MESOZOIC V^ERTEBRATA, 
35 
triangular in section, the base of the triangle internal. The external ex¬ 
tremity of the distal end is therefore an angle, and the internal a convex 
side, shorter than the anterior and posterior sides. A ligamentous groove 
marks the posterior border of the extremity at a point measuring one-third 
of its length from the external angle. The expanse of the distal extremity 
is not more than three-fourths that of the proximal. The entire bone so 
resembles a tibia as to have induced me to refer it at first to that element. 
The characters of the proximal end are such as to render such identification 
highly improbable. Such reference would- also require that the distal ex¬ 
tremity should have a fore and aft direction, an arrangement incompatible 
with the tibia. 
The displaced metapodial is flattened, and expanded at the extremities. 
One side is nearly flat, but slightly concave in the longitudinal direction; 
the other side is convex and nearly level in the longitudinal direction. The 
lateral borders of the shaft are thus narrowed. The distal end displays a 
convex condyle, and a flat, prominent ala, which is in the general plane. 
The ala is separated from the condyle by a deep groove on the convex side. 
The condyle is a half-hemisphere only, presenting only with the convex 
side of the shaft, from which it is not separated by a constriction. It is 
bounded at its distal edge by an angle, which is a continuation of the 
proximal edge of the ala. The proximal extremity is injured at one angle, 
but, with this complete, would be nearly a regular rhomboid with parallel 
longer and shorter outlines ; the acute angle of the latter being the con¬ 
tinuation of the lateral border of the shaft. The extremity is sub truncate, 
and part of the surface is irregularly excavated by pits and grooves. The 
transverse extent of the proximal end, when perfect, was probably a little 
greater than that of the distal. 
The two adjacent metapodials are subequal in length, and longer than 
the displaced one by one-fourth the length of the latter. One of these bones 
is throughout rather thicker than the other, although the transverse diameter 
of the shafts is equal; but the stouter bone is considerably more, dilated at 
the extremities. The distal end of the stouter bone is thickened in the 
direction at right angles to the plane of the limb ; but the chief expansion 
is in that plane. The angle next to the other bone is protuberant, while 
