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UINTA SELENODONTS 



ship to the oreodonts. The Uinta representatives of the latter family are still 

 more like Agriochosrus and materially diminish the gap between the two 

 groups. Even though Protagrioclicerus should eventually prove not to be the 

 direct ancestor of Agriochcerus, it certainly tends to approximate the two 

 families very closely and to render it entirely probable that both were derived 

 from a common Bridget' ancestor. That this hypothetical ancestor was in its 

 time nearly allied to the forerunner of Protylopus, and still more so to that of 

 Leptoreodon, seems also very likely, whence follows the further probability that 

 the Orcodor.tidce and Agriodiceridce, like all the other indigenous North Ameri- 

 can selenodonts, should be referred to the Tylopoda. 



SUMMARY AND CONCLUSIONS 



1. The American Tertiary Selenodonts form two distinct assemblages: 

 first, those derived by migration from the Old World, and, second, the truly 

 indigenous forms. The former includes the anthracotheres and the true 

 ruminants, while the latter has the oreodonts, agriochcerids, the Lcptomerycidce, 

 and Camclidce. 



2. The Uinta fauna is the oldest American horizon in which the seleno- 

 donts are numerous and conspicuous. 



3. The study of these Uinta selenodonts strongly suggests that all the 

 indigenous American forms are nearly related and should all be referred to 

 the Tylopoda. 



4. The Tylopoda are a highly diversified group, filling in America the 

 place taken in Eurasia by the Pecora and Tragulina, which they parallel in 

 many ways. 



5. The Uinta beds are confined to the basin south of the Uinta Mount- 

 ains, where they overlie the upper Bridger (Washakie) ; they are divisible 

 into two horizons (B and C), of which the lower is transitional from the 

 Washakie. Apparently there is an unconformity between B and C. 



6. The Uinta is to be correlated with the Lutetian of France, and belongs 

 to the uppermost Eocene or lowest Oligocene. 



7. Leptomeryx, a White River genus, retains some of the upper incisors, 

 but not the canine ; the lower canine is incisiform and p T caniniform, but 

 much reduced in size. The premolars are compressed and trenchant, but 

 complicated by internal cusps; the molars are very brachyodont and have a 



