ANCIENT AMERICA. 333 



find at once a nearer approximation than now exists 

 between the Nearctic and Palsearctic faunas. North 

 America then possessed several large cats, six distinct 

 species of the horse family, a camel, two bisons, and four 

 species of elephants and mastodons. A little earlier, in 

 the Pliocene period (although fossil remains of this age 

 are scanty), we have in addition the genus Rhinoceros 

 several distinct camels, some new forms of ruminants 

 and an Old- World form of porcupine. Further back, in 

 the Miocene period, we find a Lemuroid animal, 

 numerous insectivora, a host of carnivora, chiefly feline 

 and canine, a variety of equine and tapirine forms, 

 rhinoceroses, camels, deer, and an extensive extinct 

 family the Oreodontidse allied to deer, camels, and 

 swine. There are, however, no elephants. In the still 

 earlier Eocene period most of the animals were peculiar, 

 and unlike anything now living, but some were identical 

 with European types of the same age, as Lophotherium 

 and the family Anchitheridse. 



These facts compel us to believe that at distinct 

 epochs during the Tertiary period the interchange of 

 large mammalia between North America and the Old 

 World has been far more easy than it is now. In the 

 Post-Pliocene period, for example, the horses, elephants, 

 and camels of North America and Europe were so closely 

 allied that their common ancestors must have passed 

 from one continent to the other, just as we feel assured 

 that the common ancestors of the American and 

 European bison, elk, and beaver, must have so migrated. 

 We have further evidence in the curious fact that certain 

 groups appear to come into existence in the one continent 

 much later than in the other. Thus cats, deer, masto- 



