GEOLOGICAL SUEVEY OF THE TEERITOEIES. 609 



MIOROSYOPS, Leidy. 



Proceedings Academy Natural Sciences, 1872, p. 20. 



MiCEOSYOPS viCAEius, Cope. 



On some Eocene Mammals, &c., 1873, p. 1. 



Founded on portions of tlie mandibular rami of two individuals from 

 the Bad Lands of Cottonwood Creek, Wyoming. These represent an 

 animal considerably smaller than the Hyopsodtis pcmlus, and with proba- 

 bly only three premolars. This is believed to be the fact from the small 

 size of the last premolar, and the anterior contraction of the first molar. 

 The molars have no external ciugnlum nor an-tero-exterual tuberosity 

 described to exist in the M. gracilis, by Marsh. The cones have simple 

 aj)ices, and the oblique connecting ridges of both genera. 



Meastiremeyits. 



H. puhcs. M. vicarius. 

 M. 



Length of three molars 0.0136 0.011.5 



Length of last molar 052 . 0045 



Length of first molar 040 .0038 



Width of first molar anteriorly 041 , 0026 



Width of first molar posteriorly 043 .0029 



HYOPSODUS, Leidy. 



Proceedings Academy Natural Science, Philadelphia, 1871 ; Geological Survey Mon- 

 tana, 1871, p. 362. 



Htopsodus paulus, Leidy. 



Hayden's Survey Montana, &c., 1871, p. 363. 

 From Cottonwood and South Bitter Creeks. 



EODBNTIA. 

 PAEAMYS, Leidy. 



Geol. Survey, Montana, 1871, p. 3.57. 



Paeamys leptodus, Cope. 



On some Eocene Mammalia, &c., 1873, p. 3. (Published March 8.) 



Established on a right mandibular ramus with all the teeth preserved. 

 It indicates an animal of about the size of the P. delieatus, Leidy, and 

 P. rohustus, Marsh, but with smaller incisors, which have little more 

 than half the diameter of the same tooth in those species. The molars 

 have two anterior separate, and three posterior contiguous, cones, the 

 median smallest. The anterior and posterior of both sides separated by 

 a deep excavation. The anterior tooth is peculiar in its greater compres- 

 sion. The posterior tubercles are not separated, and the anterior inner 

 situate behind the outer, and connected with the posterior inner by a 

 concave ridge. 

 39 G s 



