1903.] Matthew, Fauna of Titatwtherium Beds of Montana. 22 1 



the drawing, especially as the other drawings of the type and 

 cotype agree well with the description and with our specimens. 

 The best upper jaw shows the molars and fourth premolar. 

 The premolar is simpler than that of 

 Oreodon, lacking internal cingulum and 

 antero-external accessory ridge, and con- 

 sisting of external and internal crescent, 

 the former with slightly concave external 

 surface, the latter with a short postero- 

 internal cingulum. The molars are com- pig. i^. Bathygenys 



^ r r , , r xi alpha. Upper teeth, crown 



posed of tour crescents, no trace ot the view, natural size, 

 paraconule remaining on m^ or m3; 

 m^ is a little worn, so that it is uncertain whether or not a 

 minute pi. existed. The anterior halves of m^ and m^ are 

 wider transversely than the posterior, the protoselene pro- 

 jecting further inward on the palate than does the hyposelene. 

 The posterior half of m3 is nearly as wide as the anterior half, 

 as in Agriochosnts and the Uinta Oreodonts, instead of re- 

 duced in width as in Oreodon and the other Oreodontidae. 

 The exterior surface of the inner crescents is slightly concave, 

 as in Agriochosrus, instead of strongly concave as in the later 

 Oreodonts, or convex as in Protorcodon. The exterior surface 

 of the outer crescents is nearly flat. 



The fourth lower premolar is oreodont in type, but differs 

 from Oreodon and resembles Promcrycochceras, Merycochoerus, 

 and Merychyus, in that the entoconid is a ridge extending 

 down and back from the deuteroconid, instead of a separate 

 cusp or distinct ridge. \\\ Protorcodon the, entoconid is rudi- 

 mentary. This tooth is a little narrower anteriorly than 

 p^ in Oreodon, wider than in Protorcodon, Merychyus, or Pro- 

 merycoclioerus. The molars are proportioned nearly like those 

 of Oreodon, but are more brachyodont. Thej^ are shorter, 

 higher, and with more crescentic cusps than those of Pro- 

 torcodon. 



Bathygenys is in most respects between Oreodon and Prot- 

 orcodon, but considerably nearer to the former. Some 

 characters point toward a nearer relationship with the 

 Merycochoerid group of Oreodonts than with Oreodon itself. 



