Measurements . M. 



Length of four molars 0.0195 



'* three true molars > . . .0149 



" last " molar 0055 



" first " " 0043 



Width " " " in front 0025 



" " " " posteriorly 0031 



Depth ramus at front of M. 3 0075 



" " P. M. last 0055 



This species differs from the last in the presence of the posterior 

 tubercles on the M. 2-3, and the absence of external cingulum. The 

 sizes are not very different. 

 From the Bluffs of the Upper Green River. 



The genus to which this species belongs differs from Hyopsodus in the 

 carnivorous form of the last premolar, which has a well-developed an- 

 terior cusp. I refer it to the same genus as the last species, though its 

 characters have never been pointed out by the author of the name (Prof. 

 Marsh), nor are the characters which distinguish it from Homacodon of 

 the same author discoverable. He states that the cusps in H. vagans are 

 "isolated," a character which does not apply to A. furcatus, in which 

 they are related much as in Hyopsodus. 



Oligotomus cinctus. Cope, gen. et sp. nov. 

 Char. Gen. Molars constructed much as in Hyopsodus and LopMo- 

 therium, viz. : with two external subtrihedral cusps which wear into cres- 

 cents, the posterior connected by a low oblique ridge with the basis of 

 the anterior cone of the inner side ; the latter with two conic cusps. It 

 differs from these genera and Orotlierium in the possession of but two 

 premolars; the inferior molars are probably six, leaving four true molars. 

 Char, specif. In this animal the cusps of the molars are elevated, the 

 external most so, the anterior being somewhat bilobate. Premolars with 

 two fangs. There is a rudimental posterior tubercle in M. 1 and 2, and 

 a strong cingulum round the outer side of the crown. In an adult with 

 worn teeth the enamel is obscurely rugose. 



Measurements. M. 



Length of five molars 0.0326 



" two premolars 0120 



" M. 2 .0067 



Width " anteriorly 0050 



" " posteriorly 0050 



Depth ramus at front of P. M. 1 0126 



From Cottonwood Creek, Wyoming. 



Orotheeitjm sylvaticum. Leidy. 

 LopMotherium sylvaticum, Leidy. Proceed. Acad. Nat. Sciences, 

 Philadelphia, 1870, 126. Orotliermm, Marsh, Am. Journ. Sci. Arts, 

 1872, August 13. From Black's Fork, Wyoming. 



