THE PRJEVALSKY HORSE. 51 



Tlie difference between it and the same bone of tlie Tarpan consists 

 mainly in the form of the articular surfaces which are much the 

 larger in the Prjevalsky horse. The elevations and depressions 

 are very sharply defined and stand out conspicuously. The deltoid 

 tubercle is very strongly developed, as it is also in the skeleton of 

 the Tarpan which is preserved in the Zoological Museum. Its 

 length reminds one mostly of that of the humerus of a pony, the 

 dimensions of which ai*e cited by Nehring.* In the following 

 table are given the dimensions of the humerus of E. prjevalskii, 

 the Tarpan and Nelu-ing's dun pony side by side, in order to bring 

 out clearly the dift'erences between these animals : — 



E. prjevalskii. Tarpan. Pony. 



Greatest length ... 



Length from the articular head to the distal arti- 1 ., 

 en lar surface ... ... ... ... ... J 



Greatest ■width of the upper part 

 Width of the articular heail 

 Greatest width of the lower part 

 Width of the distal articular surface ... 

 Width at the narrowest part ... 

 Width of the anterior articular surface 

 Width of the deltoid tubercle ... 



THE RADIUS AND ULNA (Fig. 21).— These bones in the Prje- 

 valski horse are remiarkable for the same peculiarities of dimensions 

 a.s were found in the humertis. They are also much stronger than 

 in those other species of Eqiius in which the humerus is of similar 

 length. I shall again employ the before-mentioned pony of 

 Nehring for the purpose of comparison. Although the forearm of 

 E. prjevalskii is longer than that of the pony, the difference in 

 the relative thickness is greater than the difference in length. In 

 the following table the measurements of the bones of the fore- 

 arm of E. ijrjevahkii and the pony are placed side by side : — 



Greatest length of radius and ulna taken in their connected 



condition ... 

 Greatest length of the radius 

 Medium length of the radius 

 Length of radius on the outer side 

 Greatest width of the upper part of radius 

 Width oi proximal articular surface of radius ... 

 Greatest width of radius below 

 Width of carpal articular surface of radius 

 Width of radius at its narrowest part ... 



* Op. cit., p. 124. 



4* 



