_Origin_ in a depression on the lateral surface of the maxillary bone, just craniad of the last premolar tooth. The fibres pass craniad, diverging, toward the whiskers, and have their insertion into the pad of tissue on which the whiskers rest. _Action._--Retracts the whiskers and raises the upper lip. =M. buccinator.=--A thin muscle against the mucous membrane of the upper lip, partly united with the orbicularis oris and lying beneath M. caninus. _Origin_ on the outer surface of the superior maxillary bone in the depression between the infraorbital foramen and the first premolar tooth. The fibres pass ventrad, diverging, and mingle with those of the deep part of the orbicularis oris. _Relations._--Outer surface with the caninus and with the orbicularis oris. Inner surface with the mucous membrane of the upper lip. _Action._--Raises the upper lip. =M. myrtiformis= (probably corresponds to a part of the human M. nasalis) (Fig. 64, _h_).--A thin sheet of muscle-fibres lying craniad of the levator labii superioris alæque nasi and passing from the whiskers to the nose and upper lip. It is distinguishable from the alæque nasi by the direction of the fibres. _Origin_ from the pad upon which the whiskers rest. The fibres diverge and have their _Insertion_ upon the wing of the nose and into the skin of the upper lip near the median line. _Action._--Dilator of the nares and elevator of the upper lip. =M. “moustachier”= (Str.-D.) (probably corresponds to one of the Mm. incisivi).--It lies on the upper lip near the median line. _Origin_ from the outer surface of the premaxilla near the suture along the ventral border of the narial opening. The fibres diverge and pass caudad into the upper lip within the superficial fibres of the orbicularis oris. _Insertion._--The skin of the upper lip just craniad of the whiskers. Some of the fibres pass into the pad on which the whiskers rest. _Action._--It carries the lip craniad. =M. quadratus labii inferioris.=--A thin flat band extending almost the length of the lower lip. _Origin_ from the alveolar border of the mandible, between the molar tooth and the canine. The fibres pass dorsad into the lower lip, where they intermingle with those of the orbicularis oris. The muscle is perhaps not constant. _Action._--Depressor of the lower lip. Sometimes a few fibres arising from the cranial portion of the alveolar border of the mandibula pass mediad, seeming to join corresponding fibres from the opposite side. Such fibres would constitute a M. transversus menti. B. DEEP MUSCLES OF THE HEAD. (_a_) _Muscles of Mastication._ =M. digastricus= (Fig. 65, _b_).--The digastric is a thick prismatic muscle lying mediad of the angle of the lower jaw, connecting it with the base of the skull.