THE PKJEVALSKY HOESE. 



41 



A plance at the above table shows that the relation between 

 the breadth and length of the cheek-teeth of the Prjevalsky horse 

 is the same as in the domestic horse, the Asiatic ass and the 

 African ass. In all species of the genus Equus, the relation 

 betAveen the length and breadth of the premolars and molars of 

 the iijDper jaw is quite different from that of the lower teeth. 

 Only in Pg and M3 is there a complete correspondence in this 

 respect in the two series of teeth : the length considerably ex- 

 ceeding the breadth. This is explained by the circumstance that 

 the growth of Pg forwards and M3 backwards meets no resistance, 

 since it is not restrained by a neighbouring tooth. A certain 

 amount of variation appeared in the relation between the length 

 and the breadth of the upper P.;. In No. 5,216, the length and 

 breadth were equal ; whereas, in No. 3,092, the length slightly 

 exceeded the breadth. In the other premolars and molars 

 of the upper jaw the breadth exceeds the length : in the mandible 

 the relation is reversed. With the exception of Po and JVI3, in 

 whioh there is the same relation of length to breadth as in the 

 corresponding teeth in the upper jaw, the breadth of all the teeth 

 in the lower jaw is greatly surpassed by the length. 



Precisely the same relation is met with in the domestic horse, 

 in the Asiatic ass, and in the donkey, as is demonstrated in the 

 following table. In order to avoid a needless multiplication of 

 tables, I give here the measurements taken from one skull only 

 of each of the three species. These correspond in all respects to 

 the teeth in the remaining skulls in the collection. 



