MESODONTA. 
]4;5 
This smaller species is represented by bones of the feet^ chiefly posterior. 
The inferior extremity of the tibia has the usual form, and fits exactly the 
trochlear superior face of the astragalus. The inner face of the inner mal¬ 
leolus forms an open angle with the subtransverse face posteriorly, and 
nearly a right angle anteriorly. This form represents the relation between 
the superior and interior faces of the astragalus from behind forward. Me¬ 
dially, the two faces are but little defined, while at the neck they are distin¬ 
guished by a short angulation. This angulation is at the middle of the 
neck; inside of it, the surface is depressed to receive the inferior extremity 
of the internal malleolus. The superior trochlear face is oblique and at the 
middle plane, and it is separated by a sharp angle from the nearly vertical 
external or fibular face. The neck is elongate and the head is incurved. 
The navicular face is transverse and convex in both directions. This astraga¬ 
lus resembles somewhat that of the Bidymictis lyrotenus. The calcaneum, like 
that of the Creodonta, is shorter in proportion to its width than in true Car¬ 
nivora, the shortening being in front, and the expansion in the lateral astrag- 
alar facets. Thus, the anterior extremities of the astragalus and calcaneum 
do not terminate in the same vertical plane as in Ursus, Canis, and Felis, and 
many other Mammalia, but the neck and head of the former project far 
beyond the cuboid facet of the latter. As a consequence, the cuboid bone 
is relatively longer, and the navicular shorter, than in the other forms men¬ 
tioned. -The cuboid facet is in a vertical plane, and is oblique to the long 
axis of the bone. The posterior portion is of moderate length, and com¬ 
pressed in an oblique plane. Distal end, a wide irregular oval. Only one 
entire metacarpal bone is preserved, with the extremities of several others. 
The former is not long in proportion to its distal diameter. The head pre¬ 
sents a fore-and-aft convex surface, which is slightly concave transversely. 
Two others are convex fore and aft, and plane and convex in transverse 
section. The distal end of the entire metacarpal is depressed, with an inferior 
keel, and strong lateral ligamentous fossae. The phalanges are depressed, 
with subinferior distal articular face, which has a shallow trochlear emar- 
gination. An ungual phalange is compressed, with a dorsal keel, and is 
moderately curved. There is a strong basal ligamentous insertion, with a 
deeply-placed nutritive foramen on each side. Apex lost. 
