1884, ] 505 [Cope, 
The present paper is chiefly devoted to the {proper 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.S, 
Geolog, Survey Terrs,, vol, ili, fF. V. Hayden in charge. 
OREODON Leidy. 
Proceedings Academy Philadelphia, 1857, p. 288. Ancient Fauna of 
Nebraska, Smithsonian Contrib. to Knowledge, 1858, p. 29. Extinct 
Mammalia Dakota and Nebraska, 1869, p. 72. Report U. 5. Geological 
Survey Terrs., 1873, I, p. 201. Merycotdodon Leidy, Proceeds. Acad. 
Philada., 1848, p. 47 (nomen nudum). Ootylops Leidy, Loe. cit., 1851, 
p. 239. 
Premaxillary bones distinct from each other. Otic bull not inflated. 
No lachrymal vacuity of the face ; nasal bones normal. Premolars four 
in both jaws. 
Dental formula I. $; ©.+; P-m. 4; M. $; the series uninterrupted. 
Crowns of the molars robust, well distinguished from the roots. Grind- 
ing surface of the true molars simply selenodont, ¢. ¢., with but two pairs 
of crescents. Superior premolars composed of a single external compressed 
cusp with 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- 
