60 GEOLOGICAL SURVEY OF THE TERRITORIES. 



longing' to the Pliocene period, which in other countries contains more 

 or less species identical with living ones. 



But this fauna comprises more than thirty species, all of them new 

 to science, and not one of them identical with any living species. Over 

 thirty species have been found along the Niobrara and Loup Fork, and 

 others may be looked for on more careful examination. 



Among the carnivora were four species of wolves, one about the size 

 of the large wolf of the plains, the others of smaller size ; two cats, one 

 intermediate in size between the panther and lynx, and the other nearly 

 as large as the panther. 



Among the rodentia was a porcupine about the size of the crested por- 

 cupine of Europe, and a small beaver about half the size of the living 

 one. Of the ruminants there were some remarkable species — two species 

 of deer, about the size of the common red deer of this country, and four 

 species of camel, one about the size of the common Bactrian camel, a 

 second species two thirds as large, and the third about the size of the 

 llama of South America. The fourth species was closely allied to the 

 living camel, but was of smaller size. Another species was more nearly 

 allied to the mountain-sheep, another was ruminant — hogs like the 

 Oreodon of White River. The solij)edia were remarkably well rep- 

 resented, there being remains of not less than a dozen species of horses. 



There were two species of the genus Uquus; one of them (jE/. excelsus) 

 was about the size of the largest varieties of the living species; the 

 other was smaller. The remainder were of various sizes and forms; one 

 of them was not larger than a ^Newfoundland dog. 



It is the law in animal development that groups reach their culmi- 

 nating period and decline. It would seem that during the latter Ter- 

 tiary period the horse tribe reached its highest point of development, 

 and that now it is on the decline. Among the pachyderms was a species 

 of rhinoceros about the same size and apparently closely related to the 

 living Indian rhinoceros, B. Indicus ; a species of Mastodon much smaller 

 than the one whose remains are so common in all x^arts of North Amer- 

 ica in the recent quaternary deposits. 



The remains of the elephant occur in the Niobrara, which is remark- 

 able for being a third larger than any other ever known, extinct or re- 

 cent. In view of this fact. Dr. Leidy named it JElepJms imperator — the 

 emperor of all the elephants. 



There was also one species of turtle in this more recent deposit, and 

 a species in the White River beds. The latter was exceedingly numer- 

 ous in this great fresh-water lake, for the specimens are scattered all 

 over the country, many of them preserved with great perfection. We 

 know that this was purely a fresh-water lake from the fact that numer- 

 ous species of fresh-water and land shells of the genera Helix, Planorbis, 

 Fhysa, Linnea, &c., are found in fine state of preservation. There are 

 also some indistinct remains of fishes. From these two faunas, as well 

 as the fauna and flora of other formations of this valley, there are some 

 instructive lessons to be learned. 



The fauna of White Eiver, although entirely extinct as to species, 

 contained representations of some living genera. The greater part 

 of the fauna of the Niobrara and Loui3 Fork belonged to living genera, 

 although every species was extinct, but the latter fauna is more closely 

 allied to the living fauna of Asia than to anj^ of our own continent. 



Indeed, it seems to have a true oriental character, and it is shown 

 clearly that, geologically speaking, our continent should be called the 

 Old World instead of the eastern continent. There are several other 



