xiv DISTRIBUTION 005 



In the lower Eocene none of the Mammals belong to existing 

 genera, but in the upper Eocene are found Didelphys (Opossum), 

 Rhinoceros, Viverra (Civet), Mustela (Weasel), and possibly Canis. 

 The period is also remarkable for the number of annectent or 

 linking forms. There are, for instance, species connecting Dogs 

 with Bears and with Civets, Civets with Hyenas, Hyaenas with 

 Cats, Pigs with Pecora, Deer with Chevrotains, Tapirs with Rhino- 

 ceroses and with Horses, and so on. It is perfectly clear that the 

 orders, sub-orders, and families of Mammalia, as we now under- 

 stand them, were, during the Eocene period, becoming gradually 

 differentiated from common ancestral forms. 



In the Miocene period the Proboscidea (Elephant and Mastodon) 

 make their appearance, as well as a Gibbon (ITylobates), and some 

 other Anthropoidea. Many existing families have arisen, such as 

 Hedgehogs, Shrews, and Moles, Mice, Rabbits, and Porcupines; 

 Whales and Dolphins ; Tapirs, Hippopotami, Swine, and Antelopes ; 

 and species of Felis and Canis. The Rhinoceroses of the period 

 still have no horns, and the antlers of the Deer are small or absent. 

 The Tapir-like ancestors of the Equidae found in the Eocene have 

 developed into more Horse-like forms, and the ancestors of the 

 Camels (Poebrotherium) still retain upper incisors and distinct 

 metacarpals. Numerous Diprotodont Marsupials lived in South 

 America during this or the preceding period. 



The Pliocene fauna has a still more modern aspect, a large 

 proportion of the animals composing it belonging to existing 

 genera, although most of the species are extinct. Complex antlers 

 have appeared in the Deer, horns in the Rhinoceroses, and tusks 

 in the Pigs. The occurrence of Giant Tortoises (Testudo) in 

 the pliocene of both Palasarctic and Nearctic regions, and of a 

 Chimpanzee and a true Ostrich (Struthio) in deposits of this age 

 in India and the Crimea, indicates the northern origin of these 

 forms. Indeed it seems probable that most of the higher Verte- 

 brata, except Penguins and the New- World Edentates, have 

 originated in the Holarctic region. 



In the Pleistocene period many existing species have made 

 their appearance, but their geographical distribution is very diffe- 

 rent from that of the present day. For instance, the European 

 fauna includes many forms now confined to the Ethiopian and 

 Oriental regions, such as Apes, large Felidae, Hyenas, Tapirs, 

 Rhinoceroses, Hippopotami, Horses, and Elephants, all of which 

 appear to have been driven southward by the cold of the Glacial 

 epoch. In some parts of the world the Pleistocene fauna includes 

 remarkable and often gigantic forms now extinct, the most notable 

 being the great Edentates (Megatherium, Mylodon, G-lyptodon, etc.) 

 of South America, the gigantic Marsupials (Diprotodon, Nototherium) 

 of Australia, and the great flightless Birds (Dinornis, ^pyornis, 

 etc.) of Madagascar and New Zealand. The occurrence of a Monkey 



