Peterson : Miocene Beds of Nebraska and Wyoming 



45 



Dr. Matthew, who kindly compared this specimen with the types 

 of the above-mentioned species, states that he would refer it to 

 Brachypsalis rather than to Potamotherium, and that it is a " decidedly 

 more primitive species than B. pachygnathus ," which is from the 

 upper Miocene. This species may represent the ancestral form of B. 

 pachygnathus. 



Specific Characters. 



±2-, Cy, P^, M^. The lower jaw is short and heavy. The inferior 

 border is evenly curved from the canine to opposite M-, where the 

 mandible is injured. The external face of the jaw is convex from 

 above downward. The temporal fossa is indicated as deep and of 

 large size. There are two mental foramina ; one near the canine, and 

 the other below P^. The canine is short, robust, and oblong in cross- 

 section. P T is close to the canine and one-rooted, with a low simple 

 crown. P^ is of nearly the same size as P^ ; the former is two-rooted, 

 with a small postero-internal heel, and is obliquely placed in the 

 alveolar border. P3- is like P^, but its position in the alveolar border 

 is not oblique. P T is a larger tooth, with the protoconid located 

 nearer the middle than in the preceding teeth, and the posterior heel 

 is also somewhat better developed. Unfortunately the carnassial 

 tooth is broken off in front ; the heel is complete and is rather short 

 antero-posteriorly. M^ is small and has a low crown. The dental 

 series curves outwardly in an unusual manner, P ¥ marking the location 

 of the greatest angle of the curve. The specimen represents a fully 

 adult animal. 



Fig. 10. 1. External view of right ramus of Bi'achypsalis simplicidem. 2. 

 Superior view of Brachypsalis simplicidens. § nat. size. Type, No. 1553- 



