scott: toxodonta OF THE SANTA CRUZ beds. 
21 I 
tively somewhat longer than in Nesodon, is rather less distinctly trihedral 
and has a more concave posterior border and the interosseous crest is 
much less prominent. The styloid process and carpal facet are similar 
to those of Nesodon , but are proportionately narrower and thicker 
palmo-dorsally. 
The radius (PI. XXVII, figs. 12-15) differs from that of Nesodon in a 
number of unimportant details. It is somewhat more slender in propor- 
tion to its length and the shaft is more irregular in shape, with less marked 
antero-posterior compression, and very feebly developed interosseous crest ; 
the proximal articular surface is more distinctly divided into two facets 
for the humeral trochlea and, near the internal side, the anterior border 
is raised into a more prominent and pointed process, and on the external 
side of the head is a large facet for the attachment of a sesamoid bone. 
On the distal end, the two carpal facets are more distinctly demarcated 
than in Nesodon and the external portion of the scaphoid facet does not 
notch the dorsal border so deeply, while the lunar facet is narrower 
palmo-dorsally. 
The manus (PI. XXI, figs. 4, 7) is of exactly the same type as in Neso- 
don and, save in size and in a few details of proportion, the differences 
are quite insignificant. The scaphoid is slightly lower and narrower, in 
proportion to its dorso-palmar thickness, than in Nesodon , and there are 
several differences in the shape of the facets. The proximal surface, for 
the radius, narrows more and is less elevated toward the palmar side ; 
the facet for the trapezoid is narrower and less deeply concave and that 
for the magnum contracts more toward the palmar border. There is no 
surface for the trapezium. On the ulnar side, in addition to the proximal 
facet for the lunar, there is a very small distal one for the same bone, 
which is not present in Nesodon. The lunar is of almost identical form 
in the two genera, but there are some differences in the facets. In 
Adinotherinm , the dorsal portion of the proximal surface is more convex 
and is reflected farther down upon the dorsal face of the lunar, while the 
palmar portion is decidedly narrower, as is also the palmar prolongation 
of the unciform facet, between which and the magnum facet there is no 
such emargination from the palmar border as occurs in Nesodon. On 
the ulnar side, as in the latter, there is no proximal contact with the 
pyramidal and the distal articulation is confined to a very narrow strip. 
The pyramidal is broad transversely, but very short proximo-distally, 
