THE MAMMALIA OF THE UINTA FORMATION. 471 



Part 1 1. 



nv wrr,LTA:\r r, scott. 



THE CREODONTA, RODENTIA, AND ARTIODACTYLA. 



PRIMATES. 



HYOPSODUS GRACILIS Uar^h. 



This species is the only one of the pseudo-lemuroids whieh has as yet heen 

 reported from the Uinta deposit s. This group is exceedingly abundant in tlie Bridger, 

 especially in the Bridger liasin ; it has become moi'c rare in the Washakie, and 

 although the Uinta has yielded but one species as yet, others Avill no doiilit be found. 

 The change from the Bridger will, however, almost certainly remain a vei-y striking 

 one in the reduction of these animals. They are not certainly known to occur in the 

 White River, though some specimens have been I'efcrred to the group {Laopithecus, 

 Menotlierhan). 



CREODONTA. 



MESON YX Cope. 



M. uintexsis Scott (No. 10, pj). 1G8, KiO); PI. X, Fig. 0. The specimen upon 

 which this species is founded consists of five isolated lower molar and premolar teeth, 

 an incisor, a canine, one upper premolar and fragments of the mandible, including the 

 condyle. The reference to Mesonyx is somewhat uncertain on account of the absence 

 of the upper molars ; there can be no doubt, however, that the species belongs to the 

 family MesonyrJifdup, and it is of interest as being the largest and latest known mem- 

 bei- of that long-lived and most curious group of creodonts. This species may be 

 distinguished from those of the earlier Eocene formations by very much greater size 

 and by the fact that the anterior basal cusps of the lower molars arc much reduced. 



The incisor is peculiar and consists of a l)road and rounded sim]>le crown; it is 

 of large size and contrasts strongly with the incisors of the Bridger species 3L obfn- 

 s ideas f the canine and upper premolar dilRi' from the corrcHponding teeth of the 



