198 
COEYPHODOK 
was a small amount of rotation, the inner malleolus being the fixed point. 
The fibula is entirely distinct, and has an oblique proximal surface of attach¬ 
ment to the tibia. The shaft is rather slender, and the distal end is expanded 
in an antero-posterior direction, so as to support a large, subround, oblique, 
inward-looking face for the astragalus. 
Posterior foot .—The posterior foot has, like the anterior, five toes, of which 
the second, third, and fourth do not differ much in length, while the hallux is 
about two-thirds as long as the third. The general form of the only complete 
hind foot which I obtained, is not so short in relation to its width as the fore 
feet, the width of the sole being but little greater than the length of the four 
bones of the third toe. The foot is completely plantigrade, and the heel 
very short. The free part of the calcaneum is not longer than the anterior 
width, and is depressed at the base. The astragalus is flat above, or slightly 
concave in both directions. Its anterior part has greater transverse extension 
than the posterior, being produced inward in a hook-like extension. The 
inner border is thus obliquely concave for the reception of the inner malleo¬ 
lus ; the external border is gently convex, and occupied by a longitudinal 
facet for the fibula. There is a posterior tuberosity at the angle Avitli the 
inner border. The distal end of the astragalus is divided by a low tuber¬ 
osity; but Avhile the internal and longer portion is entirely occupied by the 
navicular facet, the external half is only partly covered by an articular sur¬ 
face. Of the latter, the inner and larger part is for the ectocuneiform bone, 
while the outer is in contact with the cuboid. This articulation of the ecto¬ 
cuneiform with the astragalus is found in several and probably all of the 
species here described, and is one of the striking peculiarities of the foot of 
Corypliodon. 
The cuboid bone is transverse, and has greater length internally than , 
externally. Its two proximal facets present an angle to each other, Avhile 
the two distal facets are in one plane. The navicular is an L-shaped bone, 
with the anterior limb transverse, and is very thin in the longitudinal direc¬ 
tion. The posterior end of the longitudinal and exterior limb is a tuberosity. 
The distal extremity is divided into the three cuneiform facets, of which the 
median is largest. The ectocuneiform is the largest of its series. The pha¬ 
langes are similar to those of the fore foot, but the metatarsals differ in that 
