346 MEMOIRS OF THE CARNEGIE MUSEUM. 
nearer the palmar border of the trapezoid in Nestoritherium, so that the large 
excavated area back of this facet seen in Moropus is confined to a small surface on 
the extreme postero-ulnar angle. 
In Macrotherium from Sansan the outline of the trapezoid is similar to that 
in Moropus, but it is of relatively larger size and the structure of the bone is also 
quite different in minor details. The dorsal face of the bone in Macrotherium is 
more unevenly convex supero-inferiorly with a greater projection in the ulnar 
direction, though not nearly as great as in Nestoritherium. Radially the facet for 
the scaphoid, though very convex transversely and extending well down, does not 
reach the facet on the distal face for Me. II as does the facet on the trapezoid 
of Moropus elatus. There was probably no trapezium in Macrotherium. The 
palmar face of the trapezoid is also much less angular both in Macrotherium and 
Nestoritherium. 
MEASUREMENTS OF TRAPEZOID. 
No. 1604 No. 1700 
(M. elatus), (M. petersoni), 
mm. mm. 
Greatestitransverseidiame tele een nen nnenrnnt nea eener 56 48 
Greatest antero-posterior diameter ..................-+..-- 55 41 
Greatest venticalidiametensn earn moree een ere enencrrer 48 35 
The Magnum (Fig. 86).—The magnum of Moropus elatus is of large size and 
has the greatest antero-posterior diameter of all the carpals. Its dorsal face is 
highly characteristic, having a heavy truncated protuberance which extends well 
dorsad and forms on the distal face a rough articular surface for the proximo-ulnar 
angle of Me. II (Fig. 86, 1, 2, 3, 5, and 6), as described by Peterson (cf. The Am. 
Naturalist, Vol. XLI, p. 747 (1907)), and also well illustrated in the articulated 
carpus (Pl. LXVIII, Figs. 1 and 2). On the radial face are seen four articular 
facets (Fig. 86, 2). The largest of these facets is for Me. II. This facet is quite 
irregular in outline, convex supero-inferiorly, and also slightly convex antero- 
posteriorly. Immediately above this facet is a deep excavation, which continues 
in the palmar direction and forms part of the large sinus between the trapezoid 
and magnum on the palmar face of the manus. Directly above the excavation 
mentioned is a small oblong facet for the trapezoid near the proximal angle; a 
second and larger facet for the trapezoid is seen immediately anterior to the 
excavated area, which is nearly square in outline. Continuously with, and directly 
above the latter facet, is the fourth facet, which is round in outline, shallow, and 
basin-shaped, receiving the projecting tuberosity of the scaphoid described above. 
On the ulnar face is a large, plane, articular surface, which is suboval in outline 
