I2O THE NEOG^EIC REALM. [CHAP. 



are abundant in the North American Tertiaries New World deer 

 (Cariacus], horses (Equidce) of various genera, tapirs (Tapirid&\ 

 peccaries (Dicotylidte), and mastodons. Among the rodents, 

 squirrels, the various genera of Muridce, and the hares, likewise at 

 this epoch made their first, appearance on the scene. Opossums 

 also at this time effected an entrance into the land which has now 

 become their chief home. That this new fauna came in from 

 North America, and not from any other part of the world, may be 

 regarded as certain from the presence of such essentially New 

 World types as raccoons and their allies, skunks, peccaries, 

 Cariacus, and Camelidce (exclusive of the Old World genus 

 Came/us, which is of late origin), coupled with the absence of 

 true deer (Cervus), pigs (Sus), Old World monkeys, and lemurs. 



At the same time this union of the northern and southern 

 halves of the New World allowed certain members of the original 

 Neogaeic fauna to make their escape into North America, glypto- 

 donts, as already said, making their appearance in the Nebraska 

 stage of the Loup-Fork group of the United States, while the 

 ground-sloth Megalonyx occurs in the Blanco Beds. 



Although it is not universally admitted 1 , there is some 

 evidence to indicate that this land connection was of com- 

 paratively brief duration, seeing that none of the characteristic 

 extinct types of South American ungulates, nor any of the peculiar 

 Neogaeic rodents, reached the northern half of the continent. 



During the whole time that the alluvial deposits of the Parana 

 and Paraguay rivers were being laid down, and well on into the 

 human period, the mammalian fauna of the Pampean epoch, formed 

 by an admixture of southern and northern types, continued to 

 flourish, until the time when there came a complete sweep of all 

 the larger forms, clearing off the whole of the ground-sloths, 

 glyptodonts, mastodons, toxodonts, macrauchenias, horses, sabre- 

 toothed tigers, and the larger members of the camel tribe, and in 

 the Argentine leaving only armadillos, guanacos, a few deer, a 

 number of rodents, various cats and foxes, as well as skunks and 

 certain other members of the weasel family, to represent the vast 

 assemblage of strange and giant creatures that once roamed over 



1 See Gregory, op. cit. p. 300. 



