82 



Annals of the Carnegie Museum. 



importance. When compared with Achcenodon the teeth of Parahyns 

 vagus are proportionally larger in relation to the size of the jaw, 



Fig. 12. Parahyus vagus. From a cast in the Carnegie Museum. No. 3448. 

 Original type specimen in Peabody Museum of Natural History. 



which is much slenderer and has a different contour from that of 

 Achcenodon, the under border being straighter fore-and-aft. Dentition 

 I?3". Cy, P3, M3-. Premolars more compressed laterally than in 

 Achcenodon, especially A. uintense. The dentition is proportionally 

 longer, M-g- being one third narrower while of the same actual length 

 as in A. rohustus. The cross- valleys between the posterior and 

 anterior tubercles of the molars are wider and the heel of Mg- is more 

 distinctly separated from the main body of the tooth than in Achce- 

 nodon. 



In the type of Parahyus aberrans Marsh the external tubercles of 

 the upper molar possess more conical symmetry than in Achcenodon, 

 and, as in the lower teeth of the type of Parahyus vagus, the tubercles 

 of the upper tooth of Parahyus aberrans are also separated by more 

 clearly defined valleys than in Achcenodon. 



Family AGRIOCHCERID.E. 



Genus Protoreodon Scott and Osborn. 



22. Protoreodon medius sp. nov. (Plate XL, Figs. 1-16). 

 Type: Greater portion of the skeleton, C. M. No. 2962. 

 Horizon: Uinta Eocene, Horizon C. 



Locality: Six miles east of My ton, on the Duchesne River, Utah. 

 Besides the type specimen there are numerous fragmentar\- remains, 



