HOLLAND AND PETERSON: OSTEOLOGY OF THE CHALICOTHEROIDEA. 303 
is convex antero-posteriorly and very soon succeeded by an oblique area, which 
ascends steeply upward and outward and terminates in an exceedingly high and 
sharp ridge, the highest point of the head of Me. III (Fig. 89, 2). On the ulnar 
side of this high ridge is located the facet for the unciform. This facet is slightly 
concave supero-inferiorly and convex antero-posteriorly; it is sub-triangular in its 
general outline and is located nearer the dorsal than the palmar face of the bone. 
There is on the ulnar face, as in Me. IJ, an overhanging projection, underneath 
which is located a large and obliquely placed facet for Mc. IV. A second facet 
for Me. IV is located near the palmar face and is separated from the one dorsally 
by a narrow, but quite decided sinus, which seems to be persistent in a great number 
of individuals examined (see Fig. 89, 1). The surface below these facets is quite 
rugose for a considerable distance on the shaft, and, as on Me. II, terminates in a 
slight eminence. The posterior face of the head is produced in the palmar direction, 
and is transversely narrow. ‘The shaft is less cylindrical than in Me. II, the part 
next to the head being sub-quadrate and the portion lower down suboval in cross- 
section. Distally the shaft terminates in rugosities which are especially prominent 
on the radial and ulnar angle of the dorsal face. The articulating surface for the 
proximal phalanx is very convex and is oblique, though considerably less so than 
in Me. II; the carina being in a more nearly antero-posterior line with the long 
axis of the shaft. The radio-plantar angle of the distal end is quite curiously 
produced in a downward and inward direction so that the facet for the sesamoid 
on the radial side of the carina has an inferior position to that on the ulnar side. 
The carina is well developed and confined entirely to the plantar face. Judging 
from the oblique position of the distal articulation of Me. III it is quite evident 
that the first phalanx pointed in the same direction as the first phalanx of the 
second digit. 
As represented in the cast Me. III of Nestoritherium is broken off distally. 
The head has a much less conspicuous ridge separating the facets for the magnum 
and unciform than in Moropus. The facet for the unciform in Nestoritherium 
occupies a more lateral position near the dorsal face continuing backward to the 
palmar angle in very nearly a straight line and has not the decided interlocking 
characters seen in this region in Moropus and Macrotherium. The shaft is also 
distinctly more trihedral in cross-section with a backward bend, while in Macro- 
thertum the shaft is slightly curved forward, and in Moropus it is more nearly 
straight. Its anterior face is curiously flat and broad as represented in the speci- 
men in Munich. 
The general outline of Mc. III in Macrotherium is on the whole more similar 
