The Zoogeographical Regions into which the world is usually divided (Palæarctic or Europo-Asiatic, Oriental or Indian, Ethiopian or African, Australian, Nearctic or North American, Neotropical or South American) do not lend themselves any better than the ordinary divisions of physical geography to the study of the distribution of Snakes. Contrary to what we find in dealing with the Tortoises, Australia does not show any special affinity to South America, and, as in the case of the Lizards, it must be regarded as an impoverished extension of the Indo-Malay fauna; as with the Lizards, also, Europe and Africa hang together, whilst Madagascar stands apart, distinguished by many negative features and some points of agreement with South America (Boidæ). There is a greater difference between the Snakes of Europe and those of Eastern Asia than there is between the latter and those of North America, whilst in Lizards a primary distinction must be made between the Old World and the New. Southern Asia east of Persia (the Oriental Region) is the great Ophidian centre, all the groups mentioned above, with the exception of the Dasypeltinæ, having representatives within its limits, and a large and very distinct family, the Uropeltidæ, being confined to it. The Pythoninæ occur along with the Boinæ, the Viperinæ with the Crotalinæ, and the Elapinæ are represented by varied forms, as they are also in Africa and still more in Australia, where they form the overwhelming majority, and in some parts, as well as in Tasmania, the exclusive Ophidian population. The coasts of India and Malaya are also the home of the great majority of the Hydrophiinæ. Large genera like _Tropidonotus_, _Zamenis_, and _Coluber_, extend over the Europo-Asiatic and North American regions, but they are equally well represented in the Oriental. The great difference between Madagascar and Africa is, as we have said, very striking. Madagascar possesses Boidæ generically identical with those of South America, but otherwise only Typhlopidæ, Colubrinæ, and Dipsadomorphinæ; whilst in the greater part of Africa the Boinæ are replaced by the Pythoninæ, and the Glauconiidæ, Elapinæ, and Viperinæ are generally distributed. North America agrees with Asia and South America in its Crotalinæ, otherwise its Ophidian fauna is not very different from that of Europe, although much richer, and South America shares the Glauconiidæ with Africa and the Ilysiidæ with Southern Asia. South America is rich in Colubrinæ and Dipsadomorphinæ, nearly all generically different from those of other parts of the world, and the Elapinæ are represented by the single genus _Elaps_, with many species, two of which extend to the southern parts of North America.