THE OSTEOLOGY OF ELOTHERItJM. 305 



all, it must have been in a very reduced and rudimentary condition, having lost all 

 functional importance. 



The trapezoid is high, narrow and thin ; it is closely interlocked with the magnum, 

 lying in a depression on the radial side o£ that bone. The facet for the scaphoid is 

 simple and strongly convex. Three facets for the magnum occur on the ulnar side, one 

 proximal and two distal ; the former is much the largest of the three, but is confined to 

 the dorsal part of the ulnar side. Of the two distal facets, one is dorsal and one palmar ; 

 they are separated by a narrow space and are situated in different planes, almost at right 

 angles to each other. On the radial side, near the distal end, is a shallow depression. 

 which may have lodged a rudimentary trapezium, though there is no facet for such a bone. 

 The distal side of the trapezoid bears a small, plane facet, of triangular shape, for the 

 rudimentary second metacarpal. 



The trapezoid is not yet known in connection with the Euroj^ean species of Eloihe- 

 rium, or with Anthracotheriuni. In Hippopotamus it is lower and broader and of more 

 functional importance than in Elotherlum, as it also is in Sus, and in the latter, differing 

 from all of the other genera mentioned, it articulates extensively with the third meta- 

 carpal. 



The magnum is a relatively large and massive bone, the three diameters of which are 

 nearly equal, though the dorso-palmar dimension somewhat exceeds the other two. The 

 dorsal moiety of the bone is the lower, quite a prominent head rising proximally from 

 the palmar portion. The palmar hook is represented by a short, but broad, rough and 

 massive ridge. The proximal end is unequally divided between the facets for the 

 scaphoid and lunar ; dorsally the former is much the wider and occupies almost the entire 

 breadth of the bone, but it does not extend so far posteriorly and on the head is con- 

 fined to the antero-internal aspect of that elevation. The lunar facet is very narrow on 

 the dorsal side, and lateral rather than proximal in position, but posteriorly it widens and 

 covers nearly the entire head. When viewed from the ulnar side, the lunar facet 

 appears to be of a horseshoe-shape, narrow arms extending far down upon the dorsal 

 and palmar borders, and separated below by a very large sulcus. These two arms of 

 the lunar facet are obscurely demarcated from the two small facets for the unciform, in 

 which they may be said to terminate distally. The distal end of the magnum is covered 

 by the large, saddle-shaped surface for the third metacarpal, which is convex transversely 

 and concave antero-posteriorly ; and proximal to this, on the radial side, is a small facet 

 for the second metacarpal. On the radial side also is a depression, running almost the 

 full vertical height of the magnum, for the reception of the trapezoid. The depression 

 contains a larger proximal and two smaller distal facets for the trapezoid, corresponding 

 to those already described on the latter. 



