THE MIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 293 



appears in the valleys. Of these several phyla of horses the Hypohippus 

 is closest to the Middle Miocene A nchitheriuni of Europe; in fact, it was 

 believed by Scott ^ to belong to this genus. Widely distinguished by its 

 elongate or sub-hypsodont molar teeth is the plains-living, probably grass- 

 eating horse Mery- 

 chippus of Colorado, 

 certain species of 

 which lead into the 

 true equines or Hip- 

 potheriinae. 



The tapirs are still 

 sparingly represented 

 in the remains of ad- 

 vanced types. 



Dominant mem- 

 bers of the artiodactyl 

 fauna are the oreo- 

 donts and camelids, 

 both of which show a 

 high degree of adap- 

 tive radiation. Among 

 the oreodonts Mery- 

 cochcerus and Mery- 

 chyus persist. Pro- 

 merycochoerus is again 

 abundant in the Deep 

 River beds of Mon- 

 tana. The very char- 

 acteristic and wide- 

 spread genus Ticho- 

 leptus is probably a 

 direct and slightly 

 modified descendant of Eporeodon of the summit of the Oligocene, while the 

 small and extremely broad-skulled Cyclopidius suggests Leptauchenia of the 

 Upper Oligocene. 



The camels are now still more clearly divided into the browsing types 

 with short-crowned teeth, and the grazing types with long-crowned teeth. 

 Among the former the remarkable 'giraffe camel' Alticamelus replaces 

 Oxydachjlus of the Lower Miocene. The recognition by Matthew - of 

 this parallel with the Old World giraffes was a most interesting con- 

 tribution to the Miocene zoology of America. The existence of long- 

 limbed, long-necked, brachyodont types of camels browsing from the 



' Scott, W. B., Mammalia of the Deep River Beds, 1895, p. 181. 



* Matthew, W. D., Fossil Mammals of the Tertiary of Northeastern Colorado, 1901. 



Fn;. 145. — Skull, neck, und limbs of the large Middle Mio- 

 cene "giraffe camel," Alticamelus altus, of Colorado. In the 

 American Museum of Natural History. After Matthew. 



