1898] MAMMALIA IN EUUOFE AND NORTH AMERICA 385 



typically eastern animals comprise the saiga antelope, the jerboa, 

 the tailless hare, and Myogalc moschata ; while among the numerous 

 southern types may be mentioned the lion, leopard, hyaena, and 

 hippopotamus. The principal forms which have since become 

 extinct are Machaerodus latidens, Ursus spelacus, Cervus giganteus, 

 Trogontherium cuvieri, Elephas primigcnius, E. antiquns, Rhinoceros 

 antiguitatis, and the great remarkable Paissian rhinoceros, Elas- 

 motherium sibiricitm. Of these latter, the so-called Irish deer 

 {Cervus giganteus) is the only one which seems to have survived 

 until the dawn of historic times. 



The Pleistocene deposits of North America yield much fewer 

 mammals than those of Europe ; but there is a similar mingling 

 of northern and southern types in the central region. It is also 

 interesting to note that one of the commonest skeletons represents 

 the latest known species of Mastodon {M. amcricanns). The mam- 

 moth, musk-ox, reindeer, elk, and bison are present ; bears have 

 now arrived, and the lion may also perhaps be represented ; but 

 Equus has already become extinct, and there are no traces of the 

 woolly rhinoceros (R. antiquitatis), the cave bear, or the hyaena. 

 In the surface deposits of the southern United States some of the 

 ■typically South American edentates occur (Megatherium, Mylodon, 

 Glyptodon), these having apparently wandered northwards on the 

 emergence of the isthmus of Panama in the early part of the 

 Pliocene period. 



North American v. Old World Mammals 



Having thus traced the series of mammalian faunas through 

 the Tertiary formations both of the Old World and of North 

 America, it is interesting to speculate as to where the various 

 elements arose. At the base of the Eocene it is evident that the 

 faunas of the east and the west were essentially identical. As they 

 are traced upwards they gradually diverge. 



The first noteworthy difference is the great development of the 

 Condylarthra in America, and the rise in the Eocene of the large 

 specialised Amblypoda, of which only a single genus (Conjphodon) 

 has been found in the corresponding fauna of Europe. On the 

 other hand, the still larger hoofed animals of the sub- order 

 Proboscidea seem to have originated in the Old World, and did 

 not reach America until the late Pliocene. 



The Perissodactyla — the tapirs, rhinoceroses and horses — appear 

 to have advanced on a parallel course on the two continents ; though 

 in America both the rhinoceroses and horses became extinct at the 

 close of the Pliocene, the former without acquiring the characteristic 

 horn. 



Among Artiodactyla, both the deer and pigs seem to have been 



