THE PKJEVALSKY HOKSE. 31 



from 104 to 110 mm. ; whereas, with the exception of a single speci- 

 men, it did not exceed 109 mm. in the Asiatic ass. Indeed, in the 

 majority of twelve asses' skulls, it was found to be from 101 to 

 103 mm. In the African ass, the maximum width of the skull 

 in this region amounted to 102 mm. ; but in the majority of speci- 

 mens it did not exceed 89 mm. In fifteen skulls of the domestic 

 horse, the width reached 108 mm. in two specimens only, and in 

 the majority it varied from 97 to 108 mm. 



Similar remarks are applicable to the narrowest width of the 

 cranium (taken behind the orbital cavities). In this also E. 

 prjevalskii takes first place ; since, in this species, the narrowest 

 part of the cranium (measuring from 87 to 94 mm.) was wider 

 than the corresponding region of the donkey's skull, where the 

 minimum width was 66 mm., and the maximum 84 mm. In the 

 Asiatic ass, the diameter measured from 73 to 86 mm. ; and, in 

 the domestic horse, from 80 to 87 mm. Therefore, the cranium 

 of the domestic horse resembles that of the Asiatic ass ; and its 

 maximum narrowest width corresponds to the minimum narrowest 

 width of the skull of E. 2^rjevalskii. An examination and com- 

 parison of the foregoing figures justifies the conclusion that the 

 Prjevalsky horse has the broadest cranium of any member of the 

 genus Equiiii. 



The length of the cranium (from the posterior end of the inter- 

 nasal suture to the occipital crest) is greater in E. prjevalskii than 

 in either the donkey or the Asiatic ass. It measured from 241 

 to 255 mm. : while, out of twelve skulls of the Asiatic ass, only one 

 attained the length of 254 mm., and in the others it did not exceed 

 245 mm. — 186 mm. being the minimum. In the skulls of the 

 doakey (with the exception of the Somaliland ass, which gave the 

 enormous length of 261 mm.), the length of the cranium was 

 not greater than 226 mm. In the domestic horse the cranium 

 varied greatly in length ; the maximum being 250 mm. If the 

 relatively small variations in the length of the cranium of E. 

 2)rjevahkii be taken into account, we must admit that in this 

 respect also it takes first place among the Eqt/idce. 



W!ten the length of the cranium is compared witli the length of 

 the vertex of the entire skull (as indicated in Index IV.), the skull 

 of E. pryV"?;a/.s/'-i?; differs from the skulls of the other Equidce in 

 the pcseession of a remarkably short cranium. In the Prjevalsky 

 horse, the h ngtl< of the cranium was to the total length of the 

 vertex as 100.211-227. That is to say, the cranium forms con- 

 siderably less than one-third of the total length of the skull. In 

 the Asiatic ass the relation was as 100 : 195-213 : and in the donkey 

 as 100 : 195.5-218. The domestic horse resembled the wild horse 



