Peterson: Material Discovered in Uinta Basin. 131 



placed in Amynodou adveiiiim (Marsh)"" while the larger are referred to 

 Amynodon intermedium Osborn."^ Of the smaller specimens those 

 which have the upper and lower premolars preserved show three in 

 either jaw, which according to Osborn's reidentification (/. c, 1889, 

 page 507) would, except in size, agree with Amynodon advenum. 

 The best preserved specimen representing the larger species, is C. M. 

 No. 3200, the greater portion of a skull of an adult, perfectly symmetri- 

 cal. Unfortunately, however, the dentition is represented only by 

 the roots of the posterior premolars, the roots of the molars, and a 

 portion of the crown of M^ (PI. XLVII, Fig. 5). This portion of M^- 

 and the general large size of the teeth agree with A. intermedium and 

 an outline drawing of the dentition of the type as figured by Osborn 

 (/. ("., PI. X, Fig. 10) is here added in connection with the palatal view, 

 in order to better aid the student in comparative work (See PI. XLVII, 

 Fig. 6). A side view of the specimen in the Carnegie Museum is 

 given in Fig. 7 on the same plate, in order to supplement the figures 

 given by Osborn of the dentition and maxillary region, the only por- 

 tions of the type specimen preserved. The description of the skull, 

 which belongs to the articulated young skeleton exhibited in the 

 American Museum of Natural History, referred to A. intermedium 

 by Osborn"^ appears to agree quite well with the present cranium. 



Subfamily HYRACODONTIN^. 

 Genus Prothyracodon Scott and Osborn. 

 40. Prothyracodon obliquidens Scott & Osborn (Plate XLVI, Figs. 

 1-9). 



Proc. Amer. Philos. Soc, Vol. XXIV, Sept. 2, 1887, p. 260. 



Generic Characters: If, c\, P^^, M^. Incisors subequal in size; 

 upper canine followed by a short diastema, loiver canine close to Ij; 

 a general advance of the cheek dentition toivards the Ilyracodonts and 

 Rhinoceroses of the Oligocene; that is, a decided development of the crista, 

 crochet, and anticrochet together with the Rhinocerotic structure of M- 

 (Prothyracodon nintense, vide infra). Fore limb proportionally shorter 

 than in Triplopns. Animals larger than Triplopus. . 



It is a matter of surprise to find such differences in the proportionate 



1'^ Awer. Jour. Sci., Vol. IX, 1875, p. 244. 



118 "The Mammalia of the Uinta Formation," Trans. Amer. Philos. Soc, Vol. 

 XVr, 1889, p. 508. 



^^^ Bull. Amer. Mus. Nat. Hist., Vol. VII, 1895, p. 95. 



