444 



MEMOIRS OF THE CARNEGIE MUSEUM. 



The anconeal fossa is 



the large entepicondyle and prominent supinator ridge, 

 very deep and of considerable height (See Fig. 31.) 



The proportionate length of the radius and ulna is approximately like that of 

 Rhinoceros bicornis. In the fossil form the shafts of both radius and ulna are, how- 



FiG. 31. Diceratherium. cooki Peterson. No. 2473, Coll. Carnegie Museum. Posterior and anterior 



views of humerus. X J. 



ever, flatter than in the African species. In fully adult and old individuals this is 

 chiefly due to the rugose and prominent ridges, which actually come in contact with 

 each other throughout the whole length of the bones, while in the recent form the 

 median region of the shafts is rounded and the two bones are separated by a consider- 

 able space. The shaft of the radius is quite straight, while the ulna as a whole is much 

 bent backward, especially the upper half, a characteristic seen in the recent form. 

 The carpal articulations differ from those in the African form to a marked degree. 

 Thus the lunar articulates exclusively with the radius in Diceratherium, while 

 in R. bicornis it encroaches to a considerable extent on the distal face of the ulna. 

 On the other hand it is observed in a number of cases in Diceratherium that the 

 cuneiform extends over upon the radius, forming a minute facet on the extreme 

 ulnar border as well as on the palmar face. There is a considerable variation, 

 especially in length and robustness, of the fore-arm of D. cooki, which is undoubtedly 

 due to sexual and individual variation as well as age. 



Manus. Pis. LXIII; LXIV. The height and breadth of the carpus are 



