no. 2086. 



SOME MAMMALS OF THE PLEISTOCENE— HAY 



533 



molars, but not so strongly expressed. In the domestic horses ob- 

 served the hinder border of the anterior style is not at all or only 

 slightly rolled backward. In the Arabian horse skull (No. 172454, 

 National Museum) the border turns rather strongly backward. In 

 the type of E. niobrarensis it is not at all rolled backward. Probably 

 in each species there is in this character a good deal of individual 

 variation. 



In all the cheek-teeth of E. hatcheri the inner face of the protocone 

 is distinctly convex, whereas in the type of E. niobrarensis this face 



772 



m 



rrv 3 



a b 



Fig. 3. — Lower premolars (a) and lower molars (6) of Eqdus hatcheri. X^. 



of the protocone is divided by a distinct groove into an anterior lobe 

 and a larger posterior one. In the domestic horses the inner face of 

 the protocone is usually, but not always, either flat or somewhat 

 concave. 



As regards the plication of the enamel which surrounds the lakes 

 in the upper molars, it may be said that no essential differences have 

 been observed on comparison with the cheek teeth of the domestic 

 horses. In the type of E. hatcheri the plication is less developed than 

 in some domestic horses, more so than in others. Opposite the head 

 of the anterior inner valley, at the hinder inner angle of the anterior 



