38 THE PKJEVAL8KY HC)E8E. 



Crimean tarpan, No. 521). With such great variations, it is very 

 difficult to regard the li eight of the skull as having diagnostic 

 value. Nevertlieless, by comparing the maximum and minimum 

 in all the species of Equidm, the conclusion is arrived at that, in 

 this respect, E. jtrjevalskii resembles the donkey and the wild ass 

 more closely than the domestic horse. 



By way of summary, the following conclusions with regard to 

 the skull of E. prjevahJcii may be stated : 



(1). In E. prjiefa/.s'^/i, Franck's index resembles that of the 

 skull of the horse, and is different from the same index in the ass. 



(2). The form of the naso-f rental and naso-lachrymal sutui-es is 

 the same as in the skull of the horse. Measurements of the naso- 

 frontal region also point to the relationship of E. iwjevalskii with 

 the domestic horse, and not with the asses. 



(3). The form of the post-orbital process of the frontal bone fur- 

 nishes a feature of very doubtful diagnostic value. 



(4). The Prjevalsky horse has a very large head. Tlie average 

 length of the skull exceeds that of other species of the genus. 



(5). From the frontal width, E. iirjevaJshii may be classed 

 among the horses with a forehead of medium width ; although 

 skulls are met with of the broad or narrow forehead type. 



(6). The size (width, length and height) of the cranium of E. 

 2)rjevalskii exceeds the dimensions of the cranium in other species. 



(7). E. prjevalskii has a very long face, the dimensions of which 

 are greater than those of the Asiatic ass and the other asses. The 

 ratio between the length of the face and the length of the vertex 

 of tlie whole skull (Index IV.) in the Prjevalsky agrees with the 

 ratio in the domestic horse, but differs from that of the Asiatic 

 ass and the other asses. 



(8). The nasal width is greater than in other species of Eqttus. 



(9. In shape, the lower jaw of E. j^TJcvahkii resembles the corre- 

 sponding bone of the horse, and differs from that of the asses. 

 In its dimensions also, it closely resembles the lower jaw of the 

 horse. 



(10). In the leng-th of the diastema and in the height of the 

 skull, E . prjevalskii more closely resembles the Asiatic ass than 

 the horse. 



From the consideration of the foregoing craniometric features, 

 we may conclude that the Prjevalsky horse belongs to a special 

 and separate type, which, however, is more closely allied to the 

 domestic horse than to the ass. 



THE TEETH.— In general, the teeth of all the horse tribe (the 

 genus Equus in the wider sense) show great similarity as regards 



