272 DAVIDSON BLACK 



INTRODUCTORY 



The material on which this study is based was obtained through 

 the courtesy of Professor H. F. Osborn and Dr. W. D. Matthew 

 and is a part of the Exchange Palaeontological Collection pre- 

 sented by the American Museum of Natural History to the 

 ]\Iuseum of the Department of Anatomy of the Peking Union 

 JNIedical College. 



The extinct artiodactyl ungulates comprising the family Oreo- 

 dontidae were primitive ruminants presenting such a peculiar 

 admixture of characters as to induce Leidy to refer to them as 

 ruminating hogs (v. Leidy, 20, and Scott, 28, p. 372). These 

 animals were restricted in their distribution to North America 

 where their remains have been found in large numbers in the 

 middle Tertiary deposits of that continent. 



Many genera of this family have been distinguished ranging 

 in time from upper Eocene to lower Pliocene. The specimens 

 here described are all of Middle Oligocene age and w^ere taken 

 in the Oreodon Zone of the White River Group of the Big Bad 

 Lands in South Dakota (v. Osborn, 2Ji., map and sections, figs. 

 20 and 22). 



Two of the specimens, numbers II and IV respectively, were 

 identified as Oreodon culbertsonii, Leidy, which by right of pri- 

 ority should read Merycoidodon culbertsonii, Leidy. ^ The other 

 specimens labeled Oreodon are also of the genus Merycoidodon. 



Of the five natural casts here described, specimen I was already 

 prepared for study when it came into my hands. The tech- 

 nical work in connection with the preparation of the other speci- 

 mens has been done in the Anatomical Laboratory of this insti- 

 tution. 



The natural endocranial cast of Oreodon has been previously 

 figured and briefly described by Leidy {21, pp. 14, fig. 11) but 

 unfortunately this paper is not accessible to me. It is desirable, 

 however, that a further study be made of this interesting material. 



1 In his original descriiDtion of this genus Leidy {20) made use of the name 

 Merycoidodon, though it was subsequently discarded by him and by many suc- 

 ceeding writers in favor of the name Oreodon (vide Hay, 17). 



