Page:Encyclopædia Britannica, Ninth Edition, v. 20.djvu/486

Rh 4(58 REPTILES [GEOGRAPHICAL Dipsadidse, are more numerous (eighteen species) than in the other equatorial regions. Elachistodon and Hologerrhum may be mentioned as remarkable tyjes not found elsewhere, but with a very local distribution. The development of Lycodonts India has in common with Africa ; but the genera, six in number, are distinct. Also the presence of gigantic Snakes of the genus Python is a feature which India shares with Africa. Of Erycidx three species are Indian, Gongylophis and Cursoria being peculiar to the region. Poisonous Snakes are numerous, the proportion to innocuous Snakes being as 1 : 10. Out of forty-six species, only two belong to the family of true Vipers, and they are restricted to the Indian peninsula with Ceylon, oue (Echis) being even specifically identical with the African species, and the other (Daboia) having its only congener in the Mediterranean district. The remainder of the poisonous Snakes belong to the Elapidas and Crotalidaz or Pit Vipers. The former are represented by six genera, of which no less than five are highly characteristic of the region, whilst the Cobras (Naja) are equally distributed over Africa. Of Pit Vipers five genera have been distinguished, the most characteristic being an arboreal form, Trimeresurus, with seventeen species. Also the other five genera are peculiar to India, with the exception of the genus Halys which is Central- Asiatic. >tiles The relations of the Indian region to the others will be considered Fapan. as we proceed with the accounts of those faunas. Japan, with regard to its Reptilian fauna as a whole, must be referred to this region. This is clearly shown by the presence of species of Ophites, Callophis, Trimeresurus, Tachydromus, characteristically Indian forms, with which species of Clemmys, Trionyx, Gecko, Halys, and some Colubrines closely allied to Chinese or Central- Asiatic species are associated. The few Reptiles inhabiting the northern part of Japan are probably Palrearctic species. ican 2. The African Region. Owing to its strictly continental ion - character and diminished variety of physical features, this region is inhabited by a much smaller number of Reptiles than one might be led to expect from the large extent of its geographical area. There are but few small outlying islands, furnishing a small number of interesting additions to this fauna. Madagascar, indeed, would supply a con- siderable contingent of distinct forms, but it is questionable whether this large island should be united with the African region, as we shall see hereafter. ,. The African region is characterized by the development ians. of three of the four principal divisions of terrestrial Chelonians, viz., Testudinidx, C/ielydidx, and Trionycidse ; the Emydidse are absent, being represented by one species only, in the north-western corner of the region (Emys platyceps). The thirty-seven species are distributed thus : Testudo, with 16 species 21 Chersine, Pyxis, Cinyxis. Emys, Dumeriiia, ... Sternotherus, Pelomedusa,. Trionyx, Cycloderma, The majority of the genera are peculiar, viz. , Chersine, Pyxis, Cinyxis, Dumeriiia, Sternothcrus, Pelomedusa, and Cycloderma ; and no other region shows a similar development of Land Tortoises. This last type has not only diverged into four genera, but is also represented by several of those gigantic forms which survived into geologically recent times. In the African region they inhabited only the neighbouring oceanic islands, viz., the Aldabra group, Mauritius, and Rodriguez ; out of the eight species, which have been recognized chiefly from their osseous remains, one only sur- vives at the present day. Also in Madagascar fossil remains of gigantic species, which must have been contemporaries of^Spyornis, have been discovered by Grandidier ; but on the continent no trace of these large creatures has been found hitherto. The Chelonians of the eastern and western halves of the continent do not essenti- ally differ from each other, but Trionyx does not extend southwards beyond the tropic. ico- Of Crocodilidse, Crocodilus is represented by three or ans. four species. Alligators are absent. "is. occur in the southern portion. Agamidx are numerous, and represented chiefly by terrestrial forms. The Gecko- nidss, Sdncidfe, Lacertides, and Varanidas are likewise well represented ; Eublepharidx by a single genus and species in West Africa. The presence of several genera of Ampkisbacnidse, some of which are even identical with South-American, is highly suggestive. Gerrhosauridss, Zonuridse, and Anelytropidx are peculiar to tropical Africa ; but the most important feature of this Lacertilian fauna is the almost universal distribution of Chamaeleons in numerous and highly specialized species. Leaving aside, for the present, the island of Madagascar, Ophi- we estimate that the number of species of African Snakes does not exceed two hundred, which are referable to about seventy genera, of which no less than fifty do not range beyond the limits of the region. On the whole the east coast genera are different from those of the west coast, but in the southern parts no such differentiation can be shown. Very little is known as regards the range of the species and genera towards the central districts. As regards higher groups only two families, the Dctsypeltidse and Dinophidx, are peculiar to Africa; and, although they have a wide range over the region, they consist of very few species only. Other families show a greater variety of genera and species here than in any other part of the globe. The almost entire absence of the genus Tropi- donotus and the scanty representation of Colubers are very noticeable features. Poisonous Snakes are numerous, all the various families being well represented, with the exception of the Pit Vipers ; singularly enough innocuous Colubrine Snakes with facial pits occur (Bothrophthalmus, Bothrolycus). Of Typhlopidas nearly forty species have been described, and, besides, the Stenoslomatida& are represented by seven species. Eight out of ten Calamaroid genera are peculiar to this fauna, and remarkable is the frequency with which among them the sub-caudal shields coalesce into a single series. The Caronellidae are represented by some twenty species, but no true Coluber occurs, the four species which approach this type most closely belonging to distinct genera (S'caphiophis, Xenurophis, Herpetaethiops). Almost entire absence of Tropidonotus is a characteristic feature of this fauna. Also of other Freshwater Snakes only six genera with seven species are known. The small family of Psammophidse is well represented by three genera and nine species, of which six belong to Psammophis. Of Tree-Snakes there are six genera, of which Ah&tulla (Philo- thamnus) is most generally distributed, in twelve species. Of Dipsadidse there are five genera and ten species, four of which belong to Dipsas proper. The Lycodonts are as well developed as in India, by seven genera and fourteen species ; all the genera are peculiar to Africa, and some of them are modified for an arboreal mode of life. Of Pythons three species are distinguishable ; but, besides, a mem- ber of the Booid family (Pelophilus fordii) occurs on the west coast. Two species of Eryx occur. Poisonous Snakes are extremely numerous, the proportion to innocuous Snakes being as 1 : 5. Of Elapidas four genera occur, among which Naja figures with at least two species ; besides this family the Dinophidse are a remarkable and characteristic type, having assumed entirely the appearance and mode of life of Tree Snakes. The Atractaspididse, with three genera and thirteen species, are likewise almost entirely African, only one other type (Dinodipsas) having been recently discovered in Venezuela. Pit Vipers are absent, but the largest forms of Viperidss are developed in this region, this family being represented by four genera and twelve species. The singular genus Atheris is a real Tree Viper with prehensile tail. The Reptilian fauna of Madagascar is a most remarkable mixture of types belonging to different regions, which cannot be accounted for in the present state of our knowledge of the geological changes that have taken place whilst the present fauna was already in existence. The Chelonians 1 offer a marked point of distinction from those of 1 The Chelonians of Madagascar require a thorough critical examina- tion ; some of the species which are recorded as having been brought from that island have been evidently introduced from the African continent. Others, as also certain species of Snakes, are certainly not natives of Madagascar.
 * r- Of the families of Lizards inhai >iting Africa the majority