356 GEOLOGICAL SURVEY OF THE TERRITORIES, 



teeth discovered by Professor Hay den, who refers them to the lowest bed 

 of the tertiary formation of the mauvaises terres. The animal approached 

 in size the common ox. 



PERISSODACTYLA. 



This name, originally employed by Professor Owen, I have used to 

 include all the uneven-toed pachyderms of Cuvier, except the solidun- 

 gulate or equine animals. Thus restricted, the order is represented by 

 seven genera, in the tertiary formations of our Western States and 

 Territories. 



Rhinocerotidce. 



Among the most interesting paleontological discoveries in this coun- 

 try is that of the former existence of the rhinoceros family on the 

 North American continent. Remains of a number of species have been 

 detected in Dakota, Nebraska, Texas, California, Oregon, Colorado, 

 Wyoming, and traces even in New Jersey. 



RHINOCEROS. 



The existing species of this genus are now confined to Asia and 

 Africa. Remains of extinct species have been found in great abund- 

 ance throughout Europe and Northern Asia.* The living species are 

 provided with one or two horns ; some of the extinct ones were hornless, 

 and have, on this account, been referred to a different genus, with the 

 name of Aceratherium. 



Rhinoceros occidentalis. — A hornless species, distinguished by the above 

 name,. and little more than half the size of the common Indian rhinoceros, 

 is indicated by an abundance of remains in the miocene tertiary deposits 

 of the mauvaises terres, of White Eiver, Dakota. Its dentition is the same 

 as in the living unicorn rhinoceroses ; that is, it possesses two incisor and 

 seven molar teeth on each side of both jaws. 



The length of the skull of this species is one foot and a half. 



Rhinoceros crassus. — This species, about the size of the Indian rhinoce- 

 ros, is indicated by a few fragments of jaws and teeth discovered by Pro- 

 fessor Hayden in the pliocene sands of the Niobrara Eiver, Nebraska. 



Rhinoceros meridianus. — A third species, intermediate in size with the 

 two former, is indicated by an imperfect molar tooth, discovered by the 

 late Dr. B. F. Shumard in a tertiary formation of Washington County, 

 Texas. 



Rhinoceros hesperius. — A fourth species, under this name, has been 

 viewed as distinct from the former ones, and was founded on specimens 

 submitted to the writer by Professor J. D. Whitney. The specimens, con- 

 sisting of the greater portion of a lower jaw with the teeth, and some 

 fragments of upper molars, were derived from a tertiary deposit of Cal- 

 averas County, California. The species was about the size of the R. 

 occidentalis of the mauvaises terres. 



Recently some remains, probably of the same species, were sent to 

 the writer for examination by the Rev. Thomas Condon, who obtained 

 them on the John Day River, Oregon. 



HYRACODON. 



This genus has been proposed by the writer, founded on abundance 

 of remains of a small rhinoceros, which differs from all others previously 



