GEOLOGICAL SURVEY OF THE TERRITORIES. 609 



MICROSYOPS, Leidy. 



Proceedings Academy Natural Scieuces, 1872, p. 20. 



MiCROSYOPS VICARIUS, Copc. 



Ou some Eocerie Mammals, &c., 187.3, p. 1. 



Founded ou portious of the mandibular rami of two individuals from 

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

 animal considerably smaller than the Eyopsodns paulus, and withi^roba- 

 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 cingalum uor autero-exterual tuberosity 

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

 apices, and the oblique connecting ridges of both genera. 



Measurements. 



H.pulus. M. vicarius. 

 M. 



Length of three molars 0.0136 0.0115 



Length of last molar. . . .\ 052 . 0045 



Length of first molar 040 . 003S 



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. 



HYOPSODUS PAULUS, Leidy. 



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

 From Cottonwood and South Bitter Creeks. 



EODENTIA. 

 PARAMYS, Leidy. 



Geol. Survey, Montana, 1871, p. 357. 



Paramys leptodus, Cope. 



Ou 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. delicatus, 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 

 conca^-e ridge. 



39 G s 



