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99 



UINTA SELENODONTS 



for the most part clearly recorded, extending, as it does, through the Loup 

 Fork at the top of the Miocene. During this long period they were nearly 

 or quite the most abundant of North American mammals, but they were very 

 conservative and underwent relatively little change, and so far as is known 

 they never migrated to any other continent. Throughout this time they re- 

 tained their characteristic form of skull and dentition, together with the same 

 short neck, long body and tail, short limbs and feet, which we find in the Uinta 

 Protoreodou. In their general appearance and proportions there is little to 

 suggest relationship with the Tylopoda, but much to suggest a connection with 

 the suillines, though any such connection must be exceedingly remote. 



While the line of descent from Protorcodon is thus reasonably clear, it is 

 not yet possible to determine the ancestors of that genus. In some respects 

 the molars of the smaller species of the Bridger Helohyiis suggest the deriva- 

 tion of the Uinta genus from it, but, on the whole, Hoviacodon, or some nearly 

 allied form, seems to be the more probable ancestor, which is as much as to 

 say that the oreodonts appear to lead back to the same group of Bridger 

 artiodactyls as do the other Uinta selenodonts. If this conclusion is sustained 

 by future discovery, it will completely justify Schlosser's opinion, already 

 quoted, and will show that the oreodonts represent a peculiar side-branch of 

 the tylopodan stem, standing in somwhat the same relation to the Cainelidce 

 proper as the tragulines do to the Pecora. It will also serve to explain the 

 many resemblances which are to be noted between the oreodonts on the one 

 hand and such genera as Leptovicryx and Protoceras on the other, resemblances 

 which are exceedingly puzzling on any other hypothesis. 



These conclusions are of great interest, and if sustained they will help to 

 clear up many obscure problems of phylogeny, but it must not be forgotten 

 that they are still only tentative ; new discoveries among the artiodactyls of 

 the Washakie and Bridger proper may at any time overthrow them. I think, 

 however, that they are justified by the evidence now at hand. 



Hyomeryx Marsh. 

 Amer. Journ. Sci., 3d Ser., xlviii., p. 268. 



I have not seen any specimens of this genus, which is described as having 

 lost all the upper incisors. Marsh's figure also shows that the upper molars 

 are different from those of Protorcodon in having much less concave external 

 crescents and less prominent outer buttresses. 



No White River genus is known that can be regarded as a descendant of 



