Troxell — Hyrachyus and its Subgroups. 



•U 



gulum surrounds all of the tooth except the outer side and 

 the base of the lrypocone. 



The second specimen (fig. 2) described by Marsh con- 

 sists of a portion of the left mandibular ramus with the 



Fig. 1. 



J 103 5 TYPE 

 Y. P. M. 



Fig. 1. — Cotype, Hyrachyus bairdianus (Marsh). Part of the maxillary 

 with three molars. Nat. size. 



three lower molars. Although the teeth agree closely 

 in their width, M 3 is 3 mm. larger than M : . The cross 

 ridges of Mj are most nearly parallel, those of M 3 

 least so. 



Fig. 2. 



71057 TYPE 

 Y P M 

 Fig. 2. — Cotype, Hyrachyus bairdianus (Marsh). Crown and side view 

 of the lower molars, facing to the left, Xote the uniform size of these teeth. 

 Nat. size. 



