CLASSIFICATION OF ASSES. 419 



tween zebras and asses in general. The fact, as pointed 

 out by Professor Ewart, that the true Burcbell's zebra has 

 a well-developed ist premolar (p. 49) on each side of the 

 upper jaw, may probably come under this heading. The 

 stripes, as pointed out by Messrs. Tegetmeier and Suther- 

 land (Horses, Asses, Zebras, and Mules), are not a good 

 generic distinction, because all the Equidse are occasionally 



Fig. 447.— Tables of incisors of a 14 year-old horse (nat. size). 



more or less marked in this manner. Even in individual 

 cases of 'zebras, the nature of the stripes is subject, more 

 or less, to variation, and they are seldom uniform on both 

 sides of the body. The stripes on the neck are continued 

 through the hairs of the mane. 



Classification of Asses. — Some naturalists divide 



asses into two species, namely, the African Wild Ass, 



27* 



