SUCCESSIVE MAMMALIAN FAUNAS 231 



portions, some being extremely heavy, with very short legs 

 and feet, and these were the commonest, while others had 

 longer legs and less massive bodies. Tapirs, on the contrary, 

 would seem to have been scantily represented ; at least, they 

 are rare among the fossils. The extraordinary, aberrant 

 fchalicotheres, perissodactyls with claws instead of hoofs, 

 still persisted, but are far better known from the lower Miocene, 

 in connection with which they will be described. The domi- 

 nant perissodactyl family was that of the horses, of which 

 no less than five genera are already known. There were 

 some with very low-crowned teeth, which must have fed 

 principally by browsing upon leaves and such soft diet ; but 

 the grazing kinds, which had high-crowned, cement-covered 

 and very complex grinding teeth, had come to the fore. Still 

 retaining three toes in each foot, with the middle toe so en- 

 larged as to bear nearly the entire weight, save in snow or 

 soft ground, these eminently cursorial animals, which had 

 the slender limbs of a deer, must have roamed the plains in 

 great herds. 



Still commoner were the Artiodactyla. Many species 

 of grazing camels, which were the predominant artiodactyl 

 family in North America during upper Miocene times, were 

 the ancestors both of the true camels of the Old World and the 

 South American llamas. fGiraffe-camels have not yet been found 

 and no doubt they were much less abundant than in the middle 

 Miocene, but that they had not completely disappeared is 

 shown by their recurrence in the Pliocene. As compared with 

 earlier ages, the foreodonts had begun a rapid decline and had 

 lost notably both in numbers and variety, but one most curious 

 beast {]Pronomotherium, Fig. 197, p. 375) marked the final step 

 in the development of the short-faced, proboscis-bearing series, 

 which may be traced back to its beginnings in the Ohgocene. 

 In this wonderful creature the skull was so short and deep as 

 to suggest that of a gorilla or some other great ape. No other 

 artiodactyls even approximate these later proboscis-bearing 



