148 DINOCERATA. 



The face for the navicular is fully twice as large as that for the 

 cuboid. It is somewliat convex from side to side, but is nearly flat 

 from before backward, and is bounded along its outer, or fibular, and 

 posterior side by a low rounded ridge, indicating the limit of the cuboid 

 face. This facet is more or less triangular in outline, the apex pointing 

 backward and inward. It is only moderately convex. 



The relation of the navicular face to the articulation for the tibiale 

 bone is well shown in woodcuts 140 and 142, below. 



The outer, or fibular, side of the astragalus (Plate XLVII, figure 4) 

 presents a convex articulation for the fibula. This face is confluent above, 

 with the tibial surface, and usually, also, in a mvich less degree, with the 

 outer face for the calcaneum. In some specimens, however (numbers 

 1248, 1528, 1531), these faces are quite separated. 



In an anterior view of the astragalus (figure 5), the exterior, or 

 dermal, surface is seen to be very short, ^jroportionally shorter than in the 

 elephant, but varying within such limits that the longest in the Binucerata 

 may nearly or quite equal in length the shortest in the elephant. 



Posteriorly, the astragalus extends backward much farther on the 

 inner, or tibial, side than on the outer side, and is tuberculated. This 

 surface of the bone is, in some specimens, deeply notched near the middle, 

 as in figures 141 and 142, below, but more commonly the notch is 

 converted into a foramen by a bridge of bone, as in Plate XLVII, figure 

 6, and figures 139 and 140, below. The tibial articular surface is not 

 usually confluent with the calcaneal surface, as is sometimes the case in 

 the elephant. A near approach to confluence is seen in one specimen, 

 number 1209. 



The astragalus in Conjphodon is very similar in form to that in the 

 Dinocerata, but is shorter. It has essentially the same articular faces, and 

 the facet for the tibiale is equally well marked. The hind foot of 

 CoryphodoH is shown in figure 151, in Chapter XIV. Its general 

 resemblance to the corresponding foot in Dmoceras is striking, and the 

 structure of the two is essentially the same. The resemblance between 

 the fore foot of Dinoceras and that of Coryphodon is equally marked. 



