(iv) The Egypto-Syrian district extends along the south-eastern shores of the Mediterranean from Tripoli to North Syria, and eastward to the Euphrates valley. Lower Egypt alone belongs to this portion, the fauna of Upper Egypt being of an entirely tropical character, and belonging to the Ethiopian Region.

Lower Egypt.—The Mollusca of Lower Egypt stand in the unique position of belonging, half to the Palaearctic, and half to the Ethiopian Region. The land Mollusca are of a distinctly Mediterranean type, while the fresh-water, directly connected as they are by the great highway of the Nile with regions much farther south, contain a large admixture of thoroughly tropical genera (Ampullaria, Lanistes, Melania, Cleopatra, Corbicula, Cyrena, Iridina, Spatha, Mutela). The Helices, which are not numerous, are rather a mixture of circum-Mediterranean species than of a specially distinctive character. H. 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.

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.

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—

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.

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

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.

Genera and Subgenera occurring in the Cingalese District, but not in N. and Central India

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.

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.

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

(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.