Cxipe.} 1^^ [Dec. 16, 



Measurements. M. 



Width M. ir 0040 



Length M. Ill; (No. 2) 0050 



Width " ." OOdO 



Deptli ramus at P-m. IV ; (No. 1) OOOO 



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. 

 The species of Pantolestes may be distinguished as follows : 



a. Fourth premolar trenchant everywhere, longer than second molar. 

 Length of true molars M. .0150 ; second molar with but one anterior inner 



cusp P. secans. 



aa. Fourth premolar with blunt heel, not longer than second molar. 



Length of true molars .0160 ; all with double cusps P. chacensis. 



Length of true molars .0140 ; fourth premolar with minute anterior cusp, 



and long lieel P. longicaudus. 



Lengtli of true molars .0130 ; fourth premolar with double anterior cusp, 



and short heel ; molars with double cusps P. metsiacus. 



Length of true molars .0105 ; fourth premolar small, .0035, without an- 

 terior cusps, and with two ridges on heel ; true molars with double an- 

 terior inner cusps P. nuptus. 



Pantolestes nuptus, sp. nov. 



This is the last 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 

 tlie 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 develoyjed 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 

 basal lobes separates it. The well developed pair of anterior inner tuber- 

 cles of the true molars sliows that it cannot be an abnormal Hyopsodus vica- 

 rius, with which it agrees in size. The first anterior tubercle is more widely 

 separated from the second anterior than in any of the species of the genus, 

 and is quite as in species of Pelycodus. It is smaller than the second ante- 

 rior inner, which equals in size the anterior outer. The heel is wide, en- 

 closing a basin, which is bounded externally by an angular ridge. Its 

 posterior inner angle supports a cusp, which is separated by a deep notch 

 from the anterior inner cusp. External to it on the posterior border of 

 the crown is a small tubercle." No basal cingula. 



Measurements. M. 



Length of three molars 010 



.^. „,, , f anteroposterior 004 



Diameters of M. 1 ^ ^ rt„<, 



( transverse Ulw 



Depth of ramus at P-m. IV 007 



Basin of the Big-llorn : J. L. Wortman. 



