_Action._--Raises the snout. =M. rectus capitis posterior medius= (Fig. 71, _d_). (This is in man a part of the rectus capitis posterior major.)--It lies beneath the rectus capitis posterior major (Fig. 71, _a_). [Illustration: FIG. 71.--DEEP MUSCLES OF THE NECK, AFTER THE REMOVAL OF MM. BIVENTER CERVICIS AND COMPLEXUS. _a_, M. rectus capitis posterior major; _b_, M. obliquus capitis inferior; _c_, M. semispinalis cervicis; _d_, M. rectus capitis posterior medius; _e_, M. obliquus capitis superior; _f_, M. longus atlantis; _g_, M. scalenus (part of cervical portion); _h_, cut end of M. levator scapulæ.] _Origin_ from the cranial end of the axial spine. It forms a triangular prismatic mass which passes craniad and has its _Insertion_ into an elongated area on the occipital bone, ventrad of the median half of the lambdoidal crest. _Relations._--Dorsal surface with the rectus capitis posterior major (Fig. 71, _a_). Ventral surface with the atlas and the rectus capitis posterior minor. _Action._--Assists the rectus capitis posterior major. =M. rectus capitis posterior minor.=--A small triangular muscle beneath the rectus capitis posterior medius (Fig. 71, _d_). _Origin_ by the apex of the triangle from the cranial border of the dorsal arch of the atlas for about two millimeters laterad of the median line. The muscle passes over the ligament which connects the atlas to the occiput and adheres to it. _Insertion_ into an elongated area on the occipital bone, ventrad of the insertion of the rectus capitis posterior medius for about five millimeters next to the median line. _Relations._--Dorsal surface with the rectus capitis posterior medius. Ventral surface with the posterior atlanto-occipital membrane. _Action._--Assists the rectus capitis posterior major. =M. obliquus inferior= (Fig. 71, _b_). _Origin_ from the whole lateral surface of the spine of the axis. The parallel fibres form a thick mass which passes laterad and craniad. _Insertion_ into the dorsal surface of the transverse process of the atlas along a narrow area near its lateral margin. _Relations._--Outer surface with the rectus capitis posterior major (Fig. 71, _a_), the complexus (Fig. 69, _b_), and the obliquus superior (Fig. 71, _e_). Inner surface with the axis. _Action._--Rotates the head. =M. obliquus capitis superior= (Fig. 71, _e_; Fig. 72, _e_).--This is a triangular muscle passing from the outer border of the atlas laterad of the recti capitis posteriores to the occiput. _Origin_ from the lateral border of the transverse process of the atlas on its ventral margin. The fibres pass craniad and diverge. _Insertion_ into the caudal side of the mastoid process of the temporal bone and into a line parallel with the lambdoidal ridge and ventrad of it, from the mastoid process to within one centimeter of the median line.