AETIODACTYLA. 717 



dentition ; that is, the superior molars have a greater transverse diameter 

 than the inferior ones. In this they agree with alHed genera ah-eady found 

 in Europe, as Choeropotamus Cuv., Anthracotherium Blv., and show a greater 

 resemblance to the ruminant division than do the recent hogs. The last- 

 named genus approximates Hyopotamtis, which is still nearer the lowest 

 Ruminantia. 



PANTOLESTES Cope. 



Proceed. Anier. Pbilos. Soc, 1872, p. 467. (Separata, August 30.) Report U. S Geol. Surv. W. of 100th 



Mer., iv, p. 145. 



The type of this genus resembles in structural characters of the denti- 

 tion of the lower jaw the Hyopsodus and Sarcolemur, already known in the 

 collections of the different explorations of the Rocky Mountain lake basins. 

 While it possesses the normal number of molar teeth belonging to these, it 

 preserves a sectorial character of the premolars more posteriorly than in 

 any of the genera named. The premolars are all two-rooted, except the first. 

 The fourth is a simple flattened triangular cusp, with a small tubercle at 

 the base behind, and wanting the inner cusp of other genera. The molars 

 exhibit the usual four cusps, the external cresoentoid, the inner discoid in 

 section, excepting the inner anterior, which is generally duplicated by an 

 anterior twin-cusp of smaller size, closely united with it. 



Six species of this genus have been described from lower jaws only, 

 and in one only, the M. hracJiijstomus, are both superior and inferior molars 

 known In the P. secans the sectorial character of the fourth inferior pre- 

 molar is most strongly marked; in P. lonrjicaudus that tooth has a wider heel 

 than the other species. The species of Pantolestes may be distinguished as 

 follows : 



a. Fourth premolar treucbaut everywhere, longer than second true molar. 

 Leug'tli of true molars M. .0150 ; second molar \vith but one anterior inner cusp . P. secans. 

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



Length of true molars .0230; no anterior cusps of premolars P. etsagicus. 



Length of true molars .0100; all with double cusps P. chacensis. 



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



heel , P. longicaudus. 



Length of true molars .0130; fourth premolar large, .005, with double anterior cusp, 

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



