MAMMALIA. 



517 



all the limb bones of the two types. The humerus of the 

 ox has a very prominent great tuberosity which bends over 

 the condyle as a hook-shaped process and the bicipital 

 groove is single; in the horse there is a double bicipital 

 groove and the great tuberosity is simple. The ulna of 

 the ox extends down the side of the radius for the whole 

 distance, whereas that of the horse has fused on to the 



P'ig. 356. — TiBIOFIBULA OF A 



Horse x >^. {Ad tiat.) 



A, Anterior View. 

 B, View of Distal Extremity. 



Fibula. 



Fig. 357. — Right P'emur of 

 A Horse. {Ad nat.) 



Anterior View X \. 



Head. 



Lesser 



Trochanter. 



radius more completely, and can be traced only at most 

 about half-way down. In the carpus the suture separating 

 the OS magnum and the unciform is in the middle line, 

 whereas in the horse the magnum is much larger than the 

 unciform and the dividing suture is towards the outer side. 

 This is directly connected with the important difference in 

 the manus. Both have been evolved from a pentadactyle 

 type, but the ox has lost the first digit or pollex, followed 



