AESINOITHEEIUM. 



57 



angle. When the astragalus and calcaneum are articulated their fibular facets form 

 an almost continuous convex surface. 



The calcaneum diflfers from that of JElephas 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 octal. Probably the foot approached the 

 plantigrade 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 tp the hinder border of the bone ; the middle (c. 2) is depressed, slightly 



Text-fig. 33. 

 ast. 



Left navicular of ArsinoitJierium zitteli: A, from front; B, from above; C, from belovr. 



ast, facet for astragalus ; c. 1, c. 2, c. 3, surfaces for the cuneiforms ; 

 cub., facets for cuboid, g 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 (cub.), and 

 there seems to have been a less distinct facet for the same bone on the lower 

 border. 



I 



