AKSINOITHEKIUM. 
57 
angle. When the astragalus and calcaneum are articulated their fibular facets form 
an almost continuous convex surface. 
The calcaneum differs from that of Elephas in (1) its much shorter and stouter 
form, (2) the much smaller size of the cuboid surface, (3) in having the sustentacular 
facet for the astragalus larger than the ectal. Probably the foot approached the 
])lantigradc condition more nearly than is the case in Elephas. 
The calcaneum in the Dinocerata is somewhat more similar, but has the astragalar 
facets more nearly equal in size and convex, and the sustentacular portion of the 
bone is more prominent. 
The navicular (text-fig. 33) is of great width and at the same time is very short. 
Its proximal surface {ast.) for the astragalus is gently concave. The distal surface 
is divided into three facets ; of these the inner {c. 1) is slightly convex and extends 
nearly to the hinder border of the bone ; the middle (c. 2) is depressed, slightly 
Text-fig. 33. 
Left navicular of Arsinoitherium zitteli: A, from front; B, from above; C, from below. 
ast., facet for astragalus ; c. 1, c. 2, c. 3, surfaces for the cuneiforms ; 
cud., facets for cuboid. | nat. size. 
concave from side to side, and is limited posteriorly by a deep pit ; the outer (c. 3) 
projects considerably below the others, so that this region of the bone is much 
deeper than the rest, with the surface roughly triangular in outline. These three 
facets must have articulated with the three cuneiforms, none of which are known ; 
the ectocuneiform must have been a very small element. The outer (cuboid) face of 
the bone bears along its upper edge a well-marked facet for the cuboid [cuh.), and 
there seems to have been a less distinct facet for the same bone on the lower 
border. 
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