THE REIGN OF MAMMALS. 



221 



hollow-horned ruminants appear for the first time in America 

 in the Lower Pliocene ; and no ancestry has so far been at- 

 tempted to be traced for them. The antelopes of this group, 

 as well as the gigantic Sivatherium of India, ^ allied to the 

 modern prong-horned antelope of North America, were pro- 

 minent in the Old World in the Miocane, 



A very noteworthy and specially American group of mammals 

 is that of the Edentates^ the Sloths and Ant-eaters, a group 

 which h priori wt should hj've supposed would have been one 

 of the earliest in time. They appear, however, first in the 

 Miocene, without even any suggested ancestry, and are repre- 

 sented from the first by large species, though they attain their 



Fig. 177. — OreodoK major. A generalised Miocene ruminant, with affinities to the 

 Deer, Camel, and Hog. Greatly reduced. — After Leidy. 



grandest stature in the Megatherium and Mylodon of the Post- 

 Pliocene (Figs. 178, 179), which were sloths of so gigantic size 

 that they must have pulled down trees to feed on their leaves, 

 unless, indeed, there were trees equally colossal for them to 

 climb. But before the modern time, like the American horses, 

 the larger herbivorous forms suddenly disappear, and are now 

 represented only by a few diminutive South American species, 

 which can scarcely, by any stretch of imagination, be supposed 

 to be descendants of their gigantic predecessors. The history 

 of these animals, like those of the great Tertiary marsupials ot 

 Australia and the many Miocene elephants of India, affords a 

 1 See Frontispiece to this Chapter, 



