HOLLAND AND PETERSON: OSTHEOLOGY OF THE CHALICOTHEROIDEA. 345 
points of view it is more quadrate in appearance. Dorsally the bone presents a 
heavily rugose surface, which terminates abruptly near the inferior face and is 
succeeded by the beak-like process of the distal articulation pomting outward, 
downward, and slightly overhanging the superior anterior angle of Mc. II. Superi- 
orly the bone is almost entirely taken up by the large facet for the scaphoid, which 
is irregularly convex from side to side and concave antero-posteriorly. On the 
radial angle the transverse convexity is very pronounced and the continuation of 
the surface descends perpendicularly to accommodate the overhanging tubercle 
on the postero-radial face of the seaphoid. The facet for the trapezium is located 
on this vertical and broad articular surface, and is not separated above from the 
articulation for the scaphoid (see Fig. 85, 2, 6). On the ulnar face are two rather 
small facets for the magnum; one is located in- 
feriorly and near the palmar angle, and the other 
is located more superiorly and in the middle of 
the bone nearly equidistant between the dorsal 
and palmar faces of the trapezoid. The two 
facets are separated by a large and deep exca- 
vation, the posterior facet being surrounded on 
three sides by this deep fossa. In front of the 
anterior facet is also asinus of less depth, pro- _—*‘F16- 85. Trapezoid of left foot of M. elatus 
duced by the very prominent ridge on Me. II, No: ee ot J dorsal ee ey IDCTOE 
: ; ‘ view; 3, inferior view; 4, palmar view; 5, ulnar 
separating thetrapezoidand magnumnear their 
dorsal faces. Posteriorly the trapezoid termi- 
nates in a sharp ridge which is nearly vertical in position. On the radial side of this 
ridge are the facets for the scaphoid and trapezium and on the ulnar side is the rough 
and deeply excavated surface described above. Distally the large facet for Me. IT is 
divided into two nearly sub-equal portions by a sinuous and gently rounded ridge.” 
The facet as a whole has an oval outline with a concave surface antero-posteriorly 
and unevenly convex transversely. 
The trapezoid of Nestoritherium, as represented by the cast, differs from that 
of Moropus in its general outline as well as in its details of structure. The dorsal 
face is more irregular in outline than in Moropus, due to the development of a 
broad process on the ulnar side, extending well down over the head of Me. II. 
The posterior portion of the facet for the scaphoid is hemispherical in order to 
receive the concave facet of the latter bone, while in Moropus this portion of the 
facet is concave transversely. The articulation for the magnum is also located 
view; 6, radial view. 
8 In some individuals this ridge is practically absent, the facet being single. 
