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UINTA SELENODONTS 



conule, an interpretation confirmed by the asymmetrical shape of these teeth in 

 many Uinta selenodonts. Bunoiiiayxis evidently descended from the Bridger 

 Homacodon and should be referred to the Homacodoniidce , a family which seems 

 to bear the same relation to the Tylopoda as the Dicliobunidcz bear to the Pecora. 



26. Protoreodoii (Uinta) is already a true oreodont, the family being dis- 

 tinctly differentiated as such in the Uinta. The dentition resembles most that 

 of Oreodon and is without diastemata, the lower canine being incisiform and pj 

 caniniform. In some species the upper incisors are reduced to two or even to 

 one. The premolars are somewhat simpler than in Oreodon, and the molars 

 broader and more distinctly brachyodont ; the upper molars retain the fifth 

 cusp (protoconule), and the lower molars are very like those of Agriochcerus. 

 The skull is also like that of Oreodon, but resembles that of Agriochm'us in 

 the narrow, elongate cranium, the incompletely closed orbit, and the absence 

 of a lachrymal pit. The vertebral column and limbs differ from those of 

 Oreodon only in minor details. In the carpus the lunar has shifted less com- 

 pletely upon the unciform and the poUex is somewhat larger. The pes is 

 almost exactly like that of the White River genus, except for a rudiment of 

 mt. i. attached to the ento-cuneiform. 



27. The genus Proioreodon seems to include two lines of development, 

 one represented by P. parvus and leading to the later oreodonts, the other 

 composed of species with reduced upper incisors, which became dominant in 

 the true Uinta beds, but seems to have died out without descendants. 



28. The OreodontidcE probably should be considered an offshoot of the 

 Tylopoda. 



29. Hyomeryx is distinguished from Proioreodon by the absence of upper 

 incisors and by the less concavity of the external crescents of the upper molars. 



30. Proiagriochcerus has a dentition much like that of Proioreodon, but 

 with somewhat more complex upper premolars, and molars with much more 

 concave external crescents and less prominent median ribs, and the external 

 median buttress is penetrated farther by the median valley. The skull, which 

 is very imperfectly known, seems to agree with that of Proioreodon. The 

 tarsus has considerable resemblance to that of Agriochoents , and though not 

 so broad and short, is much more so than in Proioreodon. 



31. Protagriochcerus is not sufficiently well known to make its taxonomic 

 position clear, but it seems to be the ancestor of AgriocJmrus. 



32. The Agrioehceridee are probably nearly related to the OreodoniidcE, and 

 derived from a common Bridger ancestor, and if so, they are aberrant Tylopoda. 



