dition in _Captorhinus_.

The coronoid process in _Captorhinus_ is not oriented vertically, but
slopes inward toward the midline at approximately 45 degrees,
effectively roofing the Meckelian fossa and limiting its opening to the
median surface of each ramus. When the jaw was adducted, the coronoid
process moved upward and inside the cheek. A space persisted between
the process and the cheek because the process sloped obliquely away
from the cheek and toward the midline of the skull. The external
surface of the process presented an area of attachment for muscles
arising from the apposing internal surface of the cheek.

_Palate_

The palate of _Captorhinus_ is of the generalized rhynchocephalian type
(Romer, 1956:71). In _Captorhinus_ the pterygoids and palatines are
markedly arched and the relatively large pterygoid flange lies almost
entirely below the lower border of the cheek. The lateral edge of the
flange passes obliquely across the anterior lip of the Meckelian fossa
and abuts against the bottom lip of the fossa when the jaw is closed.

The palatines articulate laterally with the maxillary bones by means of
a groove that fits over a maxillary ridge. This presumably allowed the
halves of the palate to move up and down rather freely. The greatest
amplitude of movement was at the midline. Anteroposterior sliding of
the palate seems impossible in view of the firm palatoquadrate and
quadrate-quadratojugal articulations.

The subtemporal fossa is essentially triangular, and its broad end is
bounded anteriorly by the pterygoid flange. The fossa is lateral to
much of the adductor chamber; consequently muscles arising from the
parietals passed ventrolaterally, parallel to the oblique quadrate
ramus of the pterygoid, to their attachment on the mandible.

_Musculature_

These osteological features indicate that the adductor muscles of the
jaw in _Captorhinus_ consisted of two primary masses (Figs. 1, 2, 3).
The first of these, the capitimandibularis, arose from the internal
surface of the cheek and roof of the skull and inserted on the bones of
the lower jaw that form the Meckelian canal and the coronoid process.

[Illustration: FIG. 1. _Captorhinus._ Internal aspect of skull, showing
masseter, medial adductor, and temporal muscles. Unnumbered specimen,
coll. of Robert F. Clarke. Richard's Spur, Oklahoma. x 2.]

[Illustration: FIG. 2. _Captorhinus._ Internal aspect of skull, showing
anterior and posterior ptery