130 



OSTEOLOGY 





is termed the superior nuchal line. That part of the squama which lies above 

 the highest nuchal lines is named the planum occipitale, and is covered by the 

 Occipitalis muscle; that below, termed the planum nuchale, is rough and irregular 

 for the attachment of several muscles. From the external occipital protuberance 

 a ridge or crest, the median nuchal line, often faintly marked, descends to the fora- 

 men magnum, and affords attachment to the ligamentum nuchae; running from 

 the middle of this line across either half of the nuchal plane is the inferior nuchal 

 line. Several muscles are attached to the outer surface of the squama, thus: 

 the superior nuchal line gives origin to the Occipitalis and Trapezius, and insertion 

 to the Sternocleidomastoideus and Splenius capitis: into the surface between 



Inferior Angle 



FIG. 130. Occipita bone. Inner surface. 



the superior and inferior nuchal lines the Semispinalis capitis and the Obliquus 

 capitis superior are inserted, while the inferior nuchal line and the area below 

 it receive the insertions of the Recti capitis posteriores major and minor. The 

 posterior atlantooccipital membrane is attached around the postero-lateral part 

 of the foramen magnum, just outside the margin of the foramen. 



The internal surface is deeply concave and divided into four fossae by a cruciate 

 eminence. The upper two fossa? are triangular and lodge the occipital lobes of 

 the cerebrum; the lower two are quadrilateral and accommodate the hemispheres 

 of the cerebellum. At the point of intersection of the four divisions of the cruciate 

 eminence is the internal occipital protuberance. From this protuberance the upper 

 division of the cruciate eminence runs to the superior angle of the bone, and on 



