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UINTA SELENODONTS 



large compressed claws taking the place of the hoofs. In the oreodonts, on 

 the other hand, the cranium was somewhat shortened, the orbit became closed 

 behind by the union of the postorbital processes from the frontal and jugal, 

 and a deep pit appeared on the lachrymal ; the molar teeth assumed a tetra- 

 selenodont pattern much like that of the nwdern deer, while the skeleton of 

 the trunk, limbs, and feet underwent comparatively little modification, and 

 even in long subsequent periods the changes in the skeleton never were 

 extreme or radical. 



Although the White River members of the oreodonts and agriochoerids 

 had thus become widely separated, the Uinta representatives of the two fami- 

 lies were still very close together, and, were it not for their subsequent history, 

 no one would hesitate to include them all in the same group. Not only are 

 Protoreodon and Protagriocha:rus very much alike in all known parts of their 

 structure, but the former even has a great deal about it to suggest relationship 

 with Agriochixrus, and it lacks but comparatively little of being itself the 

 common ancestor of both families. The skull is of a pattern from which both 

 the oreodont and the agrlochcErid type might readily be derived, as is also the 

 dentition, save only the upper molars. The latter seem to have already pro- 

 gressed too far in the direction of the true oreodonts to be ancestral to the 

 curious upper molars of Agrioclicems. The lower molars, on the contrary, 

 are very much like those of the White River genus. The feet also would 

 appear to have undergone changes in the same direction and away from the 

 primitive condition which was common to the two families. 



The connection between the two Uinta genera becomes all the closer 

 when the various species of Protoreodon are studied with reference to this 

 point. The species which I formerly called Agriothermm paradoxicum, and 

 which I regarded as probably ancestral to Agriochcerus, tends to bridge the 

 gap between Protoreodon and Protagriochcents , and, indeed, stands almost mid- 

 way between the two genera. I said of it : " The differences between Pro- 

 toreodon and Agriotheriian are such as strongly to suggest the inference that, 

 while the former is the ancestor of the oreodonts, the latter stands in a similar 

 relation to the agriochoerids. This determination can at present only be pro- 

 visional until more is learned concerning the foot-structure of the present 

 genus. At all events, if Agriotlierium be not the desired ancestral form, we 

 may feel confident that that form when found will prove to be of a very similar 

 character." ('98, p. 80.) The discovery of Protagrioch(xrus renders it highly 

 probable that this genus is the " similar form" sought for and is the actual 



