ediad component would increase as the jaw
approached full adduction. Neither is there anatomical evidence for an
adductor arising from the quadrate wing of the pterygoid. The bone is
smooth, hard, and without any marks that might be interpreted as muscle
scars.

The internal adductor or pterygoid musculature in _Captorhinus_
consisted of anterior and posterior components. The anterior pterygoid
arose from the lateral edge and the dorsal surface of the pterygoid
flange. The burred dorsal recurvature of the edge resembles that of the
flange of crocodiles, which serves as part of the origin of the
anterior pterygoid in those animals. In _Captorhinus_ the attachment of
the anterior pterygoid to the edge of the flange was probably
tendinous, judging from the extent of the development of the edge of
the flange. From the edge the origin extended medially across the
dorsal surface of the flange; the ridging of this surface is
indistinct, leading to the supposition that here the origin was more
likely to have been fleshy than tendinous.

The anterior pterygoid extended obliquely backward and downward from
its origin, passed medial to the temporal muscle and inserted on the
ventral and medial surfaces of the splenial and angular bones beneath
the Meckelian fossa. The spatial relationship between the palate and
quadrate-articular joint indicate that the muscle was probably a minor
adductor in _Captorhinus_.

When the jaw was adducted, the insertion of the anterior pterygoid was
in a plane nearly level with the origin. Contraction of the anterior
pterygoid when the jaw was in this position pulled the mandible forward
and did not adduct it. Maximum depression of the mandible produced
maximum disparity vertically between the levels of the origin and
insertion. The force exerted by the anterior pterygoid upon the
mandible when fully lowered most nearly approached the perpendicular to
the long axes of the mandibular rami, and the resultant force acting on
the mandible was adductive.

The adductive component of force therefore decreased as the jaw swung
upward, with the result that the anterior pterygoid could only have
been active in initiating adduction and not in sustaining it.

The evidence regarding the position and extent of the posterior
pterygoid is more veiled. On the medial surface of the mandible, the
prearticular and articular bones meet in a ridge that ventrally rims
the glenoid cavity (Fig. 4). The ridge extends ante