_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. desertorum_, however, belonging to the group

_Eremophila_, 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 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_ has several curious types with

a constricted aperture, and the Agnatha are represented by _Libania_, a

peculiar form of _Daudebardia_. A prominent 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_ are abundant. The Dead Sea contains no Mollusca, but Lake

Tiberias has a rich fauna, including the above-mentioned genera, with a

_Corbicula_ and several _Unio_.

[Illustration: FIG. 200.--=A=, _Buliminus_ (_Petraeus_)

_labrosus_ Oliv., Beyrout; =B=, _Buliminus_ (_Chondrula_)

_septemdentatus_ Roth., Palestine.]

_Upper Mesopotamia_ appears to possess a mixture of Syrian and

Caucasian forms, including a _Parmacella_. Lower Mesopotamia 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 Mediterranean 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 (Hellado-Anatolic) of the Mediterranean sub-region proper.

These districts, however, appear to possess scarcely sufficient

individuality to warrant their separate consideration.

A prominent characteristic of the Pontic Mollusca is the great

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_ (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, _Pseudomilax_, _Trigonochlamys_, 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 predominant groups of _Helix_

are _Euloto_, _Cartusiana_, _Xerophila_, and _Fruticocampylaea_, the

last being peculiar. _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 _Pomatias_.

The Caspian Sea, like Lakes Baikal and Tanganyika, is distinguished

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.[367] According to Brusina,[368] the Caspian fauna, 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 _Cardium_

(_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_) _The 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 proximity,

to Madeira and the Canaries. No less than 74 species, or almost

exactly one-half, belong to _Helix_, and 9 to _Patula_. A considerable

number of the Helices are not only specifically but generically

peculiar, the genera bearing close relationship to those occurring

in the Mediterranean region. As a rule they are small in size, but

often of singular beauty of ornamentation. Various forms of _Pupa_

are exceedingly abundant (28 sp.), as is also _Ferussacia_ (12 sp.).

There are also 3 _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.

[Illustration: FIG. 201.--Characteristic land Mollusca from the

Madeira group: =A=, _Helix_ (_Irus_) _laciniosa_ Lowe, Madeira;

=B=, _Helix_ (_Hystricella_) _turricula_ Lowe, Porto Santo; =C=,

_Helix_ (_Iberus_) _Wollastoni_ Lowe, Porto Santo; =D=, _Helix_

(_Coronaria_) _delphinuloides_ Lowe, Madeira.]

_The Canaries_ have about 160 species, only about a dozen of which are

not peculiar. As many as 75 of these belong to _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 _Ferussacia_ 7. _Cyclostoma_ has two

indigenous species, which, with one _Hydrocena_ and one _Craspedopoma_,

make up the operculate land fauna.

_The Azores_ are comparatively poor in Mollusca, having only 52

species, nearly two-thirds of which are peculiar. _Helix_ has 15

species, _Patula_ 4, and _Pupa_ 8. _Ferussacia_, so abundant in

Madeira and the Canaries, is entirely absent, its place being taken by

_Napaeus_ (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 _Pisidium_ 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 _Leptaxis_, which is common to Madeira and the Canaries.

_Ferussacia_ 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 _Ennea_, a _Melania_, and an _Isidora_.

It will be noticed how little 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 common 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 are

purely oceanic, and have been colonised from the western coasts of the

Mediterranean, _i.e._ from the direction of the prevailing 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 imperfectly known; indeed,

it is only at a few points that anything 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 it

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 Mediterranean 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 _Macrochlamys_.

=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 including 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.

In this vast extent of land two distinct centres of influence are

prominent--the Indian and the Chinese. Each 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 continental 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

intermingle in such a way that no very definite line of demarcation can

be drawn between them.

Thus we have--

{ { (_a_) Indian Province

{ 1. _Indo-Malay Sub-Region_ { (_b_) Siamese Province

=Oriental Region= { { (_c_) Malay Province

{ { (_d_) Philippine Province

{

{ { (_a_) Chinese Province

{ 2. _Chinese Sub-Region_ { (_b_) Japanese Province

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

_Nanina_ 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, as a whole, is distinctly inferior to the Indian.

Another characteristic 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_) _The 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 gradually assimilates with the

Siamese on the one hand and the Chinese on the other. Roughly speaking,

the line of demarcation follows the mountain ranges which separate

Burmese from Chinese territory, but the debatable ground is of wide

extent, and Yunnan, 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 maximum. _Helix_ 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 _Boysia_, with its twisted upturned mouth,

while _Lithotis_ is a peculiar form allied to _Succinea_, to which

group also probably belongs _Camptonyx_, a limpet-like form with a very

small spire, peculiar to the Kattiawar peninsula. _Camptoceras_, an

extraordinarily 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. Australia. _Cremnoconchus_ is

a form of _Littorina_, peculiar to the W. Ghâts, 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 _Melania_ and

_Paludomus_), _Stomatodon_, _Larina_, _Fossarulus_, _Tricula_, and

others. The bivalves are neither numerous nor remarkable; _Velorita_, a

genus of the Cyrenidae, is peculiar.

[Illustration: FIG. 202.--Characteristic Indian Mollusca: =A=,

_Hypselostoma tubiferum_ Blanf.; =B=, _Camptoceras terebra_

Bens.; =C=, _Camptonyx Theobaldi_ Bens.]

[Illustration: FIG. 203.--_Streptaxis Perroteti_ Pfr., Nilghiri

Hills: =A=, adult; =A´=, young form.]

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 _Ennea_ occur,

while _Streptaxis_ is practically confined to the extreme south and

north-east.

_Land and Fresh-water Mollusca of India proper_

Streptaxis 9

Ennea 8

Helicarion 15

Girasia 14

Austenia 11

Ibycus 1

Africarion 2

Durgella 4

Ariophanta 15

Xesta 8

Macrochlamys 78

Microcystis 7

Sitala 20

Kaliella 35

Hemiplecta 15

Sesara 3

Trochomorpha 5

Trochomorphoides 1

Parmacella (?) 1

Tebennophorus 1

Anadenus 4

Plectopylis 11

Plectotropis 3

Trachia 12

Thysanota 1

Camaena 1

Amphidromus 2

Boysia 1

Petraeus 14

Cerastus 6

Rachis 5

Cylindrus 1

Pupa 15

Hapalus 4

Clausilia 10

Subulina 2

Opeas 6

Glessula 49

Geostilbia 3

Succinea 11

Lithotis 2

Vaginula 1

Camptonyx 1

Coelostele 1

Carychium 3

Ancylus 1

Limnaea 7

Camptoceras 3

Planorbis 10

Ampullarina 1

Melania 17

Mainwaringia 1

Paludomus 10

Stomatodon 1

Larina 1

Cremnoconchus 3

Fairbankia 2

Tricula 1

Bithynia 9

Fossarulus 1

Stenothyra 3

Vivipara 4

Valvata 1

Ampullaria 4

Assiminea 9

Acmella 2

Pomatias 4

Diplommatina 63

Pupina 1

Streptaulus 1

Coptochilus 3

Alycaeus 49

Lagochilus 1

Cyclophorus 12

Scalaina 1

Micraulax 2

Jerdonia 10

Spiraculum 4

Otopoma 1

Cyclotopsis 2

Georissa 1

Modiola 1

Scaphula 1

Unio 40

Solenaia 1

Cyrena 13

Sphaerium 1

Pisidium 5

Velorita 2

Tanysiphon 1

Novaculina 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 S. 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 S. 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 (_Corilla_) smaller, with a singularly

toothed aperture. While the _Corilla_ 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 decisively separating that

island from India, Burmah, and Siam, forms a most interesting problem

in the history of distribution. _Eurystoma_, with a single species (_E.

vittata_ Müll.), is also peculiar.

As usual when _Helix_ gains ascendancy, the Naninidae retrogress.

_Durgella_, _Austenia_, and _Girasia_ are absent altogether, while

_Macrochlamys_, _Sitala_, _Kaliella_, etc., are present in greatly

diminished numbers. The sub-genus _Beddomea_ is peculiar, a form

directly related to _Amphidromus_ (Siam and Malacca). The fresh-water

operculate _Philopotamis_ is peculiar, but for one species found in

Sumatra; while _Tanalia_ is quite peculiar. But the forms which, next

to the _Helices_, most emphasise the separation of the Cingalese

district are the land operculates. There are eleven genera or

sub-genera 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 abundant in India, have not yet been discovered in Ceylon.

Among the slugs, _Tennentia_ is a peculiar genus, whose nearest

relation occurs in the Seychelles.

[Illustration: FIG. 204.--_Helix_ (_Acavus_) _Waltoni_ Reeve,

Ceylon, showing embryonic shell (_emb_). × ⅔.]

_Genera and Subgenera occurring in the Cingalese District, but not in

N. and Central India_

Streptaxis

Tennentia

Acavus

Eurystoma

Corilla

Beddomea

Philopotamis

Tanalia

Theobaldius

Leptopomoides

Craspedotropis

Pterocyclus

Aulopoma

Ditropis

Cyathopoma

Mychopoma

Cataulus

Nicida

Opisthostoma

The district consisting of _Upper Burmah_, _Pegu_, _Tenasserim_, 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 representative 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 _Hyalimax_ is

common only to the Andamans, Nicobars, and Mascarene Is. _Hypselostoma_

(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

peculiar _Raphaulus_ and _Hybocystis_ (Fig. 205), a very remarkable

form, of which another species occurs at Perak. Two _Helicina_ mark the

most westward extension of the genus on the mainland. In the extreme

north of Upper Burmah, Indian and Chinese forms intermingle.

[Illustration: FIG. 205.--_Hybocystis gravida_ Bens. Young and

adult.]

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 _Cremnoconchus_ 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 tide-way (see Fig. 9, p. 14); and _Martesia_, 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

_fluminalis_ from its exclusive residence in the Irawadi R.; _Iravadia_

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--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.) in 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 _Omphalotropis_, 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 _Ennea_, 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 Chinese element. _Amphidromus_, with 33

species, is the most characteristic land pulmonate. Several genera,

whose nucleus of distribution lies among the islands farther east,

appear to have penetrated as far as these coasts. Such are _Chloritis_,

_Camaena_, and _Obbina_ among the Helicidae, _Trochomorpha_, and, of

the operculates, _Helicina_.

[Illustration: FIG. 206.--_Cyclophorus siamensis_ Sowb., Siam.]

Land operculates are very richly developed. In all, there are 17 genera

and 104 species known. 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

Ennea 3

Helicarion 7

Microcystis 3

Sesara (?) 1

Medyla 1

Xesta 4

Macrochlamys 6

Kaliella 5

Hyalinia (?) 1

Hemiplecta 14

Rhysota 2

Trochomorpha 6

Trochomorphoides 3

Plectopylis 5

Stegodera 2

Plectotropis 12

Trachia 3

Fruticicola 2

Acusta 2

Chloritis 8

Dorcasia 1

Camaena 5

Hadra 5

Obbina 1

Amphidromus 33

Bocourtia 2

Buliminus 4

Hypselostoma 2

Tonkinia 1

Clausilia 15

Opeas 7

Spiraxis (?) 2

Subulina 1

Succinea 4

Vaginula 7

Limnaea 7

Planorbis 6

Canidia 13

Melania 39

Faunus 1

Bithynia 9

Wattebledia 1

Stenothyra 4

Hydrobia 1

Pachydrobia 9

Jullienia 6

Lacunopsis 6

Chlorostracia 4

Vivipara 39

Valvata 1

Ampullaria 15

Assiminea 7

Procyclotus 6

Dasytherium 2

Opisthoporus 5

Rhiostoma 7

Myxostoma 1

Pterocyclus 7

Cyclophorus 28

Leptopoma 10

Lagochilus 6

Pupina 8

Hybocystis 3

Alycaeus 6

Cataulus (?) 1

Diplommatina 2

Helicina 4

Georissa 2

Modiola (f. w.) 2

Dreissensia 3

Anodonta 17

Mycetopus 1

Pseudodon 18

Dipsas 4

Unio 64

Arconaia 1

Cyrena 6

Batissa 1

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.

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 accompanying map, the red line on which

is intended to show what would be the result of an elevation of the sea

bottom for no greater amount than 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, comparatively 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 members

of the island series--Bali, 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

peculiarities 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.

[Illustration: FIG. 207.--_Ariophanta Rumphii_ v. d. B., Java.]

The Malay peninsula is practically another island of somewhat the same

shape and general trend as Sumatra, and about one-half the size. Its

general relations--and the remark applies 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.

[Illustration:

Map to illustrate the

GEOGRAPHICAL DISTRIBUTION

of the Land Mollusca of the

EAST INDIAN ARCHIPELAGO

_The red line marks the 100 fathom line_

London: Macmillan & Co. _London Stanford’s Geog^l. Estab^t_.]

It seems not impossible, from the point of view of the land Mollusca

only, that the Sunda Islands may at one time have stretched much

farther into the Bay of Bengal, prolonged, perhaps, 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 comparatively

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 represented by 3 species in Sumatra and only 2

in Java, in Borneo it has as many as 19, _Rhiostoma_ 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 of a single _Papuina_ (Moluccas eastward) is very remarkable.

[Illustration: FIG. 208.--=A=, _Opisthostoma Cookei_ E. A. Smith,

Borneo; =B=, _Opisthostoma grandispinosum_ G.-A., Borneo. Both ×

8.]

_Amphidromus_ is a genus characteristic of the great Sunda Islands,

attaining its maximum in Java (12 sp.). The Indian _Glessula_ still

has one species each in Sumatra, Java, and Borneo. One species of

_Streptaxis_[369] occurs in Malacca, but _Ennea_ (3 sp.) reaches as

far east as Borneo and the Philippines. _Parmarion_, _Helicarion_,

_Ariophanta_, and other groups of the Naninidae are well represented.

_Hemiplecta_ and _Xesta_ are abundant and large, while the _Rhysota_

of Borneo contain some huge sinistral forms. _Rhodina_ is a remarkable

form from Malacca, whose exact generic position is not yet settled.

_Clausilia_ 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 _Island of Celebes_ marks the beginning of a distinct decrease in

the Indo-Malay element. The Naninidae lose ground, in proportion to the

Helicidae, _Macrochlamys_, for instance, being represented by 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 Moluccas N. Guinea

_Nanina_ (all genera) 26 32 51 22 36 40

_Helix_ (all genera) 7 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 3 to 1 in Java, and

rises again to 4 to 1 in Borneo (showing the essentially continental

character of the island); in Celebes it further falls to 3 to 2, while

in the Moluccas the scale turns and _Helix_ has the advantage by about

8 to 5, and in N. Guinea by more than 2 to 1.

[Illustration: FIG. 209.--_Amphidromus perversus_ L., Java.]

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 S. 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 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 Bali 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 altogether

wanting. In Timor Laut we have Moluccan influence appearing in 3

_Chloritis_, and there is one (supposed) _Corasia_. Two _Helices_ of a

marked Australian type (_Rhagada_) occur, one in Flores, the other on

Dama I., south-west of Timor. The configuration 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 Ké Is.

The Ternate group shows decidedly closer relations with New Guinea than

the Amboyna group. Thus, among the _Helices_, the markedly Papuan genus

_Papuina_ 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 eastward

from India, gain the ascendancy over the Naninidae, the numbers being,

_Helix_ 55, _Nanina_ 36. If we take the groups separately, we find that

in the Amboyna group the proportion is 22 to 23, while in the Ternate

group it is 33 to 13, an additional 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). _Amphidromus_ is not

reported on sufficient authority to warrant its insertion in the list.

_Land Mollusca of the Moluccas._ (T = Ternate, A = Amboyna[370] group)

Helicarion 1 A

Euplecta 1 A

Xesta 6 A, 4 T

Macrochlamys 1 A

Lamprocystis 4 A, 2 T

Macrocycloides 4 A

Sitala 1 A

Kaliella 3 A, 1 T

Trochomorpha 3 A, 3 T

Endodonta 1 A

Patula 1 A

Plectotropis 1 T

Eulota 1 A

Chloritis 8 A

Planispira 5 A, 12 T

Cristigibba 1 A, 4 T

Obbina 1 A, 1 T

Phania 4 T

Albersia 3 T

Camaena 1 T

Papuina 1 A, 7 T

Pupa 3 A

Vertigo 2 A

Clausilia 1 T

Opeas 4 A, 4 T

Subulina 1 A

Tornatellina 1 A

Vaginula 1 A

Melania 18 A, 4 T

Faunus 1 A

Vivipara 1 A

Acmella 1 A

Diplommatina 4 A, 2 T

Registoma 1 T

Pupinella 1 A

Callia 2 A

Leptopoma 4 A, 5 T

Lagochilus 1 A, 1 T

Ditropis 3 A

Cyclotus 4 A, 6 T

Omphalotropis 3 A

Georissa 1 T

Helicina 6 A, 3 T

(_d_) _The Philippine Province._--In the extraordinarily rich

development of their Mollusca, the Philippines form a remarkable

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 element, and a remarkable

development of individual characteristics.

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, living 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.

[Illustration: FIG. 210.--_Cochlostyla_ (_Chrysalis_)

_mindoroensis_ Brod., Mindoro, Philippines.]

[Illustration: FIG. 211.--_Cochlostyla_ (_Orthostylus_) _Portei_

Reeve, Luzon. × ⅔.]

The distribution of the sub-genera of _Cochlostyla_ on the 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

S. 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-Romblon-Sibuyan are entirely deficient in certain

sub-genera which occur on the islands surrounding them on all

sides.[371]

Other forms peculiar to the Philippines are _Diaphora_, a section of

_Ennea_ with a curiously produced mouth, and several sub-genera of the

Naninidae (_Vitriniconus_, _Vitrinoidea_, _Hemitrichia_). The great

_Rhysota_ here find their metropolis. Another very marked group of

_Helix_ is _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

_Trachia_ 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 S. Leyte. Amongst the

slugs, _Mariaella_ occurs again only in the Seychelles, and _Tennentia_

only in Ceylon.

[Illustration: FIG. 212.--_Helix_ (_Obbina_) _rota_ Brod.,

Philippines.]

_Land and Fresh-water Mollusca of the Philippines_

Streptaxis 1

Ennea 10

Mariaella 3

Tennentia 1

Helicarion 21

Vitrinopsis 5

Vitrinoidea 1

Rhysota 17

Trochonanina 2

Euplecta 28

Hemiplecta 11

Hemitrichia 15

Xesta 2

Macrochlamys 5

Microcystis 3

Lamprocystis 17

Bensonia 4

Vitriniconus 16

Sitala 2

Kaliella 8

Trochomorpha 21

Endodonta 1

Plectopylis 3

Plectotropis 1

Aulacospira 3

Pupisoma 1

Satsuma 2

Dorcasia 2

Chloritis 7

Obbina 19

Papuina 1

Phoenicobius 7

Cochlostyla 247

Amphidromus 2

Hapalus (?) 4

Hypselostoma 1

Pupa 4

Clausilia 1

Subulina 3

Prosopeas 2

Opeas 4

Geostilbia 1

Tornalellina 1

Succinea 3

Vaginula 2

Ancylus 1

Limnaea 3

Planorbis 3

Physa 2

Melania 50

Pirena 2

Bithynia 1

Vivipara 7

Ampullaria 5

Acmella 2

Diplommatina 41

Arinia 6

Pupina 5

Registoma 7

Hargreavesia 1

Callia 2

Pupinella 3

Helicomorpha 4

Coptochilus 1

Alycaeus 1

Leptopoma 42

Lagochilus 11

Cyclophorus 31

Ditropis 7

Cyathopoma 5

Cyclotus 19

Omphalotropis 3

Helicina 18

Georissa 3

Anodonta 1

Cyrena 3

Corbicula 7

_Islands adjacent to the Philippines._--The Philippines are connected

with Borneo by two distinct ridges or banks of elevation, 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 _Amphidromus_ 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 _Obba_, from N. Celebes, the _Camaena_ possibly in a 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.

(2) The =Chinese Sub-region=.--The _Chinese Sub-region_ includes 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 Vladivostok, 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_,

_Ariophanta_, _Rhysota_, _Hemiplecta_, _Diplommatina_, _Opisthoporus_,

_Pterocyclus_, _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 _Satsuma_, _Cathaica_,

_Aegista_, _Acusta_, _Euhadra_, _Plectotropis_, and _Plectopylis_.

Sinistral forms (compare Fig. 213) are rather prevalent. In several

cases--_e.g._ _Trichia_, _Gonostoma_, _Fruticicola_--there is 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 Mollusca are not abundant,

and are represented by _Rathouisia_ (a peculiar genus of naked slug),

_Ennea_, and _Streptaxis_. In the western provinces _Buliminus_ is

abundant in several sub-genera, one of which appears to be the European

_Napaeus_.

[Illustration: FIG. 213.--_Helix_ (_Camaena_) _cicatricosa_

Müll., China.]

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), is 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 peculiar forms of fresh-water

operculates, whose exact position is hardly yet assured.

_Land and Fresh-water Mollusca of the Chinese Province_

Rathouisia 1

Streptaxis 7

Ennea 12

Parmarion 2

Helicarion 15

Euplecta 3

Macrochlamys 19

Microcystina 2

Microcystis 7

Kaliella 16

Sitala 8

Ariophanta 1

Rhysota 5

Hemiplecta 1

Trochomorpha 2

Limax 1

Philomycus 1

Patula 2

Gonostoma 4

Metodontia 2

Vallonia 1

Plectotropis 9

Fruticicola 11

Satsuma 14

Trichia 10

Cathaica 22

Aegista 10

Armandia 3

Acusta 15

Obbina 1

Camaena 5

Euhadra 14

Plectopylis 19

Stegodera 6

Chloritis 1

Hel. Inc. sed. 39

Buliminus 21

Buliminopsis 3

Buliminidius 3

Napaeus 14

Rachis (?) 4

Pupa 10

Clausilia 102

Opeas 12

Euspiraxis 1

Subulina 5

Stenogyra (?) 12

Succinea 8

Vaginula 7

Limnaea 2

Planorbis 6

Melania 44

Paludomus 3

Bithynia 12

Lithoglyphus 3

Melantho (?) 1

Pachydrobia 1

Prososthenia 2

Stenothyra 2

Hydrobia 2

Mecongia 1

Oncomelania 9

Margaracya 1

Rivularia 4

Delavaya 1

Fenouillia 1

Vivipara 34

Diplommatina 20

Pupina 6

Alycaeus 23

Leptopoma 2

Lagochilus 10

Cyclophorus 18

Coelopoma 1

Pterocyclus 3

Opisthoporus 4

Cyclotus 10

Scabrina 4

Ptychopoma 12

Omphalotropis 1

Realia 2

Pseudopomatias 1

Helicina 3

Georissa 4

Heudeia 1

Cyclas 1

Corbicula 50

Unio 53

Monocondylaea 1

Anodonta 55

Mycetopus 12

Pseudodon 1

Dipsas 4

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

occurrence 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 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); (_b_) Indo-tropical species; (_c_) 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 _Helices_ belong to sub-genera common to China

(_Plectotropis_ 8, _Euhadra_ 21, _Acusta_ 23?); 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--(_a_) 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; (_b_) the _Queensland Province_,

or the strip of N.E. Australia from C. York to the Clarence R. (about

29° S. lat.); (_c_) 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 one hand in characteristic Papuan

_Helices_, while on the other they form the north-western limit of

_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. Australia to the south and south-east, and of

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 _Cristigibba_ (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 _Corasia_ 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 occurrence 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 represented. Not that an Indo-Malay

element is altogether absent. We still have _Xesta_ (5), _Hemiplecta_

(8), and even _Sitala_ (2), but the great predominance of _Helix_

seems to have barred the progress, 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 Queensland, 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 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

_Isidora_ (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 1

Helicarion 2

Rhysota 1

Hemiplecta 11

Xesta 2

Microcystis 3

Microcystina 2

Sitala 2

Oxytes (?) 2

Conulus 1

Trochomorpha 8

Nanina (?) 3

Charopa 1

Thalassia 3

Ochthephila(?) 1

Chloritis 13

Planispira 5

Cristigibba 9

Insularia 17

Obbina 1

Albersia 3

Hadra 4

Pedinogyra 1

Papuina 35

Corasia (?) 1

Bulimus (?) 1

Calycia 4

Partula 3

Pupa 1

Stenogyra 1

Tornatellina 1

Perrieria 1

Succinea 1

Vaginula 1

Limnaea 2

Isidora 3

Melania 28

Faunus 1

Vivipara 4

Diplommatina 1

Pupina 4

Pupinella 3

Omphalotropis 2

Bellardiella 2

Leptopoma 16

Cyclotus 5

Cyclotropis 5

Helicina 15

Unio 4

Cyrena 3

Corbicula 1

Batissa 8

_Waigiou_ 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.[372]

The _Aru Is._ 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 unmistakable 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 _Glaucomya_

to Malacca and the Philippines, while the single _Batissa_ is also

found in New Zealand.

_Land and Fresh-water Mollusca of the Aru Islands_

Xesta 4

Microcystis 1

Hyalinia(?) 1

Trochomorpha 1

Patula 1

Eulota 1

Chloritis 5

Cristigibba 2

Albersia 1

Papuina 4

Pupa 2

Stenogyra 2

Planorbis 1

Segmentina 1

Melania 14

Leptopoma 3

Moussonia 1

Realia 1

Cyclotus 3

Helicina 3

Cyrena 2

Glaucomya 1

Batissa 1

The _Louisiades_, 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 peculiar 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 Is._, 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 Is._ is the

extraordinary development of _Papuina_, which here culminates 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 Philippines, 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 growing 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 link with the New 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, is very

noteworthy, the nearest species being from the Philippines.

_Land and Fresh-water Mollusca of the Solomon Islands_

Streptaxis (?) 1

Rhytida 1

Paryphanta (?) 1

Helicarion 2

Xesta 1

Macrochlamys 1

Hemiplecta 3

Microcystis 2

Trochomorpha 22

Nanina (?) 2

Patula 1

Thalassia 2

Chloritis 3

Philina 2

Hadra 3

Papuina 50

Merope 1

Corasia (?) 10

Placostylus 16

Partula 13

Succinea 1

Melania 18

Diplommatina 2

Pupina 4

Leptopoma 4

Omphalotropis 2

Cyclotus 1

Cyclotropis 2

Helicina 7

Unio 1

(_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 its maximum. _Panda_,

_Pedinogyra_, and _Thersites_ are three remarkable groups in a rich

_Helix_ fauna. _Parmacochlea_ is a peculiar form akin to _Helicarion_.

The carnivorous Mollusca are represented 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_). _Ampullaria_ and _Anodonta_ are entirely absent from

Australia and New Zealand.

[Illustration: FIG. 214.--Characteristic Australian _Helices_:

=A=, _H._ (_Hadra_) _pomum_ Pfr.; =B=, _H._ (_Thersites_)

_richmondiana_ Pfr. × ⅔.]

[Illustration: Map D. _To face page 322._

MAP

to illustrate the relations

OF THE LAND MOLLUSCA OF

NEW GUINEA WITH THOSE

OF NORTH AUSTRALIA.

_The red line marks the 100 fathom line_

London: Macmillan & Co.]

_Land Mollusca of the Queensland Province_

Diplomphalus 1

Rhytida 10

Elaea 1

Parmacochlea 1

Helicarion 7

Nanina 3

Hyalinia 10

Thalassia 4

Charopa 5

Patula (?) 4

Macrocyclis (?) 1

Helicella 10

Planispira 8

Hadra 51

Chloritis 5

Pedinogyra 1

Thersites 1

Papuina 6

Panda 2

Helix (inc. sed.) 6

Bulimus (?) 1

Stenogyra 1

Tornatellina 4

Pupa 3

Vertigo 4

Perrieria 1

Succinea 3

Vaginula 1

Janella 1

Georissa 1

Pupina 16

Hedleya 1

Callia 1

Diplommatina 3

Ditropis 2

Dermatocera 1

Helicina 8

(_c_) _The Melanesian Province_ includes those islands on which

the remarkable group _Placostylus_ occurs, the metropolis of whose

distribution is 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 containing _Placostylus_ as far to

the west as Faro I., form, as has been already stated, a transitional

district to the Papuan province.

_New Caledonia._--The 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 peculiar form _Pseudopartula_, but _Helix_ has

almost entirely disappeared. Polynesian influence is represented by

_Microcystis_ (3 sp.), the so-called _Patula_ (13 sp., many of which

are probably _Charopa_), _Tornatellina_ (2 sp.), and _Helicina_ (20

sp.). _Partula_ does not reach so far south, but there are two species

of _Janella_. The recurrence of _Melanopsis_ (19 sp.), absent from

the whole Oriental region, is curious, and forms another link with

New Zealand. The curious sinistral _Limnaea_ (_Isidora_), common with

Australia and New Zealand, is abundant.

[Illustration: FIG. 215.--_Placostylus caledonicus_ Pet., New

Caledonia, × ⅔.]

_The New Hebrides_ link New Caledonia and the Solomons by 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 _Papuina_, 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 limit 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.), _Helicina_ (11 sp.), and

_Omphalotropis_ (11 sp.), is very strong. The _Microcystis_ (9 sp.) and

_Trochomorpha_ (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. _Limax_ is not indigenous, though several species

have become naturalised. The bulk of the fresh-water species belong to

_Isidora_, and it is doubtful 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_ (?), 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 _Liparus_, a form intermediate

between _Helix_ 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

Hyalinia 1

Patula 7

Chloritis 2

Gonostoma 2

Trachia 3

Xerophila 1

Rhagada 8

Hadra 5

Liparus 10

Pupa 4

Succinea 3

Cyclophorus 2

Helicina 1

In _Eastern 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 abundant 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 Tasmania, 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; _Endodonta_

and _Charopa_ are rare, and _Hadra_ has entirely disappeared, but

_Pupa_ and _Succinea_ occur. Carnivorous genera are represented by

_Paryphanta_, _Rhytida_, and _Rhenea_. _Anoglypta_ is a peculiar

section of _Helix_, 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.[373]

_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 _Rhytida_ 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,

indicate the same affinity. _Otoconcha_ is peculiar. The fresh-water

Mollusca, besides the _Isidora_ characteristic of the sub-region, are

partly related to New Caledonia through the occurrence of _Melanopsis_,

partly to Tasmania through _Potamopyrgus_, while the peculiar _Latia_

is possibly akin to _Gundlachia_ (Tasmania). The land operculates

number only 5 genera and 14 species in all, excluding a doubtful

_Diplommatina_.[374]

_Land and Fresh-water Mollusca of the Neozealanian Province_

Schizoglossa 1

Paryphanta 5

Rhytida 6

Rhenea 2

Helicarion 1

Otoconcha 1

Microcystis 1

Trochonanina 1

Phacussa 3

Thalassohelix 5

Gerontia 2

Allodiscus 10

Pyrrha 1

Therasia 7

Phenacohelix 3

Suteria 1

Flammulina 13

Laoma 23

Endodonta 10

Charopa 28

Placostylus 1

Carthaea 1

Tornatellina 1

Janella 3

Latia 2

Ancylus 2

Limnaea 5

Amphipeplea 2

Planorbis 1

Isidora 7

Melanopsis 2

Potamopyrgus 4

Paxillus 1

Lagochilus 7

Omphalotropis 1

Realia 4

Hydrocena 1

Unio 9

Sphaerium 1

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 (_a_)

the Polynesian province proper, and (_b_) the Hawaiian province, which

includes the Sandwich Is. only.

[Illustration: FIG. 216.--Characteristic Polynesian Mollusca:

=A=, _Achatinella vulpina_ Fér., Sandwich Is.; =B=, _Partula

planilabrum_ Pease, Society Is.]

(_a_) The general features of the _Polynesian province_ are very

similar throughout, although the Mollusca of each island group are

in the main peculiar. The species are mostly small and obscure.

_Helix_ scarcely occurs, its place being taken by small Zonitidae

(_Microcystis_, _Charopa_, _Trochomorpha_, etc.), 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.; _Tornatellina_, _Pupa_, and _Vertigo_ occur throughout.

The land operculates consist chiefly of _Omphalotropis_, _Pupina_,

_Realia_, and _Helicina_. _Diplommatina_ and _Palaina_ are abundant

on the Pelews, and a _Moussonia_ occurs in the Samoa Is. _Ostodes_, a

small form of _Cyclophorus_, is found in some of the southern groups.

The fresh-water operculates are _Melania_, _Neritina_ (including

_Clithon_, a sub-genus furnished with spines), and _Navicella_; there

are no Unionidae, while fresh-water _Pulmonata_ are very scarce.

(_b_) The land Mollusca of the _Hawaiian province_ are distinguished

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 mountain 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 operculates, 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 _Isidora_, absent

from the central Pacific groups, is remarkable, and _Erinna_ 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 peculiar, and takes, especially in W.

Africa, some curious forms (_Columna_, _Perideris_, _Pseudachatina_).

Carnivorous Mollusca (_Ennea_, _Gibbus_, etc.) are highly developed,

especially in the south and east, the largest known helicoid form

(_Aerope_) being from Natal. In the possession of these types of the

Agnatha, Africa is more closely related to the Australasian than to the

Oriental region. The true _Cyclostoma_ are entirely peculiar to the

region, but are absent from West Africa.

Fresh-water Mollusca are abundant and characteristic, especially in and

near the Great Lakes. _Lanistes_, _Cleopatra_, and _Meladomus_, among

the operculates, together with _Mutela_ and _Aetheria_ (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 predominance in the

extreme south, but the species are nearly all insignificant in size

and colouring. It is only in Madagascar that _Helix_ asserts itself.

_Arion_, _Limax_, _Hyalinia_, _Clausilia_, and a 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 6½ in.,

_Limicolaria_, _Perideris_, and _Pseudachatina_ are the characteristic

forms. The Agnatha are represented by _Ennea_, _Streptaxis_, and

_Streptostele_. _Rachis_ and _Pachnodus_, sub-genera of _Buliminus_,

occur also on the east coast. A special feature is the development of

several peculiar slug-like genera, _e.g._ _Oopelta_, perhaps a form of

_Arion_; _Estria_, a slug with an external shell, akin to _Parmacella_;

and _Aspidelus_, a form intermediate between _Helicarion_ and _Limax_.

_Claviger_, a handsome group akin to _Cerithium_, 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 not yet

been well explored. _Tomostele_, a genus allied to _Streptostele_, is

peculiar, and _Pseudachatina_ attains its maximum.

[Illustration: FIG. 217.--_Columna flammea_ Müll., Princes I.]

_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 species have as yet been

discovered in either of the islands.

The _Angola and Benguela District_, extending 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. _Helix_ reappears, while the characteristic

West African genera are almost entirely wanting.

(_c_) The _East 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, includes

no genus which does not occur on the west coast, except _Cyclostoma_

(2 sp.). _Trochonanina_ (4 sp.), _Urocyclus_, a characteristic African

slug (2 sp.), _Rachis_ (6 sp.), _Pachnodus_ (2 sp.), and _Achatina_ (5

sp.), are the principal groups.

[Illustration: FIG. 218.--_Urocyclus comorensis_ Fisch.,

Comoro Is.: =G=, Generative orifice; =M=, mucous 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 carnivorous 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,

supplants _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_ is fairly

well known through recent explorations, especially those associated

with Emin Pasha. _Streptaxis_ (6 sp.) and _Ennea_ (24 sp.) are

numerous, _Helix_ is wanting, and the Naninidae are represented by

_Trochonanina_ (7 sp.), and other forms at present grouped under

_Nanina_ or _Hyalinia_. On the high ground _Buliminus_, _Cerastus_, and

_Hapalus_ replace, to some extent, the _Achatina_ and _Limicolaria_ of

the marshy plains. Land operculates (_Cyclophorus_ 1, _Cyclostoma_ 8)

are 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 (_Mutela_, _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 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 peculiar operculate genera, belonging principally to the

Melaniidae and Hydrobiidae. Several of these possess a solidity of form

and compactness 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 represents

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

Melaniidae; _Tiphobia_ (Fig. 219), which is allied to _Paludomus_, is a

compact shell with angulated spinose whorls; _Lacunopsis_, _Ponsonbya_,

_Limnotrochus_, and _Tanganyicia_ are probably forms of _Lithoglyphus_,

some, as their names denote, being of decidedly marine facies;

_Syrnolopsis_ and _Turbonilla_ (?) look like Pyramidellidae, _Horea_

and _Reymondia_ like _Rissoina_; _Bourguignatia_ appears to belong

to _Vivipara_, with which has now been merged the genus _Neothauma_.

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 like hardy northern plants on a

mountain in low latitudes. _Helix_, _Vitrina_, and _Pupa_ abound,

with a few _Clausilia_ and even a _Limax_. 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. 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 _Trochomorpha_ is Indian. Indian influence, indeed, comes out

unmistakably throughout the province. Thus in Socotra there are two

_Cyclotopsis_, in Abyssinia two _Africarion_ (closely related to the

Indian _Girasia_), two _Microcystis_, and a _Glessula_, and in the

Scioa district there is a _Sitala_. The fresh-water Mollusca of Socotra

are Indian forms.

[Illustration: FIG. 219.--_Tiphobia Horei_ E. A. Smith, L.

Tanganyika.]

[Illustration: FIG. 220.--Mollusca characteristic of L.

Tanganyika: =A=, _Nassopsis nassa_ Woodw.; =B=, _Spekia zonata_

Woodw.; =C=, _Syrnolopsis lacustris_ E. A. Smith.]

[Illustration: FIG. 221.--_Achatina zebra_ Lam., S. Africa. × ½.]

(2) =The South African Sub-region.=--The principal characteristic of

the Mollusca of S. Africa is the occurrence of numerous small species

of Helicidae, belonging chiefly to the groups _Pella_, _Phasis_,

_Dorcasia_, and _Sculptaria_, all of which are practically peculiar.

Carnivorous genera are also prominent, _Ennea_ here attaining its

maximum. _Rhytida_ (to which several species still regarded as _Pella_

belong) is common only to the S. Pacific and Australasia, and forms,

with _Isidora_ among the fresh-water pulmonates, a remarkable link of

connexion. _Aerope_, the largest of all helicoid carnivorous genera,

and _Chlamydephorus_, a carnivorous slug with an internal shell, are

peculiar. _Achatina_ is still abundant, but _Limicolaria_ is wanting.

_Livinhacea_, a form with a continuous peristome, perhaps akin to

_Bulimus_; _Apera_, a form of slug; and _Coeliaxis_, a genus perhaps

akin to the Papuan and Queensland _Perrieria_, are all peculiar. The

land operculates, which are not numerous, are of the East African type.

_Land Mollusca of the S. African Sub-region_

Chlamydephorus 1

Ennea 31

Aerope 5

Rhytida 3

Helicarion 3

Trochonanina 1

Trochozonites 1

Limax 1

Apera 1

Vitrina 7

Nanina 6

Conulus 2

Patula 2

Pella 44

Dorcasia 8

Phasis 1

Sculptaria 2

Helix (inc. sed.) 4

Rachis 1

Pachnodus 3

Buliminus (?) 4

Pupa 20

Vertigo 2

Achatina 18

Livinhacea 1

Stenogyra 4

Coeliaxis 1

Succinea 3

Vaginula 2

Cyclophorus 1

Cyclostoma 7

Cyclotus (?) 1

Blanfordia 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.[375] The genera are--

Hyalinia 1

Patula 4 (3 extinct)

Endodonta 10 (7 extinct)

Bulimulus 7 (5 extinct)

Pachyotus 1 (extinct)

Tomigerus (?) 1 (extinct)

Pupa 2 (extinct)

Succinea 3

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 S.

Atlantic. _Patula_ and _Endodonta_ are essentially Polynesian forms,

occurring abundantly on all the island groups in the Central Pacific.

_Pachyotus_, _Tomigerus_ (assuming its correct identification), and

_Bulimulus_ are all S. American forms, the two former being especially

characteristic of Brazil. How this mixture 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 time much more widely distributed. _Endodonta_ (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 _Limax_, 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 (_Ennea_,

_Gibbus_), the occurrence of a considerable number of true Helicidae of

great size and beauty, and the prominence of the genus _Cyclostoma_.

(_a_) _The Madagascan Province._--The land Mollusca of Madagascar,

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 development of both these

groups. For size, colouring, and beauty of shape, the Helicidae of the

two sub-genera _Ampelita_ and _Helicophanta_ rival, if they do not

surpass, any in the world. They are quite peculiar to this sub-region,

not a trace of them occurring on the Mascarenes, Seychelles, or even

on the Comoros. _Helicophanta_ is distinguished by the enormous size

of its embryonic 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 represented by

two species, but _Achatina_, so abundant on the mainland, 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 Helicidae, this genus is

not restricted to Madagascar; several species occur on the mainland,

6 on the Comoros, one on the Seychelles, and 16 in Mauritius. The

sub-genera _Acroptychia_ and _Hainesia_ are peculiar.

[Illustration: FIG. 222.--_Pachyotus auris vulpina_ Desh., St.

Helena (sub-fossil).]

[Illustration: FIG. 223.--_Helix_ (_Helicophanta_) _Souverbiana_

Fisch., Madagascar, showing embryonic shell. × ⅔.]

[Illustration: FIG. 224.--_Cyclostoma campanulatum_ Pfr.,

Madagascar.]

The fresh-water Mollusca of Madagascar contain further 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 East Indian faunas. Several of the _Melania_ and the two

_Bithynia_ are of a type entirely wanting in Africa, but common in the

Indo-Malay sub-region. Not a single one of the characteristic African

fresh-water bivalves (_Mutela_, _Spatha_, _Aetheria_, _Galatea_, etc.)

has been found in Madagascar. On the other hand, certain African

Gasteropoda, such as _Cleopatra_ and _Isidora_, 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.

_Land and Fresh-water Mollusca of Madagascar_

Ennea 9

Urocyclus 2

Helicarion (?) 1

Macrocyclis (?) 1

Kaliella 1

Nanina (inc. sed.) 9

Ampelita 35

Helicophanta 17

Pachnodus 2

Rachis 2

Leucotaenia 2

Clavator 2

Achatina 3

Opeas 2

Subulina 3

Vaginula 4

Limnea 2

Planorbis 3

Isidora 3

Melania 7

Melanatria 4

Paludomus 2

Vivipara 1

Bithynia 2

Cleopatra 2

Ampullaria 6

Cyclophorus 2

Cyclotus (?) 1

Cyclostoma 54

Otopoma 5

Lithidion 1

Acroptychia 3

Hainesia 3

Unio 1

Corbicula 2

Sphaerium 1

Pisidium 1

_The Comoro Islands._--This isolated group possesses about 100 species,

almost all of which are peculiar. The principal feature is the rich

development of _Ennea_ (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 isolation of the group from

Madagascar. We have--

Fresh-water Peculiar to

Total sp. Land sp. sp. Peculiar group

Mauritius 113 104 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 Australasian.

The genus _Pachystyla_ (Naninidae) is quite peculiar, forming the main

portion of the land snails proper. It attains its maximum 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 extraordinary development of the carnivorous

genus _Gibbus_, which has 27 sp. in Mauritius, 8 in Bourbon, 4 in

Rodriguez; in the Seychelles, it is replaced by _Edentulina_ 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 indication that this group was, not long ago, much more abundant,

for of the 16 _Cyclostoma_ known from Mauritius 10 are sub-fossil. The

operculates form a decided feature of the land fauna; thus in Mauritius

there are 32 species, or more than 28 per cent of the whole.

[Illustration: FIG. 225.--Characteristic Mauritian land shells:

=A=, _Gibbus palanga_ Fér.; =A´=, young of same; =B=, _Gibbus

lyonetianus_ Pall.]

Indian and Australasian affinities are unmistakably present. Thus

_Omphalotropis_, a genus characteristic of _small_ islands, is

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 relationship.

_Cyclotopsis_, _Cyathopoma_, and _Geostilbia_ are markedly Indian

genera. _Microcystis_, _Patula_, and _Tornatellina_ are Polynesian.

_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

_Tennentia_. Not a single representative of these eleven genera has

been found even in Madagascar.

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 at one

time undoubtedly existed between India and Eastern Africa began to

be less continuous,[376] 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 the

Seychelles continued in more or less direct union with that island

sufficiently long to receive the progenitors of _Stylodonta_ (a

peculiar group of _Helix_), 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, _i.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

is so poor in genera, while those which occur are generally of small

size, with scarcely anything remarkable either in colouring or form.

The elongated land shells (_Clausilia_, _Buliminus_), so characteristic

of Europe, are entirely wanting, but a few _Bulimulus_, of Neotropical

origin, penetrate Texas, and from the same sources come a few species

of _Glandina_ (as far north as S. 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 consists 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 midway between _Testacella_ and

_Limax_, whose metropolis is on the Pacific slope, but which spreads

eastward into the Antilles. Among the Limacidae, _Limax_ is common

to both sub-regions, but _Tebennophorus_ (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 _Mesomphix_

and _Gastrodonta_ (peculiar to this sub-region), and _Hyalinia_ proper.

_Patula_ is well represented. 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_).

[Illustration: FIG. 226.--Characteristic North American Mollusca.

=A=, _Helix_ (_Mesodon_) _palliata_ Say, Ohio. =B=, _Helix_

(_Polygyra_) _cereolus_ Mühlf., Texas. =C=, _Patula alternata_

Say, Tennessee.]

The poverty of the land fauna is atoned for by the extraordinary

abundance and variety of the fresh-water genera. A family of

operculates, the Pleuroceridae, with 10 genera and about 450 species,

is quite peculiar, a few stragglers only reaching 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 S. America in the absence of a

fringe to the mantle and in being oviparous. They do not occur 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

(_Trypanostoma_, with the four genera _Io_, _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 of the Unionidae may be gathered from the fact that Wetherby

states[377] 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.[378]

[Illustration: FIG. 227.--_Helix_ (_Arionta_) _fidelis_ Gray,

Oregon.]

(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. _Selenites_ here has

its metropolis, and _Pristiolma_ is a remarkable group of small

_Hyalinia_ (_Zonites_), but the larger forms of the Eastern States are

wanting. Several remarkable and quite peculiar forms of slug occur,

namely, _Ariolimax_ (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. _Pompholyx_ is a very remarkable ultra-dextral form of

_Limnaea_, apparently akin to the _Choanomphalus_ of L. Baikal.

_Bithynia_, absent from the Eastern States, is represented 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

Selenites 6

Limax 4

Vitrina 4

Vitrinozonites 1

Mesomphix 15

Hyalinia 22

Conulus 1

Gastrodonta 9

Pristiloma 2

Tebennophorus 4

Ariolimax 6

Prophysaon 2

Hemphillia 1

Binneya 1

Patula 18

Punctum 2

Arionta 20

Praticola 2

Glyptostoma 1

Mesodon 27

Stenotrema 11

Triodopsis 21

Polygyra 23

Polygyrella 2

Gonostoma 1

Vallonia 1

Strobila 2

Pupa 18

Vertigo 8

Holospira 2

Cionella 1

Bulimulus 6

Macroceramus 1

Succinea 21

Vaginulus 1

Helicina 2

=F. The Neotropical Region=

The land Mollusca of the Neotropical Region stand in complete 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 little 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 development appears to

lie 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 is most strongly developed in the Greater Antilles,

which possess several peculiar groups of great beauty. In Central

America _Helix_ is comparatively scarce, but in the northern portions

of the continent several fine genera (_Labyrinthus_, _Isomeria_,

_Solaropsis_) occur, which disappear altogether towards the south.

Carnivorous land Mollusca 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 continent, _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 throughout, 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 S. America in

exceedingly remote ages from its headquarters in Eastern Asia. No

species survives in N. America, and a single straggler is found in

Porto Rico. The genera _Macroceramus_, _Cylindrella_, and _Strophia_,

are characteristic West Indian forms, which are only slightly

represented on the mainland. _Homalonyx_, a curious form akin to

_Succinea_, is peculiar to the region.

[Illustration: FIG. 228.--_Homalonyx unguis_ Fér., Demerara.

_sh_, Shell (shown also separate); _p.o_, pulmonary orifice.]

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 Chili, Patagonia, and Southern Brazil,

but is not found in the tropical portion of the continent. Of the

fresh-water Pelecypoda _Mycetopus_, _Hyria_, _Castalia_, _Leila_, and

_Mülleria_ 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 containing an Antillean element, belong to

the mainland of S. 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 S. Florida; (_b_) 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 follows:--

Cuba Jamaica San Domingo Porto Rico

Inoperculate 362 221 152 75

Operculate 252 242 100 23

It appears, then, that the proportion of operculate to inoperculate

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 operculates 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 peculiar to the islands, one or two species

of most of them occurring in Central or S. America, but of the several

hundreds of operculate species which occur on the islands, not two

score are common to the mainland.

[Illustration:

Map to illustrate the

GEOGRAPHICAL DISTRIBUTION

of the Land Mollusca of the

WEST INDIES.

_The red line marks the 100 fathom line._

London: Macmillan and C^ọ. _London: Stanford’s Geog^ḷ Estab^ṭ._]

The next special feature of the sub-region is a remarkable development

of peculiar sub-genera of _Helix_. In this respect the Antilles

present a striking contrast to both Central and S. America, where the

prime feature of the land Pulmonata is the profusion of _Bulimus_

and _Bulimulus_, and _Helix_ 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 individual islands.

Here, too, is the metropolis of _Cylindrella_ (of which there are 130

species in Cuba alone), a genus which just reaches S. 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 maximum in Cuba, is entirely wanting

in Jamaica, and has its last representative in S. Croix. One species

irregularly occurs at Curaçao.

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 connexion, more or less

intimate, between the W. Indies and the mainland. The genera are all of

small size. The characteristic N. American _Hyalinia_ 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 concerned, 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 S. 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 S. American element may 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 S. 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).

(_a_) _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 to 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. _Thelidomus_ 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); _Cysticopsis_ 9 (Jamaica

6); _Eurycampta_ 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. 247).

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.

_Blaesospira_, _Xenopoma_, and _Diplopoma_ are peculiar. The

Helicinidae consist mainly of _Helicina_ proper (58 sp.), which here

attains by far its finest development in point of size and beauty,

and of _Eutrochatella_ (21 sp.), which is peculiar to the three great

islands (Jamaica 6 sp., San Domingo 6 sp.).