THE FORE LIMBS. 93 



Tlie articular surfaces of the radius and the ulna for each other were 

 nearly parallel with the axes of those bones, and allowed of little else than 

 a sHg'ht antero-posterior gliding motion. The roughenoil and co-adapted 

 surfaces of the bones indicate that, during life, all movements of pronation 

 and sujunation were prevented by j)0werful ligaments. 



The radius does not appear so distinctly to cross the ulna as in the 

 Proboscidians, being, at the upper end, iu front of that bone, and 

 proportionally much larger, then passing down obliquely inward to a 

 position within the distal end of the ulna. 



The pro])ortion of the two bones to each other is much nearer that 

 seendn'the rhinoceros and hippopotamus, than that in the elephant. 



The Radius. (Plate XXIX; and woodcuts lOS-lO'l, below.) 



The radius in Dinoccras is a strong bone, with its shaft about equal in 

 size to that of the ulna. It is considerably larger than that bone at the 

 lower end, and smaller at the upper end. 



The head, or superior articular face, occupies the entire surface of the 

 proximal end. This surface is elongate oval in outline, the long diameter 

 being placed transversely, and nearly twice as great as the short diameter. 

 The latter is antero-posterior in direction, in the ordinar\-, nearly vertical 

 position of the bone. It crosses the surface of the bone nearlv in the 

 middle, instead of toward the inner side of the middle, as in most 

 Ungulates. Antero-})osteriorlv, the articular surface is concave 

 throughout, but transversely, it is convex on the inner side, and concave 

 on the outer side of the middle line. The inner half of the articular 

 surface is thus traversed by a low fintero-posterior ridge, or elevation, 

 which moves upon the groove in the distal articular face of the humerus. 



The proximal surface of the radius differs from that of the elephant in 

 being proportionally nuicli larger, and extending quite across the humeral 

 articular surface. It differs from that of the tapir, and tlie hi[)[)Opotamus, 

 in having only a single antero-posterior ridge, as in the rhinoceros. It 

 still differs from that of the -rhinoceros, in the fact, that a transverse section 



