~_M. pterygoideus ventralis lateralis._~--The origin is fleshy and by aponeurosis on the ventral side of the palatine anterior to the palatine fossa. The insertion is fleshy on the ventromedial surface of the lower mandible and continues along the anteromedial surface of the internal angular process to its distal tip. A few fibers leave _pars lateralis_ and insert on an aponeurosis which receives also all the fibers of _M. pterygoideus dorsalis lateralis_. The latter fact may have prompted Rooth (1953:257) to make the statement that the fibers originating on the dorsal part of the palatine inserted more laterally than those originating on the ventral side. Rooth worked with _Columba palumbus_, the Woodpigeon, and his description concerned _M. adductor mandibulae internus pterygoideus_, which is composed of _Mm. pterygoideus ventralis et dorsalis_ of Lakjar (1926). His assertion that ventral fibers, that is to say, fibers arising on the ventral surface of the palatine, insert medially does not appear to be completely true for doves. Aponeuroses cover most of the lower surface of the muscle and one or two nerves extend into the substance of the muscle. The nerves run from the anterior edge of _M. pterygoideus dorsalis medialis_ and farther posteriorly from a separation in the muscle. ~_M. pterygoideus ventralis medialis._~--The origin is by aponeurosis from the ventral surface of the palatine and fleshy from the palatine fossa. The aponeurosis is the same that gives origin to the fibers of _pars lateralis_. Part of the aponeurosis becomes tendonlike in the middle of _M. pterygoideus ventralis_ and separates its two divisions. The insertion is fleshy on the lower one-third of the anterior surface of the internal angular process of the lower mandible, and by two tendons on the distal tip of that process. Many of the fibers of _pars medialis_ insert on the tendons. The fibers at their insertion are not distinctly separate from those of _pars lateralis_ and there is considerable mingling of the fibers. Consequently, the medial part of _M. pterygoideus ventralis_ cannot be removed as a part distinct from the lateral part (figs. 1, 4, 10, 21 and 22). Ordinarily _M. pterygoideus ventralis_ does not cross the ventral edge of the lower mandible, but in one white-wing the muscle was slightly expanded on the right side and it could be seen in lateral view. The homologous muscle in _Columba palumbus_ apparently is consistently visible in lateral view. (See Rooth, 1953, fig. 6.) ~_M. pterygoideus dorsalis medialis._~--The origin is fleshy on the dorsolateral surface of the palatine immediately anterior to the pterygoid and also on the anterior, dorsolateral, posterior and ventromedial surfaces of the pterygoid. The insertion is fleshy on the ventromedial surface of the lower mandible and the anterior surface of the internal angular process immediately dorsal to the insertion of _M. pterygoideus ventralis lateralis_.