192 



Anatomy of Skeleton 



the supra-occipital. At the junction of basi- and ex-occipitals the two articular 

 condyles for the Atlas are seen on the margins of the foramen magnum. 



To the outer side of the ex-occipitals the temporal bone comes into the base on 

 each side, showing the prominence of the mastoid process externally, and then a narrow 



if 

 Sphenoid. - 



articular cavity 

 styloid prates 



FIG. 161. Lower aspect of base of skull. EO, ex-occipital ; PT, inferior surface of petrous 

 part of temporal ; between EO and PT are carotid and jugular foramina. BO, basi- 

 occipital which is continuous with basi-sphenoid. Foramen lacerum (medium) is in front 

 of PT and outside BO. PO, post-occipital ; SO, supra-occipital. 



strip between the process and the ex-occipital, having a deep groove, the digastric 

 groove, for the origin of the posterior belly of the digastric muscle. 



Stretching forward and inward from this, in front of the ex-occipital, there is 

 a part of the temporal bone applied loosely to the side of the basi-occiput. This is the 

 petrous part of the temporal, the part that contains the organ of hearing, and named 

 from the extreme hardness of its bone. 



