368 MEMOIRS OF THE CARNEGIE MUSEUM. 
transversely and is situated near the distal angle of the bone (see Fig. 100, 2). 
Distally there are two distinct facets; the larger of the two is triangular in outline, 
quite plane, and articulates with the ectocuneiform, while the outline of the smaller 
is more ovate, slightly convex antero-posteriorly, and articulates with the meso- 
cuneiform. The illustration (Fig. 100, 5) indicates a third facet, that for the 
cuboid, on the fibular angle. There is apparently no facet for the entocuneiform. 
Directly posteriorly the navicular terminates in a rounded process, which is, as 
before stated, directed upward and backward, like that in the posterior tibial angle 
of the navicular in the horse. 
There is no navicular in the specimens of Nestoritherium in our material, but 
from the shape and position of the facet for this bone on the tibial proximal angle 
of the cuboid it is quite evident that this bone was much the same as in the 
genus Moropus. 
The navicular of Macrotheriwm is even thinner, and it is more sharply turned 
upward on its plantar face than in Moropus. The articulation for the cuboid is 
also apparently less prominent than in the American form. 
MEASUREMENTS OF NAVICULAR. 
No. 1706a No. 1701 
(M. elatus), (M. petersoni), 
mm mm 
Antero=posterior diameter: <2 fcccm see ma cs seat oe Ree one eee eee een 55 41 
Transverse diameter.......... BS jeg tty Sr an ee EE i 74 54. 
Vertical diameter’ a oer corak sas osm tec at ee ee eet Orbe eee Ret re OD aA ee 15 10 
Cuboid (Fig. 101)—The cuboid is low and broad as in Titanotherium. The 
bone, however, differs from that in the latter genus in an important manner, 
having but one proximal articulation, that for the caleaneum, as already pointed 
out by Peterson (/. c., p. 749). In all other Perissodactyla the astragalus 
shares the support of the cuboid to a greater or less extent, and this is also the 
case in Macrotherium. In Nestoritherium as in Moropus the cuboid did not 
have an articular facet for the astragalus. Dorsally the cuboid in Moropus 
has a rather cube-like appearance, the lateral borders (especially the fibular) 
being quite angular. The tibial face is the longest, which is chiefly due to the 
prominent plantar process. Proximally there is, as before stated, one facet for 
the caleaneum which is ovate in general outline, slightly concave antero-posteriorly, 
and again sharply deflected on the extreme plantar angle, while transversely it is 
very gently convex. On the tibial face are two facets, one superior and the other 
inferior to a prominent ridge projecting in the tibial direction. Both facets are 
long antero-posteriorly and narrow transversely, the superior facet articulates with 
