cones, the median smallest. The anterior and posterior of both sides 

 separated by a deep excavation. The anterior tooth is peculiar in its 

 greater compression. The posterior tubercles are not separated, and the 

 anterior inner situate behind the outer, and connected with the posterior 

 inner by a concave ridge. 



Measurements. 



M. 



Length molar series 0.0221 



M. 4 0060 



Width " 0055 



Length M. 1 0060 



Width " 0048 



Diameter lower incisor, transverse 0024 



.'• " " anterior posterior 0038 



From the South Bitter Creek, Wyoming. 



Paramys ttndans. Marsh. 



Sciuravus unclans, Marsh. Amer. Journ. Sci. Arts, 1871 (June 21st). 



A smaller species than the P. delicatissimus, Leidy. The dental charac- 

 ters of the mandibular series are generically indentical with those of the 

 species of Paramys. 



From Upper Green River. 



Paramys delicatissimus. Leidy. 

 Black's Fork. 



Paramys delicatior. Leidy. 

 Cottonwood Creek and Black's Fork. 



Paramys delicattjs. Leidy. 



Black's Fork. 



Pal^eosyops diaconus. Cope, sp. nov. 



Belonging to the genus Palceosyops as understood by Marsh, that is, 

 with two cones on the inner side of the last superior molar. The species 

 is as large as the Limnohyus major of Leidy, but differs in the relative 

 proportions of the teeth. Thus the last three molars have the same 

 antero-posterior length, while the space occupied by four premolars is 

 shorter. The anterior and posterior cingula of the true molars are very 

 strong, but it is not well marked on the inner side between the cones. 

 The latter are acutely conic, and the median anterior tubercle is strongly 

 developed. Although the wearing of the teeth indicates maturity, the 

 enamel is coarsely and obtusely rugose. The fourth premolar differs from 

 that of L. major in its smaller size relatively and absolutely, and in the 

 presence of a prominent vertical tubercle on the outer face, rising to the 

 angle of the deep notch between the lobes. The third premolar is as wide 

 as the fourth and about as large as the corresponding tooth in L. major, 

 but different from it in the absence of tubercle and ridge that mark its 

 external face. The first premolar has two roots, and the canine is large 

 and short. 



