THE TERTIARY PERIOD. 245 



That old tvpe of mammals, so common in Eocene times, but 

 now confined to South America, the Tapirs were represented in 

 the Pliocene of the plains by one species. Marsh, who describes 

 it, calls it Tapirus rarus. 



The hog family (SuiWce) had fewer representatives than in the 

 preceding epoch. One species of peccary alone seems to have been 

 abundant. 



Ruminants were abundant during the Pliocene in Nebraska. An 

 antelope, [Cosoryx furcatus^) described by Leidy, and intermediate 

 in character between the deers and antelopes, has left its remains on 

 the Niobrara. In company with the last was a true deer (Cervus 

 JVarreni), also described by Leidy. It was about the size of the 

 Virginia deer. 



The Oreodons, described under the Miocene, had dwindled in 

 the Pliocene to three species of the genus Merychyus. The rela- 

 tive position, form of the teeth, and their number was the same as 

 in Oreodon. The crowns of the teeth, however, were larger in 

 proportion to their breadth than in Oreodon. Merychyus major 

 was the largest species, and was near the size of the camel. M. 

 medius was intermediate in size between the llama and camel. On 

 the whole, while the number of species was less, the average size 

 was greater in this family than during the Miocene. 



The camel family (Camelidee) were even richer in genera, species, 

 and the number of individuals than during the Miocene. The 

 most characteristic genus was Procamelus, which was represented 

 by at least four species, three of which were described by Leidy. 

 Their remains are found on the Niobrara, Loup, and Republican. 

 Procamelus had one more premolar to the upper, and two more to 

 the lower series of teeth than in the modern camel. This indicated 

 a less mature condition, or a condition before they have shed those 

 teeth which reduce them to that observed in their adult form. The 

 lower true molars are also smaller in proportion to the size of the 

 jaw than is the existing camel. The molar series, though composed 

 of smaller teeth than in the camel, occupy, because of their greater 

 number, more space along the border of the jaw. Thus in the 

 camel, while the four molar teeth occupy five and a half inches, in 

 in Procamelus robustus the six: molars occupy six and a fourth 

 inches. — (Leidy.) Some of the species approximate in some of the 

 characters of the lower jaw to the llamas. Procamelus robustus, 

 the largest species, was about the size of the existing camel. The 



