of _pars
medialis_ and the insertion is by means of an aponeurosis on the medial
surface of the lower mandible, lateral to the insertion of _M.
pterygoideus ventralis lateralis_. The aponeurosis crosses the medial
side of the insertion of _M. pterygoideus dorsalis medialis_. The
fibers run in a posteroventrolateral direction and insert on the
ventromedial side of the aponeurosis (figs. 1, 6, 8, 9, 13-22).

In one individual, a Mourning Dove, the origin of _pars lateralis_ of
_M. pterygoideus dorsalis_ extended to the pterygoid. With this one
exception the muscle was uniform throughout the several species.

~_M. adductor mandibulae externus._~--This is the most complex muscle
in the jaw owing to its system of tendons and aponeuroses. Three
divisions of this muscle were described by Lakjar (1926:45-46) and the
divisions appear to be distinguishable in the doves, but there is no
clear line of demarcation for any of the parts and the following
description is based upon my own attempts to delineate the muscle.

~_M. adductor mandibulae externus superficialis._~--The origin is
fleshy from the most lateral area of the temporal fossa. Dorsally the
origin is bounded by the base of the postorbital process and ventrally
by the temporal process. The fibers converge upon a tendon that passes
beneath the postorbital ligament and runs anteriorly among the fibers
of _pars profundus_. The insertion is tendinous on the dorsal surface
of the lower mandible in common with the dorsal aponeurosis of _pars
profundus_. The insertion is immediately anterior to the ventral
aponeurosis of _pars profundus_ near the medial edge of the dorsal
surface on a tubercle at the posterior end of the dorsal ridge of the
lower mandible.

~_M. adductor mandibulae externus medialis._~--The origin is by a flat,
heavy tendon from the temporal process. The tendon is attached almost
vertically on the temporal process. It twists approximately 130 deg. as
it runs anteriorly, and becomes a thin aponeurosis, which gives rise on
its dorsal and ventral surfaces to many fibers that insert in a
fan-shaped area on the mandibular fossa. Fibers from the dorsal and
dorsomedial sides of the heavy tendon run rostrad and insert on the
ventral surface of the dorsal aponeurosis of _pars profundus_. From the
ventral surface the most posterior fibers converge on an aponeurosis
that inserts on a transverse crista on the dorsal surface of the
mandible immediately lateral to the ve