720 THE EOCENE FAUNA. 



in Esthonyx, and these inclose between them a" fossa. This fossa is closed 

 internally by the appression of the anterior inner cusps. The fourth pre- 

 molar is not so large as in P. secans, but resembles in proportions that of 

 P. chacensis. It differs from that of P. longicaudus in its very short heel 

 and its large anterior basal tubercle. The latter is double, consisting of 

 two small cusps, one within and anterior to the other. The posterior heel 

 is distinct on both sides of the ridge that marks the median line. The 

 posterior external lobe is V-shaped, and the posterior inner is a small cone. 

 Between the two is a minute median tubercle. The posterior tubercles are 

 not so elevated as in the species of Hyopsodus. A weak external cingulum ; 



enamel smooth. 



Measurements. 



M. 



Length Pm. iv, with M. i and ii (No. 1) 0140' 



Length Pm. iv 0048 



Length M. ii 0048 



Width M. ii 0040 



Length M. iii (No. 2) ...*. OOCO 



Width M. iii 003* 



Depth ramus at Pm. iv (No. 1) OOGO 



Depth ramus at M. iii (No. 2) 0070' 



Portions of four mandibles preserved. No. 2 is a little smaller than 

 No. 1, and No. 4 is a little larger than No. 1. 



From the Bis: Horn Basin. J. L. Wortman. Named from the name 

 -given by the Crow Indians to the Big Horn River. 



Pantolestes nuptus Cope. 



Paleoutological Bulletin, No. 34, p. 150, Feb. 20, 1882. Proceed. Amer. Philos. Soc, 1681, p. 150. 



Plate XXIVd, fig. 7. 



This is the least species of the genus, and is represented by a portion 

 of a right mandibular ramus which supports three molars, from the fourth 

 to the sixth, inclusive. Besides its small size, this species is distinguished 

 by the relatively small dimensions of the fourth premolar, which is shorter 

 than the first true molar, instead of longer, as in all the other species. The 

 well-developed basin of its heel, which is bounded by a ridge on each side, 

 distinguishes it at once also from P. secans, and is more distinct than in P. 

 chacensis. From the latter and P. metsiacus the entire absence of anterior 



