AESINOITHERIUM. 



41 



which it resembles far more closely than it does that of the Dinocerata. The chief 

 differences from the carpus of Elephas seem to be dependent on the circumstance, 

 that in Arsinoitherium the distal articulation of the ulna is still larger in proportion 

 to that of the radius. Weithofer (Morph. Jahrb. vol. xiv. p. 507) has shown that the 

 peculiar condition of the carpus of the Elephant, in which the lunar extends preaxially 

 so as to overlap the trapezoid, is due to the preponderance of the share taken by the 

 ulna in the formation of the wrist-joint. In Arsinoitherium this is carried still farther, 

 so that the cuneiform extends inwards over the magnum. Whether or not as in 

 Elephas the lunar overlapped the trapezoid is uncertain, but probably it did so at 

 least anteriorly. In other Ungulates in which the radial portion of the articulation 

 becomes the larger, the direction in which the proximal row of carpals becomes displaced 

 upon the distal is the opposite one. 



Text-fig. 20. 



xi 



Left scaphoid of Arsmoitherium zitteli : A, lunar face ; B, proximal end. 

 I., I.', upper and lower facets for lunar ; maff., facet for magnum ; r., surface for radius ; 



tz., facet for (?) trapezoid. 



^ nat. size. 



The scaphoid (text-fig. 20) is greatly compressed from side to side and widens out 

 considerably in a fore-and-aft direction from above downwards. The proximal end 

 is occupied by a concave surface (r.) for articulation with the poster o-internal -convex 

 portion of the end of the radius. This surface is roughly oval in outline, rather 

 broader posteriorly than anteriorly, and with a somewhat flattened outer (postaxial) 

 border, immediately beneath which there is a narrow surface [l.) for articulation with 



