THE PRJEVAL8KY HORSE. 63 



that the Tarpan possesses all the characters of the group of Oriental 

 horses, and unites the Arab, on the one hand, with the Celtic race 

 (to which the pony belongs) on the other. The Tarpan whose skull 

 and skeleton are in the Zoological Museum of the Academy of 

 Science, stands in very close craniometric relationship to E. 

 prjevalskii ; although the skull does not accord with any of the 

 skulls of adult examples of this species. Some Asiatic horses 

 agree, in their absolute measurements, more closely with certain 

 specimens of the Prjevalsky hoi'se (for example, the horse from 

 the River xldytsch district and No. 3,094 of E. 2Jrjeva?skii). But 

 when the average dimensions are expressed as indices the resem- 

 blance between the two horses is more striking. This is particu- 

 larly strong when the bones of the extremities and the shoulder 

 and pelvic girdles are compared. The resemblance may depend 

 upon tlie similarity in size of the two animals. Naturally, it is 

 very difficult to come to any conclusion so long as there is only a 

 single skeleton of the Tarpan available for comparison. At all 

 events, the bones of E. j^fjevalskii are distinguishable from those 

 of the Tarpan on account of their considerable bulk, their width 

 in comparison with their length, and their very pronounced 

 eminences. The number of lumbar vertebrae is the same in the 

 Prjevalsky horse and the Tarpan : both possess five. But great 

 significance cannot be attached to this feature, which is generally 

 held to be characteristic of the ass; for other races of the horse 

 have five vertebrte, while it is alleged that the ass sometimes has 

 six. 



External characters play a very important part in the comparison 

 of the Prjevalsky horse and the Tarpan. The most important of 

 these is the black colouration of the limbs from the knee to the 

 hoof. This is very constant in E. jn-jevalskii and distinguishes 

 it from the Asiatic wild ass, in which the lower part of the limb 

 is always light-coloured or even quite white. Another not 

 unimportant character in the Prjevalsky horse is the striping of 

 the limbs, which, although also occasionally found in the domestic 

 horse {cf. Darwin's " Variation of Animals and Plants under 

 Domestication "), serves as a broad distinguishing character for E. 

 prjevalskii, even if it is one not absolutely constant. The dorsal 

 stripe constitutes a much more constant feature ; although this 

 also cannot be accounted a character which wovild place the 

 Prjevalsky horse and the Tarpan close to the Asiatic ass and the 

 African ass. In domestic horses of certain colours — mouse-fawn, 

 dun and especially light-coloured horses — 'there is almost always 

 a dorsal stripe ; while in some Asiatic asses (E. hamdr, H. Sm) 

 it is absent. At all events, the constancy of this character justifies 



