scott: toxodonta OF THE SANTA CRUZ beds. 
213 
more prominent, though less rugose. On the radial side, the facet 
for the trapezium is somewhat smaller and the proximal surface for 
the trapezoid is rather less concave ; the projection from the ulnar 
side, which abuts against the magnum, overlaps the head of me. Ill less 
extensively and the facet on the distal side of this projection is consider- 
ably narrower. The shaft, save for its smaller size and slightly more 
slender proportions, does not differ from that of Nesodon , but the distal 
trochlea is rather more symmetrical and the carina is even less prominent. 
Metacarpal III differs in only a few details from that of Nesodon. 
The proximal facet, which is overlapped by me. II, is narrower and, 
on the ulnar side, the process which articulates with the unciform 
is smaller and the facet for the unciform is narrower, especially toward 
the palmar side ; the two large, concave facets which articulate with cor- 
responding surfaces on me. IV, are more completely separated, not con- 
nected by a narrow, articular band. The shaft has a slightly dif- 
ferent shape, being of a more uniform width and not broadening distally 
so much. 
Metacarpal IV is slightly longer in relation to me. II, which it almost 
exactly equals in length, than is that of Nesodon , though, owing to 
the manner of articulation with the carpus, me. IV. extends distally below 
me. II. This outer metacarpal differs in a few respects, besides relative 
length, from that of Nesodon : The proximal facet which is covered by the 
head of me. Ill is narrower and is confined to the dorsal moiety of 
the head ; the two projections on the radial side, which fit into correspond- 
ing depressions on the ulnar side of me. Ill, are more completely 
separated and the palmar one is more prominent and, on the ulnar side, 
the facet for me. V is narrower. The shaft is somewhat straighter 
and less irregular than in the larger animal. A small and very irregular 
nodule represents the vestigial remnant of me. V ; it has three well- 
defined facets, for me. IV, the unciform and pyramidal respectively, for it 
has the remarkable peculiarity of articulating with the proximal carpal as 
well as with the distal one. I have not seen this bone in Nesodon , 
though there can be no doubt as to its presence in that genus. Judging 
from Ameghino’s figure of the manus in Xotopvodon (’94^, 246, fig. 1) it 
is relatively longer and narrower than in Adinotherium. 
The phalanges are very much like those of Nesodon , but smaller and 
relatively lighter. Those of the lateral digits (II and IV) are of almost 
