The tibia (Plate XII, Figs. 6-11) is a little more than three-fifths
the length of the femur, and has a much-dilated proximal extremity,
a slender, curved, subtrihedral shaft, and a moderately expanded
lower extremity. The distal end is curved backward so that the
truncated distal extremity is at an angle of nearly forty-five degrees
with the long axis of the bone. The greater diameter of the
proximal articular surface is nearly transverse in position in the
articulated skeleton. The cnemial elevation in front is not very
broad or high, the surface on the outer side of it partly underlying
the fibula in articulation; that on the inner side is convex. The
distal extremity is subangular on the inner anterior part; the other
sides more rounded.
The fibula (Plate XIII, Figs, 2, 3), hitherto almost unknown
among the Texas reptiles, is a very slender bone, and is distinctly
longer than the tibia, the planes of its two extremities slightly twisted
on the longitudinal axis at an angle of ten or fifteen degrees. The
proximal end is convex on its outer dorsal side, gently concave on
the tibial, the proximal articular surface long and narrow, oblique
both inwardly and anteriorly. The distal extremity, much the
broader, is also convex on the dorsal, concave on the ventral
side, with a round distal outline, extended higher up on the more
expanded inner side. The articular surface, long and narrow with
a slight sigmoid curve, is directed somewhat obliquely forward. The
slender shaft is nearly straight in its middle part, or slightly
curved in outline.
