1884.] 



505 



LCope. 



The present paper is chiefly devoted to the Iproper distinction of these 

 species and genera or cranial characters only. Figures of all will be 

 given in my volume which embraces this subject, in the Report of the 

 U. S. Geological Survey of the Territories. 



Coloreodon ferox Cope, one-half natural size. Original ; from Report U. 8. 

 Geolog. Survey Terrs., vol. iii, P. V. Hayden in charge. 



OREODOIV Leidy. 



Proceedings Academy Philadelphia, 1857, p. 238. Ancient Fauna of 

 Nebraska, Smithsonian Contrib. to Knowledge, 1853, p. 29. Extinct 

 Mammalia Dakota and Nebraska, 1869, p. 72. Report U. S. Geological 

 Survey Terrs., 1873, I, p. 201. Merycoidodon Leidy, Proceeds. Acad. 

 Philada., 1848, p. 47 (nomen nudum). Ootylops Leidy, Loc. cit., 1851, 

 p. 239. 



Premaxillary bones distinct from each other. Otic bullae not inflated. 

 No lachrymal vacuity of the face ; nasal bones normal. Premolars four 

 in both jaws. 



Dental formula I. f ; C. % ; P-m. £ ; M. f ; the series uninterrupted, 

 Crowns of the molars robust, well distinguished from the roots. Grind- 

 ing surface of the true molars simply selenodont, i. e., with but two pairs 

 of crescents. Superior premolars composed of a single external compressed 

 cusp witb crescentic section, and internal cingula or crescent. The fourth 

 premolar with a well developed internal crescent ; the first three with rudi- 

 mental internal crescents in the form of basal cingula. Superior canines 

 distinct. Inferior premolars of two kinds ; the first canine-like in form 

 and function ; the others consisting of a single external cutting edge rep- 



