

Fam. 34. Vermetidae.— Visceral sac greatly produced,
irregularly spiral, no copulatory organs (radula, Fig. 126, p.
223), shell tubular, irregularly coiled, last
whorls often free, aperture circular; operculum
corneous, circular, nucleus central. Carbo-
niferous Principal genera: Vermetus ;
Siliquaria (Fig. 153, p. 248), a long fissure,
or series of holes, runs along a considerable
part of the shell, operculum with outer face
Fic, 276. — Develop- spiral, elevated.

nent ek Cec aa Fam. 35. Strombidae.— Foot narrow, arched,

showing the gradual
formation of septa; metapodium greatly produced, snout long, eye

ter ca ae aah peduncles long, thick, eyes elaborate, siphon

tum; s’s’, second short, penis prominent, bifureate; central tooth

septum. (After de : 5 ; :

Folin.) B, adult With strong median cusp, marginals falciform,

ae Eig oH slender, edge more or less denticulate ; shell

sold, spire conical, outer lip generally dilated
into wings or digitations, channelled before and behind, a labial
sinus at the base, distinct from the anterior canal; operculum small
for the aperture, corneous, claw-shaped, edge notched. Lias
Genera: Strombus (Fig. 99, p. 200); Perevraea (Miocene),
Pteroceras (Fig. 277; digitations of the outer lip very strong),
Rostellaria (spire produced, anterior canal very long), Limedlla,
Piterodonta, Terebellum (base of shell truncate, spire short).

Fam. 36. Chenopodidae (= Aporrhaidae).—Foot flat; lateral
and marginal teeth not denticulate; shell resembling that of
Strombus, outer lip dilated, wing-like, no labial sinus. Jurassic
Genera: Chenopus (= Aporrhais), Diastema, Malaptera,
Harpagodes, Alaria (last four from Secondary strata).

Fam. 37. Struthiolariidae—Radula allied to that of Strombus,
marginals occasionally multiphed; shell buccinoid, very solid,
outer lip thickened, canal short, operculum claw-shaped, notched,
nucleus terminal. Tertiary : Single genus, Struthiolaria
(sube., Perissodonta, marginal teeth multiplied).

Fam. 38. Cypraeidae—Mantle with two large lateral lobes
reflected and meeting over the shell, siphon small; central and
lateral teeth bluntly tricuspid or multicuspid, laterals fairly
broad, edges cusped or finely pectinate; shell polished, solid,
spire generally concealed in the adult or overlaid with enamel,
aperture straight, narrow, nearly as long as the shell, toothed at

XIV MONOTOCARDIA—-TAENIOGLOSSA 419

the sides, channelled at each end, labium inflected; no operculum.
J urassic——. Genera: Ovula (including Amphiperas, Trans-
ovula, Cyphoma, Radius, Simnia), Pedicularia, Cypraea (with
sube., Cypraeovula, Cypraedia, and Trivia), and Erato.

Fam. 39. Doliidae.—Foot expanded, wider and longer than
the shell, truncated and thickened in front, siphon very long and
narrow ; central tooth with very strong median and small lateral

Fia. 277.—Three stages in the growth of Pteroceras rugosum Sowb., E. Indies,
showing the development of the ‘ fingers.’

and basal cusps, lateral and marginals bluntly falciform; shell
ventricose, without varices, spire short, outer lip generally simple,
anterior canal rather wide, no operculum. Cretaceous
Genera: Doliwm (subg. Malea, outer lip thickened, denticulate,
reflected) ; Pirwla, mantle with two lateral lobes reflected over
part of the shell, shell fig-shaped (Fig. 278).

Fam. 40. Cassididae—Foot broad, siphon long (radula, Fig.
125, p. 223); shell ventricose, with varices, spire short, outer
lip reflected or thickened, anterior canal short, recurved narrow ;
operculum semilunar, with ribs radiating from a marginal

420 MONOTOCARDIA—TAENIOGLOSSA CHAP.

nucleus. Cretaceous Genera: Cassis (subg. Semicassis
and Cypraecassis), Morio (= Cassidaria), Oniscia.

Fam. 41. Colwmbellinidae Shell solid, ribbed, usually
cancellated, with an oblique posterior canal, columella callous,
more or less reflected. Genera: Columbellina, Columbellaria,
Zittelia, Petersia, Alariopsis (?). Secondary strata only.

Fam. 42. 7ritonidae.—Foot short, narrow ; siphon short, not
prominent; radula allied to that of Cassididae; shell thick,
varicose ; outer lip inflected and thickened, canal long, perios-
tracum often thick and hairy, operculum
corneous, nucleus terminal or sub-marginal.
Cretaceous Genera: Triton (Fig. 191,
p- 275; subg., Hpidromus, Plesiotriton, Sim-
pulum, Ranularia, Argobuccinum); Persona,
aperture toothed, narrow; columella reflected
upon the last whorl; Lanella, shell dorso-
ventrally compressed, generally with two con-
tinuous lateral varices, posterior canal present.

The position of the following four families
is doubtful -——

Fam. 43. Oocorythidae.—Siphon short,
foot broad, eyes absent, radula taenioglossate ;
Fic. 278.—Pirula Dus- shell buccinoid or cassidiform, operculum cor-

sumiert Val., Philip- ; = we

pines. x}. neous, spiral.—Recent. Single genus, Oocorys.

Fam. 44. Subulitidae.—Shell elongate,
fusiform, smooth; suture shallow, base truncate or rounded,
aperture channelled or notched. Ordovician to Trias. Genera:
Subulites, Fusispira, Huchrysallis.

Fam. 45. Sequenziidae.—Radula taenioglossate, shell trochi-
form, aperture channelled, columella twisted, operculum multi-
spiral, nucleus central. Pliocene Single genus, Sequenzia.

Fam. 46. Choristidae.—Anterior tentacles united by a frontal
veil, posterior simple ; eyes absent, foot with tentaculae before and
behind; three central teeth, outer marginal with a basal plate ;
shell helicoid, suture deep, peristome continuous, operculum
corneous, paucispiral. Pliocene : Single genus, Choristes.

Section II. HetERorpopa.—Foot fin-shaped, not flat.

The Heteropoda are free-swimming Mollusca, being, like the
Pteropoda, Gasteropoda modified to suit their pelagic environ-
ment. Their nervous system is streptoneurous, and they are

XIV HETEROPODA 421

therefore probably derived from the Prosobranchiata, but they
are highly specialised forms. Pelseneer considers them far more
widely removed from the Streptoneura than the Pteropoda are
from the Euthyneura. They swim on the surface “ upside down,”
i.e. With the ventral side uppermost.

The tissues and shell are transparent, permitting observation
of the internal organs. In the Pterotrachaeidae the foot takes
the form of a fan-shaped disc, usually furnished with a sucker.
The body is compressed at the posterior end, often with a ventral
“fin.” In Adlanta the foot consists of three very distinct parts :
a propodium, a mesopodium, on which is a small sucker, and a
metapodium, which carries the operculum. The branchiae are
carried on the visceral sac, and are free in Pterotrachaea, slightly
protected by the shell in Carinaria, and entirely covered in
Atlanta ; absent altogether in Firoloida.

The head carries two tentacles (except in Pterotrachaea), with
large, highly organised eyes on short lobes at their outer base.
The alimentary tract consists of a long protrusible proboscis,
with a taenioglossate radula (Fig. 132, p. 227), a long oesophagus,
and a slightly flexured intestine. In Adlanta the visceral sac is
spiral and protected by a spiral planorbiform shell; in Carin-
aria the visceral sac is small, conical, protected by a very thin
capuliform shell. There is no shell in Pterotrachaea or
Firoloida.

The Heteropoda are dioecious. In the male there is a
flagellum behind the penis, which is near the middle of the right.
side. Pterotrachaea lays long chains of granular eggs, and has
been noticed to produce a metre’s length in a day. The eggs
of Atlanta are isolated. The embryo has a deeply bilobed
velum.

Fam. 1. Pterotrachaeidae.—Body long, with a caudal “ fin ;”
branchiae dorsal, free or partly protected by a shell; foot consist-
ing of a muscular disc, with or without a sucker.

Pterotrachaea proper has no mantle, shell, or tentacles. The
branchiae are disposed round the visceral sac, at the upper part
of which is the anus. In Firoloida the body is abruptly trun-
cated behind, with a long filiform segmented caudal appendage ;
visceral sac at the posterior end: fin-sucker present or absent in
both male and female. Cardiapoda resembles Carinaria, but the
visceral sac is more posterior and is only slightly protected by

422 MONOTOCARDIA—-GYMNOGLOSSA—-RACHIGLOSSA cuHap.

a very small spiral shell. Carinaria (Fig. 279) has a rugose
translucent skin, visceral sac sub-median, apparently peduncu-
lated, covered by a capuliform shell. The larval shell, which
persists in the adult, is helicoid. |

Fam. 2. Atlantidae-—Shell spiral, operculate, covering the
animal. Branchiae in a
dorsal cavity of the mantle ;
foot trilobed, with a small
sucker on the mesopodimn.

The shell of Atlanta is
discoidal and sharply keeled,
while that of Oxygyrus 1s
nautiloid, with the spire

concealed, no keel, aperture
Fia. 279.—Carinaria mediterranea Lam., Naples: qi]ated
: ome ; ated.
a, anus ; br, branchiae ; 7, foot ; 7, intestine ;
m, mouth; p, penis; s, sucker; sh, shell ; ¢, (c) (GYMNOGLOSSA.—Ra-

Seng dula and jaws absent ; pro-
boseis prominent, sexes probably separate, penis present. The
section is probably artificial and unnecessary, the families com-
posing it being, in all probability, Taenioglossa which have lost
their radula in consequence of changed conditions of life (pp.
To ,e2 29):

Fam. 1. Hulimidae.-—Proboscis very long, retractile, mantie
forming a siphonal fold; shell small, long, subulate, polished ;
suture shallow, aperture continuous, operculum present or absent.
Animal often parasitic, sucking the juices of its host by its long
proboscis. Trias Genera: Hulima (subg. Subularia, Arcu-
ella, Apicalia, Mueronalia, Stiliferina, and others), Stilifer,
Scalenostoma, Niso, and Hoplopteron.

Fam. 2. Pyramidellidae—Tentacles auriform, proboscis as in
Eulimidae, a prominent mentum or flap under the buccal orifice ;
shell usually small, conical; suture shallow, apical whorls (the
embryonic shell) sinistral (p. 250), operculum corneous, pauci-
spiral; nucleus excentrical. Trias Genera: Pyrami-
della (subg. Syrnola, Otopleura, Chrysallida, Mumiola), Odostomia,
Eulimella, Murchisoniella, Turbonilla (subg. Dunkeria and
Cingulina).

(d@) RACHIGLOSSA (p. 220).—Proboscis long, retractile ; siphon
distinct, radula without uncini, sometimes without laterals ; teeth
strongly cusped; shell generally wholly external.

XIV MONOTOCARDIA

RACHIGLOSSA A283

Fam. 1. Muricidae—Eyes sessile at the outer base of the
tentacles, penis large, behind the right tentacle, radula within
the retractile proboscis, central tooth (Fig. 119, p. 220) with at
least three strong cusps, laterals plain ; shell solid, more or less
tuberculate, spiny and varicose, anterior canal varying from a
mere notch to a long channel. Cretaceous Principal
genera: (1) Muricinae, nucleus of operculum sub-terminal; Zrophon,
Typhis, Murex (with many subdivisions), Ocinebra (including
Cerastoma, Vitularia, and Hadriania), Urosalpinx, Eupleura,
Pseudomurex. (11) Purpurinae, nucleus of operculum lateral ;
Rapana (including Latiaxis), Purpura (with subg. Cuma, Lopas,
Veailla, and Pinaxia), Monoceros (including Chorus), Purpuroidea
(Secondary strata), Pentadactylus, Sistrum, Concholepas.

Fam. 2. Coralliophilidae—Animal living in Madrepores,
resembling Purpura, radula absent ; shell variously shaped, often
deformed or tubular, operculum that of Purpura, if present.
Miocene——. Principal genera: Lhizochilus, Coralliophila,
Leptoconchus, Magilus (Fig. 29, p. 75), Rapa.

Fam. 3. Columbellidae.—(Radula, Fig. 123, p. 222.) Shell
small, solid, fusiform, aperture narrow, canal short, outer lip
thickened. Miocene——. Single genus, Colwmbella (sube.,
Nitidella, Anachis, Meta, Strombina, Atilia, Conidea, Amphissa,
Mitrella, and others).

Fam. 4. Nassidae.—Foot long and broad, often with terminal
appendages ; siphon long, eyes on outer base of tentacles, central
tooth of radula arched, multicuspid, lateral strongly bicuspid,
with small denticles between the cusps; shell rather small, buc-
cinoid, columella more or less callous, outer lip thickened, often
toothed ; operculum corneous, edges often toothed. Miocene
Principal genera: Nassa (with many sections),
Amycla, Desmoulea, Cyclonassa, Canidia (subg. Clea and Nas-
sodonta), Dorsanum, Bullia (= Buccinanops, Fig. 62, p. 185),
Truncaria.

Fam. 5. Buccinidae—Siphon rather long, eyes at outer base
of tentacles; central tooth of radula with 5 to 7 cusps, laterals
bicuspid or tricuspid (Fig. 118, p. 220); shell more or less fusi-
form, thick, covered with a periostracum, canal of varying length,
outer lip simple or thickened; operculum corneous, nucleus vari-
able in position. Cretaceous Principal genera: Group
i. Chrysodomus (with sections Neptunea, Volutopsis, Pyrolofusus,

424 MONOTOCARDIA—-RACHIGLOSSA CHAP.

Jumala), subg. Sipho; Stphonalia (subg. Kelletia). Group ii.
Liomesus ( = Buccinopsis). Group ii. Buccinum (Fig. 1B, p. 6;
subg. Volutharpa, Neobuccinum). Group iv. Cominella, Triton-
idea, Pisania, Huthria; Anura (Miocene),
Genea (Pliocene), Metula, Engina. Group v.
Phos, Hindsia. Group vi. Dipsaccus (=
Hburna), Macron. Group vii. Pseudoliva.

Fam. 6. Turbinellidae—Central tooth
of radula tricuspid, median cusp strong,
lateral bicuspid, cusps unequal (Fig. 117,
p- 220); shell fusiform or pear-shaped,
heavy, canal often long, operculum corneous,
claw - shaped, nucleus terminal. Miocene
——. Principal genera: Turbinella, Cyno-
donta, Tudicla (subg. Streptosiphon); Piropsis
(Cretaceous), Perissolax (Cretaceous), Strep-
Fre, 280.—Turbinella pyr- sidura (Kocene, subg. Whitneya), Melapium,

um Lam., Ceylon. x8- Hyulour ( = Busycon, Fig. 150, p. 249, in-
cluding Sycotypus), Melongena (subg. Pugilina, Myristica) ; Lio-
stoma (Hocene), Hemifusus (subg. Megalatractus), Ptychatractus,
Meyeria.

Fam. 7. Fasciolariidae.—kEyes at the outer base of the tenta-
cles (radula, Fig. 121, p. 221); shell
fusiform, spire long, canal often very
long, columella often with a fold at
the base; operculum corneous, nucleus
terminal. Cretaceous—-—. Principal
genera; Fusus (including Sinistralia,
Aptyxis, Troschelia), with subg. Serri-
fusus (Cretaceous), Clavella (subg.
Thersites), Fasciolaria, Latirus (subg.
Polygona, Peristernia, Leucozonia,
Lagena ; Mazzalina (Eocene), Chascaz).

Fam. 8. IMitridae—Siphon rather
long, with anterior appendages, eyes
on the side of the tentacles, proboscis
very long; radula variable, laterals Fie. 281.— Latirus (Leucozonia)
sometimes lost (Fig. 120, p. 221); eungulatus joes, Toe
shell fusiform, solid, spire more or less pointed, columella with
several prominent folds, the posterior the largest, aperture rather

XIV MONOTOCARDIA—-RACHIGLOSSA 425

narrow, no operculum. Cretaceous Principal genera :
Mitra (with many sections), subg. Strigatella,
Mitreola, Mutyca, Dibaphus ; Plochelaea (Ter-
tiary), Thala; Turricula (with several sec-
tions), Cylindromitra, and Imbricaria.

Fam. 9. Volutidae—Foot broad in front,
head laterally dilated into lobes, on which are
placed the sessile eyes ; siphon prominent, with
appendages at the base (radula, Fig. 122,
p- 221); shell thick, often shining, fusiform,
globular or cylindrical, columella projecting
anteriorly, with several folds, the anterior of
which is the largest, aperture notched, canal
not produced, operculum generally absent. Fie. 282.—Voluta ni-
Cretaceous Principal genera: Crypto- ee
chorda (Kocene), Zidona, Provocator, Guivillea,

Vetus (= Cymbium), Voluta (with many sections); Volutolithes
(chiefly Eocene), Volutolyria, Lyria, Enaeta, Volutomitra.

Fam. 10. Marginellidae.—Foot broad, siphon without ap-
pendages, mantle largely reflected over the shell; radula without
laterals, central tooth comb-lke, cusps rather blunt; shell oval
or conoidal, polished, aperture narrow, outer lip
thickened, columella with many folds ; no oper-
culum. Hocene Principal genera : Mar-
ginella, with many sections and so-called sub-
genera; Persicula, Pachybathron (?), Cystiscus,
Microvoluta.

Fam. 11. Harpidae.—Foot large, with a
transverse groove, separating off a semi-lunar
propodium; mantle partly reflected over the
shell; shell ventricose, polished; spire short,
strongly longitudinally ribbed, ribs prolonged
over the suture, columella callous; no oper-
culum. Eocene Single genus, Harpa
Fria. 283.— Oliva por- (sul yor Silia).

phyria Lam., = Snr E i

Panama. Fam. 12. Olividae-—Propodium semi-lunar,

with a longitudinal groove above, mesopodium
reflected laterally over the shell; central tooth of radula_ tri-
cuspid on a very broad base, lateral simple, hooked; shell sub-
cylindrical or fusiform, polished; aperture narrow, operculum

426 MONOTOCARDIA—TOXOGLOSSA CHAP. XIV

present or absent. Cretaceous——. Principal genera: Oliva
(Figs. 285 and 98, p. 200), Olivancillaria (in-
cluding Lintricula and Agaronia), Olivella,
Ancilla (subg. Ancillina).

(e) TOXOGLOSSA (p. 218).—Radula with nor-
mal formula 1:0°1., teeth large; oesophagus
with a large poison gland; animal carnivorous,
exclusively marine.

Fam. 1. Yerebridae—Hyes at the end of
the tentacles, shell subulate,
many whorled, operculum

with terminal nucleus.
Kocene ———. Single
genus, Zerebra, with several
sections.

Fam. 2. Conidae.—Eyes
on outer side of tentacles,
siphon prominent; shell coni-
Fra, 284.—Terebrasub- eal or fusiform, aperture nar-

ulata L., Ceylon. ‘
row. Cretaceous

Principal genera: Conus, shell solid, spire
short, aperture narrow, straight, internal par-
titions partly absorbed; Conorbis, Genotia Fie. 285.—Pleurotoma
(with several sections, chiefly Tertiary), Pus- {arime Tam. E.
ionella, Columbarium, Clavatula, Surcula, Pleu- <

rotoma; Borsonia (Eocene), Drillia (subg. Spirotropis), Bela,
Mangilia (including Daphnella, Clathurella, and others), Halia.

Fam. 3. Cancellartidae—Proboscis short, usually no radula, shell
oval, columella strongly plicate ; no operculum. Cretaceous
Single genus, Cancellaria (sube. Merica, Trigonostoma, Admete).

CHAPTER XV

CLASS GASTEROPODA (continued): OPISTHOBRANCHIATA AND
PULMONATA

Order III. Opisthobranchiata.

VISCERAL loop not twisted (except in Actacon) in a figure of 8
(Euthyneurous type, p. 203), auricle usually behind the ventricle,
ctenidium often replaced by secondary branchiae, pallial cavity,
if existing, more or less open, shell present or absent, operculum
absent (except in Actaeon), animal hermaphrodite, with separate
sexual openings, marine only.—Carboniferous to present time.

The character of their nervous system decisively removes the
Opisthobranchiata from the Prosobranchiata, and approximates
them to the Pulmonata. Actaeon, however, which is strepto-
neurous, as well as possessing an operculate shell with prominent
spire, forms an interesting link with the Prosobranchiata. At
the opposite extreme to <Actaeon stand forms like Siphonaria
and Gadinia, which are probably close links with the Pulmonata
(p. 19). The generative system of the whole group, which is,
as in the Basommatophora, of the hermaphrodite type, without
mutual fecundation, is another link of connexion with the
Pulmonata. The respiratory organs present the most varied
forms, sometimes consisting of one ctenidium (never two), some-
times of secondary branchiae, variously placed, while sometimes
no special organ exists.

The prolongation of the foot into lateral epipodia or parapodia
(possibly to aid in swimming), and the effect of the epipodia
upon the shell, according as they involve it completely or
partially, are among the most instructive features of the
Opisthobranchiata. If the epipodia are developed on the

428 OPISTHOBRANCHIATA CHAP.

anterior portion of the body, and do not become reflected, they
may, as in most Pteropoda Thecosomata, not directly affect the
shell. But when, as in the Tectibranchiata, the epipodia are
medio-lateral, and tend to envelope the shell, their effect may be
traced by a series of forms varying in proportion to the amount
of shell-surface covered by the epipodia. The two principal lines
along which modification takes place are the gradual reduction
of the spiral nature of the shell,and the gradual lessening of
its solidity. Both these changes are the direct result of the

Fic. 286.—Illustrating the transition Fic. 287.—Ilustrating the gradual covering

of form in the shell of Tecti- of the shell in the Tectibranchiata by the
branchiata from the pointed spiral epipodia and mantle: A, Maminea ; ‘8B
to the almost flattened plate: A, Sceaphander ; C, Aplustrum ; D, Aplysia ;
Actaeon ; B, Aplustrum ; ©, Cyli- E, Philine ; c.d, cephalic disc; ep, ep,
chna; D, Atys; E, Philine; F, epipodia ; sh, shell. (Not drawn to scale.)

Dolabella ; G, Aplysia ; H, Pleu-

robranchus. (Not drawn to scale.)
additional protection afforded to the visceral mass by the
reflected epipodia, which renders the existence of a shell less
and less necessary. A precisely similar line of change is seen
in the Pulmonata, culminating in forms like Arion (p. 174).

The habits of life of the Opisthobranchiata are very varied.
Some, especially the heavier types, burrow in sand, and are then
usually furnished with a broad cephalic disc, as a digging
apparatus; some (certain Bulla) flit about in shallow pools on
mud flats; others (Phyllirrhoe and the Pteropoda) swim freely
in the open sea; others (most Nudibranchiata) crawl slug-like on
sea-weeds or corallines, and in colour singularly harmonise with

XV OPISTHOBRANCHIATA : HABITS, CLASSIFICATION

429

their environment (p. 71 f.); others again (Siphonaria, Gadinia),
stick lmpet-lke to rocks between tide marks. As a rule, they
occur only in clean salt water, but Hmbletonia has been found in
the Victoria Docks at Rotherhithe, as well as in parts of the
Baltic, where the water has only 7 parts of salt in 1000, while
Limapontia occurs in nearly fresh water at Bornholm and
Gothland.

Their food varies greatly. As a rule, they are frugivorous,
but many cases of carnivorous habit occur. Scaphander has
been seen to swallow Dentaliwm six at a time, and in six hours
the shells of all were reduced to tiny fragments. Glaucus devours
the soft portions of the pelagic Porpita and Velella; Idalia
elegans eats its way into the test of Ascidians, and completely
buries itself in the body of its prey.?

The Opisthobranchiata may be classified as follows :—

Bulloidea
Aplysioidea
Plewrobranchoidea
Siphonarioidea

1. TECTIBRANCHIATA

Opisthobranchiata < 2. AscocLossa
5 Cladohepatica
3. NUDIBRANCHIATA 5 ;
Holohepatica
Thecosomaia
4, PTEROPODA .

* | Gymnosomata

Sub-order I. Tectibranchiata.— Right ctenidium usually
present, more or less concealed by the mantle fold, visceral
ganglia united by a very long commissure, shell variable in
form, more or less enveloped in folds of the mantle and foot,
often becoming rudimentary.

SEcTION I. BuLLOIDEA.—Shell more or less spiral, internal or
external, epipodia more or less developed, a broad cephalic
disc, distinct from the dorsal region, usually no tentacles, eyes
sessile.

Fam. 1. Actaeonidae——Shell spiral, solid, entirely covering
the animal; spire generally prominent, operculum corneous,
visceral loop streptoneurous, no epipodia, radula miultiseriate,
teeth numerous, very small. Carboniferous Genera :
Actacon (Fig. 286 A.); Volvaria (Tertiary), Fortisia (Eocene) Actae-

1 J. Power, Ann. Mag. N. H. (2) xx. p. 334; P.Z.S. 1836 p. 118; Arch. Zool.
Exp. Gén. (3) i. 1898, p. 105.

430 TECTIBRANCHIATA . CHAP.

onina (Carboniferous), Cylindrites (Secondary strata), Actaconella
(Cretaceous).

Fam. 2. Yornatinidae.— Shell spiral, cylindrical, entirely
covering the animal; spire concealed, cephalic disc with two
large tentaculform appendages behind, no radula. Genera:
Tornatina (= Utrieulus), Volvula.

Fam. 3. Scaphandridae.—Shell more or less external, covering
all or nearly all the animal, spire concealed, cephalic disc simple
or notched behind, epipodia well developed, radula with first
lateral very large, stomach sometimes with powerful gizzard.
Genera: Scaphander (Fig. 287 B); Sabatia (Pliocene), Smaragdi-
nella, Atys (Fig. 286 D), Cylichna (Fig. 286 C), Amphisphyra.

Fam. 4. Bullidae—Shell external or partly internal, spire
quite or nearly hidden, cephalic disc broad, without appendages,
epipodia often large; radulausually multiseriate. Genera: Bulla
(subg. Haminea), Acera, mantle with long filiform appendage,
epipodia touching over the shell; Cylindrobulla, Volvatella.

Fam. 5. Aplustridae.—Shell partly internal, overlaid by the
posterior part of the cephalic disc, spire not prominent, epipodia
reflected, tentacles auriform. Single genus, Aplustrum (Fig. 286
B; subg. Hydatina).

Fam. 6. ingiculidae—Shell small, solid, covering all the
animal; spire somewhat prominent, aperture narrow, plicated ;
peristome thick, sometimes channelled, cephalic disc with a kind
of posterior siphon. Genera: Lingicula ; Avellana (Cretaceous).

Fam. 7. Gastropteridae.—Shell completely internal, nautiloid,
small; epipodia very large, rounded, united behind; cephalic disc
simple. Single genus, Gastropteron.

Fam. 8. Philinidae—Shell completely internal, thin, slightly
spiral; epipodia thick, cephalic disc large, thick, simple; stomach
usually with powerful gizzard. Genera: Philine (Fig. 287 E),
Colpodaspis, Colobocephalus, Chelinodura, Phanerophthalmus, Crypt-
ophthalmus.

Fam. 9. Doridiwidae.— Shell completely internal, a mere
pellicle with a small spiral nucleus, mantle with two posterior
lobes and a caudal filament, epipodia reflected. Single genus,
Doridiwm.

Section IJ. ApiLysioipEA.—Shell small, usually not spiral,
sometimes absent, no cephalic disc, head prominent, with two
pairs of tentacles, epipodia large, more or less reflected.

XV TECTIBRANCHIATA—ASCOGLOSSA 431

Fam. Aplysiidae.—Characters those of the section. Genera:
Aplysia (Fig. 287 D), shell arched, flattened, animal large (the
“sea hare”); Dolabella, shell sub-triangular (Fig. 286 F); Dola-
brifer, shell sub-quadrangular, not spiral; Motarchus, shell micro-
scopic, spiral; Phyllaplysia, body very depressed, oval, no shell.

SECTION III. PLEUROBRANCHOIDEA.— Dorsal region protected
by a wide notaewm or dorsal covering, or by a shell; no epipodia,
ctenidium large, external, between the right under surface of the
notaeum or shell and the foot; head short, shell present or
absent.

Fam. 1. Plewrobranchidae.—Shell internal or absent, notaeum
with spicules, radula multiseriate. Genera: Plewrobranchus
(Fig. 286 H), (2) Haliotinella, Pleurobranchaea, (2) Neda.

Fam. 2. Runcinidae.—Branchial lamellae few, under the
posterior right notaeum, no shell. Single genus, Rwncina.

Fam. 3. Umbrellidae.—Shell external, depressed patelliform,
not covering all the animal; foot very thick, ctenidium large,
head depressed, small; radula multiseriate, teeth innumerable,
very small. Genera: Umbrella (Fig. 54, p. 10), Tylodina.

SECTION IV. SIPHONARIOIDEA.—Shell patelliform, branchia
replaced wholly or in part by a pulmonary sac, pulmonary
orifice closed by a small lobe, radula multiseriate, teeth very
small.

Fam. Siphonarvidae.—Characters those of the section. Genera:
Siphonaria (branchia as well as pulmonary sac), Gadinia (no
branchia). These genera, hitherto placed among the Pulmonata,
have been recently shown (see p. 19) to be modified Opistho-
branchiata.,

Sub-order II. Ascoglossa..—Branchia, mantle cavity, and
shell generally wanting, liver ramified, rami enclosed in external
papillae (cerata) or beneath the dorsal surface, kidney not com-
pact, branched ; radula with one series of strong teeth (Fig. 288),
worn out teeth at the front end not dropping off, but preserved
in a special sae (acxKds).

According to Bergh, the Ascoglossa form a link between the
Tectibranchiata,—especially the Aplysiidae and Bullidae—and the

1 In deference to Bergh’s high authority, the position of a sub-order is here
given to the Ascoglossa. It may be doubted whether that position will stand the
test of further investigation, and whether the families concerned will not be added
to the Cladohepatic Nudibranchs.

Ne, ASCOGLOSSA—-NUDIBRANCHIATA cHaP,

Cladohepatie Nudibranchs, while the Pleurobranchidae form a
somewhat similar link between the Holohepatic Nudibranchs and
the other Tectibranchiata.

Fam. 1. Oxynoeidae.'— Animal long, tentacles. auriform,
epipodia large, simple, or wing-like, a ctenidium and branchial
chamber on right side, shell small, thin,
slightly spiral, not covering much of
the body. Genera: Oxynoe ( = Lophocer-
cus), Lobiger.

Fam. 2. Hermaeidae.— Body de-
pressed, cerata in several rows, no
branchiae, no shell. Genera: Hermaea,
Phyllobranchus, Stiliger, Alderia.

Fic. 288.—Radula of one of Fam. 3. Elysiidae.—Body depressed,
Ascoglossa (Hlysia viridis ;
Mont. x40). head rather elevated, tentacles auriform,

sides of body dilated into two large
wings, Which enclose branches of the liver and sometimes fold
over the dorsal surface, no branchiae, no shell. Genera: Hlysia,

Thridachia, Placobranchus.

Fam. 4. Limapontiidae.—Body slug-like, liver scarcely rami-
fied, no branchiae, shell, or appendages. Genera: Limapontia,
Actaeconia, Cenia.

Sub-order III. Nudibranchiata.—Shell absent in the adult,
no ctenidium proper, or osphradium, cerata dorsal or dorso-lateral,
nervous system concentrated, kidney not compact, ramified, penis
retractile, jaws and radula usually present.

SECTION I. CLADOHEPATICA.—Cerata usually latero-dorsal,
elongated, or arborescent, buccal mass strong, jaws present, liver
generally ramified, rami generally entering the cerata.

Fam. 1. Aeolidiidae.—Body slug-like, head with tentacles and
rhinophores, dorsal area with rows of cerata, which usually con-
tain sting-cells, radula variable. Genera: -Aeolis, Cratena,
Tergipes, Coryphella, Favorinus, Facelina, Flabellina, Fiona,
Glaucus, Janus, Hero, with many sub-genera.

Fam. 2. Tethymelibidae.—Body slug-like, large, cerata very
large, no sting-cells, head large, cowl-shaped, no tentacles, rhino-
phores much folated, no radula. Genera: Tethys, Melibe. The
cerata of Tethys, which are capable of independent movement

' This family has also been classified with the Bulloidea and with the
Aplysioidea,

s

XV NUDIBRANCHIATA 433

when severed, have been described as parasitic worms. Tethys
feeds on molluses and Crustacea.

Fam. 3. Lomanotidae.—Body slug-like, dorsum prominent,
undulating or lobed, with one row of small cerata, no tentacles,
rhinophores much foliated, radula with uncinated dentate laterals.
Single genus, Lomanotus.

Fam. 4. Dotonidae.—Body slug-like, small, two rows of cerata,
each ceras surrounded by a ring of tubercles, rhinophores simple,
radula uniseriate. Single genus, Doto.

Fam. 5. Dendronotidae—Body slug - like, somewhat com-
pressed, two rows of arborescent cerata, no tentacles, frontal
margin with arborescent papillae, rhinophores arborescent, radula
multiseriate. Genera: Campaspe, Dendronotus.

Fam. 6. Bornellidae—Two rows of dorsal papillae, with
branchiform appendages at the base, rhinophores foliate, radula
multiseriate. Single genus, Bornella.

Fam. 7. Scyllaeidae.—Body oblong, compressed, two large
fohated cerata with branchial appendages on the inner side, no
tentacles, rhinophores large, radula multiseriate. Single genus,
Scyllaea.

Fam. 8. Phyllirrhoidae.—Body much compressed, with bovine
head and neck, tail tapering, no tentacles, rhinophores simple,
teeth few, no marginals. Single genus, Phyllirrhoe.

Fam. 9. Plewrophyllidtvidae——Body elongate-oval, snout broad,
covered by an arched shield with lateral angles prolonged,
branchiae consisting of two rows of lamellae placed between the
notaeum and the foot, no tentacles, rhinophores short, hidden,
radula multiseriate. Single genus, Plewrophyllidia.

Fam. 10. Plewrolewridae.—Animal resembling Pleurophyllidia,
but without the branchial lamellae. Single genus, Plewrolewra.

Fam. 11. Zritoniidae—Body long, two rows of unequal
arborescent cerata, rhinophores with ramose appendages, liver not
prolonged into the cerata. Genera: Zritonia, Marionia.

SECTION 2. HOLOHEPATICA.—Cerata medio-dorsal, retractile
or not, usually paucifoliate, liver never ramified, usually no
jaws.

Fam. 1. Dorididae.—Branchia consisting of a circle or semi-
circle of pinnate leaves united at the base, surrounding the anus,
almost always retractile into a cavity, rhinophores foliate, no
suctorial proboscis, radula multiseriate. Genera: Bathydoris,

VOL. II 2F

A34 NUDIBRANCHIATA CHAP.

Hexabranchus, Archidoris (Fig. 289), Discodoris, Diaulula,
Cadlina, Centrodoris, Platydoris, Chro-
modoris, Miamira, with many — sub-
genera.

Fam. 2. Doriopsidae.—Branchia and
rhinophores as in Dorididae, oral aper-
ture pore-shaped, suctorial, no radula.
Single genus, Doriopsis.

Fam. 3. Phyllidiidae.—PBody oval,
depressed, leathery, a ring of branchial
lamellae, only interrupted by the head
and genital papilla, under the pallial
edge, oral aperture pore-shaped, suc-
Fic. 289.—Doris (Archidoris) torial, no radula. Genera: Phyllidia,

tuberciata L., Britain: a, Hryeria. Bergh unites this and the

anus; 67, branchiae sur- ; : :

rounding the anus ; m, male preceding family in the group Porosto-

organ ; rh, rh, rhinophores. qty, which, with Fam. 1, form the

xia: eats ‘
group Dorididae cryptobranchiatae.

Fam. 4. Polyceridae—Body slug-like, branchiae not retractile,
usually surrounding the anus, rhinophores foliate, tentacles
simple, radula variable, central tooth generally wanting. Genera:
Notodoris, Triopella, Aegires, Triopa, Issa, Triopha, Crimora,
Thecacera, Polycerella, Palio, Polycera, Ohola, Trevelyana, Nem-
brotha, Euplocamus, Plocamopherus, Kalinga.

Fam. 5. Goniodoridae.—Body oval, depressed, branchia multi-
foliate, usually disposed in shape of a horse-shoe, rhinophores
folate, retractile or not, mouth with a large suctorial proboscis,
radula variable. Genera: Akiodoris, Doridunculus, Acanthodoris,
Adalaria, Lamellidoris, Calycidoris, Goniodoris, Idalia, Ancula,
Drepania.

Fam. 6. Corambidae—Body otherwise Doris-like, but with
two posterior branchiae under the mantle edge, jaws present, no
central tooth, about five laterals. Single genus, Corambe (=
Hypobranchiaea). Bergh unites this and the two preceding
familes in the group Dorididae phanerobranchiatae.

Sub-order IV. Pteropoda.— The Pteropoda are pelagic
animals in which the lateral portions of the foot are modified
into fins, which are innervated by the pedal ganglia. Their
systematic position has undergone recent revision. It has been
the custom to regard them as an Order of equivalent value to the

XV PTEROPODA 435

other four, while some have held them to be a subdivision of
Cephalopoda. Modern authorities, chief among whom is Pel-
seneer, regard the Pteropoda not as a primitive, but as a derived
and recent group. They are “ Gasteropoda in which the adapta-
tion to pelagic life has so modified their external characters as
to give them an apparent symmetry.”

The principal point which relates the Pteropoda to the
Gasteropoda is the asymmetry of the visceral organs, intestine,
heart, kidney, and genital gland, which results from their
development on one side only of the body. Their hermaphro-
ditism and the structure of their nervous system relate them to
the Euthyneura rather than to the Streptoneura. Resemblances
in the organs of circulation and generation approximate them to
the Opisthobranchiata rather than to the Pulmonata, while of
the two groups of the former, they tend to closer relationship
with the Tectibranchiata than with the Nudibranchiata. The
two sections of Pteropoda have been considered of distinct origin,
the Thecosomata being derived from the Bulloidea, the Gym-
nosomata from the Aplysioidea.'

Thus the Pteropoda are a group whose true relations are
masked by the special conditions of their existence, which have
tended towards the development of certain organs, the so-called
“wings” and the shell, which give them an apparent symmetry ;
this symmetry disappears on a closer investigation of the internal
organs. They are hermaphrodite; the genital gland has a single
efferent duct (except in some Cavolinia), a seminal groove leading
to the copulatory organ, which in the Thecosomata is on the
right side of the head, in the Gymnosomata on the right side of
the foot. The genital system resembles that of the Opistho-
branchiata and of the “ digonoporous ” Pulmonata.

SECTION 1. THECOsoMATA.—Shell or cartilaginoid test always
present, fins united by an intermediate lobe, ctenidia as a rule
absent, replaced by secondary branchiae, no very distinct head
or eyes, one pair of tentacles; cerebral ganglia on the sides of
and under the oesophagus; radula with three rather large teeth
in a row, generally unicuspid, jaw in two pieces, stomach with
horny plates, anus generally on the left side.

The Thecosomata feed on Protozoa and the lower Algae;

1 It appears more convenient to treat the whole group together, rather than deal
with the two sections separately.

436 PTEROPODA—THECOSOMATA CHAP.

they have no proboscis, and the intestine is flexured. The fins
are always closely connected with the head, or what answers to
it. About 42 species are known, belonging to 8 genera.

Fam. 1. Limacinidae—Fins very large, branchial chamber
dorsal, anus on right side; shell spiral, sinistral (ultra-dextral,
see p. 249), operculate. Genera: JLimacina, shell -helicoid,
deeply umbilicated (ZL. helicina swarms in Arctic seas and
furnishes food for many Cetacea); Peraclis, spire turreted,
aperture large, elongated, produced anteriorly, no umbilicus;
operculum sinistral, in spite of the shell being ultra-dextral.

Fam. 2. Cavoliniidae—F ins large, branchial chamber ventral,

Fic. 290.—Illustrations of Pteropoda Thecosomata: A, Zimacina australis Eyd.; B,
Cleodora cuspidata Bosc. (shell only) ; C, Cuvierina columnella Rang ; D, Creseis
virgua Rang; E, Clio balantium Rang; f, /, fins; 7, liver; 0, ovary ; sh, shell.
(After Souleyet.)

shell a non-spiral cone, angular or round, very thin, embryonic
portion distinct, or formed of two separate plates.

In Cavolinia ( = Hyalaea, Fig. 5, B, p. 10) the shell consists of
two plates, the ventral being convex, with one to three sharp
spines at the posterior end, the dorsal flatter, without spines.
The aperture is broad, contracted dorso-ventrally. Two long
pointed prolongations of the mantle project from the lateral slits
of the shell, and probably serve to balance the bulky body when
swimming. Fins trilobed at the margin. Cleodora has only
rudimentary lateral prolongations, fins bilobed, shell triangular,
angles greatly produced, aperture very wide, dorsal side keeled.
In Cuvierina the shell is straight, sub-cylindrical, with a median
partition, shghtly expanding towards the apex, which is truncated
in the adult. The principal sub-genera of Clio are Creseis, which
has an elongated sub-cylindrical shell, sometimes shghtly curved,

XV PTEROPODA—-GYMNOSOMATA 437

smooth or grooved; and Clio proper, in which the shell is long,
angular, with a dorsal rib, apex (=embryonic shell) rounded,
constricted. Styliola and Hyalocyliz also belong to this group.

Fam. 3. Cymbuliidae—Test (which is not homologous with
the shell of other Thecosomata) slipper-shaped, cartilaginoid,
simply a thickening of the mantle; embryo with a calcareous,
spiral, operculate shell. Genera: Cymbulia, Cymbuliopsis, Gleba.

Three other families, Hyalthidae, Pterothecidae, and Conu-
lariidae, from Palaeozoic strata, are generally added to the Thecoso-
mata. All are fossil only, and it is doubtful whether they are
really Molluscan. Pelseneer holds that no true fossil Pteropoda
occur until the lower Tertiaries.

SECTION 2. GyMNosoMATA.—Mantle and shell absent in the
adult, fins not connected by a lobe, no branchial chamber, head
well developed, with two pairs of tentacles, eyes on the posterior
pair; cerebral gangha above the oesophagus; buccal cavity pro-
vided with a pair of protrusible “ hook-sacs,” radula generally
with 4 to 12 hooked laterals, central tooth triangular, jaw in one
piece, composed of horny plates, no horny plates in stomach,
anus on the right side.

The Gymnosomata are carnivorous, feeding on Thecosomata
and other pelagic animals, being provided for this purpose with
a formidable buccal armature of hook-sacs and suckers. The
intestine, as usual in carnivorous groups, passes straight from the
stomach to the anus; the fins are not attached to the head, but
to the anterior part of the body. The larva has a straight shell,
which disappears in the adult. About 21 species are known,
belonging to 7 genera.

Fam. 1. Pnewmodermatidae——Animal fusiform, tins rather
small, head prominent, anterior part of buccal cavity protrusible,
with suckers on the ventral side, hook-sacs well marked ;
branchia on right side, skin soft, pigmented. Genera: Dewxio-
branchaea, no posterior gill, hook-sacs short; Spongiobranchaea,
posterior gill circular ; Pnewmoderma, gill tetraradiate, hook-sacs
long.

Fam. 2. Clionopsidae-——Body barrel-shaped, proboscis three
times the length of the body, no buccal appendages, hook-sacs
short, no lateral gill, posterior gill tetraradiate, skin not pig-
mented. Clionopsis is the single genus.

Fam. 3. Notobranchaeidae—Body ovate, buccal appendages

438 PTEROPODA—-GYMNOSOMATA CHAP.

conical, no lateral gill, posterior gill with three radiating crests,
skin pigmented. Notobranchaea is the single genus.

Fam. 4. Clionidae-—Body long, angulated behind, proboscis
short, mouth with two or three pairs of appendages, no jaw, no
gills.

Clione limacina is so abundant in Arctic seas as at times to
colour the surface for miles. Each of the cephalic appendages
has about 60,000 minute pedicellated suckers.

Fia. 291.—A, An-
terior portion of
Pneumoderma ;
B, Clione lima-
cind Phipps ;
C, Halopsyche
Gaudichaudi
Soul. ; 7A, / fins;
his, h.s, hook -
sacs 3 /.f, lobe of
the foot; s, s,
suckers ; 0, pos-
terior genital
OWNS. ty i
tentacles. (After
Souleyet.)

Fam. 5. Halopsychidae.—Body ovate, thick, rounded behind,
no gill or proboscis, fins long, narrow, broadened at the ends,
epidermis sub-cartilaginoid.

Halopsyche (= Eurybia) has the power of withdrawing its
head completely into a sort of pocket, which is closed by an
anterior fold of the mantle. There are two long non-retractile
buccal appendages.

Order IV. Pulmonata

Gasteropoda with two pairs of tentacles, visceral loop euthy-
neurous, ganglia concentrated round the oesophagus; breathing
air by a pallial cavity formed by the union of the front edge of
the mantle with the cervical region, sexes united, shell present
or absent, no operculum? (except in Amphibola).

Sub-order I. Basommatophora.—tEyes generally at the base
of the tentacles, which are not retractile, male and female genital
orifices separate, radula (p. 235) multiseriate, shell always present,
external. Fresh water or-quasi-marine.

1 An operculum is said to exist in the young forms of Auricula and Parmacella.

XV PULMONATA—BASOMMATOPHORA 439

Fam. 1. Auwriculidae—Breathing organ a pulmonary sac or
true lung; shell spiral, conoidal, internal partitions usually
absorbed, aperture more or less
strongly toothed. Jurassic
Genera: Auricula, Carychium,
Scarabus, Alexia, Tralia, Pleco-
trema, Cassidula, Melampus, Leu-
conta, Pedipes (Fig. 292).

Fam. 2. Otinidae.—Shell auri-
form, spire very short. Genera:
Otina, Camptonyx— Recent only.

Fam. 3. Amphibolidae. — A
pulmonary sac on right side of
neck, eyes almost pedunculate,
shell turbinate, rudely sculptured,

Fic. 292.—Examples of the Auriculidae :
A, Auricula Judae Lam., Borneo; B,

operculate. — Recent. Genus, = Scarabus Lessoni Blainv., E. Indies ;

ation a 993): om C, Cassidulu mustelina Desh, N.
Amphibola (Fig. 93); subg. Zealand ; D, Melampus castaneus
Ampullarina. Miihlf., S. Pacific; E, Pedipes quad-

Fam. 4. Limnaeidoe.— Pul- "#2" Pit» Jamaica.

monary sac protected by an external lobe; shell variable, fragile.
Jurassic (i.) Aneylinae, shell more or less limpet-shaped.
Genera: Ancylus, Gundlachia, Latia. (i1.) Limnaeinae, shell spiral.
Genera: Limnaea, Amphipeplea, Erinna, Lantzia, Pompholyx, Choa-
nomphalus (with Carinifex). (dii.) Planorbinae, shell sinistral, spire
flattened or elevated. Genera: Planorbis, Isidora (= Bulinus).

Fam. 5. Physidae-——Mantle more or less reflected over the
shell (radula, Fig. 141, C, p. 235); shell sinis-
tral, lustrous. Jurassic Genera: Physa,
Aplecta.

Fam. 6. Chilinidae.—Lobe of pulmonary
sac large, tentacles broad; shell ventricose,
rather solid; columella plicate. Miocene
Single genus, Chilina.

Sub-order II. Stylommatophora. — Two
pairs of retractile tentacles (except in Janella), eyes at the tip of
the upper pair, male and female orifices united (except in Vaginu-
lidae and Onchidiidae), no distinct osphradium.

Fam. 1. Testacellidae—Animal carnivorous, slug-like or
spirally coiled, no jaw (whence the name Agnatha, often given
to this group), radula with usually few, large, sickle-shaped

Fic. 293.— Amphibola
avellana Chem.

440 PULMONATA—STYLOMMATOPHORA CHAP.

teeth (p. 232), shell variable, rarely absent, usually external.
Cretaceous Principal genera: Chlamydephorus (shell a
sunple plate, internal), <Apera,
Testacella (slug-lke, shell ter-
minal), Strebelia, Streptostyla,
Glandina, Salasiella, Petenia,
Pseudosubulina, Streptostele,
Tomostele, Streptaxis (Fig. 203),
Gibbus, Ennea, Daudebardia (Fig.
193), Schizoglossa, Guesteria,
Aerope, Paryphanta, Rhytida
Fic. 294.—A, Ennea (Gibbulina) palanga (subg. Diplomphatus, Hlaea and
Fér; A’, young of same; B, Gibbus Thenea.)

lyonetianus Pall. Fam. 2. Selenitidae. — Shell
internal, external, or absent; jaw present, radula Testacellidan,
central tooth present. Tertiary : Genera: Selenites,

Plutonia, Trigonochlamys, Pseudomilax (?), Rathowisia (7).

Fam. 5. Limacidae—Shell present or absent, internal or
external, spiral or not, tail often with a mucus pore, jaw (Fig.
107, A, p. 211) with projecting rostrum on cutting edge, radula
with central tooth tricuspid, laterals bi- or uni-cuspid, marginals
aculeate. Eocene Genera: Otoconcha, Urocyclus, Maria-
ella (subg. Tennentia), Parmarion, Helicarion, Cystopelta, Aspi-
delus, Estria, Vitrinopsis (subg. Vitrinoidea, Parmella), Damay-
antia, Nanina (= Ariophanta, mncluding Pachystyla, Rhysota,
Hemiplecta, Trochonanina, Euplecta, Orpiella, Xesta, Macrochlamys,
Microcystis, Sitala, Kaliella, Durgella, Austenia, Girasia, Parma-
cochlea, Africarion, Sesara, Macroceras, and others), Vitriniconus,
Parmacella, Limax (subg. Amalia, and many sections), Vitrina,
(subg. Vitrinozonites, Velifera), Zonites (subg. Stenopus, Moreletia,
Mesomphi«, Hyalinia, Gastrodonta, Pristiloma, Poecilozonites,
Thyrophorella).

Fam. 4. Philomycidae—Shell absent, jaw limacidan, radula
helicidan, shield covering all the body. Single genus, Philomycus
(= Tebennophorus), with subg. Pallifera.

Fam. 5. Helicidae—Shell present or absent, internal or ex-
ternal; jaw of various types, radula with central tooth tricuspid,
equal in size to the first laterals, laterals bi- or tri-cuspid, margi-
nals smaller, cusped. EKocene———. Principal genera: Oopelta
(no shell), Arion (shell absent or formed of calcareous granules),

XV PULMONATA—STYLOMMATOPHORA 441

Ariolimax, Geomalacus, Anadenus (subg. Prophysaon), Hemphillia,
Cryptostracon, Binneya, Helix (see below), Cochlostyla, Bulimus,
(subg. Borus, Orphnus, Dryptus, Strophochilus, Pachyotus, and pos-
sibly Caryodes, Leucotaenia, Liparus, Livinhacea, Pachnodus, Rachis,
Atopocochlis, Cerastus, Clavator belong here, or with Buliminus),
Berendtia, khodea. Pilsbry proposes! to group Helix as follows:

A. Eggs or young very large at birth:

(1) Maerodn, incl. Acavus, Pyrochilus (= Phania), Stylodonta,
Helicophanta.

B. Eggs or young smaller or minute at birth:

(2) Belogona—Female genital system with dart sac and
mucus gland. Helix [restricted] (with
sections Arionta, Campylaea, Chilotrema,
Pomatia, Macularia, Tachea, Iberus, Lep-
taxis, Hulota, Fruticicola, NXerophila ;
Dorcasia, Acusta, Plectotropis, Aegista,
Cathaica, Satsuma, Euhadra ; Lysinoe),
Gonostoma, Leucochroa, Allognathus,
Cochlostyla, Polymita, Hemitrochus (with
sections Plagioptycha, Dialeuca, Coryda,
JSeanerettia), Glyptostoma, Acanthinula,
Vallonia.

(3) Leleophalla.— Female system
without accessories, male with flagellum
and appendix on penis; no epiphallus. Sua ee eee
Sagda, Cysticopsis. Helicophanta Souverbiana

(4) Epiphallophora.mFemale system ees eee aay,

5 © 5)
without accessories, male with epiphallus — *%-
on penis; no appendix. Caracolus (with
sections Lucerna, Dentellaria, Isomeria, Labyrinthus, Eurycratera,
Parthena, Polydontes, Thelidomus, Cepolis), Camaena (ancl. Phoe-
nicobius), Obba, Chloritis (nel. Hadra), Papuina, Planispira (subg.
Cristigibba).

(5) Haplogona.—aAll accessory organs absent, jaw soldered
into one piece. Polygyra (incl. Daedalochila, Triodopsis, Mesodon,
Stenotrema), Endodonta (incl. Libera, Charopa, Gerontia, Therasia,
and others), Patula, Trochomorpha, Anoglypta. °

(6) Polyplacognatha—aAll accessory organs absent, jaw com-
posed of 16-24 separate plates. Punctum, Laoma.

1 Proc. Ac. Philad. 1892, p. 390.

442 PULMONATA—STYLOMMATOPHORA

CHAP.

Genera of doubtful position : Strobilops, Ampelita, Pedinogyra,
Polygyratia, Macrocyclis, Solaropsis.

Fam. 6. Orthalicidae.—Radula, p. 233. Shell external, large,
bulimoid. Single genus, Orthalicus; sube. Liguus, Porphyro-
baphe, Corona.

Fam. 7. Bulimulidae—Radula, p. 233; jaw, p. 211; shell
usually external. Genera: Bulimulus (incl. Plecochilus, Gonio-
stomus, Drymaeus, Liostracus, Otostomus, Navicula, Scutalus,
Peronacus, Eurytus, Hudioptus, Plectostylus, Mesem-
brinus, Mormus, ete.; Thawmastus, Nesiotis), Placo-
stylus (incl. Charis), Amphidromus, Partula, Calycia
(7), Peltella (animal lmaciform, shell internal),
Pellicula, Amphibulimus (nel. Simpulopsis).

Fam. 8. Cylindrellidae—Radula, p. 233 ; shell

many whorled, long turriculate, last whorl often
detached, apex often truncated (Fig. 169, p. 260).

Fre. 296.—Odon-
tostomus pan-

Kocene Genera: Cylindrella (with sec-

tagruelinus

Morie., S.
Brazil. x.

tions Callonia, Thaumasia), Leia, Macroceramus,
Pineria.
yo ia)

Fam. 9. Pupidae. — Radula, pp. shell
external, spire usually long, aperture often narrowed, more or
less toothed, often with internal lamellae. Carboniferous :
Genera: Anostoma (Fig. 154, p. 248), Hypselostoma (Fig. 202, A,
p. 302); Anastomopsis (Cretaceous), Lychnus (Cretaceous), Boysia,
Odontostomus (incl. Tomigerus), Buliminus (incl.
Petraeus, Napaeus, Zebrina, Mastus, Chondrula,
Ena, and perhaps Rachis, Pachnodus, Hapalus,
and others), Pupa (incl. Torquilla, Pupilla,
Sphyradium, Leucochila, ete.), Zospeum, Vertigo,
Megaspira, Strophia, Holospira, Eucalodium
(inel. Coelocentrum), Coeliaxis, Perrieria, Balea ;
Rillya (Kocene), Clausilia (with many sub-
genera) Rhodina (?).

Zod 4

.

r

Fic. 297.—A, Clausilia

Fam. 10. Stenogyridae.—Radula, p. 234; — crassicosta Ben,

shell long, spiral, shining, more or less trans- ‘Sicily; B, Claw-

3 SH : Sore silia Macaranda

lucid, apex blunt, sometimes decollated. Zieg., Dalmatia;

Eocene Genera: Stenogyra(subg.Rumina, 8B» clausilium of
e 5 same.

Obeliscus, Opeas, Melaniella, Spiraxis, Leptinaria,
Nothus, Subulina, Glessula), Ferussacia (subg. Cionella, Azeca),
Caecilianella (subg. Geostilbia), Achatina (shell large, ventricose,

XV PULMONATA—STYLOMMATOPHORA 443

columella strongly truncate), with the sub-genera Perideris,
Limicolaria, Columna, Pseudachatina, Homorus, probably belongs
to a distinct family.

Fam. 11. Achatinellidae—Radula, p. 234; shell small, buli-
moid, indifferently dextral or sinistral. Genera: Achatinella
(subg. Auriculella, Amastra, Carelia), Tornatellina.

Fam. 12. Suecineidae——Radula, p. 234; lower pair of ten-
tacles wanting or small; shell internal or external, thin, spiral
or not, last whorl large. Eocene
Genera: Succinea, Homalonyx, Hyalimax,
(2?) Lithotis, (?) Catinella.

Fam. 13. Janellidae.-—Radula, p. 234 ;
animal slug-like, no lower tentacles, shell
an internal plate. Single genus, Janella
( = Athoracophorus), with subg. Aneitea.

Fam. 14. Vaginulidae. — Radula, p.
234; animal slug-like, covered with a
coriaceous mantle, lower tentacles bifid,
genital orifices widely separated, male
behind the lower right tentacle, female
on inferior median part of right side,
anus and pulmonary orifice nearly terminal;

‘ ; Fic. 298.—Achatina zebra
shell absent. Single genus, Vaginula ee, Roe a

(= Veronicella).
Fam. 15. Onehidiidae.—Body oval, mantle thick, often warty,

ce

sometimes set with “eyes” (p. 187), two tentacles, genital orifices
widely separate, anus and pulmonary orifice as in Vaginula ; no
shell. Genera: Peronia, Onchidium, Onchidiella. The family
appears to be an instance of Pulmonata reverting to marine
habits of life.

CHAPTER XVI

CLASSES SCAPHOPODA AND PELECYPODA

CLASS SCAPHOPODA

HEAD rudimentary, mantle edges ventrally concrescent, forming
a tube opening before and behind, and
covered witha shell of the same shape; sexes
separate.

The Scaphopoda form a small but very
distinct class, whose organisation is decidedly
of a low type. The body is usually slightly
curved, the concave side being the dorsal ;
muscles near the posterior end attach the
body to the shell. The foot, which can be
protruded from the anterior or wider aper-
ture, is rather long, pointed, and has some-
times two lateral lobes (Dentaliwm), some-
times a terminal retractile disc (Siphonoden-
talium), sometimes a retractile dise with a
central tentacle (Pulsellum). The cephalic
region, as in Pelecypoda, is covered by the
mantle. The mouth is situated ona kind of

; projection of the pharynx; the buccal mass,
Fie. 299.— Anatomy of 5 ap ie

Dentalium: a, anterior Containing the radula (p. 236), is at the

aperture of mantle; 7, base of the foot, and the intestine branches

foot ; g, genital gland; ,
é Gane 7, liver, forward from the front part of the stomach.

an Lacaze -Du- The liver (Fig. 299) is paired, and consists
niers, 5 ae

of a number of symmetrical, radiating coeca.
There are no eyes, but on each side of the mouth are small

bunches of exsertile filaments (captacula), which appear to act as

CHAP. XVI | SCAPHOPODA AAG

tactile organs for the seizing of food. There is no special respir-
ing apparatus, heart or arterial system, breathing being conducted
by the walls of the mantle. The nervous system has already
been described (p. 205).

Two kidneys open on either side of the anus. The genital
gland is large, occupying nearly all the posterior part of the body,
the sexual products being emitted through the right kidney.
The veliger has already been figured (p. 131, Fig. 44). The
embryonic shell is formed of two calcareous laminae, which sub-
sequently unite to form the tube.

With regard to their general relationships, the Scaphopoda
resemble the Gasteropoda in their univalve shell, and in the
possession of a radula; while the pointed foot, the non-lobed
velum in the veliger, the generative system, the bilateral symmetry
of the organs generally, and the absence of any definite head,
eyes, or tentacles, are points which approximate them to the
Pelecypoda.

The Scaphopoda are known from Devonian strata to the
present time. They are found at a depth of a few fathoms to
very deep water. The only three genera are Dentaliwm, Siphono-
dentalium (subg. Cadulus), and Pulsellum, which differ in the
structure of the foot, as described above.

CLASS PELECYPODA

Cephalic region rudimentary, mantle consisting of two sym-
metrical right and left lobes, covering the body and secreting a
bivalve shell hinged at the dorsal margin; no radula, sexes usually
separate. Reference has already been made to the reproductive
system (p. 145), breathing organs (p. 164 f.), mantle (p. 172),
nervous system (p. 205), digestive system (p. 237 f.), and nomen-
clature of the various parts of the shell (p. 269 f.).

The shape of the shell, in many Pelecypoda, involving as it
does the position, size, and number of the adductor muscles, is
probably due to mechanical causes, depending on the habits and
manner of life of the individual genus. Thus in a typical
dimyarian or two-muscled bivalve, eg. Mya (Fig. 300, A), the
adductor muscles lie well towards each end of the long axis of the
shell, with the hinge about midway between them. In this
position they are best placed for effectually closing the valves.

446 PELECYPODA CHAP.

and since they are nearly equidistant from the axis of motion, é.e,
from the hinge, they do an equal amount of work, and are about
equal in size. But in a form like Modiola, where the growth of
the shell is irregular in relation to the hinge-line, the anterior
muscle is brought nearer and nearer to the umbones, where its
power to do work, and therefore its size, becomes less and less.
But the work to be done remains the same, and the posterior
muscle has to do it nearly all ; hence it moves farther and farther
away from the hinge-line, and at the same time gains in size.
In shells lke Ostrea, Pecten, and Vulsella, the anterior muscle,
having drawn into line with the hinge and the posterior muscle,
becomes atrophied, while the posterior muscle, having double work
to do, has doubled its size.

The development of the foot, again, largely depends upon habits

A

Fia. 300.—Tllustrating changes in the position and size of the adductor muscles accord-
ing to the shape of the shell: A, Mya; B, Modiola; C, Vulsella. The upper
dotted line shows the hinge-line, the lower connects the two muscles.

of life. It is well developed in burrowing forms, while in sessile
genera (Ostrea, Chama, Spondylus) it becomes unnecessary and
aborts. Even in Pecten, which does not become sessile, but has
ceased to use the foot as an organ of progression, a similar result
follows. Forms which burrow deeply often “ gape ” widely, some-
times at one end only, sometimes at both. Venus, Donax, Tellina,
Mactra, which are shallow burrowers, do not gape; Solen, Lutraria,
and to a less degree Mya, burrow deeply and gape widely. In
order to burrow deeply the foot must be highly developed, and
the larger it becomes, the more will it tend to keep the valves
apart at the place where it is habitually protruded. Burrowing
species always remain in communication with the surface by means
of their siphons, the constant extension of which tends to keep
the valves apart at the end opposite to the foot. Burrowing

1 Compare Jackson, Amer. Nat. xxv. p. 11 f.

XVI PELECYPODA—PROTOBRANCHIATA 447

species, again, tend to burrow in such a way as to descend most
easily, and not be impeded by their own shells; in other words,
they act as a wedge, and descend with their narrowest part fore-
most. But the burrowing organ, the foot, has to follow suit, and
gradually draws round to the narrowest part of the shell, so that
the habitual deep burrower, such as Lutraria, lies with its long
axis exactly at right angles to the surface, its siphons protruding
from, and keeping open, the uppermost or posterior margin of the
shell, and the foot producing the same effect upon the lower
or anterior margin. The deeper the burrower, the more elongated
does the shell become, until, through forms like Pholas and
Saxicava, we arrive at Solen, the most highly specialised burrower
of all, in which the breadth of the shell is equal throughout,
and no obstructive curve exists to impede its rapid ascent or
descent.

The Pelecypoda have been classified in various ways; by the
completeness or sinuation of the pallial line, depending on the
absence or presence of siphons, by the number of adductor
muscles, by the character of the hinge-teeth, and by the number of
the branchiae. For various reasons, none of these methods have
proved entirely satisfactory. That adopted here was suggested by
Pelseneer, and depends upon the character of the branchiae them-
selves, as suggesting successive stages of development (p. 166 f.).

Order I. Protobranchiata

Branchial filaments not reflected, the two rows inclined at a
right angle (more or less), ventral surface of foot more or less
flattened, byssogenous apparatus little developed, a single anterior
aorta, kidneys distinct, sexes separate, each genital gland open-
ing into the corresponding kidney.

Fam. 1. Nuculidae.—Lahbial palps very large, rows of branchial
filaments at right angles to one another, mantle edges open,
siphons contracted, foot disc-shaped, elongated; shell equivalve,
oval, or produced, interior generally nacreous, hinge with numerous
saw-like teeth. Silurian———. Principal genera : Nucula (heart
dorsal to the rectum); Palaconeilo (Devonian), (?) Sarepta, Leda,
Yoldia, Malletia; Tyndaria (Upper Tertiary), Lyrodesma (Silurian),
Actinodonta (Silurian), Babinka (Silurian).

Fam. 2. Solenomyidae.—Labial palps united, one row of

448 FILIBRANCHIATA CHAP.

branchial filaments pointing dorsally, the other ventrally; mantle
edges in great part united postero-ventrally, a single siphonal
orifice with two very long tentacles, foot probosciditorm, with a
round denticulate disc at the end; shell equivalve, resembling a
Solen, with a strong corneous periostracum ; no hinge-teeth, liga-
ment internal. | Single genus, Solenomya. (7) Cretaceous

Order II. Filibranchiata

Rows of branchial filaments parallel, pointing ventrally, re-
flected, and provided with interfilamentary ciliated junctions, foot
usually with a well-developed byssogenous apparatus.

Sub-order I. Anomiacea.— Heart dorsal to the rectum, a single
aorta, foot small, anterior adductor very small; shell ostreiform,
no hinge-teeth, fixed by a calcified byssus traversing the right
valve (Fig. 173, p. 262).

Fam. Anomiidae. Jurassic-——. Genera: Anomia, Placuna-
nomia ; Carolia (Kocene), Placuna ; Hypotrema (Jurassic), Placun-
opsis (Oolite).

Sub-order II. Arcacea.—Mantle edge open, both adductors
well developed, heart with two aortae, branchiae free, without
interlamellar junctions, no siphons; renal and generative aper-
tures distinct. :

Fam. 1. Arcadae—Mantle edge with composite eyes; shell
round or trapezoidal, solid, often with stout bushy periostracum ;
ligament often external, on a special area; hinge with numer-
ous lamelliform teeth. Ordovician :
Principal genera: Arca (incl. Barbatia,
Scaphula, and Cucullaea), heart dorsal to
rectum; Pectunculus, Glomus, Limopsis ;
Trinacria and Nuculina (Tertiary).

Fam. 2. TLrigoniidae—Foot large,
hatchet-shaped, with ventral disc; no
byssus, mantle edge with ocelli; shell
sub-trigonal, hinge-teeth few, strong; in-
Tre BO =a noMt neces terior violet -nacreous. Devonian

nata Lam. Sydney, Genera: Zrigonia ; Myophoria and Schiz-

ae odus (Trias), Cyrtonotus (Devonian).

Sub-order III. Mytilacea.— Mantle edges fused at one point,
anal orifice distinct, anterior terminal adductor small, one aorta,

XVI PSEUDOLAMELLIBRANCHIATA 449

branchiae with interfoliary junctions, genital glands penetrating
the side of the mantle and opening by the side of the kidneys.
Fam. Mytilidae—Byssus well developed, shell more or less
equivalve, oval, broad; hinge-teeth evanescent. Devonian
Principal genera: Mytilus,? Myalina, Septifer, Modiola, Lithodomus,
Crenella, Dacrydium, Myrina, Idas, Modiolaria, Modiolarea.

Order III. Pseudolamellibranchiata

Mantle edges entirely open, foot lttle developed, anterior
adductor usually aborted, branchial filaments reflected, with inter-
lamellar junctions, which are sometimes vascular; genital glands
opening into the kidneys or close to the apertures of the kidneys.

Fam. 1. Aviculidae—Foot long, tongue-shaped, byssogenous
apparatus well developed, branchiae concrescent with the mantle,
adductor muscle sub-central, at times a small anterior adductor,
siphons absent ; shell usually
inequivalve, dorsal margin
straight, often very long,
winged, lateral teeth much
prolonged ; structure of shell
cellular, inside prismatic, out-
side nacreous. Palaeozoic

Principal genera : FIG. 302.—Avicula heteroptera Lam., Australia,

. : : showing the inequivalve shell and byssal
Avicula, including JMelea- sinus (6.8).
grind, Malleus; Vulsella (no
wings or hinge-teeth); Perna, including Crenatula, Inoceramus
(ligaments in a number of fossettes); Aucella and Monotis
(Palaeozoic and Secondary); Pterinaea and Ambonychia (Palaeo-
zoic); Pinna ; Aviculopinna (Carboniferous).

Fam. 2. Prasinidae-—Shell very small, umbones anterior, in-
curved, anterior side depressed, hinge-teeth replaced by dentiform
projections of the lunule fitting into corresponding grooves.
Recent. Single genus, Prasinua.

Fam. 3. Ostreidae—Heart generally ventral to the rectum,
branchiae concrescent with the mantle, no byssus; shell inequi-
valve, fixed by the left valve, form irregular. Jurassic
Genera: Ostrea ; Heligmus (Oolite), Naiadina (Cretaceous), Pern-
ostrea (Jurassic).

Fam. 4. Pectinidae—Byssus usually absent, mantle edge open,

VOL. III 2G

450 PSEUDOLAMELLIBRANCHIATA CHAP.

duplicated, folded back, with pallial ocelli; branchiae not con-
crescent with the mantle; shell
with unequal “ears” at the umbo,
hinge-teeth lamelliform, often ob-
scure. Silurian Principal
genera: Pedum, Chlamys, Hinnites,
Hemipecten, Amussium, Pecten; Avi-
culopecten (Palaeozoic), Crenipecten.

Fam. 5. Limidae.—Mantle edge
as in fPecten, tentaculate; shell
sub-equivalve, eared, fixed by a
byssus or free. Carboniferous——.
Genera: Lima (Fig. 85, p. 179).
Limea.

Fic. 303.—Pecten pallium L., East : fs. ; :
Indies. Fam. 6. Spondylidae.—Foot with

a peduncular appendage, no
byssus, numerous pallial ocelli; shell fixed by right valve,
surface often very spinose, two cardinal teeth in each valve.
Jurassic——. Genera: Plicatula, Spondylus ; Terquemia (Lias).

Fic. 304. — Spondylus
petroselinum Sowbd.,
Mauritius ; on a coral,

Fam. 7. Dimyidae—Shell ostreiform, fixed, hinge with or
without symmetrical teeth, two muscular impressions. Single
genus, Dimya (Tertiary).

XVI EULAMELLIBRANCHIATA—SUBMYTILACEA 451

Order IV. Eulamellibranchiata

Mantle edges united at one or more points, branchiae with
interfilamentary junctions which are always vascular, genital
glands not opening into the kidneys, usually two adductor
muscles.

Sub-order I. Submytilacea.— Mantle edges more or less open,
anal orifice distinct, usually no siphons, pallial line usually simple,
eardinal and lateral teeth well marked.

Fam. 1. Carditidae.—Foot with a byssus or groove, branchiae
large, unequal; shell equivalve, solid, radiately grooved, one or
two oblique cardinal teeth, one or two laterals. Silurian———.
Principal genera: Venericardia, Cardita, Carditella, Carditopsis
Milneria ; Pleurophorus (Palaeozoic), Anodontopsis (Silurian).

Fam. 2. Astartidae—aA short anal siphon, labial palps large ;
shell triangular, thick, ligament external, hinge with two or
three cardinals in each valve, laterals obscure. ? Devonian
Principal genera: Astarte; Pachytypus (Jurassic), Plesiastarte
(Eocene), Parastarte, Woodia, Opis (Secondary strata), Prosocoelus
(Devonian).

Fam. 3. Crassatellidae—Mantle with anal orifice or open;
shell equivalve, thick, subtriangular, ligament in an internal fos-
sette, hinge with two cardinals, laterals produced. Cretaceous——.
Principal genus, Crassatella.

Fam. 4. Cardiniidae—Shell equivalve, oval or triangular,
ligament external, cardinal teeth small, laterals fairly strong.
Devonian Oolite. Principal genera: Cardinia, Anthracosia,
Carbonicola, Anoplophora.

>

Fam. 5. Cyprinidae—aAnal and branchial orifices complete,
papillose, foot thick; shell variable, equivalve,
thick, umbones often spiral, hinge teeth very
variable, lgament external. Jurassic

Principal genera: Cyprina; Pygocardia (Crag),
Veniella (Cretaceous), Venilicardia (Second-
ary strata), Anisocardia (Jurassic), Lsocardia,
Libitina, Coralliophaga ; Basterotia (Eocene).
The families Pachydomidae (Palaeozoic) and
Megalodontidae (Palaeozoic—Secondary) are
probably related to the Cyprinidae.

Fam. 6. <Aetheriidae.— Anal oritice complete, foot absent, labial

Fia. 305.—Tsocardia vul-
garis Reeve, China.

452 EULAMELLIBRANCHIATA—SUBMYTILACEA CHAP.

palps large; shell irregular, free or fixed, no hinge teeth.
Fluviatile, recent only. Genera: Aetheria, Miilleria, Bartlettia.

Fam. 7. Unionidae—Foot large and thick, no byssus, anal
siphon short, branchial orifice complete or not, siphon present or
absent, embryo of certain groups passing through a glochidium
stage (p. 146); shell equivalve, sometimes very thick, nacreous
within, hinge variable. Fluviatile. Jurassic Principal
genera: Unio (subg. Arconaia), Monocondylaea, Pseudodon, Ano-
donta, Solenaia, Mycetopus, Mutela, Spatha, Hyria, Castalia, Leila.

Fam. 8. Dreissensiidae—Both siphons prominent, foot tongue-
shaped, byssiferous ; shell mytiliform, with small internal septum.
Genera: Dreissensia ; Dreissensiomya (Tertiary). The common
Dreissensia polymorpha Pall. was distributed over large parts of
Europe in later Tertiary times. From unknown causes it died
out, and has during the past two hundred years been regaining its
position, migrating N. and W. trom its original habitat, the
Caspian, by the Volga and its Oka confluent.

Fam. 9. Modiolopsidae.—Shell mytiliform, ligament exterior,
hinge teeth small, rather numerous. Palaeozoic Principal
genera: Modiolopsis, Cyrtodonta, Mytilops, Ptychodesma.

Fam. 10. Lucinidae.—Anal orifice sometimes with a siphon,
branchial orifice complete or not, sometimes a single branchia ;
foot very long, vermiform, no byssus, anterior adductor long;
shell rounded, equivalve, blanched, hinge with two cardinals and
two laterals in each valve, sometimes toothless, hgament more or
less internal. Silurian Principal genera: Lucina, Corbis,
Axinus, Diplodonta, Montacuta.

Fam. 11. Ungulinidae.—Anal orifice complete, foot vermiform,
no byssus, two branchiae; shell equivalve, subcircular, hinge
teeth variable, no laterals, adductor impressions long, continuing
the pallial line. Tertiary Single genus, Ungulina.

Fam. 12. Unicardiidae—Shell equivalve, round or oval,
cardinal shelf large, a single cardinal in each valve, ligament
external. Carboniferous — Cretaceous. Genera: Unicardium,
Scaldia, Pseudedmondia.

Fam. 13. Kellyellidae——Anal siphon prolonged, no marked
branchial orifice ; shell very small, oval or round, anterior lateral
very strong, under the cardinal. E@cene Genera: Kelly-
ella ; Allopagus and Lutetia (Tertiary), Zurtonia.

Fam. 14. Hrycinidae—Mantle edges with three apertures,

XVI EULAMELLIBRANCHIATA—TELLINACEA 453

branchial orifice on the buccal margin, foot long, broadened, with
a byssus, animal usually viviparous. Tertiary———. Genera:
Erycina, Kellia, Pythina, Lasaea, Lepton.

Fam. 15. Galeommidae.—Mantle edges more or less reflected
over the shell, apertures and foot as in Erycinidae; shell thin,
equilateral, hinge with few teeth or none. Tertiary
Genera: Galeomma, Scintilla, Sportella, Chlamydoconcha, Hinds-
iella, Ephippodonta (Fig. 32, p. 81).

Fam. 16. Cyrenidae—Siphons short, foot large, no byssus ;
shell equivalve, subtriangular, with periostracum, hinge with two
or three cardinals, laterals present; animal hermaphrodite,
viviparous. Fresh or brackish water. Jurassic-——. Genera:
Cyrena, Corbicula (subg. Batissa, Velorita), Sphaerium ( = Cyelas),
Pisidium, Galatea, Fischeria.

The families Cyrenellidae (single genus Cyrenella) and
Rangiidae (single genus Rangia) are probably to be placed here.

Sub-order II. Tellinacea.—Siphons long, separate, foot and
labial palps very large, pallial sinus deep, two adductor muscles.

Fam. 1. Vellinidae—KExternal branchial fold directed dorsally,
foot with byssogenous sht, but no byssus, branchiae small; shell
compressed, equivalve, ligament external, at least two cardinals
in each valve, laterals variable. Cretaceous———. Principal
genera: Tellina (with many sections), Gastrana.

Fam. 2. Scrobiculariidae—Animal as in Tellina ; shell orbicu-
late or long oval,equivalve,
hinge teeth weak, liga-
, ment in an internal cavity.
Tertiary Prin-
cipal genera: Serobicu-
laria, Syndosmya, Theora,
Cumingia, Semele.

Fam. 3. Donacidae.—
External branchial fold
directed ventrally; shell
equivalve, subtriangular, solid, smooth, two or three cardinals in
each valve, laterals variable, ligament external. Jurassic
Genera; Donax, Iphigenia, [sodonta.

Fam. 4. Tanerediidae—Shell donaciform, ligament external,
cardinals usually two in each valve, posterior laterals strong.
Trias——. Genera: Zancredia (Secondary strata), Hemidonax.

Fia. 306.—Tellina rastellum Hanl., East Indies.

454 EULAMELLIBRANCHIATA—VENERACEA CHAP.

Fam. 5. Cardiliidae.—Shell heart-shaped, hinge as in Mactridae,
posterior adductor resting on a myophore or shelf. Single genus
Cardilia. Tertiary

Fam. 6. Mesodesmatidae—Mantle edges largely united, with
three orifices, foot byssiferous or not; shell regular or irregular,
usually one cardinal and strong lateral teeth. Tertiary
Genera: Mesodesma, Ervilia.

Fam. 7. Mactridwe—External branchial fold directed ven-
trally, siphons fused, foot tongue-shaped; shell equivalve,
triangular-oval, hinge with lgament in an internal fossette,
another portion external, a bifurcated cardinal tooth in the left
valve, fitting into a branching tooth in the right valve, laterals
present. Jurassic Genera: JJactra, Harvella, Raéta,
Eustonia, Heterocardia, Vanganella.

Sub-order III. Veneracea.—Branchiae slightly folded, foot
compressed, siphons generally short, pallial line variable, two

adductor muscles.

Fam. 1. Veneridae—Siphons free or partly united, foot
seldom byssiferous ; shell solid, equivalve, hinge usually with three
cardinal teeth, laterals variable.
Jurassic Principal genera:
Cytherea, Circe ; Grateloupia (Ter-
tiary), Meroe, Dosinia ( = Artemis),
Cyprimeria, Cyclina, Venus, Clem-
entia, Lucinopsis ; Thetis (Creta-
ceous), Zapes, Venerupis.

Fam. 2. Petricolidae.— Animal
perforating rocks; shell oval,
slightly gaping behind, two or three cardinals, no laterals,
pallial sinus well marked. Recent Genera: Petricola,
Naranio.

Fie. 807.—Cytherea one Lam., Peru.

Fam. 3. Glaucomyidae—Siphons long, united, foot small;
shell produced, thin, hinge with three cardinals, no laterals,
palhal sinus well marked. Recent. Genus, Glaucomya (incl.
Tanysiphon).

Sub-order IV. Cardiacea.—Branchiae much folded back,
mantle edges with three apertures, foot cylindroidal, more or less
produced, siphons present or absent, one or two adductor muscles,
pallial line variable.

Fam. 1. Cardiidae—Siphons rather long, foot long, no

XVI EULAMELLIBRANCHIATA—CARDIACEA 455

byssus ; shell equivalve, more or less radiately ribbed, hinge with
one or two cardinals in each valve, laterals variable, hgament ex-
ternal, two adductors. Brackish water or marine. Devonian
Genera: Dyssocardium and Lithocardium (Tertiary), Cono-
cardium (Palaeozoic), Cardiuwm (with
many sections, including Hemicar-
dium), Limnocardium (subg. Didaena,
Monodacna, Adacna).

Fam. 2. Lunulicardiidae. — Shell
equivalve, very inequilateral subtri-
angular, anterior margin short or trun-
cated, with a deep lunule. Single genus,
Lunulicardium (Palaeozoic).

Fam. 3. Tridacnidae—Mantle ori-
fices widely separated, footy "short, bys. sos. cardiun (emaee
siferous, no anterior adductor; shell diwm) cardissa L., East Indies.
equivalve, large, thick, usually gaping
in front, one cardinal tooth and one or two posterior laterals in
each valve, no pallial sinus. | Miocene——. Genera: T'ridacna,
Hippopus. The muscular power of the great 7ridacna is immense.
Once caught between their gaping valves, a man’s hand or foot
can scarcely be withdrawn. Two valves of 7. gigas in the British
Museum weigh respectively 154 and 156 Ibs.

Fam. 4. Chamidae——Mantle orifices widely separated, foot
short, no byssus, both adductors present, ovary invading the
mantle lobes; shell fixed, irregu-
larly inequivalve, umbones spiral,
ligament external, cardinal teeth
often a mere ridge, anterior lateral
strong, nearly central, no palhal
sinus. Jurassic Genera :
Chama; Diceras (Jurassic), attached
by one umbo, umbones very promi-
nent, teeth strong; Heterodiceras
(Jurassic), Requienia (Cretaceous),

Fic. 309.—A, Requienia ammoneaGoldft., f
Neocomian, x 4; B, Hippurites left valve widely spiral, attached

cornu-vaccinum Goldf., Cretaceous. at Rt eer, ee.
oh rent valve]; pomporixe. >y eaen wmbo, rights valve small,

ture. (From Zittel.) fitting on the other as an oper-
culum, teeth obsolete; Zoucasia, Apricardia, Matheronia (all
Secondary strata).

456 EULAMELLIBRANCHIATA—MYACEA CHAP.

The four succeeding families require special study in a work
on Palaeontology.

Fam. 5. Monopleuridae—Shell very inequivalve, left valve
operculiform, right conical or spiral, fixed at the apex, hgament
prolonged in external grooves. Cretaceous Genera :
Monopleura, Valletia.

Fam. 6. Caprinidae.—Shell very inequivalve, thick, free or
fixed by apex of right valve, which is spiral or conical, left valve
spiral or not, often perforated by radial canals from the umbo to
the free margin. Neocomian and Cretaceous Principal
genera: Plagioptychus, Caprina, Ichthyosarcolites, Caprotina,
Polyconites.

Fam. 7. Hippuritidae ( = Rudistae)—Shell very inequivalve,
externally as in Caprinidae, umbo central in left valve, no lga-
ment proper, left valve with strong hinge teeth and grooves, two
adductor impressions on prominent myophores, shell structure
of the two valves differing. Cretaceous only. Single genus,
Hippurites (Fig. 309, B).

Fam. 8. Radiolitidae—Shell inversely conical, biconical, or
cylindrical, general aspect of Hippurites, umbo of left valve
central or lateral, right valve with a thick outer layer, often
foliaceous, umbonal cavity partitioned off by laminae. Cretaceous
only. Genera: Radiolites, Biradiolites.

Sub-order V. Myacea.—Branchiae much folded back, mantle
edges usually with three openings, foot compressed, siphons large,
united or not, two adductor muscles, pallial line variable.

Fam. 1. Psammobiidae—sSiphons long, not united, foot large,
not byssiferous; shell equivalve, long, oval, slightly gaping at
the ends, hgament external, prominent, two cardinal teeth in
each valve, no laterals, a deep pallal sinus. Jurassic
Genera: Psammobia, Solenotellina, Sanguinolaria, Asaphis, Eliza,
Quenstedtia (Jurassic).

Fam. 2. Myidae.—Pedal orifice small, siphons long, united in
great part; shell inequivalve, gaping at one or both ends, perio-
stracum more or less extensive, ligament internal, resting on
a prominent shelf; hinge teeth variable. Cretaceous
Genera: Mya, Tugonia, Sphenia, Corbula, Lutraria (for which
latter some propose a separate family).

Fam. 3. Solenidae.—Foot long, powerful, more or less cylindri-
cal, no byssus, siphons usually short, united or not, branchiae

XVI EULAMELLIBRANCHIATA—-PHOLADACEA AW.

narrow ; shell equivalve, long and narrow, gaping at both ends,
with periostracum, umbones flattened, hgament external, hinge
teeth variable. 7 Devonian Genera: Solecurtus, Pharella,
Pharus, Cultellus, Siliqua, Ensis, Solen,
Orthonota (?), Palaeosolen (7).

Fam. 4. Glycimeridae.— Pedal orifice
very narrow, siphons long, united in great

part, often covered with periostracum ;

shell more or less equivalve, gaping at
© co}
both ends, hinge toothless or with two
weak cardinals, hgament external ; animal
free or perforating. Cretaceous
Genera: Glycimeris, Saxicava, Cyrtodaria.

Fam. 5. Gastrochaenidae.—Foot small,
cylindrical, no byssus, branchiae narrow,
siphons long; shell perforating or
cemented to a shelly tube, gaping widely
on the anterior and ventral sides, no
hinge teeth, a deep pallial sinus. Cre-
taceous General: Gastrochaena,
Fistulana (tube with a median diaphragm,
perforated by the siphons).

Sub-order VI. Pholadacea.— Mantle
edges largely closed, siphons long, united,
foot short, truncated, disc-shaped, lhga-
ment absent, two adductor muscles;
animal perforating.

Fam. 1. Pholadidae. — Organs con-
tained within the valves, ctenidia
prolonged into the branchial siphon,
shell more or less gaping, thin, dorsal
margin in part reflected over the um-
bones, one or more dorsal accessory pleces, Pre, 310.—Teredo navalis L.:
no hinge teeth, an interior apophysis _ V, valves of shell; T, tube;

ba : P, pallets; SS, siphons.
proceeding from the umbonal cavity. (After Mobius.)
Jurassic——. Genera: Pholas, Talona,
Pholadidea (posterior extremity of the valves prolonged by a

corneous appendage, a passage to the long tube of Teredo),
Jouannetia, Xylophaga, Martesia ; Teredina (Kocene).
Fam. 2. Yeredinidae — Animal vermiform, ctenidia mainly

458 EULAMELLIBRANCHIATA——-ANATINACEA CHAP.

within the branchial siphon, siphons very long, with two cal-
careous appendages (“pallets”) near the anterior end, shell very
small, continued into a long calcareous tube, valves deeply notched,
internal apophysis as in Pholadidae. — Lias Single
genus, Teredo (Fig. 310).

Sub-order VII. Anatinacea.— External branchial fold directed
dorsally, not reflected, sexes united, ovaries and testes with sepa-
rate orifices, mantle edges largely united, byssus usually absent,
two adductor muscles, pallial line variable, shell usually nacreous
within.

Fam. 1. Pandoridae—sSiphons short, largely united, foot
tongue-shaped; shell free or fixed, imequivalve, semilunar, or
subtriangular, hgament often with calcareous ossicle, pallial line
complete or with slight sinus.
Cretaceous . Genera: Pan-
dora, Myodora, Myochama.

Fam. 2. Chamostreidae——Shell
fixed, Chama-like, thick, umbones
spiral, ligament with ossicle.
Single genus, Chamostrea.

Fam. 3. Verticordiidae. —
Siphons not prolonged; shell
heart-shaped, umbones prominent,
spiral, ligament with an ossicle,
Fic. 311.—Myochama Stutchburyi A, pallial line complete. Miocene

Ad., attached to Circe undatina : Genera: Verticordia

Lam., Moreton Bay. ;

Mytilimeria, Lyonsiella.

Fam. 4. Lyonsiidae.—Foot short, byssiferous, siphons short,
separate, shell inequivalve, hinge teeth usually absent, ligament
and ossicle in an internal groove. Eocene Single genus,
Lyonsia.

Fam. 5. Ceromyidae—Shell inequivalve, large, heart or wedge-
shaped, hinge toothless, hgament internal in one valve, external
in the other. Secondary strata Genera : Ceromya, Gresslya.

Fam. 6. Arcomyidae.—Shell equivalve, thin, surface finely
granulated, hinge toothless, cardinal edge dentiform, ligament
external. Secondary and Tertiary strata Genera: Arcomya,
Goniomya, Pleuromya, Machomya.

Fam. 7. Anatinidae.—A fourth (? byssal) pallial orifice, siphons
long, separate or fused; shell thin, sometimes inequivalve, exterior

XVI SEPTIBRANCHIATA 459

often granulose, ligament often with ossicle, hinge toothless or
with lamellae. Jurassic Genera: <Anatina, Plectomya
(Secondary), Periploma, Cochlodesma, Thracia, Tyleria, Alicia,
Asthenothaerus.

Fam. 8. Grammysiidae—Shell equivalve, oval, ligament
external, cardinal margin straight, toothless, pallial line complete.
Palaeozoic Principal genus, Grammysia, with many other
genera of toothless hinge, but whose exact affinities are uncertain.

Fam. 9. Praecardiidae—Shell thin, equivalve or not, radiately
ribbed, margins dentated, subumbonal area as in Arca, hinge
toothless. Palaeozoic Principal genus, Praecardium.

Fam. 10. Pholadomyidae—A fourth pallial orifice, siphons
very long, united, foot small; shell thin, equivalve, with radiating
ribs, ligament external, hinge toothless, pallial line sinuate.
Jurassic Single genus, Pholadomya.

Fam. 11. Clavagellidae—Foot rudimentary, siphons long,
united, contained in a long calcareous tube; shell small, one or
both valves soldered in the tube, tube with a centrally fissured
disc at the anterior end, more or less frilled at the posterior
end. Cretaceous Genera: Clavagella, Brechites (= Asper-
gillum).

Order V. Septibranchiata

Mantle edges united at three points, branchiae replaced by a
muscular septum extending from the anterior adductor to the
point of separation of the siphons, septum with symmetrical
orifices.

Fam. 1. Poromyidae.—Branchial septum with groups of
lamellae between the orifices, labial palps large, foot long and
narrow, siphons short, papillose, separated, animal hermaphrodite ;
shell small, slightly inequivalve, rounded or oblong, nacreous
within. Eocene Genera: Poromya, Silenia.

Fam. 2. Cuspidariidae.—Siphons long, united in part, foot short,
animal dioecious; shell small, slightly inequivalve, rostrate, not
nacreous, each valve with hgamentary cartilage spoon-shaped, with
a calcareous ossicle, cardinal and lateral teeth present or absent.
Jurassic Single genus, Cuspidaria, with many sections.

BRACHIOPODA

ever or
RECENT BRACHIOPODA

BY

ARTHUR E. SHIPLEY, M.A.

Fellow and Tutor of Christ’s College, Cambridge

CHAPTIR. XV I
RECENT BRACHIOPODA

INTRODUCTION—-SHELL——-BODY——DIGESTIVE SYSTEM——BODY CAVITY
— CIRCULATORY SYSTEM——EXCRETORY ORGANS——MUSCLES—
NERVOUS SYSTEM——REPRODUCTIVE SYSTEM——EMBRYOLOGY—
HABITS—DISTRIBUTION——_CLASSIFICATION.

Introduction

THE group Brachiopoda owes its chief interest to the immense
variety and great antiquity of its fossil forms. Whereas at the
present time the number of extant species amounts to but about
120, Davidson in his admirable monograph! on the British
Fossil Brachiopoda has enumerated close upon 1000 fossil species,
found within the hmits of the United Kingdom alone.

The amount of interest that the group in question has
excited amongst naturalists is evinced by the invaluable Biblio-
eraphy of Brachiopoda, prepared by the same author and his
friend W.-H. Dalton.2 This monument of patient research con-
tains over 160 quarto pages, each with the titles of from
eighteen to twenty separate papers dealing with Brachiopods,
published between the years 1606 and 1885.

Probably the first reference to Brachiopods in zoological
literature is to be found in a work entitled <Aquatilium et
Terrestrium aliquot Animalium, published in the year 1606 by
Prince Fabio Colonna at Rome. This work contains the first
description of a Brachiopod under the name of Concha diphya.
In a second edition, which is not so rare in our libraries as the

1“ A Monograph of the British Fossil Brachiopoda,” Palaeontographical Socicty,
London, vols. i.-v. 1851-84.
2 Tbid. vol. vi. 1886.

464 RECENT BRACHIOPODA CHAP.

first, the author mentions three more species of Brachiopods.
Towards the end of the same century, Martin Lister of Oxford,
in his Historia sive Synopsis methodica Conchyliorum, which
appeared in parts, described and figured a considerable number
of Brachiopods, which, under the name of Anomia, were until
the present century regarded as Molluscs, and placed in the sub-
division Pelecypoda (Lamelhbranchiata).

The first satisfactory figure and description of a Terebratula -
were published in the year 1766, in Pallas’ Miscellanea Zoologica,
still under the name Anomia. In 1781 O. F. Miller figured a
Crania under the name Patella anomala, the generic name being
subsequently altered by Cuvier into Orbicula.

Bruguiére in the year 1789 was the first to recognise the
relationship between Lingula and the other Brachiopods. He
for the first time saw the stalk of this genus, and compared it
with that of the stalked Barnacles, a class of animals which has
been more than once associated with our group.

Cuvier, in his Mémoire sur 1 Anatomie de la Lingule, 1797,
gave the first account of the internal anatomy of a Brachiopod.
The same naturalist first described the nephridia, although his
mistake in considering them lateral hearts was not rectified until
the middle of the present century, when Huxley pointed out that
these structures serve as excretory ducts for the genital products.

Duméril in 1807 proposed the somewhat unfortunate name
of Brachiopoda; and although efforts have been made by
de Blainville, who suggested Palliobranchiata, and more recently
by Haeckel, who proposed Spirobranchiata, to arrive at a name
which would be both grammatically and physiologically more
correct, the older name has maintained its position, and is now
universally in use.

In 1834 and 1835 Professor Owen published the results of
his researches into the anatomy of the Brachiopoda. He investi-
gated in these years the structure of Waldheimia flavescens, of a
species of Lingula and of a Discina, called by him Orbicula. He
regarded the group as midway between the Pelecypoda and the
Ascidians. The structure of Zingula was further investigated
by Carl Vogt, who in 1851 also supported the view that the
Brachiopoda were related to the Mollusca. But already in 1847
and 1848 Steenstrup had thrown doubts upon this relationship,
and had maintained that the Order was more closely related

XVII THE SHELL 465

to certain members of the Chaetopoda, a view which afterwards
found its ablest supporter in the American naturalist Morse.

D’Orbigny seems to have been the first observer who drew
attention to the resemblances alleged to exist between the
Brachiopoda and the Polyzoa, and Hancock, in his masterly
works On the Anatomy of the Fresh-water Bryozoa (Polyzoa) and
in his Organisation of the Brachiopoda, dwelt on these resem-
blances, and placed the Brachiopoda between the Polyzoa on the
one hand and the Ascidians on the other; a collocation which
subsequently resulted in their inclusion in the now discarded
group of Molluscoidea.

In 1854 Huxley! published what is, with the possible
exception of Hancock’s monograph, mentioned above, the most
important work upon the anatomy of the Brachiopoda with
which we are acquainted. He corrected numerous errors of his
predecessors and added many new facts to our knowledge of
the group. He was the first to describe the true nature of the
lateral hearts of Cuvier, and to describe the true heart, afterwards
so carefully figured by Hancock.

A further step was made in 1860 and 1861 by the discovery
and description of the larvae of Brachiopoda, by F. Miiller and
Lacaze-Duthiers. Since that time we owe what little advance
has been made in the embryology of the group to the researches
of Morse and of Kowalevsky.

Modern methods of research—section cutting, etc.—were
first appled to the group by the Dutch naturalist, van
Bemmelen,? from whose admirable historical account of our know-
ledge of the group many of the above facts have been gathered.
These methods have thrown considerable hght upon the histology
of the group, but have not added very much to our knowledge of
the structure or the affinities of the Brachiopoda. The modern
views as to the latter point may be best discussed after some
account of the anatomy of the various genera has been given.

The Shell

The body of a Brachiopod is enclosed within a bivalve shell,
but the two halves are not, as they are in the Pelecypoda,

1 “ Contributions to the Anatomy of the Brachiopoda,” Proc. Roy. Soc.,vol. vii.
* “Untersuchungen iiber den anatomischen u. histologischen Bau der Brachio-
poda Testicardinia,” Jenaische Zeitschrift, vol. xvi., 1883.

VOL. III PA

466 RECENT BRACHIOPODA CHAP.

one on each side of the body, but occupy a different position
with regard to the main axes of the body. What this position
is, has formed the subject of a good deal of discussion. For our
purpose, however, it will suffice to distinguish the two valves by
the most commonly accepted terms of dorsal and ventral. The
former is, as a rule, the smaller of the two, and usually hes
on the lower surface of the animal in hfe. Adopting the orienta-
tion indicated above, the stalk by means of which the Brachio-
poda are attached to the rocks and stones, ete., upon which
they live, becomes posterior, and the broader edge of the two
shells, which are capable of being opened to some extent, is
anterior,

The posterior end of the shell usually narrows, and the
ventral valve projects behind the dorsal, and may be produced
into a sort of beak or funnel, through the aperture of which the

Fic. 312. — Four specimens of
Terebratulina caput serpen-
tis, attached to a water-
logged piece of wood, from
the Clyde area.

stalk protrudes. This aperture may be completed by the ventral
shell, or the latter may only be notched, in which case the hole
is completed by the posterior edge of the dorsal shell.

The nature of the shell has been used in classifying the

group into two orders :—

I. The Ecardines, whose shell is chitinous but slightly
strengthened by a deposit of calcareous salts. There
is no hinge and no internal supports for the arms.
The alimentary canal terminates in an anus.

II. The Testicardines, whose shells are composed of calcareous
spicules. The valves are hinged together, and there
is usually an internal skeleton supporting the arms.
There 1s no anus.

The outside of the shell of recent Brachiopods is often smooth,

but many are ridged. In a recent species, Rhynchonella Déder-
leint from Japan, Davidson! has described a number of spines

1 “On a living Spinose Rhynchonella from Japan,” Ann. Mag. Nat. Hist., 5th
ser. vol. xvii. 1886.

XVII COLOUR 467

arranged in concentric circles on the ribbed shell. They are not
so long as the spines irregularly scattered on the shell of 7h.
spinosa from the Jurassic formations. Some shells are brightly
coloured, as, for instance, the various species of Cistella which
live on the coralline rock in the Mediterranean ; these exhibit
bands or rays of alternate orange and bright pink. On the
other hand, the shells of Zerebratula vitrea are of a slightly trans-
lucent white, and of the utmost delicacy. They are very large,
so that the cavity within the valves is of much greater size than
the body of the animal, but in other genera the soft parts are
packed very closely, and there is but a very small mantle-cavity
or space within the shell unoccupied by the body of the animal.
It is, however, more common for the shells of Brachiopods to be
of a dull yellowish colour, and to be somewhat massive. Most
species are attached by a pedicle or
stalk to some rock or stone at the
bottom of the sea, but in some, as in
Crania, the ventral valve becomes
closely adherent to its support, so
much so that it is difficult, or impos-
sible, to remove the animal without
leaving the ventral valve behind.
Lingula, like Crania, one of the
Beardimes, inves: im sand (Bie, 32), 21: 28. — Tiree specimens of Cra
= nia anomala on a stone dredged
p- 483), and does not use its long in Loch Fyne. The topmost
pedicle to adhere to any fixed object. spegiuien is seen tnyprp ale,

The outline of the shell varies extremely. It may be almost

round or prolonged along either axis; the edges of the valves
may be smooth or fluted in correspondence with the ridges and
erooves of the outside of the shell.

On the inner surface of the shell of the Testicardinate Brachio-
poda, at the hinder end of the ventral valve, are two lateral
teeth, which fit into corresponding sockets in the dorsal valve.
These form a hinge, which im many cases is so arranged as to
pernut the shell to be opened to only a very limited extent.
There are also certain plate-like processes which project into the
lumen of the shell, and help to support various portions of
the body; and in TZerebratula, Waldheimia, etc., these form a
complicated band-like loop, which increases in complexity with
advancing age, and serves to support the arms. In the extinct

468 RECENT BRACHIOPODA CHAP.

Spirifera the internal skeleton takes the form of two spirally
coiled lamellae, which almost entirely fill the cavity of the shell ;
the apices of the spirals point outwards (Fig. 330). The inner
surface of the shell also bears the marks of the insertion of the
numerous muscles which govern its movements.

Microscopie examination of thin sections of the shell shows
that it consists of small prisms or spicules of calcareous sub-
stance, whose long axis lies, roughly speaking, at right angles to
the surface of the shell. These spicules are held together by
an organic matrix, in which, however, no cellular elements can
be detected. In sections made through a decalcified shell the
position of the spicules which have been dissolved by the acid is
indicated by spaces, and the matrix remains as a network of fibrils,
which end on the outside in a thin cuticular layer of organic
matter. In Lingula and Discina the organic matter takes a
much larger share in the formation of the shell, which in these
genera consists of a number of alternating layers of horny and
calcareous matter. The former is described by Gratiolet as
fibrillated, the fibrils being obliquely placed, whilst the latter
consists of a number of small prisms set at right angles to the
surface of the shell.

In many genera, as in TZerebratula, Terebratella, Cistella,
Waldheimia, Crania, etc., the shell is pierced by a number of
small canals (Fig. 314), which in the dried specimens form so
many open pores, but in the living animal contain prolongations
of the mantle or body wall which secretes the shell. They con-
tain extensions of the layer of epithelial cells which lines and
secretes the shell. The canals come to the surface and at
their outer end are often slightly swollen. They are closed by
the cuticular layer which is mentioned above as covering the shell
externally. They are not found in the loops or other internal
processes of the shell. In Crania the canals depart to some
extent from the usual type; instead of running a straight course
to a somewhat swollen outer end, they break up into a number
of very fine branching tubules, which form a very minute mesh-
work near the surface of the shell. These fine branches con-
tain protoplasmic fibrils, which have their origin in the epithelial
cells which le in the tubules.

By carefully counting the number of tubules in a given area
of young and old specimens of Waldheimia cranium, van Bem-

XVII DHE SOR LR PARTS 469

melen! was able to show that the spaces between the tubules
did not increase with age. He therefore reasoned that the shells
of Brachiopoda do not increase by intussusception, and that their
increase in size must be entirely due to additions made round
their free edge.

The function of the tubules has been a matter of some dis-
cussion. They have been regarded as respiratory organs, but it
would seem more reasonable to suppose that they serve as organs
to supply nourishment, etc., to the organic matrix of the shell.”

With the exception of the genus Crania, it 1s usual for
Brachiopods to bear round the edge of their mantle rows or bundles
of chitinous setae or bristles (Figs. 315 and 319). The length and
arrangement of these structures vary in the different species ; they
are secreted from little pits in the edge of the mantle. It seems
probable that they serve to some extent as organs of defence,
especially in the larva, where they make their appearance at an
early stage; possibly they also serve as a filter, and prevent the
entrance of foreign bodies into the shell. Their presence has
been taken to indicate a certain degree of affinity between Brachio-
pods and Chaetopods, since setae are very characteristic of the
last-named group.

The Body

The shell of a Brachiopod is secreted partly by the general
surface of the body which is situated at the hinder end of the
shell, and partly by the two leaf-like extensions of the body,
which are termed the dorsal and ventral mantles. These are, in
fact, folds of the body wall, and into them the body cavity and
certain of its contents, such as the liver and generative glands,
ete., extend. The space between the two folds of the mantle,
which is limited behind by the anterior wall of the body, is
termed the pallial or mantle cavity. On each side of the middle
line the anterior wall of the body is produced into two “arms,”
which occupy as a rule a considerable part of the mantle cavity.
These arms may be but flattened portions of the general body
wall, which occupies a large part of what in other genera is the

1 Loe. cit. p. 465.

2 Shipley, ‘‘On the Structure and Development of Argiope,” Mitt. aus d. Zool.
Stat. zw Neap. Bd. iv. 1883.

470 RECENT BRACHIOPODA CHAP.

mantle of the dorsal valve, as in Cistella and Argiope ;* or they
may be outgrowths of the body wall in the form of long processes,
which are coiled and twisted in a very characteristic manner in
the various genera. In any case the cross section of the arm
shows a groove, one side of which forms a continuous lp, and
the other takes the form of a single row of tentacles, which are

| im

Fic. 314. — View of the left half of Cistella
\ go ty (Argiope) neapolitana, which has been cut
\ C.\ in two by a median longitudinal incision, to
Pelee \ Wis aa show the disposition of the organs. Partly
diagrammatic. The inorganic part of the
shell only is shown. The tubular exten-
sions of the mantle and the organic outer
layer are not indicated, and hence the pores
appear open.

1. The ventral valve.
2. The dorsal valve.
3. The stalk.
4, The mouth.
‘uli yuu Mes AL cell. 4. 5. Lip which overhangs the mouth and

‘ runs all round the tentacular arms.

6. Tentacles.

7. Ovary in dorsal valve.

8. Liver diverticula.
42 9. Occlusor muscle; its double origin is
shown.

10. Internal opening of left nephridium.

11. External opening of left nephridium.

12. Ventral adjustor. The line from 10
crosses the dorsal adjustor.

13. Divaricator muscle.

richly ciliated and capable of considerable movement. The whole
arm in Lhynchonella can be protruded from the shell, as was
noted years ago by O. F. Miiller, and although his statement to
this effect has often been doubted, its truth was confirmed by
Professor Morse,” who writes: “In the year 1872, while studying
living Rhynchonella in the St. Lawrence, I observed a specimen

1 Schulgin, ‘‘ Argiope Kowaleyskii,” Zeit. f. wiss. Zool. Bd. 41, 1885.
2 American Jour. of Sci. and Arts, 3rd series, vol. xvii. 1879.

XVII THE ALIMENTARY CANAL 471

protrude its arms to a distance of 4 cm. beyond the anterior
borders of the shell, a distance nearly equalling twice the length
of the shell.” The same observer also mentions that Lingula
has the power of partially protruding its arms. In most genera
the cirrhi or tentacles can alone be protruded.

The cilia which clothe the tentacles keep up a constant flow
of water into the mantle cavity. This stream not only serves
to aerate the blood of the animals—a process which probably
takes place through the thin inner lining of the mantle—but it
also brings with it a number of diatoms and other minute
organisms which serve as food. These particles become entangled
in the tentacles, and are ultimately lodged in the groove at their
base, and passing along this by the action of the cilia they find
their way into the wide mouth, into which the groove deepens in
the posterior median line.

The Digestive System

The mouth leads into an oesophagus; this widens into a
chamber which may be termed the stomach (Fig. 314), and which
receives the openings of two large branching glands usually
known as the liver. The stomach passes into a short intestine
which is usually bent at about a right angle with the oesophagus.
In the Testicardines the intestine ends blindly, but in the
Ecardines it is of much greater length, and terminates in an
anus, situated posteriorly in the median line in Crania, but
asymmetrical and to the right of the body in Lingula (Fig. 315)
and Discina; in both cases, however, the opening is into a
portion of the mantle cavity. The alimentary canal is supported
by a median dorsal and ventral mesentery, and by two pairs of
lateral mesenteries which pass to the body wall. The lateral
mesenteries are not always quite distinct. When they are, the
anterior pair are known as the gastro-parietal bands, and the
posterior as the ileo-parietal. In Rhynchonella there are two
pairs of renal organs, and each of these mesenteries bears the
internal openings of one pair. In all other Brachiopods there is
only one pair, and they are supported by the ileo-parietal bands.

The alimentary canal is ciliated throughout, and some inter-
esting observations have been made by Schulgin ' on the shorten-

1 Loc. cit. p. 470.

472 RECENT BRACHIOPODA CHAP.

ing of these cilia in Argiope (Cistella) when the animal is well
fed, and their elongation when the animal is hungry. Amongst
the ciliated cells certain glandular cells have been described. The
so-called liver consists of two more or less branching glands,
which open by wide apertures, one on each side of the stomach.
It seems probable that a good deal of digestion is carried on in
these glands, since the diatoms and other minute organisms
upon which the Brachiopoda lve are usually found in the
branches of these glands, and the glandular cells lining the
tubules vary much in appearance according to the animal’s state
of nutrition.

The Body Cavity

The alimentary canal and liver occupy a considerable portion
of the body cavity or general space of
the body; this space is to some extent
cut up by the various mesenteries
above mentioned. It also lodges the

sul Gy =
. \\\ f

/
Ah

reproductive organs and the excretory
ducts. Its walls are ciliated, and the
action of the cilia keeps in motion

s

=A

Z the corpusculated fluid that bathes the

)

various organs in the body cavity. The
mantles, which are nothing but flat-
tened leaf-like extensions of the body
wall lining the shell, also contain
diverticula of the body cavity, which
may be simple flattened spaces or may
be broken up into definite channels, as
in Lingula (Fig. 315). It seems not
improbable that the body cavity fluid
is aerated through the thin inner layer

vi of the mantle.
Fic, 315,—View of the inner side > :

of avvalve of Dongulavandt Running along the base of each arm

Jera (after Francois), to show are two canals, a small one at the base

the definite arrangement of , .

the channels in themantle: a, Of the tentacles, which we may term

position of mouth; 0, posic the tentacular canal, and a_ larger

tion of anus. 5 : 5

one, the canal of the lip. The

former sends a prolongation into each tentacle. The latter is,
according to Blochmann, a closed canal in Crania, Lingula, Rhyn-

a)

LIU
Wows

/ Hy

XVII THE HEART 473

chonella, and others; but according to Joubin,’ it communicates
in Crania at one point with the tentacular-canal. It is probably
originally a part of the body cavity. Blochmann? states in very
definite terms that in Crania neither the large canal nor the
small canal communicates with the general body cavity, but he
admits that in Lingula the small canal opens into that space.

The Circulatory System

The details of the discovery of the central circulatory organ
of Brachiopods form a curious and instructive chapter in the
history of modern morphological inquiry. Hancock, in his
monograph on the group, described and figured on the
dorsal surface of the alimentary canal a well-developed heart,
which had been previously noticed by Huxley, who first showed
that the organs which up to his time had been regarded as
hearts were in reality excretory organs. In connexion with this
heart Hancock described numerous arteries, distributed to various
parts of the body. The observers who have written upon the
anatomy of Brachiopods since Hancock’s time, in spite of the
fact that they had at their disposal such refined methods of
research as section cutting, which was quite unknown at the
time his monograph was written, have almost all failed to find
this circulatory system, and many of them have been tempted
to deny its existence. Blochmann,? however, in the year 1885
stated that he had found the heart, and had seen it pulsating in
several species of Brachiopoda which he had rapidly opened
whilst alive. Joubin has also described it in large specimens
of Waldheimia venosa, and recently Blochmann has published a
detailed account of his work on this subject. Both these authors
describe the heart as a vesicle with muscular walls, situated
dorsal to the alimentary canal. From this, according to Bloch-
mann, a vessel—the branchio-visceral of Hancock—runs forward
as a triangular split in the dorsal mesentery supporting the
alimentary canal. This vessel divides into two at the oeso-
phagus, and passing through some lacunae in the walls of this

1 “Recherches sur l’Anat. des Brachiopodes Inarticules,” Arch. Zool. Exp. (2),
Tome iv., 1886.

2 Untersuchungen iiber den Bau der Brachiopoden, Jena, 1892.

3 ** Vorlaufige Mittheilungen iiber Brachiopoden,” Zool. Anz. Bd. viii. 1885.

AVA RECENT BRACHIOPODA CHAP.

tube, opens into the tentacular canal, and consequently supples
the tentacles with blood. These two canals, which diverge
from the median artery, are connected ventrally by a vessel which
runs below the oesophagus; the latter is therefore surrounded
by a vascular ring. Blochmann also describes two pairs of
vessels that were seen and figured by Hancock. A pair of
these pass over the gastro - parietal mesenteries and into the
dorsal mantle sinus, the second pair pass over the ileo-parietal
mesenteries and into the ventral mantle sinus; each of these four
arteries runs to one of the four generative glands, which, as is so
usually the case in the animal kingdom, have thus a specially
rich blood supply. If this description should prove to be correct,
the vascular system of Brachiopods shows a striking resemblance
to that of the closed vascular system of the unarmed Gephyrea,
except that the former group has specialised genital vessels.
The blood is colourless.

Joubin’s description of the vascular system of W. venosa differs
in some respects from that of Blochmann. He regards the heart
as collecting the lymph which it receives from numerous lacunar
spaces in the walls of the alimentary canal, and distributing it
through various vessels, which in the main correspond with those of
Blochmann, and which run both to the “arms” and to the genera-
tive glands. The latter vessels, however, open freely into the
body cavity, and the fluid which is forced out from their openings
freely bathes the organs found in the body cavity. Whichever
of these accounts should prove to be more closely in accordance
with the facts, there is little doubt that in addition to the true
blood there is a corpusculated fluid in the body cavity which is
to some extent kept in motion by the ciliated cells that line its
walls.

The Excretory Organs

The excretory organs (kidneys) which were at one time
regarded by Cuvier and Owen as hearts, are typical nephridia—
that is to say, they are tubes with glandular excretory walls
which open at one end by a wide but flattened funnel-shaped
opening into the body cavity, and at the other end by a circular
pore to the exterior (Fig. 314). In Rhynchonella, where
there are two pairs of these tubes,—the only evidence that the
group presents of any metameric repetition of parts,—the inner

Xv THE STALK A75

ends of the anterior pair are supported by the gastro-parietal
mesenteries, and those of the posterior pair by the ileo-parietal
mesenteries. In all other Brachiopods the posterior pair alone
exists. The external opening of these nephridia is near the
base of the anus; in C%stella it is at the bottom of a brood-pouch
formed by the tucking in of the body wall in this neighbour-
hood, and in this brood-pouch the eggs develop until the larval
stage is reached.

The walls of these nephridia are lined by ciliated cells,
amongst which are some excretory cells, in which numerous
brown and yellow concretions are to be seen; these are probably
the nitrogenous excreta of the animal, and pass out of the body,
being washed away by the stream of water which is constantly
passing between the shells.

As in so many other animals, the nephridia act as genital
ducts, and through them the ova and spermatozoa, which break
off from the genital glands and fall into the body cavity, find
their way to the outer world.

The Stalk and Muscles

The body cavity of a Brachiopod is traversed by several pairs
of muscles, which are very constant in position, and whose con-
traction serves to open and close the shell, to move the animal
upon its stalk, and to govern the movements of the arms.

The stalk is absent in Crania, and the members of this
genus are attached to the rocks on which they are found by the
whole surface of their ventral valve. In Lingula (Fig. 315)
the stalk is long and hollow, containing what is probably a
portion of the body cavity, surrounded by muscular walls.
Lingula is not a fixed form, but lives half-buried in the sand
of the sea-shore (Fig. 321). Discina, the other member of
the Ecardines, has a peduncle which pierces the ventral valve
and fixes the animal to its support. Amongst the Testicardines,
Thecidium is also fixed to its supports by the surface of its
ventral valve; the other genera, however, are provided with
stalks, which, being the means of the fixation of the animals,
become at the same time the fixed points upon which their
very limited movements can be effected. The stalk protrudes
through the notch or aperture at the posterior end of the ventral

476 RECENT BRACHIOPODA CHAP.

valve, and it probably belongs to the ventral side of the body.
It is in Cistella, and doubtless in other genera, in close organic
connexion with both valves, and it seems to consist of an un-
usually large development of the supporting tissue which occurs
so frequently in the body of Brachiopods. The surface of the
peduncle is produced into several irregularities and projections
which fit into any depressions of the rock upon which the
animal is fixed.

In Cistella there are four pairs of muscles, two connected
with opening and closing the shell, and two with the movement
of the body upon the stalk (Fig. 314). The most considerable
of these muscles are the two occlusors, which have their origin,
one on each side of the middle line of the dorsal valve, and their
insertion by means of a tendon into the ventral valve. In the
species in question each of these muscles arises by a double
head, the two muscles thus formed probably representing the
anterior and posterior occlusors of other forms. The contraction
of these muscles undoubtedly serves to close the shell, which
is opened by a small pair of divaricators arising from the
ventral valve, and inserted into a portion of the dorsal shell
which is posterior to the axis of the hinge. Contraction of
these muscles would thus serve to approximate the posterior
edges of the valves and divaricate the anterior edges and thus to
open the shell.

The adjustors are four in number, a ventral pair running
from the ventral valve to be inserted into the stalk, and a corre-
sponding dorsal pair from the dorsal valve. The simultaneous
contraction of either pair would tend to raise the valve, whilst
the alternate contraction of the muscles of each side would tend
to rotate the shell upon the peduncle. The muscles of Wald-
heimia flavescens are shown in Fig. 329, and described briefly
on p. 502.

The muscles of the Ecardines differ from those of the Testi-
cardines inasmuch as they do not terminate in a tendon,
but the muscle fibres run straight from shell to shell. They
are also more numerous. In Crania there is an anterior and
a posterior pair of occlusor muscles, and two pairs of oblique
muscles, which seem when they contract together to move the
dorsal shell forwards, or when they contract alternately to
slightly rotate it. In this genus there are also a pair of pro-

XVII THE MUSCULAR SYSTEM 477

tractors and a pair of retractors, and two levators of the arms, whose
function is to draw forward or retract the arms, and an unpaired
median or levator ani muscle. In addition to these bundles of
muscles there are certain muscles in the body wall, and it seems
probable that by their contraction, when the adductors are
relaxed, the body may become somewhat thicker and the valves

of the shells will slightly open.
In Lingula (Fig. 322) the muscular system is more com-

Fic. 316.— A semi - diagrammatic
figure of the muscular system of
Crania (after Blochmann): a,
anterior occlusor ; 6, posterior
ocelusor ; ¢, superior oblique ;
d, inferior oblique ; e, retractor
of the arms; /, elevator of the
arms; g, protractor of the arms ;
h, unpaired median muscle. The
dorsal valve is uppermost.

plicated ; in addition to the anterior (=anterior laterals) and
posterior (=centrals) pairs of occlusors, there is a single divari-
cator (= umbonal), whose contractions in conjunction with those
of certain muscles in the body wall press forward the fluid in the
body cavity, and thus force the valves of the shell apart; and
there are three pairs of adjustor muscles. These latter are
called respectively the central (=middle laterals), external
(=external laterals), and posterior (= transmedians) adjustors,
whose action adjusts the shells when all contract together, and
brings about a certain shding movement of the shells on one
another when they act independently of each other.'

1 Hancock’s nomenclature is here used. The corresponding names used by King
and Brooks are placed in brackets. Their nomenclature is used by many palaeon-
tologists, and is adopted in Fig. 322.

478 RECENT BRACHIOPODA CHAP.

The Nervous System

The nervous system of Brachiopods is not very clearly
understood, and there are considerable discrepancies in the
accounts of the various investigators, even when they are
dealing with the same species. So much, however, seems certain,
that there is a nervous ring surrounding the oesophagus, that
this ring is enlarged dorsally, or, in other words, near the base
of the lip, into a small and inconspicuous dorsal ganglion, and
again ventrally or just behind the base of the tentacles into a
ventral or sub-oesophageal ganglion. The latter is, contrary to
what is usual in Invertebrates, of much larger size than the
supra-oesophageal ganglion, but like the last named, it has retained
its primitive connexion with the ectoderm or outermost layer
of the skin. Both gangha give off a nerve on each side which
runs to the arms and along the base of the tentacles and lips.
The sub-oesophageal ganglion also gives off nerves which supply
the dorsal and ventral folds of the mantle, the muscles, and
other parts.

The modified epithelium in connexion with the ganglia may
possibly have some olfactory or tactile function, but beyond this
the Brachiopoda would appear to be devoid of eyes, ears, or any
other kind of sense organs,—a condition of things doubtless
correlated with their sessile habits, and with the presence of a
bivalved shell which leaves no part of their body exposed.

The Reproductive System

The majority of Brachiopods are bisexual, and many autho-
rities regard the separation of sex as characteristic of the group ;
on the other hand, Lingula pyramidata is stated to be herma-
phrodite, and it is not impossible that other species are in the
same condition.

The generative organs are of the typical sort, that is, they
are formed from modified mesoblastic cells lining the body
cavity. These cells are heaped up, usually in four places, and
form the four ovaries or testes as the case may be (Fig. 314).
The generative glands usually he partly in the general body
cavity and partly in the dorsal and ventral mantle folds, two on
each side of the body. Along the axis of the heaped-up cells

XVII DEVELOPMENT 479

runs a blood-vessel, which doubtless serves to nourish the gland,
the outer surface of which is bathed in the perivisceral fluid.
Every gradation can be found between the ripe generative cell
and the ordinary cell lining the body cavity. When the ova
and spermatozoa are ripe they fall off from the ovary and testis
respectively into the body cavity, thence they are conveyed to
the exterior through the nephridia. The ova in certain genera,
such as Argiope, Cistella, and Thecidiwm, develop in brood-
pouches which are either lateral or median involutions of the
body wall in the neighbourhood of the external opening of the
nephridia; they are probably fertilised there by spermatozoa
carried from other individuals in the stream of water which
flows into the shell. In other species the ova are thrown out
into the open sea, and their chances of meeting with a sperma-
tozoon is much increased by the gregarious habits of their
sessile parents, for as a rule considerable numbers of a given
species are found in the same locality.

The Embryology

We owe what little we know of the embryology of the group
chiefly to Kowalevsky,! Lacaze-Duthiers,? and Morse.® The
Russian naturalist worked on Cistella (Argiope) neapolitana, the
French on Zhecidiwm, and the American chiefly on Terebratulina.

Although this is not known with any certainty, it seems
probable that the eggs of Brachiopods are fertilised after they
have been laid, and not whilst in the body of the mother. The
spermatozoa are doubtless cast out into the sea by the male, and
carried to the female by the currents set up by the cilia clothing
the tentacles.

In Theeidium, Cistella, and Argiope the first stages of develop-
ment, up to the completion of the larva, take place in brood-pouches;
in Terebratulina the eggs pass out of the shell of the mother and
hang in spermaceti-white clusters from her setae and on sur-
rounding objects. In the course of a few hours they become
ciliated and swim about freely. The brood-pouch in Vhecidium

1 Development of the Brachiopoda, 1873 (Russian).

* “ Histoire de la Thécidie,” Ann. d. Sci. Nat., Sér. 4, vol. xv. 1861.

3 “On the Early Stages of Terebratulina septentrionalis,” Mem. Boston Soc. Nat.
Hist. vol. ii. 1869. ‘‘On the Development of Terebratulina,” bid. vol. iii. 1873.

480 RECENT BRACHIOPODA CHAP.

is median, in the convex lower shell, in Cistel/a it is paired, and
arises by the pushing in of the lateral walls of the body in the
region just behind the horse-shoe-shaped tentacular arms; the
renal ducts, which also serve as oviducts, open into these lateral
recesses,

In the female Zhecidium (Fig. 317) the two median tentacles
which lie just behind the mouth are enlarged and their ends
somewhat swollen; they are bent back into the brood-pouch,
and to them the numerous larvae are attached by a short fila-
ment inserted into the second of the four segments into which
the larva is divided. In Cistel/la a similar filament attaches the
larvae to the walls of the brood sac; thus they are secured from

= Fic. 317.—Brood-pouch of Thecidium

\ mediterranewin. (After Lacaze-
Duthiers.) Part of the wall of the
pouch has been removed to show
the clusters of larvae.

1. Mouth, overhung by lip.

2. One of the two median ten-
tacles which are enlarged and modi-
fied to bear the larvae.

3. Wall of brood- pouch into
which the median tentacles are
folded.

4. Larva attached to the swollen
end of the tentacles.

being washed away by the currents constantly flowing through
the mantle cavity of the mother.

In Cistella the larva consists at first of two segments, but
the anterior one divides into two, so that in the free swimming
larva we find three segments, the hindermost somewhat longer
and narrower than the others and destined to form the stalk.
About the time of the appearance of the second segment four
red eye-spots arise in the anterior segment, which tends to be-
come constricted off from the others, and may now be termed the
head. It gradually becomes somewhat umbrella-shaped, develops
cilia all over its surface and a special ring of large cilia round
its edge.

In the meantime the second or mantle segment has grown
down and enveloped the stalk, and four bundles of setae have

XVII HABITS: OF LARVAE 481

arisen from its edge. In this stage the larva leaves its mother’s
shell and swims out into the world of water to look for a suit-
able place on which to settle down. This is the only stage in the
life history of a Brachiopod when the animal is locomotor, and can
serve to spread its species. The extreme minuteness of the larva
and the short time it spends in this motile condition probably
accounts for the fact that Brachiopods are extremely localised.
Where they do occur they are found in great numbers, rocks
being often almost covered with them, but they are not found over
large areas. When viewed under a microscope the larvae seem

Fic. 318.—Young larva of
Cistella neapolituna,
showing three seg-

ments, two eye spots, Fic. 319.—Full-grown larva of Cis-
and two bundles of tella neapolitana, with umbrella-
setae. (After Kowa- shaped head, ciliated. (After
levsky. ) Kowalevsky. )

to be moving with surprising rapidity, but judging from the
analogy of other forms, it seems doubtful if they swim a yard in
an hour.

Frequently the larva stands on its head for some time, as if
investigating the nature of the rocks on which it may settle; it
is extremely contractile, turning its head from time to time,
and seldom retaining the same outline for any length of time; the
setae are protruded, and at times stick out in every direction ;
they are possibly defensive in function. When fully stretched
out the larva is about 4 mm. long, but it frequently shortens its

VOL. III ZI

482 RECENT BRACHIOPODA CHAP.

body to two-thirds of this length. The larvae are of a pinkish
red colour, with eye-spots of ruby red. Their colour renders
them difficult to discern when they are swimming over the red
coralline rocks upon which they frequently settle. After swim-
ming about for a few hours the larva fixes itself finally,
apparently adhering by some secretion produced by the stalk
seoment. The folds of the second or body segment then turn
forward over the head, and now form the ventral and dorsal
mantle folds; these at once begin to secrete the shell on their

Vic. 320. —Stages in the development of the larva of Terebratulina septentrionalis. (After
Morse.) The youngest larva has two segments, a third then appears, the larva
then fixes itself, and the second segment folds over the first and develops bristles
round its edge.

outer surfaces. The head with its eye-spots must be to some
extent absorbed, but what goes on within the mantle is not
accurately known. The setae drop off and the tentacular arms
begin to appear as a thickening on the dorsal lobe of the mantle.
They are at first circular in outline. The various changes which
the larva passes through are well illustrated by Morse for 7ere-
bratulina, which spawns at Eastport, Me., from April till August.
The different stages are represented in outline in Fig. 320, taken
from his paper.

Habits

There is little to be said about the habits and natural history
of the Brachiopoda. When once the larva has settled down, the
animal never moves from the spot selected; occasionally it may
rotate slightly from side to side on its stalk, and from time to
time it opens its shell. As so frequently is the case with sessile
animals, the sense organs are reduced to a minimum, the eyes of
the larva disappear, and the only communication which the

/

XVII HABITS OF LINGULA

animal has with the world around it is
by means of the currents set up by the
cilia on the tentacles.

In spite of the absence of any definite
eyes, Thecidium, according to Lacaze-
Duthiers, is sensitive to hight ; he noticed
for instance that, when his shadow fell
across a number of these animals he was
watching in a vessel, their shells, which
had been previously gaping, shut up at
once,

In Cistella the tentacles can be pro-
truded from the open shell, and in Riyn-
chonella the spirally-coiled arms can be
unrolled and extruded from the shell, but
this does not seem to have been observed
in other genera, with the possible ex-
ception of Lingula. The food of these
animals consists of minute fragments
of animal and vegetable matter, a very
large proportion of it beimg diatoms and
other small algae.

Lingula differs markedly from the
other members of the group, inasmuch
as it 1s not firmly fixed to a rock or
some such body by a stalk or by one of
its valves, but lives in a tube in the
sand. Some recent observations of
Mons. P. Francois’ on living specimens
of Lingula anatifera which he found
living in great numbers on the sea-
shore at Nouméa in New Caledonia
may be The presence of
the animal is shown by a number of
elongated trilobed orifices which lead
into the tube in which the Lingula lives.
The animals, like most other Brachi-
opods, live well in captivity, and he was
able to watch their habits in the aquaria

mentioned.

Fic. 321.—Figures illustrating

the tubes in which Lingula
anatifera lives. The upper
figure is a view of the tri-
lobed opening of the tube.
The lower figure shows the
tube in the sand laid open
and the animal exposed.
The dotted line indicates
the position of the body
when retracted. The darker
portion is the tube of sand
agglutinated by the secre-
tion of the stalk, (After
Francois. )

1 **Choses de Nouméa,” Arch. d. Zool. exp. et gen. 2nd ser. vol. ix. 1891.

484 RECENT BRACHIOPODA CHAP.

of his laboratory. The Lingula place themselves vertically ; the
anterior end of the body just reaches the level of the sand; the
three lobes into which the orifice of the tube is divided corre-
sponding with the three brushes of setae which project from the
anterior rim of the mantles. These setae are described by Morse
as projecting in the form of three funnels ; currents of water are
seen continually passing in at the side orifices and out through
the central. The tube consists of two portions: an upper part,
which is flattened to correspond with the flat shape of the body,
and a lower part, in which the stalk lies. The upper part
is lined with a layer of mucus, but the sand is not glued
together to form a definite tube. The lower part of the
stalk, or the whole when the animal is contracted, is lodged
in a definite tube composed of grains of sand agglutinated by
mucus, probably secreted from the walls of the stalk. At the
least sign of danger the stalk is contracted violently, and the
body is withdrawn to the bottom of the upper portion of the
tube. The rapid retreat of the animal is followed by the
collapse of the sand at the mouth of the tube, and all trace of
the presence of the Lingula is lost.

The shells of this species are frequently rotated through a
small angle upon one another, a movement which is prevented
in the Testicardines by the hinge. In very young transparent
specimens Frangois was able to observe the movements of the
fluid in the system of tubules which penetrate the mantle; these
tubules are figured by him, and Fig. 315 is taken from his
illustration.

Davidson, in his Monograph on the British Fossil Brachi-
opoda, states that the largest “recent Brachiopod which has
come under my notice is a specimen of Waldheimia venosa
Solander, measuring 3 inches 2 lines in length, by 2 inches in
breadth, and 1 inch 11 lines in depth.” It was found in the
outer harbour of Fort William, Falkland Islands, in 1845. A
specimen of Terebratula grandis from the Tertiary deposits, how-
ever, exceeds this in all its dimensions. Its length was 43
inches, its breadth 3 inches 2 lines, and its depth 2 inches 2
lines.

Distribution in Space

Brachiopods are very localised; they live in but few places

XVII VERTICAL DISTRIBUTION 485

but when they are found they usually occur in great numbers.
During the cruise of the Challenger, dredging was conducted at
361 stations; at only 38 or 39 of these were Brachiopoda brought
up. Mr. Cuming, quoted by Davidson, records that after a great
storm in the year 1856, he collected as many as 20 bushels of
Lingula anatifera on the sea-shore at Manilla, where, he relates,
they are used as an article of food. It has been suggested above
that their abundance in certain localities is due to their limited
powers of locomotion, which are effective but for a few hours,
the larva being, moreover, so minute that unless borne by a
current it could not travel far from its parent. When once
settled down it has little to fear from the attacks of other
animals. The size of its shell relative to its body would
deter most animals from regarding it asa desirable article of food,
and as far as is known at present the Brachiopoda suffer but
little from internal parasites, the only case I know being a
minute parasitic Copepod belonging to a new and as yet unnamed
genus which I found within the mantle cavity of Cistella (Argiope)
neapolitana in Naples. Their sheht value as an article of diet
has doubtless helped to preserve them through the long periods
of geological time, through which they have existed apparently
unchanged.

Two of the recent genera of the family Lingulidae, Lingula
and Glottidia, are usually found between tide-marks or in shallow
water not exceeding 17 fathoms. Discina is also found about
the low-tide level, but one species at any rate, Discinisca atlantica,
has been dredged, according to Davidson, “at depths ranging from
690 to nearly 2425 fathoms.” Their larvae frequently settle on
the shells of their parents, and thus numbers of overlapping shells
are found clustered together. Crania is usually dredged from
moderate depths down to 808 fathoms, adhering to rocks, lumps
of coral, stones, and shells.

Of the Testicardines, Terebratula Wyvillei has probably been
found at the greatest depth, ae. 2900 fathoms, in the North
Pacific. It is interesting to note that its shell is glassy and
extremely thin. The Piachiopoda are, however, as a rule,
found in shallower water; they abound up to a depth of 500 or
600 fathoms, after which they rapidly diminish with increasing
depth. About one-half the named species occur at a depth of
less than 100 fathoms.

486 RECENT BRACHIOPODA CHAP.

The vertical range of depth of certain species is great; Zere-
bratula vitrea is recorded from 5 to 1456 fathoms, 7. Wyvillei
from 1035 to 2900 fathoms. This is to some extent explic-
able since, after a certain depth has been reached, many of
the external conditions, such as absence of temperature and
light, must remain constant even to the greatest depths of the
ocean.

The area of the ocean explored by dredging forms such an
infinitesimal fraction of the whole, that it seems superfluous to
consider the horizontal distribution of Brachiopods. A few facts
may, however, be mentioned. Certain species, as Terebratula
vitrea, T. caput serpentis, Waldhermia cranium, Megerlia trun-
cata, and Discinisca atlantica have a very wide if not cosmo-
politan distribution. The second of the above named extends as
far north as Spitzbergen, and as far south as Kerguelen Island.
Many species are, on the other hand, very localised, and have
hitherto only been found in one place. A very considerable
number of these have been dredged off Japan and Korea, and
this region may be to some extent regarded as the headquarters
of the group.

The following species have been obtained within the limits
of the British Area, as defined by Canon Norman, who has been
good enough to revise the list, which is founded on that drawn
up by Davidson in his Challenger Report. Their range of bathy-
metric distribution is given in the column on the left.

Depth in

Fathoms.

0 to 1180. Terebratulina caput serpentis Lin. . Oban, and off Cumbrae Islands,
Loch Torridon, Scotland, off
Belfast

8to 25. Terebratula (Gwynia) capsula Jeff. . Belfast Bay, E. and S. coast of
Ireland, Plymouth, Weymouth,
and Guernsey

5 to 690. Waldheimia cranium Miller. . . North British seas. Off Shet-

land

75 to 725. Waldheimia septigera Loven . . . North British seas. Off Shet-
land

20 to 600. Terebratella spitzbergenensis Dav.. . N.N.W. of Unst, Shetland

18 to 364. Argiope decollata Chemnitz . . . Two miles east of Guernsey

20 to 45. Cistella cistellulaS. Wood. . . . Shetland, near Weymouth, 8.
coast of England

650 to 1750. Atretia gnomon Jeff... . . . . . W. of Donegal Bay in 1443

faths. Between Ireland and
Rockall, in 1350 faths.

XVII CLASSIFICATION AND AFFINITIES 487

Depth in

Fathoms.

10 to 690. Rhynchonella psittacea Gmelin . . Shetland and near Dogger Bank.
This species is possibly fossil
as well as recent.

3 to 808. Crania anomala Muller. . . . . Loch Fyne, North of Scotland
690 to 2425. Discinisca atlantica King . . . . W.of Donegal Bay in 1366 faths.,

W. of Ireland in 1240 faths.,
off Dingwall Bay

Classification.

The table of classification here appended is that suggested by
Mr. Davidson in his Monograph on the Recent Brachiopoda.

I. TESTICARDINES

Family.

A. TEREBRATULIDAR. This includes the majority of genera and of species, the
latter, without counting uncertain species, amount-
ing to sixty-eight. Examples: Terebratula, Tere-
bratella, Terebratulina, Waldheimia, Megerlia,
Argiope, Cistella.

B. THECIDIIDAE, This family contains one genus, Thecidium, with two
species.

C. RHYNCHONELLIDAE. This family is made up of eight species, six of which
belong to the genus Rhynchonella, and two to
Atretia.

II. ECARDINES

D. CRANIIDAE. This family comprises the four species of Crania.

E. DIscINIDAE. This family contains one species of Discina and six
of Diserinisca.

F. LINGULIDAE. This family consists of eight species of Lingula and

three of Glottidia.

It is impossible to come to any satisfactory conclusion as to
the position of the group Brachiopoda with relation to the rest
of the animal kingdom. They have, in accordance with the views
of various investigators, been placed in close connexion with many
of the large groups into which the Invertebrates are split up. The
Mollusca, the Tunicata, the Polyzoa, the Chaetopoda, the Gephyrea,
and of recent times such isolated forms as Phoronis and Sagitta,
have all in turn had their claims advanced of relationship to this
most ancient group. As far as I am in a position to judge, their
affinities seem to be perhaps more closely with the Gephyrea and
with Phoronis than with any of the other claimants ; but I think

488 RECENT BRACHIOPODA CHAP. XVII

even these are too remote to justify any system of classification
which would bring them together under a common name. In-
vestigation into the details of the embryology of the group, more
especially into that of the Ecardines, might throw some light
on this subject, and it is much to be desired that this should be
undertaken without delay. That the group is a most ancient
one, extending from the oldest geological formations, we know ; that
the existing members of it have changed but little during the
vast lapse of time since their earliest fossil ancestors flourished,
we believe ; but we are in almost total ignorance of the origin or
affinities of the group, and we can hardly hope for any light on
the subject except through embryological research.

BRACHIOPODA

FAureiee dale
PALAEONTOLOGY OF THE BRACHIOPODA

BY

F. R. COWPER REED, M.A, FGS.

Trinity College, Cambridge

CHAPTER XVIII

PALAEONTOLOGY OF THE BRACHIOPODA

INTRODUCTION—DIVISION I. ECARDINES—-EXTERNAL CHARACTERS—
INTERNAL CHARACTERS—DIVISION II. TESTICARDINES—EX-
TERNAL CHARACTERS—-INTERNAL CHARACTERS—SYNOPSIS OF
FAMILIES—STRATIGRAPHICAL DISTRIBUTION——PHYLOGENY AND
ONTOGENY.

Introduction

THE wide distribution and vast abundance of the Brachiopoda
throughout the whole series of geological formations make this
group of especial importance to the student of the past history
of the earth; and the zoologist must always regard the fossil
forms with peculiar interest, because they not only largely out-
munber the living representatives, but comprise numerous extinct
genera, and even families, exhibiting types of structure and
characters entirely absent in the modern members of the group.
It is a most fortunate circumstance that the excellent state of
preservation in which we frequently find them, and the immense
amount of material at our disposal, enable us to determine with
accuracy and certainty the internal characters of the shells in
the great majority of cases. But it is only since the beginning of
the present century that our knowledge of the anatomy of the soft
parts of the living animal has rendered any tracing of homologies
possible. In the case of features in fossil extinct types the interpre-
tation must be to some extent doubtful. Barrande, Clarke, David-
son, Hall, King, Oehlert, Waagen, de Verneuil, and a host of other
workers have contributed to the information which we now possess ;
and their works must be consulted for details of the subject."

1 J. Barrande, Syst. Silur. Bohéme, vol. v. 1879. Halland Clarke, Zntrod. Palaco-

492 FOSSIL BRACHIOPODA CHAP.

Since all Brachiopods are inhabitants of the sea, the geologist
at once recognises as a marine deposit any bed which contains
their remains. Under favourable conditions they swarmed in the
seas of Palaeozoic and Mesozoic times. Beds of limestone are fre-
quently almost entirely composed of their shells, as, for instance,
some of the Devonian limestones of Bohemia. Often they give
the facies to the fauna and outnumber in species and individuals
all the other organisms of the period. The Ungulite Sandstone
(Cambrian) of Russia and the Productus Limestone of the Salt
Range in India of Carboniferous and Permian age are well-known
examples.

Many species seem to have been gregarious in habit; thus
Productus giganteus of the Carboniferous Limestone may generally
be found in crowded masses, as in some localities in Yorkshire.

The fact that certain species of Brachiopods characterise
definite stratigraphical horizons or “ zones ” gives them occasionally
an lnportance equal to that of Graptoltes; for instance, the
Ecardinate species 7rematis corona marks a set of beds in the
Ordovician, and the isolated Stringocephalus Burtini is restricted
to the upper part of the Middle Devonian, giving to the lime-
stone on that horizon its distinctive name. It is noteworthy also
how certain species affect a sandy and others a calcareous sea-
bottom, so that beds of the same age show differences in their
Brachiopod fauna owing to a dissimilar lithological composition.

While few of the recent Brachiopods reach a large size, some
of the extinct species measure several inches in breadth, but the
ereat Productus giganteus attained the width of even a foot.

The bright colours of the shells of the living animals are
not generally preserved amongst the fossil species from the older
rocks; yet in a Carboniferous TZerebratula we can even now
detect the purple bands in some specimens, and a Cretaceous
Lhynchonella similarly exhibits its original colour.

The Brachiopoda are evidently a group in its decline, as the
geological record shows; but they date back from the earlest
known fossiliferous rocks, in which the Eecardinate division
is alone represented. As we ascend through the stratigraphical
series the number and variety of genera and species belonging to

zoic. Brach. (Palaeont. of New York, 1892-1894). Davidson, Monogr. Brit. Foss. Brach.
(Palaeont. Soc. 1851-1884). Waagen, Salt Range Fossils (Mem. Geol. Surv. India,
1879-1885).

XVIII ECARDINES: EXTERNAL CHARACTERS 493

both divisions rapidly increase until in the united Ordovician and
Silurian there are nearly 2000 species and about 70 genera.
From this point of maximum development down to the present
day there is a gradual decrease in numbers.

According to Davidson, at least 17 Upper Tertiary species are
still living on our sea-bottoms; and many recent Mediterranean
forms occur in the Phocene rocks of the islands and shores of that
sea, and in the Crags of East Anglia.

A brief review of the chief characteristics of fossil Brachio-
poda is given below. Those genera which have the greatest
zoological or geological importance can alone be noticed owing
to the exigencies of space.

I. ECARDINES

External Characters

A considerable diversity of external form is met with even in
this division, from the hmpet-like Discina to the flattened tongue-
shaped Lingula. The valves have most commonly a smooth
external surface with delicate growth-lines; but sometimes
pittings (7rematis) or radiating ribs (Crania) are present, and in
a few forms the shell is furnished with spines (Siphonotreta),
which perhaps served to anchor it in the soft mud of the sea-
bottom. The usual mode of fixation was by means of the pedicle
(= peduncle or stalk), which either (1) passed out simply between
the posterior gaping portion of the valves (Lingula), or (2) lay
in a slit in the ventral valve (Lingulella), or (3) pierced the sub-
stance of the latter valve by a definite foramen (Discina). The
first-mentioned condition of the pedicle seems the most primitive.
Rarely the pedicle was absent, and the shell was attached by
the whole surface of the ventral valve (Crania, p. 467).

The two valves in the fossil Ecardines were held together by
muscular action, though in some familes (77rimerellidae) we see
traces of articulating processes. The “hinge line,” or line along
which the valves worked as on a hinge, is in most forms more or
less curved. <A “hinge area” (ae. that portion of the shell gener-
ally smoother than other parts of the valves, more or less tri-
angular in form, and lying between the beaks on one or both
sides of the hinge line), is usually absent in the Ecardines.

494 FOSSIL BRACHIOPODA CHAP.

Internal Characters

Owing to the rarity of well-preserved interiors of valves
in this division, our knowledge of their internal characters is still
far from satisfactory. The arrangement of the muscular impres-
slons varies greatly amongst extinct genera, but we are often able
to interpret them with a considerable amount of certainty by a
study of the scars and the muscles of the well-known recent
Lingula (Fig. 322). The extreme specialisation of the muscles in
many of the earliest genera (e.g. Lingula) is remarkable, and points
toa long but so far undiscovered ancestry in pre-Cambrian times.!
Tn fossil species of Crania and Lingula the muscle-scars correspond
closely with those in the liy-
ing representatives of these
genera. In the most highly
specialised family of the Ecar-
dines—the Zrimerellidae—
we meet with features of
peculiar interest.” The muscle-
scars in this family (Fig.
323, A, B) are most remark-
able for the development of
the so-called “ crescent,’ (q.7.s.)
which skirts the posterior
margin of both valves. as a

Fia. 322.—Muscle-sears of Lingula anatina. as : Rabin, Lo
Inner surface of A, Pedicle-valve or ventral sub-cardinal impression. It

valve. B, Brachial or dorsal valve; p.s, jg believed to be the trace
parietal scar ; uv, umbonal muscle ; ¢, trans-

medians ; c, centrals; a.m.e, laterals (a, of a strong post - parietal
anteriors ; m, middles ; e, externals). muscular wall, analogous in
position to that of Lingula. The three pairs of “lateral”
muscle-scars in the latter genus seem to be represented by
the “terminal” (s) and “lateral” (7) scars on the crescent

' The results of the investigations of King (Ann. Mag. Nat. Hist. 4th ser.
vol. xii. 1873) and of Brooks (Chesapeake Zool. Laboratory, Scientific Results, p. 35,
1879), and the simple nomenclature of these authors are here followed in preference
to those of others, owing to the difference of opinion amongst anatomists of the
functions and homologies of the muscles. The lateral muscles enable the valves to
move backwards and forwards on each other ; the centrals close the shell; the um-
bonals open it; and the transmedians allowa sliding sideways movement of one
valve across the other (see also p. 477).

* Davidson and King, Quart. Jour. Geol. Soc. xxx. (1874), p. 124.

XVIII ECARDINES: INTERNAL CHARACTERS 495

of the Zrimerellidae. A pair of “transverse” scars (¢) occurs
in each valve between the “terminals” and the antero-
lateral edge of the “platform” (j). “Cardinal” (v), “sub-
cardinal” (w), and “umbo-lateral” (#) scars also occur. The
median impression which covers the “ platform” (/) consists of a
central, lateral, and usually an anterior pair of scars; and the
impressions of the genital organs, according to Davidson and
King, he medianly posterior to the “ platform.” The “ platform ”

Fia. 325.—Trimerella. (After Davidson and King). A, Inner surface of pedicle-valve or
ventral valve: a, pseudo-deltidium ; 6, deltidial slope ; c, deltidial ridges ; d, areal
borders ; e, cardinal callosities ; 7, cardinal facet ; g, lozenge; 7, umbonal chambers
separated by cardinal buttress ; 7, platform ; %, platform vaults; 7, median plate ; m,
median scars ; 7, anterior scars; 0, lateral scars ; p, post-median scars; g, crown
crescent ; 7, side or lateral crescent ; s, end or terminal crescent; ¢, transverse scars ;
u, archlet (vascular sinuses); w, sub-cardinal scars ; 2, umbo-lateral scars. B, Brachial
or dorsal valve: e, cardinal sockets ; 7, platform ; %, platform vaults ; 7, median
plate ; m, median scars ; 7, anterior scars; g, crown crescent ; 7, side or lateral
crescent ; s, end or terminal crescent; ¢, transverse scars; wu, archlet (vascular
sinuses); v, cardinal scars ; w, sub-cardinal scars.

itself is a more or less conspicuous central calcareous elevated
area occurring in each valve, but most developed in the dorsal ;
In some cases it is double-chambered with tubular cavities
(“ platform vaults,” Fig. 323, A, B, %), in others it is more or less
solid. It appears to have originated through a posterior shifting
of the central muscular bands, that they might be inserted behind
the liver; at the same time a deposition of shelly material, to
form fulera to work the heavy valves, took place at these points.
The tunnelling-out of the platform was probably due to the

496 FOSSIL BRACHIOPODA CHAP.

continual pressure of the lobes of the liver. The division of the
umbonal cavity into definite chambers in Monomerella, and to a
less extent in other members of this family, appears, according
to Davidson and King, to have been caused by pressure of the
ovarian lobes.

In connexion with the foregoing remarks on the development
of the “platform,” it may be mentioned that the paths along
which the muscle-bands move, as the shell of Brachiopods increases
in size, are marked by elongated scars, and often by shelly
deposits; and when the members of a muscle-pair come into
juxtaposition these shelly deposits (which act as fulcra for the
muscles) combine, and by the growth of the shell form a septum,
as in the case of the median septum of Lingulepis.

The Obolidae show some important features in the internal
impressions. Obolella crassa (Hall) may be taken as a well-
known type of the family. In this species a pair of small
scars, one on each side of the pedicle-groove, lies close under the
hinge line in the ventral valve. There is also a well-marked scar
for the insertion of the pedicle-muscle at the end of the pedicle-
groove. <A pair of much elongated lateral impressions extending
forward from the “cardinals” may be homologous with the
“laterals” of Lingula; and the two small central scars between
them may be compared with the “centrals” of Lingula which
are in a somewhat similar position. In the dorsal valve of 0.
crassa a pair of “cardinals” is found, and on each side of a low
median rounded ridge are two small “central” scars. Indistinct
“lateral” scars arise close to or.in the central area, and diverge
anteriorly.

Sometimes a great concentration of muscle - scars occurs
round the foramen in the ventral valve, as in Siphonotreta.

As regards the minute structure and composition of the shell
in the Ecardines, we find that the Lingulidae and Discinidae
have their shell composed of alternating layers of phosphate of
lime and a corneous substance; the former layers are pierced by
microscopic canals. The Craniidae have calcareous shells tra-
versed by tubules, which divide into many fine branches near
the external surface; a thin periostracum covers the exterior.
The Zrimerellidae have heavy thick calcareous shells, for which
they required the previously-described elaborate arrangement of
muscles to open and shut them.

XVIII TESTICARDINES: EXTERNAL CHARACTERS 497

Il —TESTICARDINES

External Characters

It is to this division that the great majority of the Brachio-
poda belong; and the diversity of form, of ornamentation, and
of internal characters is correspondingly greater than in the
Ecardines.

A transversely or longitudinally oval shape of shell is the
commonest ; but sometimes it is triangular, as in Rhynchonella
(Fig. 327), or bilobed, as in Pygope (= Terebratula diphya). The
ventral valve is usually more convex than the dorsal, and the
former may be prolonged into a tube by the accelerated growth
and infolding of the anterior and lateral margins, producing a
very abnormal form (Proboscidella). The external surface of the
valves is frequently ornamented with more or less prominent
radiating ribs; and fine concentric growth-lines are commonly
shown, and may be developed into coarse ridges or wrinkles,
particularly in old individuals. The members of the family Pro-
ductidae are usually furnished with tubular spines, which are some-
times of great length, and served to anchor the free shells in the
mud, or were twisted round Crinoid stems and similar objects.

In the ventral valve of many genera there is a median sinus,
with a corresponding fold in the dorsal valve, and rarely vice
versd ; sometimes the fold and sinus are double.

The hinge line is either curved or straight, and the valves
are articulated by means of a pair of “ hinge-teeth ” (Fig. 329, ¢)
in the ventral valve, which fit into corresponding sockets in the
opposite valve. Some genera have the teeth very rudimentary,
or have lost them altogether. The teeth are frequently sup-
ported by “dental plates,” and the sockets by “socket plates”
(e.g. Conchidium, Figs. 324, 325). A few genera with a long
hinge line have the whole of it denticulated (Stropheodonta). In
the dorsal valve medianly close under the hinge line is a shelly
protuberance—the “cardinal process ”—to which the diductor
muscles are attached. It is sometimes of great length and
forked (Stringocephalus, Fig. 326), or tripartite, or even quadri-
partite; but in Rhynchonella and some other genera it is rudi-
mentary.

VOL. III 2K

498 FOSSIL BRACHIOPODA CHAP,

A “hinge area” (Fig. 334, ¢.a) is often present on one or both
valves, and may be of great size, as in Clitambonites, but im
Productus it is wholly absent. In those genera that possess 1t a
triangular fissure—the “ deltidial fissure ”—frequently traverses

Fie. 325.—Conchidium galeatum.
Transverse section. d, Dor-
sal valve; d.s, dorsal septum ;
s, socket plate; v, ventral

Fic. 324.—Conchidium galeatum. valve; v.s, ventral septum ;

Wenlock Limestone. d.p, dental plate,

it on both valves; in the dorsal valve the fissure is merely the
space between the dental sockets, and may be occupied by the
cardinal process (Fig. 334, C) or covered by a shelly plate—the
“chilidium.” In the ventral valve it gives passage to the pedicle,

Fic. 326.—Stringocephalus Burtini. (Modified from Woodward.) Devonian. A, Interior
of dorsal valve. B, Side view of interior of shell ; a, adductor (=occlusor) sears ;
c, erura; ¢.p, cardinal process; d.s, dorsal septum ; h.p, hinge plate ; 7, brachial
loop; sp, shelly processes ; ¢.s, dental sockets; v.s, ventral septum.

and may be partly or entirely closed by a similar plate (Fig.
334, d) known as the “ pseudo-deltidium,” especially large in
Clitambonites, or remain open (Orthis). This pseudo-deltidium
is a primitive character, and arises in an early stage of the

XVIII TESDICARDINES: INTERNAL CHARACTERS 499

development as a shell-growth on the dorsal side of the animal,
becoming attached to the ventral valve subsequently. The pedicle
in many genera passes out through a special foramen in the beak
of the ventral valve; and its proximal portion is often embraced
by a pair of small plates—the deltidial plates or “ deltidium ”
—which are formed on lateral extensions of the ventral mantle
lobe, according to Beecher. These plates lie on each side of the
pedicle, or grow round and unite in front of it (Rhynchonella,
Wie. 327), or constitute merely its anterior border (Zerebratula,
Fig. 328). In some cases this foramen becomes closed in ald age.

The dorsal valve in a few cases has its beak perforated by a

Fria. 327.—Rhynchonella Boueti. Fia. 328.—Terebratula sella.
(Cornbrash.) d, Deltidium ; (Lower Greensand.) d,
J foramen. Deltidium ; /, foramen.
foramen—the “visceral foramen.” This foramen is in no way

connected with the pedicle foramen, but points perhaps to the
existence in the early Testicardinate genera of an anal aper-
ture. In Athyris concentrica (Devonian) this foramen is connected
internally with a cylindrical tube, which extends longitudinally
to about one-third the length of the valve. In Cenéronella the
aperture in the cardinal plate is rounded and complete; and in
Strophomena and its allies the opening lies between the cardinal
processes. If this feature is correctly interpreted, it suggests a
retrogression of the group since Palaeozoic times not only in
numbers, but in structure; and other evidence points the same
way.

Internal Characters

The interior of the shell is sometimes more or less divided up
by septa. A median septum occurs in one or both valves of
many genera as a low ridge or strongly developed partition ( Wald-

500 FOSSIL BRACHIOPODA CHAP.

heimia, Fig. 329, ss; and Stringocephalus, Fig. 326, B,v.s). Con-
chidium (Fig. 325) has its dental plates of great size, and unit-
ing to form a V-shaped chamber or “ spondylium,” supported by a
median double septum ; and by means of these with a pair of septa
and the large socket-plates in the dorsal valve the interior of
the shell of this genus is divided up into several chambers.

The interiors of several other genera are somewhat similarly
divided up.

In the Carboniferous genus Syringothyris two special plates,
situated between the dental plates, are rolled into an incomplete
tube, so as to enclose probably the anal extremity of the al-
mentary canal; and in several genera a sub-umbonal “ cardinal

Fra. 829.— Waldheimia (Magellania) Navescens. A, Interior of ventral valve: a, adductor

scars ; v.d, ventral adjustors ; d, divaricators ; a.d, accessory divaricators ; p, pedun-

cular muscle ; dm, deltidium ; f, forarnen ; ¢, teeth. B, interior of dorsal valve :
a.a, anterior adductor (ocelusor) scars ; @.p, posterior adductor (occlusor) scars ;
c.p, cardinal process ; cr, crura; d.s, dental sockets ; hp, hinge-plate ; 7, brachial
loop ; ss, septum. (After Davidson. )

plate” is present, which is perforated (Athyris) or sht in some
cases for the passage of the anal tube.

For the support of the fleshy “spiral arms” the calcareous
structures forming the “brachial apparatus” are of two main
types—(1) the loop type; (2) the spiral-cone type. In the
Strophomenidae no special calcareous support seems to have been
usually present (Fig. 334), though in some species of Leptaena
spirally-grooved elevated areas supported the fleshy arms; in the
Productidae it is probable that the ridges enclosing the “ reni-
form impressions ” (Fig. 333, 7) served for a similar purpose.

The Terebratulidae show the “loop type” of brachial appa-
ratus. In Waldheimia (Fig. 329), which may be taken as ‘an

XVIII TESTICARDINES : INTERNAL CHARACTERS 5ol

example, we notice first in the dorsal valve the “crura” (cr),
from which arise the two “descending branches” which run
forwards and then are bent back to form the “ascending
branches ” which are united by the “ transverse band.” In some
genera the “ascending branches” may be reduced to mere points,
and the “transverse band” become a median vertical plate; the
“erura,” too, may be fused so as to form a “crural band”; and
the “descending branches” may be connected by a cross band—
the “jugal band.” In Stringocephalus (Fig. 326, /, sp) the loop
is furnished on its inner edge with radiating processes; and
in Argiope the loop is simple, not reflected, and fused with
marginal septa; while in the Zhecidiidae it is more or less fused
with the shell itself, and with the mass of calcareous spicules
secreted by the mantle.

The “spiral-cone type” of brachial apparatus is found in the
Spiriferidae, Atrypidae, and Koninchinidae, and consists of two
spirally-enrolled calcified lamellae, forming two cones with their
apices directed laterally (Spirifera, Fig. 330), or towards the
interior of the dorsal valve (dirypa, Fig. 352), or towards
each other (Glassia); or forming two flat spirals in the same
plane (Koninchinidae). A “jaugal band” is generally present, but
varies much in position,
and in some genera has
compheated posterior pro-
CeSses.

The Rhynchonellidae
have no loop or spiral
cones, but merely a pair

bP)

of short “ erura

The principal modifi-
at] sin the attacl nts Fia, 330.—Spirifera slriuta. (Carboniferous Lime-
cations mm the attachments stone.) Showing brachial spires.

of the muscles in the

Testicardines are illustrated by Productus giganteus (Fig. 333),
Leptaena rhomboidalis (Fig. 3354), and Waldheimia flavescens
(Fig. 329).

In Productus (Fig. 333) we see in the ventral valve a pair of
dendritic ocelusor, often called adductor, impressions and a pair
of large flabellate divaricator impressions. In the dorsal valve the
large “ cardinal process” served for the attachment of the divari-
eator, and a low median septum separated the dendritic occlusor

5iO2 FOSSIL BRACHIOPODA CHAP.

scars, which are rarely divisible into anterior and posterior

pairs.
In Leptaena (Fig. 334) the occlusor scars (@) in the ventral

Fic. 331.—Alrypa reticu- Fic. 332.—Interior of the same, seen
laris. (Wenlock Lime- from the dorsal side, showing
stone. ) brachial spires. (After Hall.)

valve are narrow and median, and are enclosed by a pair of
flabelliform divaricator impressions (7.7) ; in the dorsal valve two
pairs of occlusor scars (aa, p.a) are well marked, and accessory
posterior occlusor scars are traceable 1m some specimens. The

LP
oe A

\
i Not

\\ NANNY
\ i y

AWN
NUN

I RUT LLA wwASS ‘

\
u

Fic. 333. — Productus giganteus. (After Woodward.) Carboniferous Limestone. A,
Interior of dorsal valve. B, Interior of ventral valve. C, Transverse section of valves.
D, Hinge line of A: a, occlusor scars ; d, divaricator scars; 7, ‘‘reuiform impres-
sions”; ca, cardinal process ; h, hinge line; p, brachial prominence ; s, cavity
for spiral arms ; do, dorsal valve ; ve, ventral valve.

vascular sinuses (v.s) and genital areas are conspicuous in many
species of this and other genera.
In Waldheimia (Fig. 329) a sub-umbonal “ peduncular muscle ”

XVIII TESTICARDINES: INTERNAL CHARACTERS S03

scar (p) in the ventral valve has before it a pair of “accessory
divaricator ” scars (a.d) flanked by a pair of “ventral adjustor ”
(v.a) and a pair of “ divaricator ” impressions (7), between which
lie the two occlusor scars (@). In the dorsal valve anterior and
posterior pairs of occlusor scars (@.a, @.p) are visible.

The minute structure of the calcareous shell of the Testi-
cardines is of flattened fibrous prisms inclined at a very acute

Sane
a = Fig. 334.—Leptaena rhomboidalis. (Silurian. )
A, External view of ventral valve. B, In-
terior of ventral valve: a, occlusor scars ;
\\N d, pseudo-deltidium ; d.v, divaricator scars ;
A c.a, hinge area; ¢, teeth. OC, Interior of
dorsal valve: @.a, anterior occlusor scars ;
p.a, posterior oc-
clusor scars; ¢.4,
hinge area ; ¢.p, car-
dinal process ; d,
chilidium ; s. dental
sockets 3 v.s, Vascu-
lar sinuses.

angle to the surfaces. In many forms minute tubes more or
less closely arranged pierce through the fibrous shell-substance ;
but in some genera (Productus) they do not reach the outer
surface (see p. 468). Alhed genera, however, differ much in the
punctate or lmpunctate character of the shell.

SYNOPSIS OF FAMILIES

J. ECARDINES

Family : Lingulidae

Shell elongated, composed of alternating chitinous and calcareous layers,
the latter of which are perforated. Attached by a pedicle passing between
apices of valves.

Arms have no calcified supports.

(For muscles see Fig. 322.)

RaNnGE.—Lower Cambrian to Recent.

Principat Genera.—Lingula, Lingulella, Lingulepis.

504 FOSSIL BRACHIOPODA CHAP.

Family : Obolidae

Shell varies in shape. Ventral valve provided with pedicular groove
or foramen. Cardinal border thickened. No brachial supports. Shell
composed of alternating chitinous and calcareous layers.

(For muscles see p. 496.)

RawcE.—Lower Cambrian to Devonian.

PRINCIPAL GENERA.—Obolus, Obolella, Kutorgina, Linnarssonia, Siphono-
treta, Acrotreta, Neobolus.

Family : Discinidae

Shell rounded, valves more or less conical, fixed by pedicle passing
through slit or tubular foramen in ventral valve. No calcified brachial
supports. Shell structure chitino-calcareous.

RanGE.— Ordovician to Recent.

PRINCIPAL GENERA.—Discina, Orbiculoidea, Trematis.

Family : Craniidae

Shell calcareous, subcircular ; fixed by surface of ventral valve ; dorsal
valve the larger, depressed-conical. Shell structure punctate.

Four principal muscular scars in each valve, with central triangular pro-
tuberance in ventral valve (see p. 476).

RanGE.—Ordovician to Recent.

PRINCIPAL GENUS.—Crania.

Family : Trimerellidae

Shell thick, calcareous, inequivalve; beak of ventral valve usually
prominent ; rudimentary teeth may be present ; hinge area well developed,
with psendo-deltidium. In interior of valves muscular platform, “ crescent,”
and sometimes sub-umbonal chambers (see p. 494, Fig. 323).

Ranex.— Ordovician and Silurian ; maximum in Wenlock.

PRINCIPAL GENERA.—Trimerella, Monomerella, Dinobolus, Rhinobolus.

Il. TrsrrcARDINES

Family : Productidae

Shell entirely free, or fixed by ventral valve or spines. Concavo-convex,
more or less covered with tubular spines. Hinge line straight. Hinge-teetl
absent or rudimentary.

Cardinal process prominent.

Reniform impressions in dorsal valve.

(For muscular impressions see p. 501, Fig. 333.)

RancE—Silurian to Permian. Genus Productus very characteristic of
the Carboniferous.

PrINcIPAL GENERA. -— Productus, Chonetes, Strophalosia, Proboscidella,
Aulosteges.

XVIII SYNOPSIS OF FAMILIES 505

Family : Strophomenidae

Shell very variable in shape ; concavo-convex, plano-convex, or biconvex ;
hinge line usually straight ; frequently with an area on each valve ; foramen
may or may not be present. Shell structure near always punctate. Ventral
valve usually furnished with hinge-teeth ; and dorsal valve with cardinal
process.

Brachial supports completely absent or very rudimentary.

(For muscular impressions see p. 502, Fig. 334.)

RanGE.—Wholly Palaeozoic.

PRINCIPAL GENERA. — Orthis with many sub- genera, Clitambonites,
Skenidium, Strophomena, Orthothetes, Leptaena, Stropheodonta, Plectambonites.

Family : Koninckinidae

Shell plano-convex or concavo-convex. Brachial apparatus composed of
two lamellae spirally enrolled in the same plane, or in the form of depressed
cones, with the apices directed into the ventral valve.

RanGE.—Silurian to Lias.

PRINCIPAL GENERA.—Koninckina, Koninckella, Coelospira, Davidsonia.

Family : Spireferidae

Shell biconvex. Brachial apparatus consisting essentially of two descend-
ing calcareous lamellae which by spiral enrolment form a pair of laterally-
directed cones (Fig. 330).

RaneGE.—Chiefly Palaeozoic, but a few forms pass up into the Lias.

PRINCIPAL GENERA.—Spirifera, Cyrtia, Uncites, Athyris, Merista.

Family : Atrypidae

Brachial apparatus consists of two descending calcareous lamellae which
bend outwards at the extremity of the crura and are coiled into two spiral
cones, the apices of which either converge towards each other (Glassia) or
towards the dorsal valve (Atrypa, Fig. 332), or diverge towards the dorsal
valve (Dayia) ; shell structure impunctate.

RanGcE.— Ordovician to Trias.

PRINCIPAL GENERA.— Atrypa, Dayia, Glassia.

Family : Rhynchonellidae

Shell biconvex, hinge line usually curved.

Beak of ventral valve incurved, with foramen.

Calcareous brachial supports reduced to a pair of short curved crura.

The septa, dental and socket plates may be highly developed and divide
up the cavity of the shell into chambers (Stenochisma, Conchidium).

Shell structure fibrous, rarely punctate ; muscular impressions as in
Tercbratulidae.

Raner.— Ordovician to Recent : majority of the genera are Palaeozoic.

PRINCIPAL GENERA.— Rhynchonella (Fig. 327) Stenochisma, Stricklandia,
Conchidiwm.

506 FOSSIL BRACHIOPODA CHAP.

Family : Terebratulidae

Shell structure punctate.

Arms supported by a calcareous loop, usually bent back on itself.

(For muscular impressions see p, 502, Figs. 328, 329.)

Beak of ventral valve perforated by foramen, furnished with deltidium.

RaneE.— Devonian to Recent ; maximum development in Mesozoic times.

PRINCIPAL GENERA.—Terebratula, Terebratulina, Waldheimia, Terebratella,
Kingena, Magas, Centronella.

Family : Argiopidae.

Large foramen for passage of pedicle. Marginal septa present in both
valves. Calcareous brachial loop follows margin of shell and is more or less
fused with the septa. Shell structure punctate.

RANGE Jurassic to Recent.

PRINCIPAL GENERA. Argiope, Cistella.

Family : Stringocephalidae

Shell subcireular, punctate. Cardinal process highly developed, bifid.
Brachial apparatus composed of two calcareous free lamellae, prolonged at
first downwards, then bent back, upwards and outwards to run parallel to
margin of shell and to unite in front, thus constituting a wide loop.

RaNGE.—Silurian and Devonian.

SOLE GENvus.—Stringocephalis.

Family : Thecidiidve

Shell usually fixed by beak of ventral valve, plano-convex. Sub-cardinal
apophysis in ventral valve for attachment of occlusors. Marginal septa in
dorsal valve. Caleareous brachial loop more or less fused with shell, and
with calcareous spicules of mantle. Shell structure: inner layer fibrous,
outer layer tubulated.

RaNnGE.— Carboniferous to Recent.

PRINCIPAL GENERA.—Thecidium, Uldhamina.

STRATIGRAPHICAL DISTRIBUTION OF BRACHIOPODA

It is remarkable that some of the earliest types of Brachiopoda
exist generically unchanged at the present day. Such are Lingula,
ranging from the Cambrian; Discina, and Crania, ranging from
the Ordovician ; and amongst the hinged forms Zerebratula from
the Devonian, and Rhynchonella from the Ordovician.

In the lowest Cambrian (Olenellus beds) the most important
genera are Linnarssonia and Kutorgina. The hinged forms
appear in the Cambrian, being represented by Orthis; but the
majority in this formation belong to the Ecardines. Lingula,
Lingulella, and Obolella are characteristic.

In the Ordovician many new genera of the Testicardines

XVIII STRATIGRAPHICAL DISTRIBUTION 507

make their appearance, such as Strophomena, Leptaena, Atrypa,
Rhynchonella, Clitambonites, etc., but the extraordinary abundance
and variety of Orthis is most remarkable. The Ecardines are
reinforced by such forms as Zrematis and Siphonotreta. It is,
however, in the Silurian that the Testicardinate Brachiopoda
attain their maximum, for in addition to a great development of
species amongst the older forms, a host of new genera for the
first time oceur here (Spirifera, Athyris, Conchidium, Stricklandia,
Chonetes, Cyrtia, etce.); and the Zrimerellidae are especially
characteristic of the Wenlock.

With the commencement of Devonian times many species and
genera become extinct, but new forms come in (Terebratula,
Orthothetes, Productus, ete.), and some genera are wholly confined
to this formation (Uncites, Stringocephalus). The Carboniferous is
marked by the maximum development of Productus and Spirifera;
Orthothetes, Stenochisma, and Athyris are also abundant, but there
is a considerable extinction of the older genera and species, and a
ereat diminution in the number of individuals and species of
those that persist.

A further reduction occurs in the Permian, where the most
important genera are Productus, Strophalosia, and Stenochisma ;
but Aulosteges is a new form pecuhar to this period. In the
Trias a new era commences; the principal families and genera
of the older rocks disappear entirely ; a few spire-bearing genera
persist (Spiriferina, Athyris), and the genus Koninekina 1s
restricted to this formation.

The enormous development of species of the Terebratulidae
and Rhynchonellidae is the most noticeable feature in Jurassic
times; and a few ancient types linger on into the Lias (Spiri-
ferina, Suessia, a sub-genus of Spirifera); Koninckella here occurs.

The Cretaceous Brachiopoda are closely allied to the Jurassic ;
Magas and Lyra are peculiar to the period,and the Terebratulidae
and Rhynchonellidae are very abundant, together with the
Ecardinate genus Crania.

With the commencement of Tertiary times the Brachiopoda
have lost their geological importance, and have dwindled down
into an insignificant proportion of the whole Invertebrate fauna.

The distribution of the Brachiopoda in past time is shown
in the following table :—

Palaeozoic Mesozoic

+
5
i} | = ry
f=I 3 [| D
| = iS) = S Bs 5 2 3 Pe ww
Fa S = oI S| 3 = = Z
| @ | 6 |e (8 | S hee lg |e oles eee
= i) = = r= m = e > BH °
| 3 e =| = Co @ m e = & 3
| ‘S) 2) n - S) a x 5 iS a aa]
ECARDINES rr F
| Lingulidae Moxbategoh key pe fp Sg. | eee
Lingulella . . |__ |

| Obolidae Obolus =) cook ae | | |
| Obdedlay | | |
Ikquinonfeaey GG J |
Linnarssonia . |___
‘remvatish Wee pee | aoe
Siphonotreta . —— |

Acrotreta . . as | | |
Discinidae Discinay tne jeoeees Ee
_ Craniidae Cranial) 4: aa | |
_ Trimerellidae Trimerella . . es

Dinobolus .. ae

TESTICARDINES |
Productidae Productus . . | a Nal a
Chonetes . . DE sr PE

Strophalosia . ee ee |

iStrophomenidae, JOrthise =, 9) 2-2 ae
Skenidium .. ee |e
Clitambonites . —
Strophomena . ee)
Stropheodonta . RS a ea
Leptaena | |
Orthothetes . a ae
Davidsonia. . |jcoa

Koninckinidae Koninckina. . Le ES)
Konineckella .
Spiriferidae Spirifera . |

Spiriferina .. | Lise
Cymtiay jee te —— |
Syringothyris . Lia et
| Uncites ss) s- Paseo
| INDRA 5 5c pe al PS |S re Eh ee
| iMeristasyaet el
Retzia
Atrypidae Atrypa :
Dayia =... —
Coelospira .. ees
Rhynchonellidae Rhynchonella . | eens tee
Stenochisma . ee ae es
Stricklandia . —
Conchidium . ———

Terebratulidae Terebratula. . a

Terebratulina

Waldheimia | Lect
Terebratella

Kingena. . . | ——|——_

Centronella . ————

Maras! a —.

Argiopidae Argiope .

| Stringocephalidae Stringocephalus ——

Oldhamina. . =

Cistella. . acre

Thecidiidae Thecidium . . | | ee

CHAP. XVIII PHYLOGENY AND ONTOGENY 509

PHYLOGENY AND ONTOGENY

Wherever successive stages in the life history of an individual
resemble in important anatomical features the adult imdividuals
of other species occurring in successive members of a strati-
graphical series, the development of the individual may be
regarded as an epitome of the development of the species; it
also generally throws light on the origin and relationships of
allied genera and families.

In the case of the fossil Brachiopoda comparatively lttle
work has yet been done in tracing their ontogeny or phylogeny,
though the abundance, variety, and excellent state of preserva-
tion of the extinct species offer a promising field for investiga-
tion. It is to Dr. C. E. Beecher and other recent American
palaeontologists that we owe our advance in this branch of the
subject.

In the first place, in about forty genera, representing nearly
all the leading families of the group, the important fact has been
established of the presence of a common form of embryonic shell,
termed the “ protegulum,” which is “ semicircular or semielliptical
in shape with a straight or arcuate hinge line and no hinge
area” (Beecher). Its minute size and delicate texture cause its
preservation to be rare, but its impression is not uncommonly
left on the beak of the adult shell.

The main features of this embryonic shell are exhibited in the
adult Lower Cambrian Brachiopod Obolus (Kutorgina) labradoricus
(Billings); the sub-equal semielliptical valves have lines of growth
running concentrically and parallel to the margin of the shell,
and ending abruptly against the straight hinge lne; and this
indicates that there has been no change in the outhne and
proportions of the shell during its stages of growth, but only a
general increase in size. It is very significant that we have
here a mature type possessing the common embryonic characters
of a host of widely separated genera, and we may therefore regard
it as the most primitive form known.

Many genera pass through this so-called “ Paterina” stage
either in the case of both their valves, or more generally in the
case of the dorsal valve only; but modifications in the form of
the protegulum arise, which are due to the influence of accelerated

l Amer. Jour. Science, 1890-1893.

510 FOSSIL BRACHIOPODA CHAP.

growth, by which features belonging to later stages become
impressed on the early embryonic shell. The most variable and
specialised. valve—the ventral or pedicle valve—naturally ex-
hibits the effect of this influence first and to the greatest
extent. The Palaeozoic adult forms of many species represent
various pre-adult stages of the Mesozoic, Tertiary, and Recent
species, as is especially well shown in the genera Orbiculoidea and
Discinisea.

In the Strophomenoid shells the protegulum in the dorsal
valve is usually normal, but in the ventral valve abbreviation
of the hinge and curvature of the hinge line are produced by
acceleration of the “ Discinoid stage” in which a pedicle notch
is present.

No marked variation has yet been noticed in the spire-bearing,
or Terebratuloid, or Rhynchonelloid genera.

The form of the shell and the amount of difference in shape
and size of the valves seem to be largely due to the length of the
pedicle and its inclination to the axis of the body, as evidenced
by the development of Zerebratulina. A series showing progressive
dissimilarity of the two valves arising from these causes can be
traced from Lingula to Crania. The greater alteration that takes
place in the ventral valve appears to be due to its position as
lower and attached valve. If the pedicle is short a transversely-
expanded shell with long hinge lne results when the plane of
the valves is vertical or ascending, but when the latter is hori-
zontal a Discinoid form is found. This mode of attachment is
often accompanied by a more or less plainly developed radial
symmetry. Shells with long pedicles, on the other hand, are
usually longer than wide.

The character of the pedicle-opening is of great significance
from an evolutional and classificatory point of view, for the sue-
cessive stages through which it passes in embryonic growth are
chronologically parallelled by different genera, and are likewise
accompanied by the successive acquisition of other important
anatomical characters, as has been shown by Beecher and others.
The first and simplest type of pedicle opening is in shells with a
posterior gaping of the valves, where the pedicle protrudes freely
between them in a line with the axis, and the opening is shared
by both valves, though generally to a greater extent by the ven-
tral valve. Paterina ( = Obolus labradoricus) and Lingula furnish

XVIII PHYLOGENY AND ONTOGENY By lel

examples of this type. In the second type the pedicle opening is re-
stricted to the ventral valve, and the direction of the pedicle makes
a right angle with the plane of the valves; in the lower forms
the pedicle lies in a slit or sinus (Zrematidae), but by further
specialisation it becomes enclosed by shell growth so as to lie
within the periphery, and finally becomes subcentral in some
genera (Discinidae). The third type shows the pedicle opening
contined to the ventral valve and submarginal. A pseudo-delti-
dium may preserve the original opening (Clitambonites); or this
shelly plate may become worn away or reabsorbed in the adult so
that the deltidial fissure through which the pedicle passes
remains quite open (Orthidae). In the fourth type the incipient
stage marks a return to the simple conditions of the first type ;
but ultimately a pair of deltidial plates develop, and may com-
pletely limit the pedicle opening below. Examples of this type are
Spirifera and Rhynchonella. By means of these four types the
Brachiopods have been divided into four Orders: the Atremata
(type i1.); the Neotremata (type i1.); the Protremata (type iii.);
and the Telotremata (type iv.).

The Velotremata were the last to appear, but the four types of
pedicle-opening with the various forms of calcareous brachial
apparatus were in existence in the Bala period of the Ordovician.

As Paterina is the most primitive form of all, we may place it
at the root of the phylogenetic tree. From it sprang the Atremata,
which gave off the Neotremata and Protremata ; the most primi-
tive Neotremata seem to be the Trematidae, while the connecting
link between the Protremata and <Atremata is furnished by the
Kutorgimdae. From the genus Conchidiwm and its allies we
may see how the Rhynchonellidae ushered in the Telotremata as
an offshoot from the Protremata. The Telotremata subsequently
gave off two main branches, which became specialised with the
loop-bearing and spire-bearing forms respectively.

The evolution and mutual relationships of genera have been
indicated with much probability by Hall, Clarke, and others.
The Obolelloid type may be connected with the Linguloid by
means of Lingulella and Lingulepis, while in Lingula itself we
find the point of divergence for the ancestors of Zrimerella, and
for a line of variation culminating in Dignomia. The Palaeo-
zoic Rhynchonelloids branched off at an early period from the
same stock as Orthis, and are connecting links between this

512 FOSSIL BRACHIOPODA CHAP. XVIII

genus and Mesozoic Rhynchonellae; and a whole series of genera
exhibit intermediate stages of structure between the Rhyn-
chonelloid and Pentameroid groups. The Terebratuloids can be
traced back to the primitive type Renssoellaria ; and amongst
spire-bearing forms, the protean genus Spirifera can be split up
into groups of species which diverge along lines tending to forms
no longer congeneric. When we come to deal with specific
differences we find frequently such a host of intermediate varieties
that the separation of many species, as in the case of Mesozoic
Terebratulae, is to a large extent arbitrary and artificial.

INDEX

References to figures are printed in thick type (248, 197) ; to systematic position,
in italics (397, 430)

ABRALIA, 391

Absorption of internal portions of shell,
259

Abyssal Mollusea, 374

Acanthinula, 441

Acanthoceras, 399

Acanthochiton, 403, 403

Acanthodoris, 434

Acanthopleura, 403 ; eyes, 188

Acavus, 303, 304, 335, 441

Acera, 245, 430

Achatina, 278, 328-337, 333, 442, 443;
jaw, 211; food, 33; size of egg, 124;
A. fulica, 279

Achatinella, 278, 326, 327, 443 ; radula,
234; musical sounds, 51

Achatinelloides, 332

Acicula, 287, 296, 414

Acmaea, 405; radula, 227

Acme, 414

Acmella, 314, 415

Acroptychia, 336, 414

Acrotreta, 504, 508

Actaeon, 250, 427, 428, 429 ; radula, 217,
230 ; streptoneurous, 203 n.

Actaeonella, 430

Actaueonia, 432

Actaeonina, 250, 429

Actinoceras, 394

Actinodonta, 447

Acusta, 306, 316, 318, 441

Adacna, 12, 297, 455

Adalaria, 434

Adamsiella, 414

Addisonia, 412

Adelphoceras, 395

Adeorbis, 416

Admete, 426

Aegires, 434

Aegista, 305, 316, 441

Aegoceras, 398

VOL. III

Aeolis, 10, 152, 432; radula, 217,
229; stinging cells, 65; mimicked
by Sagartia, 68; warning coloration,
72

Aerope, 328, 333, 440;
habits, 54

Aestivation, 25

Aetheria, 328-336, 452 ; variation, 92

Africarion, 333, 440

Agaronia, 426

Age of snails, 39

Aglossa, 7

Agnatha, habits, 51

Akiodoris, 434

Alaba, 415

Alaria, 418

Alariopsis, 420

Albersia, 320

Albino varieties, 87

Alcadia, 348-351, 410

Alderia, 432

Alexia, 439

Alicia, 459

Allognathus, 441

Allopagus, 452

Alloposidae, 384

Alvania, 415

Alycaeus, 266, 302 f., 309, 319, 414

Amalia, 440

Amalthea, 78

Amaltheus, 398

Amastra, 443

Amaura, 411

Amberleya, 409

Ambonychia, 449

Amicula, 404

Ammonites, 247, 393, 398, 398 ; sutures,
396 ; aptychus, 397

Ammonoidea, 396 f.

Amnicola, 325, 415

Amoria, radula, 222

radula, 215;

514

MOLLUSCA— BRACHIOPODA

Ampelita, 335, 442

Aimphibola, 10, 18, 439; breathing, 151 ;
radula, 236

Aimphibulimus, 352, 442; radula, 233

Amphidoxa, 358

Amphidromus, 301, 305, 317, 310, 359,
442; vradula, 233

Amphineura, 8, 400; breathing organs,
154, 168; nervous system, 203; geni-
talia, 145

Amphipeplea, 439

Amphiperas, 419

Amphisphyra, 430

Amphissa, 423

Amphitretus, 383

Ampullaria, 17, 416; self-burial, 42 ;
spawn, 125; breathing organs, 151,
158 ; jaws, 212; shell, 249, 263 ; oper-
culum, 268 ; distribution, 294, 320,
322, 343, 359

Ampullarina, 302, 439

Ampullina, 411

Aimussium, 450

Amycla, 423

Anabathron, 415

Anachis, 423

Anadenus, 24, 441

Anal glands, 241

Anal siphon, 164, 173

Anastomopsis, 442

Anatina, 274, 275, 459

Anatinacea, 458 ; gills, 167

Anaulus, 414

Anchistoma, 293, 296

Ancilla, 267, 426

Ancillina, 426

Ancistrochirus, 3891

Ancistromesus, 405

Ancistroteuthis, 391

Ancula, 434; radula, 229, 230; warning
coloration, 72

Anculotus, 417

Ancyloceras, 247, 399

Ancylus, 19, 439 ; breathing, 162 ; hiber-
nating, 27 ; radula, 235

Aneitea, 325, 443

Angitrema, 340, 417

Anisocardia, 451

Anodonta, 259, 341, 452 ; shower of, 47 ;
variation, 92; Glochidiwm, 147 ; gill,
167; otocyst, 197; nervous system,
206 ; hinge, 274; A. anatina, 24; dis-
tribution, 282

Anodontopsis, 451

Anoglypta, 325, 441

Anomia, 257, 448, 464; intestine, 241 ;
byssus hole, 262 ; hearing, 196

Anomiacea, 44S

Anoplophora, 451

Anostoma, 248, 266, 356, 358, 442 ; aper-
ture, 63

Anthracosia, 451

Anura, 424

Anus, 209, 241

Apera, 334, 440

Aperostoma, 344, 414

Aphanotrochus, 408

Aphelodoris, radula, 230

Apicalia, 422

Aplacophora, 9, 404; radula, 228

Aplecta, 354, 439

Aplustrum, 245, 428, 430; radula, 230

Aplysia, 245, 428, 431; stomach, 239 ;
purple fluid, 65

Aplysioidea, 430

Aporrhais, 418 ; radula, 215

Apricardia, 455

Aptychus, 397

Aptyxiella, 417

Aptyxis, 424

Aral Sea, Limnaea from near, 84; Car-
dium from, 91

Arca, 14, 171, 278, 448; eyes, 191

Arcacea, 448

Arcachon, oyster-parks at, 105

Arcestes, 397

Archidoris, 484, 434; protective colora-
tion, 73

Architeuthis, 378, 390, 390 ; sucker, 381

Arcomya, 458

Arconaia, 807, 452

Arctic shells, colour of, 86

Arcuella, 422

Argiope, 470, 472, 479, 487 ; parasite of,
485 ; distribution, 486 ; fossil, 501, 506,
508

Argiopidae, 506, 508

Argobuccinum, 420

Argonauta, 383, 383; egg-laying, 127 ;
hectocotylised arm, 137 ; radula, 236

Arinia, 413

Ariolimax, 441, 3413 radula, 233

Arion, 440; shell, 175, 245, 246 ; hardier
than Helix, 24; voracity, 30 f.; egg-
laying, 42 f. ; protective coloration, 70 ;
pulmonary orifice, 160 ; food, 179:
smell, 193 f.; radula, 283 ; distribution,
285

Arionta, 341, 353, 441

Ariophanta, 301, 308, 309, 316, 440 ; pro-
tective coloration, 70

Aristotle, on modified arm of polypus, 138

Artemis, 454

Arthuria, 403

Asaphis, 456

Ascoceras, 3894

Ascoglossa, 11 n., 431

Ashford, C., on pulsations of heart in
Helix, 26; on homing of Helix, 35; on
dart-sac, 143

Asolene, 416

Aspergillum, 262, 459

Aspidelus, 329, 440

Aspidoceras, 399

INDEX

515

Assiminea, 415

Astarte, 451

Asthenothaerus, 459

Astralium, 409

Athoracophorus, 443—see Janella

Athyris, 499, 500, 505; stratigraphical
distribution, 507, 508

Atilia, 423

Atlanta, 421, 422; foot, 200

Atopocochlis, 330, 441

Atremata, 511

Atretia, distribution, 486, 487

Atrypa, 501, 502, 505; stratigraphical
distribution, 507, 508

Atrypidae, 501, 505, 508

Aturia, 3938, 395

Atys, 428, 430

Aucapitaine, H.,
38

Aucella, 449

Aulopoma, 157, 304, 414;
269

Aulosteges, 504; stratigraphical distribu-
tion, 507

Auricula, 439, 439

Auriculella, 327, 443

Auriculidae, 17, 18, 260, 439, 439 ; lung,
160; eyes, 186; radula, 235

Austenia, 301, 304, 440

Avellana, 430

Avicula, 254, 258, 449, 449; eyes, 190;
genital orifice, 242; A. margaritifera,
100

Aviculopecten, 450

Aviculopinna, 449

Axinus, 452

Azeca, 442

Azygobranchiata, 155, 407

on tenacity of life,

operculum,

BABINKA, 447

Bactrites, 395

Baculites, 399

Baikalia, 290, 415

Baird, Mr., on the British Museum snail,
37

Balea, 442; B. perversa, 24, 41

Baltic, fauna of the, 12, 83, 366

Bankivia, 408

Barbatia, 448

Barleeia, 415

Barnacle, Rev. H. G., on musical sounds
produced by Mollusca, 51

Barometers, snails as, 50

Bartlettia, 452

Basilissa, 376, 408

Basommatophora, 11, 19, 181, 438

Basterotia, 451

Bateson, W., on variation in Cardiwm, 91 ;
on hearing in Anomia, 196

Bathmoceras, 395

Bathydoris, 433

Bathyteuthis, 390

| Batissa, 320, 453

Beddomea, 304

Beecher on phylogeny, 509

Beetles, prey on Mollusea, 58

Bela, 426 ; radula, 219

Belemnites, 380

Belemnitidae, 387

Belemnosepia, 390

Bellerophon, 266, 407

Beloptera, 380

Belopteridae, 388

Belosepia, 386, 388

Beloteuthis, 390

Bembizx, 376, 408

Benedictia, 290, 415

Benthobia, 377

Benthodolium, 377

Berendtia, 441

Beudant, experiments on Mollusca, 12

Bideford Bridge and mussels, 117

Binney, Dr., on epiphragm, 28

Binneya, 341, 441

Biradiolites, 456

Birds, devour Mollusca, 56 f.

Bithynella, 289, 293, 415

Bithynia, 336, 342, 415; stomach, 239 ;
habitat, 25

Bittium, 416

Bluesospira, 346, 351

Blandiella, 16, 414

Blanfordia, 414

Blind Mollusca, 185

Blood, 171

Bodo, land Mollusea, 24

Boeuf and French oysters, 107

Bolma, 409

Boltenia, 346

Boreofusus, radula, 221

Bornella, 433 ; stomach, 239

Borsonia, 426

Borus, 356-358, 441

Bourcieria, 357, 410

Bourgquetia, 417

Bourguignatia, 382

Bouvier—see Fischer

Boysia, 302, 442

Brachial apparatus, types of, 500

Brachiopoda, fossil, limestone formed of,
492; shell, 493, 497 ; muscle scars on,
494, 501; platform, 495 ; synopsis of
families, 503 ; stratigraphical distribu-
tion, 506; phylogeny and ontogeny,
509 ; Orders, 511

Brachiopoda, recent 463 ;
account of, 464; shell, 465; body,
469; digestive system, 471; body
cavity, 472; heart, 473; excretory
organs, 474; muscles, 475; nervous
system, 478 ; reproductive system, 478 ;
embryology, 479; habits, 482; distri-
bution, 484 ; classification. 487 ; affini-
ties, 487

historical

516

MOLLUSCA—BRACHIOPODA

Brachytrema, 417

Brackish-water species, 14

Branchiae, 151, 153, 164

Branchial siphon, 155, 164, 173

Braun, on self-impregnation, 44

Breathing organs — see Respiration,
Branchiae

Brechites, 459

Breeding, periodicity in, 129

Broderipia, 408

Brotia, 305

Brownia, 138

Buccinanops, 423

Buccinopsis, 424; radula, 221, 222; egg-
laying, 128

Buccinum, 6, 424; radula, 217 ; mons-
trosity, 251; breeding, 129; osphra-
dium, 195; spawn, 126

Buliminus, 24, 278, 285, 295 f., 316, 331,
339, 442; protective habits, 70; B.
pallidior, 38

Bulimulus, 278, 334, 339-359, 442;
jaw, 211, 233; radula, 233; variation,
87

Bulimus, 278, 342-359, 355, 447; radula,
233 ; egg, 124

Bulinus—see Tsidora

Bulla, 428, 430

Bullia, 155, 423 ; habits, 192; foot, 198 ;
radula, 221

Bulloidea, 429

Burrowing Mollusca, 446

Burying propensities of Mollusca, 27,

Busycon, 4243; money made from, 97 ;
egg-capsules, 125—see Fulgur

Butterell, Mr., on habits of Testacella,
52

Byssocardium, 455

Byssus gland, 201

CADLINA, 434

Cadoceras, 393

Cadulus, 376, 445

Caecilianella, 442;
186

Calcarella, 133

California, land Mollusca, 280

Calliostoma, 408 ; jaws, 212

Callistochiton, 403

Callochiton, 403

Callogaza, 408

Callonia, 442

Callopoma, 409

Calina, protective coloration, 74

Calybium, 410

Calycia, 320, 442

Calycidoris, 434

Calyptraea, 248, 412

Camaena, 305, 306, 315, 316, 441

Cambrian, Mollusca of the, 2

Camitia, 409

habitat, 48; eyes,

Campaspe, 433

Camptoceras, 302

Camptonyx, 278, 302, 439

Campylaea, 285, 289 f., 293, 441

Canal, 155

Cancellaria, 426

Canidia, 16, 305, 423

Cannibalism in snails and
33

Cantharidus, 408

Cantharus, 275 ; radula, 222

Caprina, 456

Caprotina, 456

Capulus, 412

Caracolus, 347-351, 441

Carbonicola, 451

Cardiacea, 454

Cardiapoda, 421

Cardilia, 454

Cardinal plate, 500

Cardinal process, 497, 501

Cardinalia, 408

Cardinia, 451

Cardita, 273, 451

Carditella, 451

Carditopsis, 451

Cardium, 6, 273, 455, 455; C. edule, 12,
164; modifications, 12; variation, 84,
91; nervous system, 207; distribution,
292, 297

Carelia, 327, 443

Carinaria, 9, 422, 422; foot, 200

Carinifex, 439

Carolia, 448

Cartusiana, 296

Carychium, 18, 439

Caryodes, 325, 359, 441

Casella, radula, 230

Caspia, 12, 297

Caspian Sea, fauna, 12, 297

Cassidaria, 420

Cassidula, 18, 278, 439, 439

Cassis, 255, 420; radula, 223

Castalia, 344, 452

Cataulus, 266, 304, 157, 414

Caterpillars mimicking Clausilia, 68

Cathaica, 316, 441

Catinella, 443

Cavolinia, 158, 436 ; eyes, 186

Cecina, 414

Cenia, 432; breathing, 152

Centrodoris, 434; radula, 230

Centronella, 499, 506, 508

Cephalopoda, 378 f.; defined, 5; ink,
65; egg-laying, 127; embryo, 133;
branchiae, 168 ; osphradium, 195 ; foot,
200; nervous system, 206 ; jaws, 213 ;
radula, 236

Cepolis, 349-351, 441

Cerastoma, 423

Cerastus, 331, 441

Cerata of Nudibranchs, 71, 159

slugs, 32,

INDEX

DE,

Ceratites, 397, 398 ; suture, 396

Ceratodes, 357, 416

Ceres, 21, 354, 410

Ceritella, 417

Cerithidea, 260, 417; C. obtusa, breath-
ing, 152

Cerithiopsis, 417

Cerithium, 16, 416

Ceromya, 458

Chaetoderma, 404, 404 ; breathing organs,
154; nervous system, 203 ; radula, 217,
228

Chaetopleura, 403

Chama, 257, 272, 446, 455

Chamostrea, 458

Changes in environment, effect of, 83 f.

Chank-shell, fishery of, 100

Charis, 324, 442

Charopa, 319, 323-327, 441

Chascax, 424

Chelinodura, 430

Chelotropis, 133

Chenopus, 418

Chilidium, 498

Chilina, 19, 3843, 358

Chilinidae, 439; radula, 236

Ohilotrema, 441

China, use of shells in, 101

Chiropteron, 133

Chiroteuthis, 385, 391

Chiton, 8, 158, 403; egg-laying, 126;
breathing organs, 153 f.; eyes, 188;
osphradium, 195 ; radula, 228 ; nervous
system, 203; valves, 401, 402; girdle,
403

Chitonellus, 404, 404; vaives, 401

Chittya, 16, 348, 351, 414

Chlamydephorus, 333, 440

Chlamydoconcha, 175, 245, 453

Chlamys, 450

Chloritis, 306, 311, 3819-324, 441

Chlorostoma, 408

Chlorostracia, 307

Choanomphalus, 250, 290, 439

Chondrophora, 389

Chondropoma, 346-355, 348, 414

Chondrula, 285, 295, 296, 442

Choneplax, 404

Chonetes, 504; stratigraphical distribu-
tion, 507, 508

Choristes, 420

Choristoceras, 398

Chorus, 423

Chromodoris, 4345 jaws,
230

Chrysallida, 422

Chrysodomus, 423

Chrysostoma, 409

Cingula, 415

Cingulina, 422

Cionella, 442

Circe, 454, 458

212; radula,

Circulatory system, 169
Circulus, 408

» Circumpolar species, 287

Cirrhoteuthis, 381, 382

Cistella, 467, 470, 472, 475, 476, 479,
480, 487 ; larvae, 481, 483; parasite
of, 485 ; distribution, 486 ; fossil, 506,
508

Cistopus, 385

Cistula, 349, 351, 355, 414

Cladohepatica, 432

Clanculus, 408

Classification, 5, 8; of Gasteropoda, 8,
11

Clathurella, 426

Clausilia, 442, 442; mimicked by cater-
pillars, 68 ; monstrosity, 251; distribu-
tion, 285 f., 294, 305-318, 332, 3839-356;
C. rugosa, 24; scalaris, 278

Clavagella, 262, 459

Clavator, 335, 359, 441

Clavatula, 426

Clavella, 424

Claviger, 329, 417

Clea, 16, 305, 423

Clementia, 454

Cleodora, 436, 436

Cleopatra, 294, 328, 331, 336, 476

Clessin, on duration of life, 39

Olessinia, 12, 297

Clio, 436, 436

Cliona, enemy of oysters, 112

Clione, 158, 438

Clionopsis, 437

Clitambonites, 498, 505; stratigraphical
distribution, 507, 508, 511

Clithon, 327, 410

Clydonites, 398

Clymenia, 897

Clypidella, 406

Cocculina, 408

Cochlicella acuta, 278

Cochliolepas, 77

Cochloceras, 398

Cochlodesma, 459

Cochlostyla, 124, 278, 313, 315, 441

Cockles, use of, 101, 118

Coecum, 247, 260, 417, 418

Coeliaxis, 334, 442; habitat, 49

Coelocentrum, 353, 442

Coelospira, 505, 508

Cold winter, effect on oysters, 112; on
mussels, 116

Collinge, W. E., on growth and burial of
shells, 41

Collisella, 405

Collisellina, 405 ; radula, 227

Collonia, 409

Colobocephalus, 430

Colour of arctic shells, 86

Colpodaspis, 430

Columbarium, 426

518

MOLLUSCA—-BRACHIOPODA

Columbella, 423 ; radula, 222

Columbellaria, 420

Columbellina, 420

Columna, 328, 330, 443

OCominella, 16, 424

Composition of shell, 252

Concha, 463

Conchidium, 497, 498, 500, 505 ; strati-
graphical distribution, 507, 508, 511

Concholepas, 267, 423

Conidea, 423

Conocardium, 455

Conorbis, 426

Conus, 247, 275, 426 ; poisonous bite, 65 ;
tooth, 66 ; shell, 69, 255, 260; mimicked
by Strombus, 69 ; prices given for rare,
121; spawn, 125; radula, 218, 220;
operculum, 269

Cookia, 409

Coptochilus, 314, 414

Coralliophaga, 451

Ooralliophila, 75, 423

Coralliophilidae, radula, 216

Corainbe, 434

Corasia, 311, 319-321

Corbicula, 15, 288, 292 f., 453

Corbis, 452

Corbula, 456

Corilla, 303

Corona, 27, 442

Ooronaria, 297

Coryda, 346-351, 441

Coryphella, 432

Cosmoceras, 399

Cowry used as money, 96

Coyote trapped by Haliotis, 57

Cranchia, 391

Crania, 464, 467, 468, 469,
473, 475, 476, 477, 487; distribu-
tion, 485 ; fossil, 493, 494, 504 ; strati-
graphical distribution, 506, 507, 508,
510

Craniidae, 487, 496, 504, 508

Cranopsis, 265, 406

Craspedochiton, 403

Craspedopoma, 298, 414

Craspedostoma, 408

Crassatella, 451

Cratena, 432

Crawling of Helix, 45

Cremnoconchus, 16, 302, 413

Crenatula, 75, 449

Crenella, 449

Crenipecten, 450

Crepidula, 248, 257, 412, 412; parasitic,
78

Crepipatella, 248, 412

Creseis, 436, 436 ; eyes, 186

Crimora, 434; radula, 229

Crioceras, 247, 399, 399

Oristigibba, 311, 319, 320, 441
‘rossostoma, 408

AGS, Alize

Crucibulum, 248, 412

Cryptochiton, 245, 371, 402, 404

Cryptochorda, 425

Cryptoconchus, 404

Oryptophthalmus, 430

Cryptostracon, 353, 441

Ctenidia, 151—see Branchiae

Ctenopoma, 346-351, 414

Cucullaea, 274, 448

Cultellus, 457

Cuma, 423

Cumingia, 453

Cuspidaria, 459 ; branchiae, 168

Cuvierina, 436, 436

Cyane, 410

Cyathopoma, 247, 268, 314, 358, 414

Cyclas, 453; veliger, 132; ova, 146;
otocyst, 197 ; C. cornea, thread-spinning,
29; distribution, 282

Cyclina, 454

Cyclobranchiata, 156

Cyclocantha, 409

Cyclomorpha, 414

Cyclonassa, 423

Cyclonema, 409

Cyclophoridae, origin, 21

Cyclophorus, 302, 306-319, 329-334, 344,

352-358, 414; jaws, 212; radula,
21
COyclostoma, 328, 331-338, 414, 414;

stomach, 239 ; vision, 184 ; osphradium,
195 ; nervous system, 205; C. elegans,
287, 288

Cyclostomatidae, origin, 21; radula, 224 ;
gait, 199

Cyclostrema, 408

Cyclosurus, 247, 337, 414

Cyclotopsis, 338, 414

Cyclotus, 296, 319, 320, 414

Cylichna, 428, 430 ; radula, 215

Oylindrella, 247, 260, 278, 343-355, 348,
442; monstrosity, 251, 252

Cylindrellidae, radula, 233, 234

Cylindrites, 430

Oylindrobulla, 430

Cylindromitra, 425 ; radula, 222

Cymbium, 255, 367, 425 ; radula, 221

Cymbulia, 437

Cymbuliopsis, 437

Cynodonta, 424

Cyphoma, 419

Cypraea, 178, 419 ; prices given for rare,
122 ; mantle-lobes, 177, 178; radula,
224; shell, 255, 260, 261; C. moneta,
96

Cypraecassis, 420

Cypraedia, 419

Oypraeovula, 419

Cyprimeria, 454

Cyprina, 451

Cyrena, 15, 453; distribution, 285, 294

Cyrenella, 453

INDEX

519

Oyrtia, 505 ; stratigraphical distribution,
507, 508
Cyrtoceras, 394
OCyrtodaria, 457
Cyrtodonta, 452
Cyrtolites, 407
Cyrtonotus, 448
Cyrtotoma, 414
Cysticopsis, 346-351, 441
Cystiscus, 425
Cystopelta, 325, 326, 440
Oytherea, 454, 454

DACRYDIUM, 449

Daedalochila, 441

Dall, W. H., quoted, 35; on branchiae,
164

Damayantia, 440

Daphnella, 426

Darbishire, R. D., on tenacity of life,
39

Dardania, 415

Dart-sac, 142

Daudebardia, 289, 292 f., 440

Davidsonia, 505, 508

Dawsonella, 410

Dayia, 505, 508

Decapoda, 385 f.

Decollation, 260

Deep-sea Mollusca, 374

De Folin, experiment on Cyclostoma, 157

Deianira, 410

Delage, experiments on otocysts, 197

Delphinula, 409

Deltidium, 499

Dendronotus, 433 ; protective coloration,
72; habits, 51

Dentalium, 6, 444, 445; used as money,
97 ; veliger, 131; radula, 228

Dentellaria, 350-355, 441 ;
63

Desert species, 25, 85

Deshayesia, 411

Desmoulea, 423

Development of fertilised ovum, 130 f.

Dexiobranchaea, 487

Diadema, 414

Diala, 415

Dialeuca, 441

Diaphora, 314

Diaphorostoma, 412

Diastema, 418

Diastoma, 417

D “ulula, 434

Dibaphus, 425

Dibranchiata,
system, 207

Diceras, 269, 455

Didacna, 12, 297, 455

Differences of sex, 133

Dignomia, 511

Digonopora, 134, 144

aperture,

380; eye, 183; nervous

Diloma, 408

Dimorphoptychia, 410

Dimya, 450

Dinobolus, 504, 508

Dinoplax, 403

Diotocardia, 9, 170, 405 f.

Diplodonta, 452

Diplommatina, 302-327, 413

Diplomphalus, 322, 323, 440

Diplopoma, 346, 351, 414

Dipsaccus, 424

Dipsas, 307

Discina, 464, 468, 471, 475, 487 ; distri-
bution, 485; fossil, 493, 5045 strati-
graphical distribution, 506, 508

Discinidae, 487, 496, 504, 508, 511

Discinisca, 487, 510; distribution, 485,
486

Discites, 395

Discodoris, 434

Discosorus, 394

Distortio, 255—see Persona

Ditropis, 312, 314, 414

Docoglossa, 227, 405

Dolabella, 428, 431

Dolabrifer, 431

Dolium, 419; acid secretion, 237

Donax, 269, 446, 453

Dondersia, 404

Dorcasia, 333, 441

Doridiuin, 430

Doridunculus, 4343; radula, 229

Doriopsis, 43.4

Doris, breathing
230.

Dorsanum, 423

Dosidicus, 390

Dosinia, 454

Doto, 433 ; protective coloration, 71

Dreissensia, 14, 123, 452; hibernation,
26; singular habitat, 48 ; veliger, 132,
146 ; eyes, 192

Dreissensiomya, 452

Drepania, 434

Drillia, 426

Drymaeus, 356, 442

Dryptus, 356, 441

Durgella, 301, 304, 440

Dwarf varieties, 88

Dybowskia, 290

organs, 159; radula,

EASTONTA, 454

Eburna, 267, 424; radula, 220

Ecardines, 466; muscles, 476;
493 ; families, 487, 503, 508

Eccyliomphalus, 413

Echinospira, 133

Edentulina, 338

Egg-laying of Arion, 42 f.; of Mollusca
generally, 123

Eglisia, 411

Hider-duck, shells used by, 102

fossil,

520

MOLLUSCA——BRACHIOPODA

Elaea, 322, 440

Elasmoneura, 411

Eledone, 385, 385 ; radula, 236

Elizia, 456

Elysia, 432; protective coloration, 73 ;
breathing, 152; radula, 217, 230, 432

Emarginula, 265, 406

Embletonia, 429

Eimmerieia, 415

Ena, 296, 442

Enaeta, 425

Endoceras, 394

Endodonta, 325, 334, 441

Engina, 424

Enida, 408

Ennea, 298, 302, 306, 309, 314, 316,
328-337, 440, 440 ; habits, 54 ; 2. bicolor,
279

Enoplochiton, 403, 403

Enoploteuthis, 391

Ensis, 457

Entocolax, 77, 79, 152

Entoconcha, 77, 79, 152, 216

Entovalva, 77, 82

Ephippodonta, 453 ; commensal, 81

Epidromus, 420

Epiphragm, 26 27 f.

Epipodia, 427

Erato, 419

Eremophila, 294

Ergaea, 248, 412

Erinna, 327, 439

Erosion, 276

Ervilia, 454

Erycina, 453

Escargoticres, 119

Estria, 329, 440

Estuarine species, 14

Ethalia, 409

Eucalodium, 260, 3538, 442

Euchelus, 408

Euchrysallis, 420

Eudioptus, 442

Eudoxochiton, 403

Euhadra, 316, 318, 441

Eulamellibranchiata, 457;
167

Eulima, 422 ; parasitic, 77, 79

Eulimella, 250, 422

Eulota, 296, 441

Euomphalus, 247, 413

Euplecta, 440

Hupleura, 423

Huplocamus, 434

Eurybia, 4388

Eurycampta, 346-351

Eurycratera, 349, 351, 441

Eurystoma, 304

Eurytus, 442

Euthria, 424

Euthyneura, 203

Eutrochatella, 347-351, 348, 410

gill, 166,

Exploring expeditions, 362
Eye in Mollusca, 181 f.

FACELINA, 432

Fasciolaria, 424; radula, 221

Fastigiella, 416

Favorinus, 432

Fenella, 415

Fertilised ovum, development, 130 f.

Ferussacia, 291, 2938, 297 f., 442

Fiji islanders, use of shells, 98

Filibranchiata, 448 ; gill, 166

Fiona, 432 ; radula, 217

Firoloida, 421

Fischer and Bouvier, on breathing of
Ampullaria, 158

Fischeria, 15, 328, 453

Fish devour Mollusea, 59

Fissurella, 265, 406; breathing organs,
153 ; apical hole, 156 ; nervous system,
204; radula, 227 ; growth, 261

Fissurellidaea, 406

Fissuridea, 406

Fissurisepta, 406

Fistulana, 262, 457

Flabellina, 432

Fluminicola, 415

Folinia, 415

Food of Mollusca, 30 f.; Mollusca as
food, 102 f.

Foot, 198 ; in classification, 5

Forel, on deep-water Limnaea, 162

Formation of shell, 255

Fortisia, 429

Fossarina, 413

Fossarulus, 302, 415

Fossarus, 413

Fourth orifice in mantle, 174

Fresh-water species living in sea, 12;
frozen hard, 24

Frogs and toads devour Mollusca, 58

Fruticicola, 285, 290, 316, 318, 441

Fruticocampylaea, 296

Fryeria, 434

Fulgur, 249, 424

Fusispira, 420

Fusus, 262, 424

GADINIA, 152, 431; breathing, 18, 151;
classification, 19 ; radula, 217, 230
Gain, W. A., quoted, 32, 33, 39; on taste

of Mollusca, 179
Galatea, 15, 328, 336, 453
Galeomma, 175, 453
Galerus, 248, 412; egg-capsules, 125
Garstang, W., on protective and warning
coloration, 73
Gaskoin, on tenacity of life, 38; on egg-
laying, 42
Gassies, on hybrid union in snails, 130
Gasteropoda, classification, 8, 11, 400 f.
Gastrana, 453

INDEX

B21

Gastrochaena, 457 ; habits, 64

Gastrodonta, 440

Gastropteron, 245, 4380

Gaza, 376, 408

Gena, 246, 408

Genea, 424

Genotia, 426

Geomalacus, 160, 288, 291, 441; pro-
tective coloration, 70

Geomelania, 16, 348, 351, 414

Georgia, 331, 414

Georissa, 318, 410

Geostilbia, 338, 442

Gerontia, 441

Gerstfeldtia, 290

Gibbula, 408

Gibbus, 328-338, 440, 440

Gillia, 415

Gills—see Branchiae

Girasia, 301, 304, 440

Glandina, 54, 178, 278, 292 f., 339-
355, 440 ; radula, 231, 232; habits,
53

Glands,
136

Glassia, 501, 505

rlaucomya, 320, 454

Glaucus, 429, 432

Gleba, 437

Glessula, 301, 309, 310, 333, 442

Glochidium, 147

Glomus, 448

Glossoceras, 394

Glossophora, 7

Glottidia, distribution, 485, 487

Glycimeris, 457

Glyphis, 406

Glyptostoma, 341, 441

Gomphoceras, 394, 395

Gonatus, 391

Goniatites, 397, 398

Goniobasis, 341, 417

Goniodoris, 434; protective coloration,
73; radula, 229

Goniomya, 458

Gonostoma, 291, 316, 441

Goniostomus, 442

Grammysia, 459

Grateloupia, 454

Great Eastern and mussels, 116

Greenhouses, slugs in, 35

Green oysters, 108

Gresslya, 458

Growth of shell, 40, 257

Guesteria, 440

Guildfordia, 409

Guivillea, 186, 376, 425

Gulls and Mollusea, 56

Gundlachia, 19, 325,
439

Gymnoglossa, 216, 225, 422

Gymnosomata, 437

germ, 134, 140; nidamental,

345, 352, 359,

Gyroceras, 247, 395
Gyrotoma, 417

HADRA, 306, 315, 319-325, 322, 441

Hadriania, 423

Haemoglobin, 171

Hainesia, 336, 414

Halia, 366, 426

Haliotinella, 431

Haliotis, 266, 407 : and coyote, 57 ; holes
of, 156; osphradium, 195; epipodium,
199 ; nervous system, 204 ; radula, 215,
226

Halopsyche, 159, 438, 438

Haminea, 428, 4303 protective colora-
tion, 73

Hamites, 399

Hamulina, 399

Hanleyia, 403

Hapalus, 331, 442

Harpa, radula, 425, 216, 221; self-muti-
lation, 45

Harpagodes, 418

Harpoceras, 399

Harvella, 454

Hatching of eggs, 43 .

Hazay, on duration of life, 39; on varia-
tion in Limnaea, 93

Hearing powers of Mollusca, 196

Heart, in classification, 9; action during
hibernation, 26; and branchiae, 169

Hectocotylus arm, 137 f.

Helcion, 405 ; protective coloration, 69

Helcioniscus, 405

Hele, F. M., on Hyalinia, 33; on Steno-
gyra, 34

Helicarion, 309, 316, 325, 332,
radula, 232; habits, 45, 67

Helicidae, radula, 232, 234

Helicina, 305, 306, 316-327, 338-358,
410; origin, 21; exterminated by
cold, 24

Helicophanta, 335, 336, 441, 441

Heligmus, 449

Helix, 441 ; toothed aperture, 63; protec-
tive coloration, 70 ; variation, 87 ; car-
bonic acid, 163; eye, 181, 183; food,
179; smell, 194; jaw, 211; distribu-
tion, 285 ; tenacity of life, 37 ; breed-
ing, 129

Helix alternata, 340; angulata, 350;
aperta, 38, 39, 51, 293; arbustorum,
bathing, 233; caperata, variation, 89 ;
cereolus, 340; cicatricosa, 316 ; creni-
labris, 45 ; delphinuloides, 297 ; deserto-
rum, 37, 38, 70, 2943; jfidelis, 341;
haemastoma, habits, 70; harpa, 287 ;
hortensis, 10, 279; pulsations, 26 ;
epiphragm, 28 ; rock-boring, 49; dart,
143 ; imperator, 347; habits, 45;
laciniosa, 297 ; lactea, 25, 38, 42, 279 ;
lima, 350 ; muscarum, 347; nemoralis,

440 ;

522

MOLLUSCA—BRACHIOPODA

38, 180; niciensis, 292; nua denticu-
lata, 350; palliata, 340; pisana, 25;
habits, 33 ; pomatia, 25, 34, 40; eye,
181; pomum, 322; pulchella, 279;
richmondiana, 322; rosacea, 259 ; ros-
trata, 347 ; rota, 314; rufescens, pulsa-
tions, 26 ; similaris, 279 ; sowverbiana,
336, 441 ; strigata, 293 ; tristis, habits,
49; turricula, 297; Veatchii, 38;
Waltoni, 304; Wollastoni, 297 ; zonata,
293

Helix aspersa, homing, 35; smell, 36 ;
duration of life, 39; growth, 40;
strength, 45; boring rock, 50; varia-
tion, 87, 89; eaten, 119;>: hybrid
union, 130; generative organs, 140 f.,
141 ; dart-sac, 143 ; pulmonary cham-
ber, 160; radula, 217; alimentary
canal, 237; monstrosities, 251, 252;
growth, 258 ; distribution, 279, 289

Hemiarthrum, 403

Hemicardium, 455

Hemidonax, 453

Hemifusus, 42

Hemipecten, 450

Hemiplecta, 310, 316, 319, 321, 440

Hemisepius, 389

Hemisinus, 357, 417

Hemitoma, 265

Hemitrichia, 314

Hemitrochus, 346-351, 441

Hemphillia, 245, 341, 441

Hercoceras, 395

Herdman, Prof. W. A., on cerata of Nudi-
branchs, 71 f. ; experiments on taste of
Nudibranchs, 72; on Littorina rudis,
1ayil aoe

Hermaea,
73

Hermaphrodite Mollusca, 134, 140, 145

Hermit-crabs, shells used by, 102

Hero, 432

Heterocardia, 454

Heterodiceras, 455

Heteropoda, 9, 420 f.;
foot, 200

Heudeia, 316, 410

Hexabranchus, 434

Hibernation, 25, 163

High altitudes, Mollusca living at, 24

Himella, 15

Hindsia, 424

Hindsiella, 453

Hinge area, 493, 498

Hinge, in bivalves, 272

Hinnites, 257, 450

Hipponyx, 248, 412

Hippopus, 455

Hippurites, 455, 456

Histiopsis, 391

Histioteuthis, 391

Holcostoma, 417

432; protective coloration
pa) ,

radula, 228 ;

Holohepatica, 433

Holopella, 411

Holospira, 339, 353, 442

Holostomata, 156

Homalogyra, 413 ; radula, 223

Homalonyx, 245, 343-358, 443

Homing powers of Mollusca, 34

Homorus, 330-337, 443

Hoplites, 399

Hoplopteron, 422

Horea, 332

Horiostoma, 409

Hot springs, Mollusea living in, 25

Huronia, 894

Hyalaea, 10, 436

Hyalimaz, 245, 305, 306, 338, 443

Hyaline stylet, 240

Hyalinia, 440; pulsations, 26; food, 33 ;
smell, 194; dart, 143; radula, 232,
234; distribution, 287 f., 318, 340-357 ;
H. alliaria, 279 ; smell, 194 ; cellaria,
279 ; Draparnaldi, 33

Hyalocylix, 437

Hyalosagda, 352

Hybocystis, 305, 809, 414

Hybridism, 129

Hydatina, 430; radula, 231

Hydrobia, 325, 332, 415; H. ulvae, egg-
laying, 128

Hydrocena, 298, 410; radula, 226

Hymenoptera build in dead shells, 102

Hypobranchaea, 434; radula, 230

Hypotrema, 448

Hypselostoma, 248, 302, 305, 314, 442

Hyria, 344, 452

Hystricella, 297

IANTHINA, 360, 126, 411; egg-capsules,
125; eyes, 186; radula, 224

Tapetella, 385

Lherus, 285-293, 297, 441

Ichthyosarcolites, 456

Idalia, 179, 429, 484; radula, 229, 230

Idas, 449

Idiosepion, 389

Illex, 890

Imbricaria, 425 ; radula, 221

Imperator, 409

Indians of America, use of shells, 100

Infundibulum, 408

Inioteuthis, 389

Ink-sac, 241

Inoceramus, 449

Insects eaten by Mollusca, 32

Insularia, 319, 320

Intestine, 241

Io, 16, 340, 417

Topas, 423

Iphigenia, 15, 453

Travadia, 305, 415

Tridina, 294

Irus, 297

INDEX

523

Tsanda, 409

Ischnochiton, 403

Tsidora, 298, 320-327, 333, 336, 359,
4B9

Ismenia, 404

Isocardia, 269, 451, 451

Tsodonta, 453

Tsomeria, 343, 356, 441

Issa, 434

JAMAICIA, 414

Janella, 161,
161

Janellidae, radula, 234 ; distribution, 321-
326 =

Janus, 432

Juponia, 318

Jaws, 210

Jeanerettia, 346-351, 441

Jeffreys, Dr., on Limnaea,
Neptunea, 193

Jeffreysia, 415 ; radula, 225

Jorunna, protective coloration, 73

Jouannettia, 457

Jullienia, 307, 415

Jumala, 424

443; pulmonary orifice,

345 on

KALIELLA, 301, 304, 310, 314-317, 335,
440

Kalinga, 434

Kashmir, land Mollusca, 280

Katherina, 403

Kelletia, 424

Kellia, 453

Kellyella, 452

Kidneys, 242

King, R. L., on smell in bivalves, 195

Kingena, 506, 508

Kitchen-middens, 104

Koninckella, 505; stratigraphical distri-
bution, 507, 508

Koninckina, 505 ; stratigraphical distribu-
tion, 507, 508

Koninckinidae, 501, 505, 508

Kutorgina, 504; stratigraphical distri-
bution, 506, 508 ; embryonic shell,
509

LaBIAL palps, 210

Labyrinthus, 342, 353-357, 441; aper-
ture, 63

Lacaze- Duthiers on Testacella, 52 f. ; on |

smell in Helix, 194

Lacuna, 413

Lacunopsis, 332

Lagena, 424

Lagochilus, 309, 316-319, 414

Lamellaria, 245, 411 ; habits and protec-
tive coloration, 74; parasitic, 78;
radula, 223

Lamellidoris, 434; radula, 229, 230, 231

Lampania, 417

Land Mollusca, origin, 11 f.

Lanistes, 249, 294, 328, 331, 416

Lankester, Prof. E. Ray, on shell-gland,
132 ; on haemoglobin, 171

Lantzia, 278, 338, 439

Laoma, 441

Larina, 302, 417

Larvae of Pelecypoda, 7; of insects resem-
bling Mollusca, 67 f.

Lasaea, 453

Latia, 19, 326, 439

Latiuxis, 423

Latirus, 424

Latter, O. H., on Glochidiwm, 147

Layard, E. L., on self-burying Mollusca,
41 ; on sudden appearance of Stenogyra,
47 ; on Coeliaxis, 49; on Rhytida and
Aerope, 54

Leda, 447

Leia, 348-351, 442

Leila, 344, 452

Leonia, 414

Lepeta, 405

Lepetella, 405

Lepetidae, radula, 227

Lepidomenia, 404; radula, 229

Leptachatina, 327

Leptaena, 500, 501, 502, 503, 505 ; strati-
graphical distribution, 507, 508

Leptaxis, 441

Leptinaria, 357, 358, 442

Leptochiton, 403

Leptoconchus, 75, 423

Leptoloma, 348, 351

Lepton, 453; parasitic, 77 ;
80; mantle-edge, 175, 178

Leptoplax, 403

Leptopoma, 316, 319, 338, 414

Leptoteuthis, 390

Leptothyra, 409

Leroya, 331

Leucochila, 442

Leucochloridium, 61

Leucochroa, 292, 295, 441

Leuconia, 439

Leucotaenia, 335, 359, 441

Leucozonia, 64, 424, 424

Levantina, 295

Libania, 295

Libera, 327, 441; egg-laying, 128

Libitina, 451

Licina, 414

Life, duration of, in snails, 39

Ligament, 271

Liguus, 349, 351, 442

Lima, 178, 179, 450 ; habits, 63

Limacidae, radula, 232

Limacina, 59, 249, 436, 436

Limapontia, 429, 432; breathing, 152

Limax, 245, 440; food, 31, 179; varia-
tion, 86 ; pulmonary orifice, 160 ; shell,
175; jaw, 211; radula, 217 ; distribu-

commensal,

524

MOLLUSCA—BRACHIOPODA

tion, 285, 324; L. agrestis, eats May
flies, 31; arborum, slime, 30; food,
31; flavus, food, 33, 363; habits, 35,
36; gagates, 279, 358; maximus, 32,
161; eats raw beef, 32; cannibalism,
32; sexual union, 128; smell, 193 f.

Limea, 450

Limicolaria, 329-332, 443

Limnaea, 4893; selt-impregnation, 44 ;
development and variation, 84, 92, 93 ;
size atfected by volume of water, 94;
eggs, 124; sexual union, 134; jaw,
211; radula, 217, 235; L. auricularia,
24; glutinosa, sudden appearance, 46 ;
Hookeri, 25; involuta, 82, 278, 287;
peregra, 10, 180; burial, 27 ; food, 34,
37; variation, 85; distribution, 282 ;
palustris, distribution, 282; stagnalis,
food, 34, 37; variation, 85, 95; cir-
cum-oral lobes, 131 ; generative organs,
414 ; breathing, 161; nervous system,
204; distribution, 282; ¢truncatula,
parasite, 61; distribution, 282

Limnocardium, 455

Limnotrochus, 332, 415

Limopsis, 448

Limpet-shaped shells, 244

Limpets as food for birds, 56; rats, 57 ;
birds and rats caught by, 57; as bait,
118

Lingula, 464, 467, 468, 471, 472, 473,
475, 477, 478, 487; habits, 483, 484;
distribution, 485 ; fossil, 493, 494, 503 ;
stratigraphical distribution, 506, 508,
ls gnlal

Lingulella, 493, 503 ; stratigraphical dis-
tribution, 506, 508, 511

Lingulepis, 503, 511

Lingulidae, 485, 487, 496, 503, 508

Linnarssonia, 504 ; stratigraphical distri-
bution, 506, 508

Lintricula, 426

Liobaikalia, 290

Liomesus, 424

Lioplax, 340, 416

Liostoma, 42.

Liostracus, 442

Liotia, 408

Liparus, 324, 359, 441

Lissoceras, 399

Lithasia, 340, 417

Lithidion, 414

Lithocardium, 455

Lithodomus, 449

Lithoglyphus, 294, 296, 297, 415

Lithopoma, 409

Lithotis, 802, 443

Litiopa, 30, 361, 415

Littorina, 413; living out of water, 20 ;
radula, 20, 215 ; habits, 50; protective
coloration, 69 ; egg-laying, 126 ; hybrid
union, 130; monstrosity, 251, 252 ;

operculum, 269; erosion, 276; ZL. Jit-
torea, in America, 374 ; obtusata, gener-
ative organs, 135; rudis, 150; Prof.
Herdman’s experiments on, 151 n.

Littorinida, 415

Lituwites, 247, 395

Liver, 239 ; liver-fluke, 61

Livinhacea, 333, 359, 441

Livona, 408 ; radula, 226 ; operculum, 268

Lloyd, W. A., on Wassa, 193

Lobiger, 432

Lobites, 397

Loligo, 378-389; glands, 136; modified
arm, 139 ; eye, 183; radula, 236 ; club,
381; L. punctata, egg-laying, 127 ;
vulgaris, larva, 133

Loligopsis, 391

Loliguneula, 390

Loliolus, 390

Lomanotus, 433

Lophocercus, 432

Lorica, 403

Lowe, E. J., on growth of shell, 40

Loxonema, 417

Lucapina, 406

Lucapinella, 406

Lucerna, 441

Lucidella, 348-351, 410

Lucina, 270, 452

Lucinopsis, 454

Lung, 151, 160

Lunulicardium, 455

Lutetia, 452

Lutraria, 446, 456

Lychnus, 442

Lyonsia, 458

Lyonsiella, 458 ; pranchiae, 168

Lyra, stratigraphical distribution, 507

Lyria, 425

Lyrodesma, 447

Lysinoe, 441

Lytoceras, 398

MAACKTA, 290

Macgillivrayia, 133

Machomya, 458

Maclurea, 410

Muacroceramus, 343-353, 442

Macroceras, 440

Macrochilus, 417

Macrochlamys, 296, 299, 301 f., 310, 316-
322, 440

Macrocyclis, 358, 359, 442

Macron, 424

Macroén, 441

Macroscaphites, 247, 399, 399

Macroschisma, 265, 406

Mactra, 271, 446, 454

Macularia, 285, 291, 292 f., 441

Magas, 506 ; stratigraphical distribution,
507, 508

Magellania, 500

INDEX

525

Magilus, 15, 423

Mainwaringia, 302

Malaptera, 418

Matlea, 419

Malletia, 447

Malleus, 449

Mangilia, 426

Mantle, 172 f., 173 ; lobes of, 177

Margarita, 408 ; radula, 225

Marginella, 425 ; vadula, 221

Mariaella, 314, 338, 440

Marionia, 433

Marmorostoma, 409

Marrat, F. P., views on variation, 82

Marsenia, 133

Marsenina, 411

Martesia, 305, 457

Mastigoteuthis, 390

Mastus, 296, 442

Matheronia, 455

Mathilda, 250, 417

Maugeria, 403

Mazzalina, 424

Megalatractus, 424

Megalodontidae, 457

Megalomastoma, 344, 414

Megalomphalus, 416

Megaspira, 358, 442

Megatebennus, 406

Megerlia, distribution, 486, 487

Meladomus, 249, 328, 331, 416

Melampus, 18, 199, 250, 439, 439

Melanatria, 336

Melania, 276, 417, 417 ; distribution, 285,
292 f., 316 f., 324, 336

Melaniella, 442

Melaniidae, origin, 17

Melanism in Mollusea, 85

Melanopsis, 417 ; distribution, 285, 291,
292 f., 323, 326

Melantho, 340, 416

Melapium, 424

Meleagrina, 449

Melia, 348

Melibe, 432

Melongena, 424; radula, 220; stomach,
238

Merica, 426

Merista, 505, 508

Meroe, 454

Merope, 327

Mesalia, 417

Mesembrinus, 356, 442

Mesodesina, 454

Mesodon, 340, 441

Mesomphiz, 340, 440

Mesorhytis, 377

Meta, 423

Metula, 424

Meyeria, 424

Miamira, 434

Microcystis, 323, 824, 327, 338, 440

Microgazu, 408

Micromelania, 12, 297

Microphysa, protective habits, 70

Microplax, 403

Micropyrgus, 415

Microvoluta, 425

Middendorfiia, 403

Milneria, 451

Mimicry, 66

Minolia, 408

Mitra, 425 ; radula, 221

Mitrella, 42¢

Mitreola, 425

Mitrularia, 248, 412

Modiola, 446, 449; habits, 64; genital
orifice, 242

Modiolarca, 449

Modiolaria, 449 ; habits, 78

Modiolopsis, 452

Modulus, 417

Monilia, 408

Monkey devouring oysters, 59

Monoceros, 423

Monocondylaea, 452

Monodacna, 12, 297, 455

Monodonta, 408, 408 ; tentaculae, 178

Monogonopora, 134, 140

Monomerella, 496, 504

Monopleura, 456

Monotis, 449

Monotocardia, 9, 170, 471

Monstrosities, 250

Montacuta, 452 ; M. ferruginosa, commen-
sal, 80; substriata, parasitic, 77

Mopalia, 403

Moquin-Tandon, on breathing of Lim-
naeidae, 162; on smell, 193 f.

Moreletia, 440

Morio, 420

Mormus, 356, 442

Moseley, H. N., on eyes of Chiton, 187 f.

Moussonia, 327

Mouth, 209

Mucronalia, 422

Mucus, use of, 63

Mulinia, 272

Miilleria, 344, 452

Mumiola, 422

Murchisonia, 265, 407

Murchisoniella, 422

Murex, 423; attacks Arca, 60; use of
spines, 64 ; egg-capsules, 124; eye, 182 ;
radula, 220; shell, 256

Musical sounds, 50

Mussels, cultivation of, 115 ; as bait, 116;
poisonous, 117 ; on Great Hastern, 116

Mutela, 294, 328, 331, 336, 452

Mutyca, 425

Mya, 271, 275, 446, 456; stylet, 240;
M. arenaria, variation, 84

Myacea, 456

Myalina, 449

526

MOLLUSCA—BRACHIOPODA

Mycetopus, 307, 316, 344, 452

Myochama, 458

Myodora, 458

Myophoria, 448

Myopsidae, 3&9

Myrina, 449

Myristica, 424

Mytilacea, 448

Mytilimeria, 458

Mytilops, 452

Mytilopsis, 14

Mytilus, 258, 449; gill filaments, 166,
285; M. edulis, 14, 165; attached to
crabs, 48, 78 ; pierced by Purpura, 60 ;
Bideford Bridge and, 117; rate of
growth, 258; stylet, 240

Myzxostoma, 414

NACELLA, 405

Naiadina, 449

Nanina, 278, 300 f., 335, 440 ; radula,
27, 232,

Napaeus, 296-299, 316, 442

Naranio, 454

Narica, 412

Nassa, 423 ; egg-capsules, 126 ; sense of
smell, 193

Nassodonta, 423

Nassopsis, 332

Natica, 246, 263, 417;
operculum, 268

Naticopsis, 409

‘Native’ oysters, 106

Nausitora, 15

Nautiloidea, 393

Nautilus, 254, 392, 395 ; modified arms,
140 ; eye, 183; nervous system, 206 ;
radula, 236 ; kidneys, 242

Navicella, 267, 268, 324,
origin, 17

Navicula, 358, 442

Navicula (Diatom), cause of greening in
oysters, 108

Nectoteuthis, 389

Neda, 431

Nematurella, 12, 297

Nembrotha, 434

Neobolus, 504

Neobuccinum, 424

Neocyclotus, 357, 358

Neomenia, 8, 133, 216, 228, 404, 404;
breathing organs, 154 ; nervous system,
203

Neothauma, 332

Neotremata, 511

Neptunea, 252, 262, 423; egg-capsules,
126 ; capture, 193 ; monstrosity, 251

Nerinea, 417

Nerita, 17, 410; N. polita used as money,
97

spawn, 126;

327, 410;

Neritidae, 260, 470 ; radula, 226
Neritina, 256, 410; origin, 16, 17, 21;

egg-laying, 128; eye, 181; distribution,
285, 291 f., 324, 327; N. fluviatilis,
habitat, 12, 25

Neritoma, 410

Neritopsis, 409 ; radula, 226 ; operculum,
269

Nervous system, 201 f.

Nesiotis, 357, 442

New Zealanders, use of shells, 99

Nicida, 413

Ninella, 409

Niphonia, 408

Niso, 422

Nitidella, 423

Nodulus, 415

Notarchus, 431

Nothus, 358, 442

Notobranchaea, 438

Notodoris, 434

Notoplax, 403

Novaculina, 305

Nucula, 254, 269, 273, 447

Nuculidae, otocyst, 197 ; foot, 201

Nuculina, 448

Nudibranchiata, 432; defined, 10; pro-
tective and warning colours, 71 f. ;
breathing organs, 159

Nummulina, 295

Nuttallina, 403

OBBA, 311, 315, 441

Obbina, 306, 311, 312, 314, 319

Obeliscus, 442

Obolella, 496, 504 ; stratigraphical distri-
bution, 506, 508

Obolidae, 496, 504, 508

Obolus, 504, 508 ; embryonic shell, 509

Ocinebra, 423

Octopodidae, hectocotylised arm, 137, 139,
140

Octopus, 379-386; egg-capsules, 127 ;
vision, 184; radula, 236 ; crop, 238

Ocythoe, 384 ; hectocotylus, 138

Odontomaria, 407

Odontostomus, 358, 442

Odostomia, 250, 422 ; parasitic, 78

Oesophagus, 237

Ohola, 434

Oigopsidae, 390

Oldhamina, 506, 508

Oleacina, habits, 55

Oliva, 199, 255, 275, 425, 426

Olivancillaria, 426

Olivella, 260, 267, 426;
money, 97

Olivia, 408

Omalaxis, 413

Omalonyzx, habitat, 23

Ommastrephes, 6, 378, 390

Ommatophores, 180, 187

Omphalotropis, 306, 309, 316, 324, 327,
338, 414

O. biplicata as

INDEX

Onchidiella, 443

Onchidiidae, 245; radula,
241

Onchidiopsis, 411

Onchidium, 443 ; breathing, 163;> eyes,
187

Onchidoris, radula, 230

Oniscia, 420

Onoba, 415

Onychia, 390

Onychoteuthis, 390 ; club, 386

Oocorys, 420

Oopelta, 329, 440

Opeas, 442

Operculum, 267 f.

Ophidioceras, 247, 395

Ophileta, 413

Opis, 451

Opisthobranchiata, 427; defined, 9;
warning, ete., colours, 71 f. ; generative
organs, 144; breathing organs, 158 ;
organs of touch, 178 ; parapodia, 199 ;
nervous system, 203; radula, 229

Opisthoporus, 266, 300, 314-316, 414

Opisthostoma, 248, 309, 413

Oppelia, 399

Orbicula, 464

Orbiculoidea, 504, 510

Orders of Mollusca, 5-7

Organs of sense, 177

Origin of land Mollusca, 11 f.

Ornithochiton, 403

Orphnus, 356, 441

Orpiella, 440

Orthalicus, 342-358, 355, 442; habits,
27; variation, 87; jaw, 211; radula,
233, 234

Orthis, 505 ; stratigraphical distribution,
506, 507, 511

Orthoceras, 394, 394

Orthonota, 457

Orthothetes, 505 ; stratigraphical distribu-
tion, 507, 508

Orygoceras, 247

Osphradium, 194 f.

Ostodes, 327

Ostracotheres, 62

Ostrea, 252, 258, 446, 449 ; intestine, 241

Otina, 18, 439

Otoconcha, 326, 440

Otocysts, 196 f., 197

Otopleura, 422

Otopoma, 331, 338, 414

Otostomus, 353, 442

Ovary, 135

Ovoviviparous genera, 123

Ovula, 419 ; protective coloration, 70, 75 ;
radula, 80, 224; used as money, 97

Ovum, development of fertilised, 130

Oxychona, 358

Oxygyrus, 422 ; foot, 200

Oxynoe, 4323; radula, 230

234; anus,

Oyster-catchers, shells used by, 102

Oyster, cultivation, 104-109 ; living out
of water, 110; enemies, 110 f.; repro-
duction, 112 f. ; growth, 114 ; cookery,
114; poisonous oysters, 1143; vision,
190

PACHNODUS, 329-335, 441, 442

Pachybathron, 425

Pachychilus, 354

Pachydesma crassatelloides, money made
from, 97

Pachydomidae, 457

Pachydrovia, 3807, 415

Pachylabra, 416

Pachyctus, 334, 336, 355, 358, 441

Pachypoma, 409

Pachystyla, 337, 440

Pachytypus, 451

Padollus, 407

Palaearctic region, 284 f.

Palaeoneilo, 447

Palaeosolen, 457

Palaina, 327, 413

Palio, 434

Pallial line and sinus, 270

Pallifera, 340, 440

Palliobranchiata, 464

Paludina, 4163; penis, 186; eye, 181;
vision, 184; P. vivipara, 24—see also
Vivipara

Paludomus, 332, 336, 338, 417

Panama, Mollusca of, 3

Panda, 322, 325, 335

Pandora, 458

Papuans, use of shells, 99

Papuina, 309, 319-324, 441

Paramelania, 332

Paramenia, 404

Parasitic worms, 60 f. ; Mollusca, 74 f.

Parastarte, 451

Parkinsonia, 398

Parmacella, 245, 291, 294 f., 438 n., £40 ;
radula, 232; shell, 175

Parmacochlea, 322, 326, 440

Parmarion, 309, 440

Parmella, 326, 440

Parmophorus, 406

Parthena, 349-352, 350, 441

Parts of univalve shell, 262 ; bivalve, 269

Partula, 319-327, 326, 442; radula, 233

Paryphanta, 321, 325, 440

Paryphostoma, 415

Passamaiella, 332

Patella, 405, 464; as food, 56 f. ; eye,
182 ; radula, 214, 215, 227; crop, 238;
anus, 241 ; kidneys, 242; shell, 262; P.
vulgata, veliger, 132 ; breathing organs,
etc., 156, 157

Patelliform shell in various genera, 19

Paterina, 509, 510, 511

Patinella, radula, 227

528

Patula, 297, 298, 318-338, 340, 441

Paxillus, 413

Pearl oysters, 100

Pecten, 446, 450, 450; organs of touch,
178; ocelli, 191; flight, 192 ; nervous
system, 206 ; genital orifice, 242 ; liga-
ment, 271

Pectinodonta, 405 ; radula, 227

Pectunculus, 448

Pedicularia, 75, 419 ; radula, 224

Pedinogyra, 319, 322, 442

Pedipes, 18, 199, 439, 439

Pedum, 450

Pelagic Mollusca, 360

Pelecypoda, 7, 445; development, 145 ;
generative organs, 145 ; branchiae, 166-
169 ; organs of touch, 178 ; eyes, 189 f.;
foot, 201; nervous system, 205

Pella, 333

Pellicula, 352, 442

Peltoceras, 399

Pentadactylus, 423

Peraclis, 436

Pereiraea, 418

Perideris, 328-330, 443

Periodicity in breeding, 129

Periophthalmus, 187

Periostracum, 275

Periploma, 459

Perisphinctes, 399

Perissodonta, 418

Perissolax, 424

Peristernia, 424

Perna, 449 ; ligament, 271

Pernostrea, 449

Peronaeus, 358, 442

Peronia, 443

Perrieria, 319, 442

Perrinia, 408

Persicula, 425

Persona (= Distortio), 420

Petenia, 353, 440

Petersia, 420

Petraeus, 295, 331, 442

Petricola, 454

Phacellopleura, 403

Phanerophthalmus, 430

Phaneta, 408

Phania, 312, 441

Pharella, 457

Pharus, 457

Pharynx, 210

Phasianella, 409

Phasis, 333

Phenomena of distribution, 362

Philine, 245, 428, 430 ; protective colora-
tion, 73 ; radula, 229, 230

Philomycus, 245, 318, 440

Philonexis, 138

Philopotamis, 304, 417

Phoenicobius, 315, 441

Pholadacea, 457

MOLLUSCA—BRACHIOPODA

Pholadidea, 457

Pholadomya, 459

Pholas, 245, 274, 447, 457; in
water, 15

Phos, 42.

Photinula, 408

Phragmophora, 386

Phyllidia, 434 ; breathing organs, 159

Phyllirrhoe, 360, 428, 433

Phyllobranchus, 432

Phylloceras, 398, 398; suture, 396

Phylloteuthis, 390

Physa, 439; aestivating out of water, 27 ;
spinning threads, 29; sudden appear-
ance, 46; osphradium, 195; nervous
system, 205; radula, 235; P. hyp-
norum, 23, 27

Pileolus, 410

Pileopsis, 76

Piloceras, 394

Pinaxia, 423

Pineria, 442

Pinna, 449 ; shell, 254

Pinnoctopus, 385

Pinnotheres, 62

Pinoceras, 398

Pirena, 417

Pirenella, 416

Piropsis, 424

Pirula—see Pyrula

Pisania, 424

Pisidium, 453; smell, 195; ova, 146;
P. pusillum, distribution, 282

Pitys, 327

Placobranchus, 432

fresh

Placostylus, 322, 323-325, 359, 442;
radula, 233
Placuna, 448; P. placenta used for

windows, 101

Placunanémia, 448

Placunopsis, 448

Plagioptycha, 347-351, 441

Plagioptychus, 456

Planazis, 417

Planispira, 311, 312, 319, 441

Planorbis, 27, 247, 439 ; monstrosity, 93 ;
eye, 181 ; P. albus, distribution, 282

Platyceras, 76, 412 :

Platydoris, 434

Platypoda, 4/1

Platyschisma, 413

Plaxiphora, 403

Plecochilus, 442

Plecotrema, 439

Plectambonites, 505

Plectomya, 499

Plectopylis, 303, 305, 314, 316 ; aperture,
63

Plectostylus, 358, 442

Plectotropis, 305, 306, 310, 311, 314-318,
441

Plectrophorus, 298

INDEX

Plesiastarte, 451

Plesiotriton, 420

Pleurobranchaea, 431; jaws, 212

Pleurobranchoidea, 431

Pleurobranchus, 245, 428, 437; warning
coloration, 73 ; jaws, 212; radula, 230

Pleurocera, 340, 417

Pleuroceridae, origin, 17

Pleurodonta, 348 ; aperture, 63

Pleuroleura, 433

Pleuromya, 458

Pleurophorus, 451

Pleurophyllidia, 433; breathing organs,
159 ; radula, 230

Pleuropyrgus, 357

Pleurotoma, 426, 426 ; slit, 263, 265

Pleurotomaria, 266, 373, 376, 407, 407;
prices given for recent, 122; slit, 156 ;
radula, 226

Plicatula, 450

Pliny the elder, on use of snails, 118, 120

Plocamopherus, 434

Plochelaea, 4235

Plutonia, 298, 440

Pneumoderma, 158, 437, 438

Poecilozonites, 352, 440

Poisonous bite of Conus, 65; poisonous
oysters, 114 ; mussels, 117

Polyceru, 434; radula, 230

Polycerella, 434

Polyconites, 456

Polydontes, 346-351, 347, 441

Polygona, 424

Polygyra, 340, 345-353, 441 ; aperture, 63

Polygyratia, 246, 263, 357, 442

Polymita, 346-351, 347, 441

Polyplacophora, 9, 401 f. ; radula, 228

Polytremaria, 266, 407

Pomatia, 285, 293, 295, 441

Pomatias, 288, 289, 292 f., 302, 413

Pomatiopsis, 415

Pomaulax, 409

Pompholyz, 250, 341, 439

Ponsonbya, 332

Poromya, 459 ; branchiae, 168

Porphyrobaphe, 27, 356, 442

Position of Mollusea in Animal Kingdom, 4

Potamides, 16, 416

Potamomya, 15

Potamopyrgus, 325, 326, 415

Poterioceratidae, 394

Praecardium, 459

Prasina, 449

Prices given for rare shells, 121

Primitive molluse, form of, 245;
Of.

Prisogaster, 409

Pristiloma, 341, 440

Proboscidella, 497, 504

Productidae, 497, 500, 504, 508

Productus, 492, 501, 502, 504; strati-
graphical distribution, 508

VOL. III

types

Promachoteuthis, 389

Proneomenia, 404; breathing organs, 154 ;
nervous system, 203; radula, 229

Prophysaon, 341, 441 ; habits, 44

Propilidium, 405

Proserpina, 21, 355, 410

Proserpinella, 354, 410

Proserpinidae, relationships, 21

Prosobranchiata, 9, 404 f. ;
organs, 154

Prosocoelus, 451

Protective coloration, 69 f. ; in snails, 70 ;
in Nudibranchs, 71 f.; in other Mol-
lusea, 74

Protegulum, 509

Protobranchiata, 447 ; branchiae, 166

Protoma, 417

Protremata, 511

Provocator, 376, 425

Psammobia, 456

Pseudachatina, 328-330, 443

Pseudedmondia, 452

Pseudobalea, 350

Pseudo-deltidium, 498, 511

Pseudodon, 295, 307, 452

Pseudolamellibranchiata, 167, 449

breathing

Pseudoliva, 424

Pseudomelania, 417

Pseudomilax, 296, 440

Pseudomurex, 423

Pseudopartula, 323

Pseudosubulina, 440

Ptenoglossa, 224, 4/1

Pterinaea, 449

Pteroceras, 256, 262, 418

Pteroctopus, 3884

Pterocyclus, 266, 267, 300, 316, 414;
tube, 157

Pterodonta, 418

Pteropoda, 7, 434; breathing organs, 158 ;
foot, 200 ; radula, 230

Pterotrachaea, 421; foot, 200; radula, 227

Ptychatractus, 424

Ptychoceras, 399

Ptychodesina, 452

Pugilina, 424

Pulmonata, 10, 22, 151, 185, 438 ; origin,
17, 19 ; breathing organs, 160 ; nervous
system, 203

Pulsellum, 444

Punctum, 441

Puncturella, 265, 406

Pupa, 289, 296, 325-357, 442 ; P. cinerea,
hybrid union, 129

Pupidae, radula, 233

Pupilla, 442

Pupillaea, 406

Pupina, 157, 266, 309, 318-327, 414

Pupinella, 318, 414

Purpura, 423 ; operculum, 269 ; erosion,
276; P. coronata, 367 ; lapillus, feeding
on Mytilus, 60 ; on oysters, 111; pro-

2M

530 MOLLUSCA—BRACHIOPODA

tective coloration, 69; variation, 90 ;
ege-capsules, 124; time of breeding,
129; distribution, 365 n.

Purpuroidea, 423

Pusionella, 426

Pyyocardia, 451

Pygope, 497

Pyramidella, 422

Pyramidellidae, 262

Pyrazus, 50, 416

Pyrgina, 330

Pyrgula, 415

Pyrochilus, 441

Pyrolofusus, 423

Pyrula (= Pirula), 419, 420; spawn, 125 ;
operculum, 269

Pythina, 453

QUENSTEDTIA, 456
(Juoyia, 260, 417

RacHicbLossa, 220, 422; eggs, 124
Rachis, 329-335, 441, 442
Radiolites, 456
Radius, 419
Radsia, 403
Radula, 213 f.; of JLittorina, 20; of
Cyclophorus, 21 ; of parasitic Mollusca,
79
Raéta, 454
Ranella, 256, 420
Range of distribution, 362 f.
Rangia, 15, 453
Ranularia, 420
Rapa, 423
Rapana, 423
Raphaulus, 805, 309
Rathouisia, 316, 440
Rats devouring Mollusea, 57
Realia, 316, 327, 414
Recluzia, 411
Rectum, 241
Registoma, 414
Relationship of Mollusca to other groups, 5
Renssoellaria, 512
Reproductive activity of oyster,
system in Mollusca, 123, 134 f.
Requienia, 269, 455, 455
Respiration, 150 f.
Retzia, 508
Revoilia, 331, 414
veymondia, 332
Rhabdoceras, 398
Rhagada, 311, 324
Rhenea, 325, 440
Rhinobolus, 504
Rhiostoma, 247, 266, 309, 414
Rhipidoglossa, 225, 405
Rhizochilus, 75, 423
Rhodea, 356, 441
Rhodina, 307, 310, 442
Rhynchonella, 466, 470, 471, 472, 474,

UZ 3

483, 487 ; distribution, 487 ; fossil, 492,
497, 499, 505 ; stratigraphical distribu-
tion, 506, 507, 508, 511

Rhynchonellidae, 487, 501, 505; strati-
graphical distribution, 597, 508, 511

Rhysota, 67, 310, 314, 316, 319, 440

Rhytida, 319-326, 333, 359, 440 ; habits,
54; radula, 232

Rillya, 442

Rimella, 418

rimula, 265, 406

Ringicula, 430 ; radula, 230

Risella, 413

Rissoa, 415

rissoind, 415

Robillardia, 77

Rochebrunia, 331, 414

tock-boring snails, 49

Rolleia, 349

Rossia, 3SD

Rostellaria, 418

Rudistae, 456

Rumind, 260, 442 ;

Runcina, 431; protective coloration, 73

SABATIA, 430
Sactoceras, 394
Sagda, 348-351, 441
Sayeceras, 39S

Salasiella, 358, 440

| Salivary glands, 237

Sandford, on strength of Helix, 45

Sandwich islanders, use of shells, 99

Sanguinolaria, 456

Sarepta, 447

Sarmaticus, 409

Satsuma, 314, 316, 441

Saxicava, 447, 457

Sazidomus arata, ywoney made from, 97

Scalaria, 247, 263, 417 ; radula, 224

Scaldia, 452

Scalenostoma, 422

Scaliola, 415

Scaphander, 428, 429, 430; radula, 231 ;
gizzard, 238

Scaphites, 399, 399

Scaphopoda, 444; defined, 6; breathing
organs, 160; nervous system, 208 ;
radula, 236

Scaphula, 14, 305, 448

Scarabus, 18, 278, 439, 439

Scharff, R., on food of slugs, 31 ; on pro-
tective coloration in slugs, 70

Schasicheila, 847, 351, 354, 410

Schismope, 266, 407

Schizochiton, 187, 402, 403

Schizodus, 448

Schizoglossa, 325, 440

Schizoplax, 403

Schizostoma, 413

Schloenbacia, 398

Scintilla, 175, 453

INDEX

532

Scissurella, 265, 407 ; radula, 226

Sclerochiton, 403

Serobicularia, 15, 164, 453 ; siphons, 164

Sculptaria, 333

Scurria, 405

Scutalus, 356, 442

Scutellastra, 405

Scutus, 245, 406, 406.

Scylluea, 433 ; jaws, 212; stomach, 239

Segmentina, 320

Selenites, 339, 341, 440

Selenitidae, radula, 231

Selenochlamys, 296

Self-fertilisation, 42-44

Semele, 453

Semicassis, 420

Semper, K., on habits of Limnaea, 34 ; of
Helicarion, 45, 67; on mimicry, 67 ;
on parasitic Hulima, 79; on develop-
ment of Limnaea, 84, 94; on sexual
maturity in snails, 129; on Onchidiwin,
187

Sepia, 381, 385-387, 389 ; egg capsules,
127; glands, 136; jaws, 214; radula,
236; alimentary canal, 238; ink-sac,
241 ; hectocotylus, 389

Sepiadarium, 389

Sepiella, 389

Sepiola, 389 ; glands, 136 ; radula, 236

Sepioloidea, 389

Sepiophora, 388

Sepioteuthis, 390 ; hectocotylus, 139

Septaria, 387, 338, 410

Septibranchiata, 145, 167, 459; branchiae,
166

Septifer, 274, 449

Sequenzia, 420

Sergius Orata, 104

Serrifusus, 424

Sesara, 305, 440

Sex, differences of, 133

Shell, 244 f. ; internal,
bivalve, 445

Shell-gland, primitive, 132

Shells as money, 96 f. ; as ornament, etc.,
98 f. ; various uses of, 98 f. ; prices given
for rare, 121: sinistral, 249

Shores of N. Asia, no littoral fauna, 2

Showers of shells, 47

Sigaretus, 186, 245, 267, 411 ; foot, 198

Sight, 180

Silenia, 459 ; brauchiae, 168

Silia, 425

Siliqua, 274, 457

Siliquaria, 248, 418

Simnia, 419

Simpulopsis, 345, 350, 442

Simpulum, 420

Simroth, on recent forms of Helix, 22 ;
on food of slugs, 31; on crawling of
Helix, 45

Singular habitat, 48

174; shape of

Sinistral shells, 249

Sinistralia, 424

Sinusigera, 133

Sipho, 424

Siphonalia, 424

Siphonaria, 18, 431; classification, 19 ;
breathing organs, 151, 152

Siphonarioidea, 431

Siphonodentalium, 444

Siphonostomata, 156

Siphonotreta, 493, 496, 504 ; stratigraphi-
cal distribution, 507, 508

Siphons, 173 ; in burrowing genera, 165 :
branchial, 155

Sistrum, 75, 423; vradula of S. spectrum,
79, 222

Sitala, 301, 304, 310, 314-319, 333, 440

Skargard, Mollusca of the, 13

Skenea, 415

Skenidium, 505, 508

Slit, in Gasteropoda, 265, 406

Slugs, habits and food of, 30 f. ; bite
hand of captor, 33; in bee-hives, 36 ;
in greenhouses, 36; protective colcra-
tion, 70 ; eaten in England, 120

Smaragdia, 21

Smaragdinella, 430

Smell, sense of, 192

Smith, W. Anderson, quoted, 98, 111,
ne algal

Snails as barometers, 50; plants fertilised
by, 102; cultivation for food, 118 f. ;
used for cream, 119; as medicine, 120 ;
banned by the Church, 121

Solauriella, 408 ; radula, 225

Solarium, 264, 412, 413 ; radula, 224

Solaropsis, 343, 353-357, 442

| Solecurtus, 165, 457

Solen, 171, 446, 457 ; vision, 190 ; habits, 45

Solenaia, 452

Solenomya, 275, 448

Solenotellina, 456

Solomon islanders, use of shells, 98

Somatogyrus, 415

Sophina, 305

Spallanzani, experiments on Helix, 163

Spat, fall of, 113

Spatha, 294, 331, 336, 452

Spekia, 333

Spermatophore, in Cephalopoda, 137 ; in
Helix, 142

Spermatozoa, forms of, 156

Sphaerium, 453

Sphenia, 456

Sphenodiscus, 3898

Sphyradium, 442

Spines, use of, 64

Spiraculum, 266, 414

Spiraxis, 442

Spirialis, 249

Spirifera, 468, 501, 505; stratigraphical
distribution, 507, 508, 511, 512

532

MOLLUSCA—BRACHIOPODA

Spiriferidae, 501, 505, 508

Spiriferina, stratigraphical distribution,
507, 508

Spirobranchiata, 464

Spirotropis, 426 ; radula, 218, 219

Spirula, 247, 386, 387, 388

Spirulirostra, 380, 386, 388

Spondylium, 500

Spondylus, 257, 446, 450, 450;
191 ; genital orifice, 242

Spongiobranchaea, 437

Spongiochiton, 403

Sportella, 453

Starfish eat oysters, 110

Stearns, R. E. C., on tenacity of life, 38

Stegodera, 306

Stenochisma, 505 ;
bution, 507, 508

Stenogyra, 324, 442; S. decollata, 279;
food, 384; smell, 194; Goodallii, 279 ;
octona, sudden appearance, 47

Stenogyridae, radula, 254

Stenopus, 440 ; habits, 45

Stenothyra, 415

Stenotis, 416

Stenotrema, 340, 441

Stephanoceras, 399

Stepsanoda, 358

Stilifer, 76, 77, 79

Stiliferina, 76, 42:

Stiliger, 432

Stilina, 76

Stoastoma, 348-351, 410

Stoloteuthis, 889

Stomach, 239

Stomatella, 408

Stomatia, 408

Stomatodon, 302, 417

Strebelia, 353, 440

Strength of Helix, 45

Strephobasis, 417

Strepsidura, 424

Streptaulus, 414

Streptaxis, 302, 306, 309, 314-331, 343,
357-359, 440; variation, 87

Streptoneura, 203, 404

Streptosiphon, 424

Streptostele, 329, 338, 440

Streptostyla, 343-355, 353, 440

Stricklandia, 505 ; stratigraphical distri-
bution, ue 508

Strigatella, 425

Stringocephalidae, 506, 508

Stringocephalus, 492, 497, 498, 500, 501,

ocelli,

stratigraphical distri-

422

So

506 ; stratigraphical distribution, 507,
508
Strobila, 340, 345-353
Strobilops, 42
Strombidae, habits, 64; penis, 156
Strombina, 423
Strombus, 69 200, 252, 418; mimicking

Conus, 69 ; operculum, 78, 269 ; pearls

from, 101 ;
239

Strophalosia, 504; stratigraphical distri-
bution, 507, 508

Stropheodonta, 497, 505, 508

Strophia, 343-355, 442; S. nana, 278

Strophochilus, 358, 441

Strophomena, 499, 505 ; stratigraphical
distribution, 507, 508

Strophomenidae, 500, 505, 508

Strophostoma, 248, 414

Structure of shell, 252

Struthiolaria, 99, 418 ;

Styliola, 487

Stylodonta, 339, 441

Stylommatophora, 11, 181,439 ;

Subemarginula, 406

Submytilacea, 457

Subularia, 422

Subulina, 332, 352

Subulites, 420

Succinea, 325, 327, 358, 443; jaw, 211;
S. putris, parasite of, 61

Succineidae, 443; radula, 234

Sudden appearance of Mollusca, 46

Suessia, stratigraphical distribution, 507

oui acid, 237

Surcula, 426

Sycotypus, 424

Synaptocochlea, 408

Syndosmya, 453

Syrmngeiye ce: 500, 508

Syrnola, 422

Syr nolopsis, 382, 333

Systrophia, 356, 357

; metapodium, 199 ; stomach,

radula, 216

origin, 19

TACHEA, 441

Taenioglossa, 223, 411

Taheitia, 414

Talona, 457

Tunalia, 304, 417

Tancredia, 453

Tanganyicia, 332, 415

Tanganyika, L., fauna of, 12

Tanysiphon, 454

Taonius, 391, 391

Tapes, 454

Taste, 179

Tebennophor us, 143, 340, 440

Tectarius, 413

Tectibranchiata, 10, 429

Tectura, 305, 405

Tectus, 408

Teeth in aperture of the shell, 63

Teinostoma, 247, 408

Teinotis, 407

Telescopium, 252, 4

Tellina, 446, 453, 45
tion, 84

Tellinacea, 453

Telotremata, 511

16
53; T. balthica, varia-

| Tenacity of life, 37

INDEX

Tenison- Woods, on red blood, 171; on
shell-eyes, 189

Tennent, Sir J. E., on musical sounds
produced by Mollusea, 50

Tennentia, 304, 314, 338, 440

Terebellum, 418 ; jumping powers, 64

Terebra, 246, 263, 426, 426; radula, 219

Terebratella, 468, 487 ; distribution, 486 ;
fossil, 506; stratigraphical distribu-
tion, 508

Terebratula, 467, 468, 487; size, 484;
distribution, 485, 486 ; fossil, 492, 499,
506 ; stratigraphical distribution, 506,
507, 508

Terebratulidae, 487; fossil, 500, 505, 506 ;
stratigraphical distribution, 507, 508

Terebratulina, 466, 479, 487; larva,
482; distribution, 486; fossil, 506:
stratigraphical distribution, 508 ; form
of shell, 510

Teredina, 457

Teredo, 262, 457, 458 ; nervous system,
206 ; intestine, 241

Tergipes, 432

Terquemia, 450

Testacella, 22, 52, 440; habits, etc., 49,
51 f.; pulmonary orifice, 160; eyes,
186; radula, 231; anus, 241

Testicardines, 466, 487; muscles, 476 ;
fossil, 497, 504; external characters,
497 ; internal characters, 499; attach-
ment of muscles, 501; stratigraphical
distribution, 508

Testis, 135

Tethyidae, 216

Tethys, 432

Tetrabranchiata, 397 f.

Thala, 425

Thalassia, 319

Thalotia, 408

Thapsia, 329

Thaumasia, 349, 442

Thaumastus, 356, 442

Thecacera, 434 ; radula, 229

Thecidiidae, 487 ; fossil, 501, 506, 508

Thecidium, 475, 479, 480, 483, 487; fossil,
506, 508

Thecosomata, 435

Thelidomus, 346-351, 350, 441

Theora, 453

Therasia, 441

Thersites (Helicidae), 322, 325

Thersites (Fasciolariidae), 424

Thetis, 454

Thracia, 245, 459

Thread-spinning, 29

Thridachia, 432

Thyca, 76, 79

Thyrophorella, 330, 440

Thysanoteuthis, 390

Tiedemannia, veliger, 132

Tiphobia, 332, 333, 417

,

538

Titicaca, L., Mollusca of, 25

Todarodes, 390

Tomichia, 414

Tomigerus, 334, 356, 358, 442

Tomocyclus, 354

Tomostele, 330, 440

Tonicella, 403

Tonicia, 403 ; eyes, 188

Torellia, 411

Torinia, 413; radula, 224; operculum,
269

Tornatellina, 278, 319, 323-327, 338, 358,

443

Tornatina, 250, 430

Torquilla, 442

Toucasia, 455

Touch, sense of, 177

Toxoglossa, 218, 426

Trachia, 314

Trachyceras, 397

Trachydermon, 403

Trachyteuthis, 389

Tralia, 439

Transovula, 419

Trematis, 492, 493, 504; stratigraphical
distribution, 507, 508

Trematonotus, 407

Tremoctopus, 384; yvadula, 236; hecto-
cotylus, 137

Trevelyana, 434

Trichia, 316

Trichotropis, 275, 411

Tricula, 302

Tridacna, 273, 455

Triforis, 416 ; radula, 224

Trigonellites, 397

Trigonia, 15, 254, 269, 448; jumping
powers, 65; distribution, 370

Trigonochlamys, 296, 440

Trigonostoma, 426

Trimerella, 495, 504, 508, 511

Trimerellidae, 493, 494, 496, 504; strati-
graphical distribution, 507, 508

Trinacria, 448

Triodopsis, 340, 441

Triopa, 434

Triopella, 434

Triopha, 434

Tritaxeopus, 3885

Triton, 256, 275, 420; jaws, 212

Tritonia, 433 ; protective coloration, 71

Tritonidea, 424

Trivia, 419

Trochidae, egg-capsules, 125

Trochiscus, 408

Trochita, 248, 412

Trochoceras, 395

Trocholites, 395

Trochomorpha, 306, 321, 324, 327, 333,
441

Trochonanina, 331, 440

Trochosphere, 5, 130

534

MOLLUSCA—-BRACHIOPODA

Trochotoma, 266, 407

Trochus, 263, 408; eye, 182; stomach,
239

Trophon, 423

Tropical beach, Mollusca of a, 3

Tropidophora, 414

Tropites, 897

Troschelia, 424

Truncaria, 423

Truncatella, 260, 414

Tryblidium, 405

Trypanostoma, 340

Trypho of Lampsacus, prayer against snails,
121

Tubed operculates, 157, 266, 300, 307,
309

Tudicla, 424

Tudora, 291, 349, 351, 414

Tugonia, 456

Tulotoma, 340, 416

Turbinella, 100, 262, 264, 424, 424

Turbo, 409 ; eye, 182; osphradium, 195 ;

operculum, 268
Turbonilla, 250, 332, 422
Turcica, 408
Turricula, 425 ; radula, 221
Turrilites, 399, 399
Turritella, 252, 417; radula, 215, 224
Tyleria, 459
Tylodina, 431
Tylopoma, 416
Tympanotonus, 416
Tyndaria, 447
Typhis, 423

ULTRA-DEXTRAL shells, 250

Umbonella, 409

Umbonium, 409

Umbrella, 10, 431; radula, 217, 230

Unceites, 505 ; stratigraphical distribution,
507, 508

Underground snails, 48

Ungulina, 452
Tnicardium, 452

Unio, 452; shell, 254, 259, 273, 341;
variation, 92

Union of Limaz, 128

Unionidae, origin of, 15; eaten by rats,
57; larvae, 146

Urocyclus, 331, 440

Urosalpinz, 423

Utriculus, 430

Uvanilla, 409

VAGINULA, 245, 319, 348, 352, 443
Vaginulidae, radula, 284; anus, 241
Valletia, 456

Vallonia, 441

Valvata, 133, 416 ; branchia, 159
Valves of Chitonidae, 401 f.
Vanganella, 454

Variation, 82 f.

| Varicella, 346, 348

Velates, 260, 410

Velifera, 353, 440

Veliger stage, 131; mistaken for perfect
form, 133

Velorita, 302, 453

Velum, 131

Velutina, 275, 411; radula, 223

Veneracea, 454

Venericardia, 451

Venerupis, 454

Veniella, 451

Venilicardia, 451

Venus, 270, 271, 446, 454 ; V. mercenaria,
97, 374

Verania, 391

Vermetus, 247, 418; radula, 223

Veronicella, 443

Verticordia, 458

Vertigo, 327, 442; V. arctica, 287

Verilla, 423

Vibex, 417

Vitrella, 289

Vitrina, 22, 296 f., 332, 440; hardy
habits, 24; jumping powers, 65 ; shell,
175 ; radula, 217

Vitrinella, 408

Vitriniconus, 314, 440

Vitrinoidea, 314, 440

Vitrinozonites, 340, 440

Vitularia, 423

Vivipara, 324, 348, 416

Volume of water, effect
variation, 94

Voluta, 267, 425, 425 ; spawn, 125; radula,
217, 221; distribution, 370; prices
given for rare, 122

Volutaxis, 348

Volutharpa, 267,

Volutolithes, 425

Volutolyria, 425 ; radula, 222

Volutomitra, 425 5 radula, 221

Volutopsis, 423

Volvaria, 429

Volwatella, 430

Volvula, 430

Vulsella, 75, 446, 449

in producing

424

WALDHEIMIA, 464, 467, 468, 473, 474,
487 ; size, 484; distribution, 486 ; fossil,
500, 501, 502, 506, 508

Walton and mussel cultivation, 115

Wampum, 97

Warner, R., quoted, 37

Warning coloration, 71 f.

West Coast, South America, melanism of
shells occurring on, 85

Whelks, use of, 118

Whitneya, 424

Whitstable, oyster-parks at, 106, 112

Willem, V., on vision of Mollusca, 185

' Wollaston, T. V., quoted, 32

INDEX Boe

Wood, Rev. J. G., on starfish eating YETUS, 425

oysters, 111 Yoldia, 447; genital orifice, 242
Woodia, 451
Woodward, S. P., on tenacity of life, 38; | ZAGRABICA, 297

Dr., on the same, 38 Zebrina, 285, 296, 442
Wotton, F. W., on egg-laying of Arion, 42 | Zeidora, 406
Wright, Bryce, on tenacity of life, 38 Zidona, 425

Zittelia, 420

NXENOPHORA, 412; habits, 64 Zones of depth, 361
NXenopoia, 346, 351 Zonites, 275, 440; food, 33 ; radula, 232 ;
Nerophila, 285, 296, 441 distribution, 294, 296, 340
Nesta, 310, 319, 321, 440; mimicry by, | Zospewm, 187, 442

66 f. Zygobranchiata, 154, 406
NXylophaga, 457

END OF VOL. III

Printed by R. & R. CLrark, Edinburgh.

The
Cambridge N: atural Ffistory

In issuing the first instalment of the Cambridge Natural
History, the publishers wish to call attention to the
general objects of the work.

The series, which is edited, and for the most part
written, by Cambridge men, is to consist of ten volumes,
each of which will contain about 500 pages and will be
complete in itself. The volumes have been numbered
on a definite plan, but will be published in the order in
which they are ready for press. Thus the first to be
issued is Vol. III., dealing with the Molluscs and
Brachiopods. It is hoped that Volume V., dealing with
some of the insects, may appear before the end of the
year, and Volume II. at no long interval. Other volumes,
including Volume IX., dealing with birds, are in an
advanced state of preparation.

The Cambridge Natural History is intended, in the
first instance, for those who have not had any special
scientific training, and who are not necessarily acquainted
with scientific language. At the same time an attempt
is made, not only to combine popular treatment with the
latest results of modern scientific research, but to make
the volumes useful to those who may be regarded as

Pena
serious students in the various subjects. Certain parts
have the character of a work of reference.

Although the Vertebrate animals will receive adequate
treatment in the latter volumes, the first six will be
devoted to the Invertebrates. The space has been
apportioned with due regard to the size and importance
of the several groups of animals, and the editors have
endeavoured not to overlook entirely any of the less
conspicuous divisions, whose Natural History may be no
less interesting than that of more familiar animals. The
habits and external features of each group will be con-
sidered in conjunction with its classification, geographical.
distribution, anatomical structure, development, and
paleontology. Especial attention will in most cases be
paid to the members of the British Fauna.

Complete uniformity of treatment has not been aimed
at. It has been thought of the first importance to secure
the help of contributors who are thoroughly acquainted
with the groups on which they are writing, and to allow
them to a large extent to handle their subject in the way
in which they can do it and themselves the most justice.
In some cases it is impossible to treat a class of animals
adequately without paying considerable attention to in-
ternal structure. In other cases, the purposes of the
work can be better met by devoting most of the allotted
space to habits and external structure.

Although it is neither possible nor desirable altogether
to avoid copying figures which have previously been
published, a special feature of the work will be that the
illustrations are, where possible, drawn from nature.
Chapters on geographical distribution will in many cases
be illustrated by maps.

can

The contributions will be arranged approximately

according to the following plan :—

‘Protozoa

Sponges

Wols Ia =
Jelly - fish, Sea-
Anemones, ete.

Star-fish, Sea-
Urchins, etc.

Flat Worms, etc.

Nemertines
Thread - worms,
etc.

Rotifers, etc.

Vol. II.
Polychaet Worms

Earth-worms and
Leeches

Gephyrea
Polyzoa

‘Molluses
Brachiopods
Vol. III. (Recent)
Brachiopods
(Fossil)

M. M. Hartos, M.A., Trinity College
(Professor of Natural History in
the Queen’s College, Cork).

W. J. Souas, Sc.D., F.R.S., St. John’s
College (Professor of Geology,
Trinity College, Dublin).

S. J. Hicxson, M.A., Downing Col-
lege (Beyer Professor of Zoology in
the Owens College, Manchester).

E. W. MacBripeg, M.A., St. John’s
College.

F. W. Gamsie, M.Sc. (Vict.), (De-
monstrator and Assistant-Lecturer
in Zoology in the Owens College,
Manchester).

Miss L. SHELDON, Newnham College.

A. E. SurpLey, M.A., Christ’s College.

M. M. Harrtog, M.A., Trinity College
(Professor of Natural History in
the Queen’s College, Cork).

W. B. Benuaw, D.Sc. (Lond.), Hon.
M.A. (Oxon.), Aldrichian Demon-
strator of Comparative Anatomy
in the University of Oxford.

F. E. Bepparp, M.A. (Oxon.),
F.R.S. (Prosector to the Zoological
Society).

A. E. Suip.ey, M.A., Christ’s College.

S. F. Harmer, M.A., King’s College.

A. H. Cooks, M.A., King’s College.
A. E. Surrey, M.A., Christ’s College-

F. R. C. Reep, M.A., Trinity College.

eae ca

Spiders, Mites, C. Warzurton, M.A., Christ’s Col-
ete. lege (Zoologist to the Royal Agri-
cultural Society).
Scorpions, Trilo- M. Lauriz, B.A., King’s College
bites, etc. (Professor of Zoology in St.
Mungo’s College, Glasgow).
Vol. IV. ~Pycnogonids, ete. D’Arcy W. THompson, M.A., Trinity
College (Professor of Zoology in
University College, Dundee).
Crustacea _ W. F. R. Wetpon, M.A, F.RS,
St. John’s College (Jodrell Professor
of Zoology in University College,

\ London).
Peripatus . . A. Sepcwick, M.A., F.R.S., Trinity
Vol. V. College. As
Centipedes, ete. FF. G. Sincrarr, M.A., Trinity College.
Insects. . D. Suarp, M.A., F.R.S.
Vol. VI. Insects. . D. SuHarp, M.A., F.R.S.
Balanog'lossus, S. F. Harmer, M.A., King’s College.
ete.
Ascidians and W. A. HERpMaN, D.Sc. (Lond.), F.R.S.
Amphioxus (Professor of Natural History in
VolL-VIiT. ; , :
University College, Liverpool).
Fishes. . TT. W. BripcE, M.A., Trinity College

(Professor of Zoology in the Mason

y College, Birmingham).

Vol. VIII. Amphibia and H. Gapow, M.A, F.RS., Kings

Reptiles College.
Vol. IX. Birds , . A. H. Evans, M.A., Clare College.
Vol. X. Mammals. . -F,.°E) BEppaRD, .MlA) (Oxont

F.R.S. (Prosector to the Zoological
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