234 WASATCH FAUNA. 



interior of which is flattened and strongly bifid, both points being more 

 elevated than any of the others. The cusps are nearly opposite to each 

 other, and behind the interval between the two posterior rises another, not 

 so elevated as the others, except on the posterior molar. Here it is elevated, 

 and nearly equidistant from the two in front of it. The enamel is smooth, 

 and there is no cingulum on either side. The premolar consists of a prin- 

 cipal sectorial cusp, and has a smaller but stout acute anterior cusp, with a 

 small rudiment of another behind; a stout cusp rises from the inner poste- 

 rior margin of the principal one, giving it a subbifid appearance. 



Measurements. 



u. 



Length of four molare 0195 



Ltngtli of three true molars 0149 



Length of last true molar 0055 



Length of first true molar 0043 



Width of first true molar front 0025 



Width of first true molar posteriorly 0031 



Depth of ramus at front of M. 3 0075 



Depth of ramus at front of Pm. last 0055 



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

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

 are not ver}" differnt. 



From the bluffs of the Upper Green River. 



This Mammal is about equal in size to a weasel. 



Fi-om Cotonwood, Wyoming, near Fort Bridger. 



HYOPSODUS Leidy. 



Proceed. Acad. Nat. Sci. Phila., If^'l; Geol. Surv. Montana, 1871, p. 3(52. 



The dentition of tlie mandible is in this genus characterized by the 

 simplicity of the anterior inner tubercle, and the development of cusps at 

 the angles of the heels of the molars. The fourth i)remolar has the usual 

 internal cusp at the side of the external. The dentition of the maxillary 

 bone is characterized by the presence of the full number of premolars, of 

 which the last two at least have a well developed simple internal lobe. The 

 internal lobe of the true molars is double, and there are two small inter- 

 mediate tubercles. The external cusps are two, distinct and compressed. 



