9^ Bulletin American Museum of Natural History. [Vol. X, 



little doubt that the second specimen is identical with the first and 

 can be regarded as a collateral type. 



This genus most nearly resembles Honiacodon Marsh, from the 

 Bridger Beds, although it presents some dental characters similar 

 to Dichobune of the European Eocene. The more important 

 generic characters may be stated as follows : 



Dentition, l|, C|, Pm|, M|. Superior molars, having well-defined cres- 

 centic outer cusps and a distinct mesostyle and parastyle ; first molar provided 

 w^ith two conic internal cusps (protocone and hypocone), with anterior and poste- 

 rior subcrescentic intermediates; second molar having anterior subcrescentic inter- 

 mediate, subconic protocone, a posterior subcrescentic intermediate and no 

 hj^ocone ; third molar similar to second. The superior premolars are present 

 in full number ; the two anterior have simple cutting crowns, while the crowns 

 of the third and fourth are made up of single external and internal conic cusps 

 well developed. In the lower jaw the structure of the molars is intermediate 

 between the bunodont and selenodont pattern ; there are only three premolars, 

 the anterior two of which have simple compressed crowns, while the last or 

 fourth of which is provided, in addition to the principal cusp, with anterior and 

 internal cusps, together with a well-defined heel. 



As compared with Honiacodon^ Bunomcryx is readily distin- 

 guished (i) by the possession of three premolars in the lower 

 jaw ; (2) by the crescentic character of the external cusps of the 

 superior molars ; (3) by the presence of a well-developed para- 

 style and mesostyle ; (4) by the absence of the hypocone on the 

 second superior molar, and (5) by the subcrescentic character of 

 the intermediates. (6) The internal cusp of the third superior 

 premolar is, moreover, better developed in Bunonie/yx than in 

 Homacodon, and (7) the fourth inferior premolar is much more 

 advanced in structure. The structure of the inferior molars is 

 much more selenodont in Bunonieryx than in Hotnacodon. 



From Dichobune the present genus is readily distinguished by 

 the absence of all traces of the anterior cusp of the trigon in the 

 lower molars as well as the more crescentic character of the outer 

 cusps of the superior molars, and the possession of well-defined 

 mesostyle and parastyle. The complete adult dentition of Dicho- 

 bune is apparently not known, but , there can be but little doubt 

 that it had the full number, forty-four teeth, in which case Buno- 

 nieryx would be sharply distinguished by the inferior premolar 

 formula. I cannot at present say in what manner Bitnomeryx 



