52 



distal end. Those features of the radius of the Megatherium are here 

 noticed by which it chiefly differs from the corresponding bone of the 

 Mylodon. 



321. The right scapho-trapezial bone. 



This bone is marked /• in figure 13, pi. 217- of the Ossemens Fossiles, 

 ed. 8vo. 1836, and is called by Cuvier the ' os cuneiforme :' it is indubi- 

 tably the analogue of the carpal bone which in the Sloths and Mylodon 

 consists of the confluent scaphoides and trapezium. The trapezial por- 

 tion is relatively smaller than in the Mylodon, and the articular surface 

 for the metacarpal bone of the pollex is still less. The dorsal surface of 

 the bone is excavated by an angular notch for the reception of the tra- 

 pezoides : there is a distinct articular surface on the concave distal side 

 of the bone for the os magnum. 



322. The right os lunare. 



323. The right os cuneiforme. The articular surface for the ulna is of an oval 

 shape, convex at the anterior and concave at the posterior part : it is 

 separated by a moderately wide tract from the radial surface of the os 

 lunare. The rough dorsal surface of the cuneiforme supports a well- 

 marked protuberance. 



324. The right trapezoides. The proximal surface is convex transversely, con- 

 cave from behind forwards, and joins a corresponding concavo-convex 

 surface in the scaphoides : the distal surface is principally convex : both 

 surfaces are joined by a small articular facet on the radial side of the 

 bone, which is adapted to a corresponding surface in the small metacarpal 

 bone of the thumb ; and by a more extended articular facet on the ulnar 

 side for junction with the os magnum. 



325. The right os magnum. This bone is here, as in the carpus of many 

 cmadrupeds, remarkable for its small size. 



326. The right os unciforme. It presents the figure of a transversely elongated 



hexahedron, the outer side formed by a rough projection separating the 

 cuneiform surface from that which supports the fifth metacarpal. The 



