Page:EB1911 - Volume 23.djvu/190

DISTRIBUTION] age, world-wide distribution and with exceptional facilities of distribution.

—Of crocodiles only C. Johnstoni in N. Australia and Queensland; C. porosus on the N. coast, and occurring on various Pacific islands, as far E. as the Fiji Islands. Tortoises are represented only by the pleurodirous Chelydidae, e.g. Chelodina; they are absent in Tasmania and on the Pacific islands. New Guinea possesses the aquatic Carettochelys, sole type of a family.

The bulk of the Lacertilian fauna is composed of skinks, geckos, agamoids and Varanidae, with the addition of a small family which is peculiar to the region, the Pygopodidae. A peculiar type, Dibamus, inhabits the borderlands, namely, New Guinea, the Moluccas, Celebes and the Nicobar Islands; and, finally, a single iguanoid, Brathylophus, is common in the Fiji Islands; how it came there, or how it survived its severance from the American stock, is a mystery. The skinks are in this region more highly developed and more specialized than in any other part of the world; they exceed in numbers the geckos, which generally accompany the skinks in their range over the smaller islands of the Pacific; in these islands members of these two families represent the whole of the Lacertilian fauna. The Australian agamoids are chiefly peculiar and partly much differentiated forms (e.g. Moloch and Chlamydosaurus), but some have distinct affinities to, or are even identical with, Indian genera. The Varanidae are also closely allied to Indian species.

Of snakes, amounting to about one hundred species only we note about one dozen Typhlopidae, and of Pythoninae simply Python, and the Boine Enygrus on the islands from New Guinea to Fiji. There are but surprisingly few innocuous colubrine snakes, scarcely a dozen, and all belonging to Indian genera. The bulk of the snakes belong to the poisonous Elapinae, all of genera peculiar to the region, e.g. Acanthophis, Pseudechis, Notechis. Such a preponderance of poisonous over harmless snakes is found nowhere else in the world. Tasmania is tenanted by poisonous snakes only. In Australia we meet, therefore, with the interesting fact that, whilst it is closely allied to S. America, but totally distinct from India by its Chelonians, its lizards and colubrine snakes connect it with this latter region. With regard to the other Ophidians, they have their nearest allies partly in India, partly in Madagascar, partly in S. America; and the character of the Australian snake fauna cqnsists chiefly in its peculiar composition, differing thereby more from the other equatorial regions than those do among themselves. Wallace's line marks the boundary between India and Australia only as far as Chelonians are concerned, but it is quite effaced by the distribution of lizards and snakes. Thus in New Guinea lizards of the Indian region are mixed with Pygopodidae, and an island as far E. as Timorlaut is inhabited by snakes, some of which are peculiarly Indian, whilst the others are as decidedly Australian. The islands N. of New Guinea and of Melanesia are not yet occupied by the Ophidian type, and only species of Enygrus have penetrated eastwards as far as the Low Archipelago, whilst the Fiji Islands and the larger islands of Melanesia have sufficiently long been raised above the level of the sea to develop quite peculiar genera of snakes.

—Of Crocodilia C. palustris, the “mugger” or marsh crocodile, and C. porosus; Gavialis gangeticus; Tomistoma schlegeli in Borneo, Malacca and Sumatra. Of tortoises Platysternum megacephalum, type of a family from Siam to S. China; many Trionychidae and Testudinidae, mostly aquatic; whilst the terrestrial Testudo is very scantily represented. One species which is common in the Indian peninsula (T. stellata) is so similar to an African species as to have been considered identical with it; the Burmese tortoise is also closely allied to it, and the two others extend far into western-central Asia. Thus this type is to be considered rather an immigrant from its present headquarters, Africa, than a survivor of the Indian Tertiary fauna, which comprised the most extraordinary forms of land tortoises. Wallace's line marks the E. boundary of Trionyx; species of this genus are common in java and Borneo, and occur likewise in the Philippine Islands, but are not found in Celebes, Amboyna or any of the other islands E. of Wallace's line. Agamidae are exceedingly numerous, and are represented chiefly by arboreal forms, e.g. (q.v.) is peculiar to the region, Ceratophora and Lyriocephalus exclusively Ceylonese; terrestrial forms, like Agama and Uromastix, inhabit the hot and sandy plains in the N.W., and pass uninterruptedly into the fauna of western-central Asia and Africa. The Geckonidae, Scincidae and Varanidae are likewise well represented, but without giving a characteristic feature to the region by special modification of the leading forms except the gecko Ptychozoon homalocephalum in Malaya. The Lacertidae are represented by one characteristic genus, Tachydromus—Ophiops and Cabrita being more developed beyond the limits assigned to this region. Finally, the Eublepharidae and Anguidae, families whose living representatives are probably the scattered remains of once widely and more generally distributed types, have retained respectively two species in W. India, and one in the Khasi Hills, whilst the presence of a single species of chameleon in S. India and Ceylon reminds us again of the relations of this part of the fauna to that of Africa.

The Indian region excels all the other tropical countries in the great variety of genuine types and numbers of species of snakes. Boulenger recognizes 267 species, i.e. about one-fifth of the total number of snakes known. India is the only country in the world possessing viperine, crotaline and elapine poisonous snakes (their proportion to harmless snakes being about 1 : 10), e.g. Vipera russelli, the “daboia” (see ); Lachesis, e.g. gramineus, an arboreal pit viper; Naja tripudians, the cobra; Bungarus coeruleus, the “krait”; Callophis; and Hydrophinae along the coasts of the whole region. Several sub-families and families are peculiar to the region: the Uropeltidae with Rhinophis in southern India, and Uropeltis confined to Ceylon; Ilysiidae in Ceylon and Malay Islands, elsewhere only in S. America; the opisthoglyphous Elachistodon westermanni of Bengal; the Homalopsinae, with many species from Bengal to N. Australia; further the Amblycephalidae; Xenopeltis unicolor, sole type of a family; and the Acrochordinae, a sub-family of aglyphous Colubridae, ranging from the Khasi Hills to New Guinea. Of other Colubridae, we notice numerous Tropidonotus, Coronella and Zamenis, the latter one of the most characteristic types of the warmer parts of Eurasia. Tree-snakes, e.g. Dipsas and Dendrophis, are common. Of other families we note a great number of Typhlopidae, of which T. braminus occurs even on Christmas Island. Lastly various species of Python, but no Glauconiidae, the only family not represented in the Indian region, which claims the Uropeltidae, Xenopeltidae and Amblycephalidae as peculiar to itself.

Günther remarks that to this region Japan has to be referred. This is clearly shown by the presence of species of Ophites, Callophis, Trimeresurus s. Lashesis, Tachydromus, characteristically Indian forms, with which species of Clemmys, Trionyx, Gecko, Halys, and some Colubrines closely allied to Chinese and Central Asiatic species are associated. Halys is a central Asiatic pit viper. The few reptiles inhabiting the northern part of Japan are probably of palaearctic origin.

—Of crocodiles, C. vulgaris in the E., C. cataphractus and Osteolaemus tetraspis in the W. There are many Chelonians, especially small land tortoises of Testudo, and with Cinyxis which is peculiar tothis continent; the freshwater Clemmys only in the N.W. corner; several genera of the pleurodirous Pelomedusidae, Pelomedusa galeata, which is equatorial and southern, with an outlying occurrence in the Sinai peninsula, and Sternothaerus with several tropical and southern species; of Trionychidae the tropical Cycloderma and Cyclanorbis peculiar to the country, and the large Trionyx triunguis which ranges from the Senegal and Congo into the Nile system with its big lakes, but occurring also in Syria.

Of Lacertilia the geckos and skinks, and the typically old world families of Lacertidae and Varanidae are well represented; also Amphisbaenidae; Gerrhosauridae and Zonuridae, peculiar to Africa and Madagascar; a few Eublepharinae and a few of the so-called Anelytropidae in West Africa. But the most important feature of this Lacertilian fauna is the almost universal distribution of chameleons in numerous and some highly specialized forms, Chameleon and Rhampholeon. We note the entire absence of Iguanidae and of Anguidae, the latter represented by Ophisaurus only in the north-western corner.

Of snakes only one sub-family is peculiar, the Rhachiodontinae with the sole species Dasypeltis scabra, the egg-swallowing snake. Many Typhlopidae and Glauconiidae, but no Ilysiidae; large pythons, Eryx in the N., and a boa, Pelophilus fordi in the W. of Africa. Of poisonous snakes there is an abundance, notably the Viperinae have their centre in this continent; besides Echis, which is also Indian, there are peculiar to the continent Bitis, the puffadder, Causus, Atractaspis, Cerastes, and Atheris which is an arboreal genus, all of which see under. The pit vipers are entirely absent. Elapinae are numerous, e.g. hooded cobras like Naja haje and Sepedon the “ringhals.” Many opisthoglyphous tree snakes and a considerable number of innocuous colubrines, e.g. Lycodon, Psammophis and Coronella or closely allied genera all also in India, but Coluber-like forms and Tropidonotus are very scantily represented, chiefly in the N.

On the whole the reptilian fauna of Africa is not rich, considering the huge size of the continent, but this may be accounted for by the great expanse of desert in the N. half and of veld in the S. Lastly, the enormous central forests are still scarcely explored.

and certain other islands have a fauna which is as remarkable for its deficiencies as it is for its present forms. The following well-defined groups are absent: Trionychidae and Chelydidae; Agamidae, Lacertidae, Anguidae, Amphisbaenidae, Varanidae and Eublepharinae; all the Viperidae and Elapinae, so that this large island enjoys perfect absence of poisonous snakes, not counting the practically harmless opisthoglyphous tree snakes; there are further no pythons and no ilysias.

The actual fauna consists of: Crocodilus vulgaris, which is said to be extremely abundant; of Chelonians, Pelomedusa galeata and