532 



PROCEEDIXGS OF THE XATIONAL MUSEUM. 



vol. 48. 



It is observed that the outer styles of the upper teeth of E. hatcheri, 

 both premolars and molars, are more strongly developed than in 

 the domestic horses. In the third premolar, for example, the ante- 

 rior style has a width of 8 mm., while in No. 843, referred to already, 

 the width is only 5.5 mm. ; in E. niobrarensis 6 mm. The median 

 style of this premolar in E. hatcheri is 8 mm. wide; in No. 843, 7 

 mm. ; in E. niobrarensis 5 mm. In the second molar of E. hatcheri 

 the anterior style is 6.5 wide ; the median style, 5.2 mm. In No. 843 

 the corresponding anterior style is 4 mm. wide ; the median style, 5.5 

 mm. ; therefore slightly larger than in E. hatcheri. In E. niobrarensis 



&l 



7n 



77Z* 



a b 



Fig. 2. — Upper premolars (a) axd upper molars (6) of Equus hatcheri. X&. 



the anterior style is 4 mm. wide ; the median 4 mm. The anterior style 

 in the premolars of the domestic horse are usually flattened, and a 

 slight groove runs along the face from base to summit of the tooth. 

 In E. hatcheri the outer face of the style is convex and a very shallow 

 groove is seen near the front edge of the face, while the median style 

 on the premolars shows only a trace of a groove; in the molars no 

 indication of it. 



In E. hatcheri the hinder border of the anterior style, especially 

 of the third and fourth premolars, is turned strongly backward, so 

 as to overhang conspicuously the valley which descends between the 

 anterior and the median styles. This feature is seen likewise in the 



