258 LAND MAMMALS IN THE WESTERN HEMISPHERE 



were beginning to assume the high-crowned character. From 

 this it may be inferred that those animals were, partly at least, 

 of grazing habit, which was rare among White River ungulates, 

 most of which fed upon leaves and soft and succulent plants. 

 An extinct family, the fHypertragulidse, were a greatly diver- 

 sified group of dainty httle creatures, one of which (fHijpisodus) 

 was no larger than a rabbit and had high-crowned teeth. 

 The other genera {jLeptomeryx, jHypertragulus) must have 

 resembled in form and proportions the tiny little chevrotains 

 or "mouse-deer" of the East Indian islands. Late in the 

 age arose a larger form of this family, nearly equalling the 

 Musk-Deer in size, the extraordinary genus ■\Protoceras, which 

 was, especially the males, a grotesque object. The males had 

 a pair of upper canine tusks and two pairs of prominent long 

 protuberances on the skull. This, or some similar form, must 

 have been the ancestor of the still more bizarre \Syndyoceras 

 of the lower Miocene. 



The foreodonts were by far the commonest of White 

 River mammals, and evidently they roamed the woods and 

 plains in great herds. There were several species, larger and 

 smaller, of the abundant genus {^Merycoidodon) but the largest 

 did not surpass a modern peccary in size and was somewhat 

 like that animal in appearance, but had a shorter head and 

 much longer tail. In the upper substage appeared a very 

 peculiar genus of this family {'\Leptauchenia) , animals with 

 short, deep, almost monkey-like heads, and presumably 

 aquatic in habits. The '\agriochoerids were very much less 

 common ; they may be described roughly as foreodonts with 

 very long, cat-like tails and clawed feet. 



All of the foregoing artiodactyl families were exclusively 

 North American in Oligocene distribution ; even the camels 

 did not reach Asia till the Pliocene, and the other families 

 never invaded the Old World at all. There were, however, 

 two additional families, which also occurred in the eastern 

 hemisphere, whence one of them, and possibly the other, was 



