128 THE WHITE RIVER BADLANDS 



had observed fossils of approximately five hundred indi- 

 viduals among the collections sent him for study. Few 

 general badland collections fail to show specimens of these 

 interesting creatures, but most of the material is made up of 

 skulls and detached bones. Few complete skeletons have 

 been obtained and until recent years little attempt was made 

 at restoration. The dentition is remarkably complete, the 

 total number of permanent teeth being forty-four arranged 

 in nearly unbroken series in both jaws. Of the Oreodons 

 Oreodon clubertsoni is by far the most common. Leidy says 

 that of the five hundred he had observed about four hundred 

 and fifty were of this species. Oreodon gracilis, about two- 

 thirds as large as Oreodon culbertsoni was perhaps the next 

 in abundance. Its skull was about the size of the red fox 

 and a skeleton mounted by Mr. C. W. Gilmore of the U. S. 

 National Museum measured twenty-seven inches in length 

 and is twelve and one-half inches high at the shoulders. 

 Eporeodon major, earlier called Oreodon major is still rarer. 

 It is about one-fifth larger than Oreodon culbertsoni or 

 nearly twice as large as Oreodon gracilis. 

 HYPERTRAGULIDAE 



The Hypertragulidae include some of the most interest- 

 ing fossil mammals ever discovered. They are ancient 

 selenodonts (ruminants) resembling in a way the little 

 chevrotain or "deerlet" of India and the musk deer of the 

 Asiatic highlands but they are in reality not closely related 

 to either. They seem to represent an independent offshoot 

 of the primitive ruminant stock but near relatives, either 

 ancestral or descendent are not known. 



They are distinguished from all other American rumin- 

 ants by the combination of functionally tetradactyl front 

 feet with didactyl hind feet. Of the seven genera thus far 

 recognized from the White Kiver region, Protoceras is the 

 most interesting and the best known. ( Plate 43 ) . It is found 

 only in the Upper Oligocene and because of its importance 

 the strata containing it are known as the Protoceras beds. 

 Of the other genera Leptomeryx has been most carefully de- 

 scribed but with the exception of one find of twenty-six 

 skeletons in one associated group and described by Riggs, 

 Bull. O. S. A., vol. 25, p. 145, the materials available have 

 not been so abundant nor so complete as in the case of 

 Protoceras. 



