236 WASATCH FAUNA. 



I formerly referred the specimens of this species to the Phenacodus zitni- 

 ensis, which is found in the Puerco horizon, but from which it is clearly- 

 distinct. It is dedicated to Major J. W. Powell, director of the United 

 States Geological Survey. 



From the Wasatch epoch of the Big Horn River, Wyoming, J. L. 

 Wortman. 



Hyopsodus lemoinianus Cope. 



Paleontological BuUetin, No. 34, p. 148, 1882; Proceed. Amer. PhUos. Soc, 1881, p. 148 (1882). 



Plato XXIVe, figs. 8-9. 



This Mesodont is distinguished from the known species of the genus by 

 its superior size, and the fully developed heel of the inferior third molar. 

 The anterior inner cusps of the inferior molars are simple, though robust, 

 and the same teeth have a weak external and no internal cingulum. The 

 cusps are elevated, and are not strictly opposite, the external one being a 

 little in advance of the corresponding internal one. The posterior external 

 cusp is connected by a low ridge with the two internal cusps, respectively. 

 On the first and second true molars there is a well-marked posterior median 

 cusp. The fourth premolar is a robust tooth, with a short, wide heel, and 

 a mere rudiment of an anterior basal tubercle. The heel has a principal 

 submedian keel and small marginal cusp. There is another and rudimental 

 lobe on the posterior border. The third premolar has neither internal nor 

 anterior tubercle. Its heel is short and wide, and has a low angular median 

 marginal lobe. Enamel smooth. 



Measurements. 



No. 1. M. 



Length of third and fourth premolars 0088 



Diameters fourth Eremolar)''n""^P"'"«"0'^ 0045 



C trausverse OOJO 



Diameters second true molar? ""teropoBterior 0050 



'{' 



transverse 0O40 



Depth ramus at Pm. iv 0030 



No. 2. M. 



Length of M. iii 0056 



Depth ramus at M. iii 0090 



Mr. Wortman found in the bad lands of the Big Horn, Northern 

 Wyoming, nine more or less fragmentary mandibles of this species. It is 



