132 Annals of the Carnegie Museum. 



length of the humerus and radius of Professor Cope's genus of the 

 Washakie Eocene Triplopus cubitaUs and the recently acciuired 

 material of Prothyracodon from the Uinta deposits. It is thus seen 

 that the genus from the Uinta has the fore limb much more like that 

 of the Oligocene genus Ilyracodon than is the case with the genus 

 from the Washakie. The type of the latter was, according to Pro- 

 fessor Cope, "cut from a block of calcareous sandstone" and Dr. 

 Matthew of the American Museum of Natural History assures the 

 writer that there is no doubt as to the correct association of the parts 

 of the type specimen upon which Cope founded the genus. ^'^° A re- 

 stud}' of the type of Triplopus cnbitalis, compared with the material 

 in the Carnegie Museum, results in definitely placing the form from the 

 Uinta in a separate genus, Prothyracodon, as was originally done by 

 Scott and Osborn. The generic rank of the form from the Uinta was 

 called into question by Professor Osborn in a later publication.^-^ 



Prothyracodon obliquidens is represented in the Carnegie Museum 

 by a number of individuals. These are all more or less fragmentary, 

 but serve to throw further light on the limb-structure of this cursorial 

 Rhinoceros from the Uinta Eocene. C. M. No. 2942 is represented 

 by both fore limbs and is of approximately the same size as the type 

 of Prothyracodon obliquidcns. A second specimen, C. AE No. 3199, 

 not fully adult, and slightly smaller, is represented by both fore and 

 hind limbs. The former was found by the writer in the lower portion 

 of horizon C, six miles East of Myton, Utah, while the latter was 

 found by Mr. Earl Douglass in horizon C further east in the Uinta 

 Basin. The scapula of No. 2942 is represented only by a fragment of 

 the proximal end (See Pi. XLVI, Fig. 5). It agrees with the descrip- 

 tion and illustration by Professor Cope.^-'^ In a specimen, which 

 probably pertains to another species, described on page 134, the scapula 

 Is fairly well-preserved. This bone is quite elongated, with a long neck. 

 The spine, however, rises more rapidly than that in Hyracodon of the 

 Oligocene and differs further from that genus by having apparenth' the 

 acromion process situated lower down or nearer the glenoid cavity,'-^ 

 and by having a proportionally shorter and broader blade. 



'-» Tertiary Vertebrata, p. 684, PI. L\'Ia. 



'-'"The Mammalia of the Uinta F"ormation," Trans. Aincr. Philos. Soc, \'ol. 

 X\T, 1889, p. 524. 



'22 Tertiary Vertebrata, p. 684, PI. LVIa. 



'23 The spine in this region is broken, but what still remains is proportionally 

 higher and differs otherwise from that in Hyracodon and is more suggestive of 

 Mesohi l^pHs. 



