he anterior margin of the origin is at the point where
the mandibular ramus of the trigeminal nerve enters the mandible.
Posteriorly the origin is bounded by the insertion of _M. adductor
mandibulae posterior_, and ventrally by a ridge that is situated about
halfway down the medial side of the mandible. The insertion is by
aponeurosis on the tip of the orbital process of the quadrate and
fleshily on the anterior surface of the same process. The aponeurosis
extends about three-fifths of the distance along the muscle and it is
dorsal or superficial to all of the fibers. Many fibers insert on the
ventral side of the aponeurosis (figs. 1, 5, 13, 14, 15, 16, 21 and
22).

This muscle is the most variable of all the jaw muscles. In the
Mourning Dove the muscle appears rather slender in dorsal view and in
the White-winged Dove has an enlarged lateral belly that gives the
appearance of a thicker muscle. In the Zenaida Dove _M.
pseudotemporalis profundus_ is intermediate in shape between those of
the other two species. This muscle will be discussed in detail later.

~_M. protractor pterygoidei._~--The origin is fleshy from the junction
of the sphenoidal rostrum and the interorbital septum. Fibers converge
on the pterygoid in anteroventrolateral and posteroventrolateral
directions. The posterior edge of the muscle is in contact with _M.
protractor quadrati_ with which its fibers mingle. The insertion is
fleshy on the posterior surface of the lateral half of the pterygoid to
its articulation with the body of the quadrate (figs. 6, 8, 9, 11,
13-20).

~_M. depressor mandibulae superficialis medialis._~--The origin is
fleshy from the lateral edge of the basioccipital where the muscle is
attached to _Ligamentum depressor mandibulae_ and extends in a lateral
direction to a point where the structures involved turn dorsad. The
insertion is by fibers and a light aponeurosis on the crista that is
situated on the posteroventromedial edge of the lower mandible.

~_M. depressor mandibulae superficialis lateralis._~--The origin is
fleshy from the squamosal region, slightly posteroventral to the origin
of _M. adductor mandibulae externus superficialis_. A thin aponeurosis
lies medial to the muscle fibers. The insertion is by means of an
aponeurosis that becomes tendonlike along the posteroventrolateral
crista and the posteriormost part of the ventral edge of the lower
mandible.

~_M. depressor mandibulae medialis._~--The origin is fleshy f