differences of any one of them to either of the two realms which have just been defined. The two realms that have been discussed retain their distinctness from each other and from Arctogaea for a considerable way back into the Tertiary period. It is not until we reach very early Tertiary times that Edentates are met with in North America; and then it cannot be regarded as absolutely settled that the Ganodonta are really the forerunners of the Armadillos, Sloths, etc. Nor do we find Marsupials in Europe until far back in time, and at a corresponding period in North America. Indeed the fauna of South America in late Tertiary times was even more distinct than it is now; for then we had confined to that region the Toxodonts, Glyptodonts, Macrauchenia, and other forms, while in Australia there were still Marsupials. In late Tertiary times Europe and India were by no means so distinct from Africa as they are to-day. North America does not resemble the Old World quite so much as the subdivisions of the Old World resemble each other; but, as will be pointed out later, there are and were very substantial agreements. The Elephants, Rhinoceroses, Giraffe, Hippopotamus, Orycteropus, are now distinctively African or Indian animals; but all these genera, or at least families (in the case of the Giraffe), have occurred in Europe during quite recent times. Lycaon indeed, now confined to Africa, is thought to have had a European origin from its occurrence in caves there. The Hyaena and the Lion, certain members of the Horse tribe, Apes, and other animals, were also but are not now European.
India again, and the Oriental region generally, once possessed the Hippopotamus, the Chimpanzee, Giraffidae, the Antelopes, Cobus, Hippotragus, Strepsiceros, and Orias, which are now purely African animals. It shares at present with the Ethiopian region the Catarhines, including the Anthropoid Apes, the Lemurs, Tragulina (the genus Dorcatherium is also known from fossils in India), Manis, Hyaena, the Cheetah, Elephant, Rhinoceros, and the Ratel. There is, in fact, no order of mammals which is now absent from one of these three regions though present in the others, save the Lemurs, and they occurred in past times in Europe. The Tapir of India is known fossil in Europe, and the latter continent had its Monkeys and even Anthropoids. On the other hand, North America is more distinct. It has no Lemurs, Apes, Elephants, Rhinoceroses, Tapirs, Old World Edentates (Effo-
