276 



University of California Publications. 



[Geology 



Measurements, M 8 ?. 



No. 11854 



Greatest anteroposterior diameter 

 Greatest transverse diameter 



21. mm. 

 20.2 



OREODONTIDAE 



MBEYCHYUS ( ?) , sp. 



Two molar teeth from Virgin Valley furnish the only evi- 

 dence of oreodonts from the deposits of this region. 



One specimen, no. 12606 (fig. 48) , is an upper molar two. This 

 tooth is very near the stage of devolopment of Eporeodon, but 

 the crown tends to be slightly more hypsodont and the mesostyle 

 more sharply narrowed anteroposteriorly. At the point where 



Tig. 48. Merychyus, sp. M 2 . No. 12606, natural size. Virgin Valley 

 Beds, Virgin Valley, Nevada. 



Fig. 49. Merychyus, sp. M,. No. 11825, natural size. Virgin Valley 

 Beds, Virgin Valley, Nevada. 



the horns of the hypocone and protocone crescents are united, the 

 posterior horn of the protocone crescent is a little wider than the 

 anterior horn of the hypocone crescent. 



There is only a suggestion of ribs on the outer side of the 

 paracone and metacone. The cingulum is well developed on the 

 anterior side of the protocone crescent, and between the proto- 

 cone and hypocone. It extends around the inner border of the 

 protocone as a faint ridge. The cingulum is interrupted on the 

 inner side of the hypocone, but is represented by a weak shelf 

 on the posterior side of the hypocone crescent. Faint shelves 

 are present on the cingulum of the outer side of the paracone 

 and metacone. 



A lower molar three, no. 11825 (fig. 49), shows a weak median 

 style and only faint indications of ribs on the middle of the 

 inner side of the two inner crescents. A shelf is developed on 

 the cingulum only on the anterior side of the tooth. The pos- 



49 



48 



