THE TERTIARY PERIOD. 227 



cause of its depression in the middle, bore some resemblance to a 

 pack-saddle. They probably had a small trunk about as long as 

 that of the tapirs. They had two pairs of horns, one pair being 

 above the nasals and another pair above the eyes, the hind pair be- 

 ing powerful weapons of defense. They probably were the succes- 

 sors of the Dinocerata of the Eocene. Of the Svmborodons Cope 

 has described five species. As two species of Brontotherium were 

 also described by Marsh, it is clear that the number of species was 

 great, and judging from the remains, there must have been a very 

 great number of individuals. 



Along with the Svmborodons the elephants and mastodons were 

 already represented by several species. The remains of the one 

 that I found on the White Earth, in Nebraska, were too much de- 

 cayed to identify specifically. It bore the closest resemblance to 

 the Mastodon merificus that appeared during the next or Pliocene 

 epoch. 



Among the most unexpected of all discoveries in the Nebraska 

 Miocene was the remains of rhinoceros'. One, the Rhinoceros oc- 

 cidentalis, was about three-fourths the size of the Indian rhinoceros. 

 R. Coloradoensis was found in the Miocene of the mountains. 



The curious European genus of river horses {Hyopotamus) was 

 represented during those times by at least one species. It had af- 

 finities relating it to the hog family. 



Genera closely related to the hog family (Suidce) were abundant 

 during this epoch. One of these genera (E/otherium), which was 

 first described from the Miocene of France, was represented bv 

 several species during these times in Nebraska and Dakota. Its 

 nearest allies among existing animals are first the hogs, and then 

 the peccary and hippopotamus. One of these (E. Martoni) was 

 about the size of a large hog, while another (E. ingetis) was at least 

 one-third larger. The peccaries, which are now confined to South 

 America and the southern United States were represented in Ne- 

 braska during the Miocene by several species. Five other genera 

 of the Suidae occur in these deposits. During this period, there- 

 fore, it is evident that suilline animals existed in great numbers all 

 over the land. 



The most curious fact, perhaps, connected with the animal life of 

 this epoch, was the presence of many species of the camel family. 

 At present it is confined to Asia, Africa and South America. In 

 the former it is represented by the camel proper, and in the latter 



