THE PEJEVALSKY HORSE. 37 



the maximum found in E. prjevalskii (e.g., Nos. 988 and 4,051 

 had a mandibular lieight of 238 mm.). Of course heavy draught 

 horses, in which, according to Nehring the height may be as much 

 as 281 mm., were not included. 



Poliakof* remarks that, in the length of the diastema, the 

 Prjevalsky horse resembles the domestic horse ; but that, on the 

 other hand, it is very different from the donkey, in which the 

 interdental space is shorter than in the horse. In general this 

 remark is correct if the comparison is confined to the domestic 

 horse and the donkey (E. minus and E. tceniopus) ; but tlie 

 results are somewhat different if the Asiatic ass is included in 

 the comparison. In the Prjevalsky horse, the diastema in the 

 upper jaw measured from 77 to 90 mm. ; and in the lower jaw 

 from 74 to 92 mm. In the onager and the kiang, the length of 

 the diastema was very little different ; as, in the upper jaw it 

 varied from 76 to 95 mm. ; and in the lower jaw from 68 to 92 

 mm. A minimum of 68 mm., however, must be taken as excep- 

 tional, and 76 mm. should be substituted for it. This being done, 

 the difference between the Prjevalsky horse and the onager is 

 very slight. In the comparison of the skull of a donkey with one 

 of the horse, the difference in the length of the interdental space 

 will be found to be very pronounced, and can, therefore, be used 

 as a diagnostic feature. In the donkey, the diastema of the upper 

 jaw measured from 70 to 90 mm. ; the maximum being in the 

 remarkably large skull of the Somaliland ass. In the lower jaw 

 the length was from 66 to 82 mm. These figures do not differ 

 very widely from those of the Prjevalsky horse. In the domestic 

 horse, however, the length of the diastema in the upper jaw was 

 from 76 to 108 mm. ; and in the lower jaw from 80 to 99 mm. 

 To this should be added that a length of 76 mm. — which is ex- 

 ceptionally small — appeared only once among the measurements 

 of fifteen skulls. Consequently, so far as the diastema is con- 

 cerned, E. ijrjevalshii resembles the Asiatic ass, and even the 

 African ass, more closely than it does the domestic horse. 



The Prjevalsky horse possesses a very high skull ; but the varia- 

 tions in its height — from 246 to 300 mm. — are very great. Simi- 

 lar variations were also found in the skulls of the onager, where 

 the minimum height was 248 mm., and the maximum 297 mm. 

 Consequently, in height of the skull, E. prjevalskii approximates 

 the Asiatic ass very closely. Differences were greater in the other 

 asses, and amounted to 89 mm. (minimum, 200 mm. ; maximum, 

 289 mm. in the Somaliland ass). In domestic horses, the maxi- 

 rnmn height was 318 mm. ; and the minimum 274 mm. (in a 



* Op. cit. p. 12, 



