726 THE EOCENE FAUNA. ' 



The species is about the size of the P. chacensis, and hence larger than 

 the P. longicaudus. It diflfers from both in the proportions of its teeth, and 

 especially in the large size and sectorial character of the fourth premolar. 

 The length of the latter exceeds a little that of the third true molar, while 

 in the other species it is shorter. This length is caused by the extent of 

 the anterior basal tubercle and posterior heel. The latter is entirely sur- 

 rounded by a cingulum, and its median line is elevated into a blade, which 

 is continuous with the posterior edge of the principal cusp. The fore and 

 aft edges of the anterior tubercle are also trenchant. The two cusps of the 

 anterior inner tubercle of the first and third molars are well developed, but 

 on the second molar there is but one cusp. This is probably a character 

 to be relied on in distinguishing the species from the P. chacensis. No 

 external basal cingula ; enamel smooth. 



Measurements. 



M. 



Length of last four molars 021 



L>ingth of fourth premolar 0068 



Elevation of fourth premolar 0040 



Length of last true molar 0057 



Depth of ramus at first true molar 0070 



As is the case with the species of Pantolestes already known, the P. 

 secans seems to have been rare. One specimen was found by Mr. Wortman 

 in the bad lands of the Wind River, Wyoming. 



