THE ZYGOMA TIC FO88A. Ill 



where the coronal suture crosses the superior temporal ridge is sometimes named the 

 stcpkanton ; and the region where the four bones, the parietal, the frontal, the 

 squamous, and the greater wing of the sphenoid, meet, at the anterior inferior angle 

 of the parietal bone, is named the pterion. This point is about on a level with the 

 external angular process of the frontal bone and about one and a half inches behind 

 it. This fossa is deeply concave in front, convex behind, traversed by grooves which 

 lodge branches of the deep temporal arteries, and filled by the Temporal muscles. 



The Mastoid Portion. 



The Mastoid Portion of the side of the skull is bounded in front by the tubercle 

 of the zygoma ; above, by a line which runs from the posterior root of the zygoma 

 to the end of the mastoid-parietal suture ; behind and below by the masto-occipital 

 suture. It is formed by the mastoid and part of the squamous and petrous por- 

 tions of the temporal bone ; its surface is convex and rough for the attachment of 

 muscles, and presents, from behind forward, the mastoid foramen, the mastoid proc- 

 ess, the external auditory meatus surrounded by the tympanic plate, and, most 

 anteriorly, the temporo-maxillary articulation. 



The point where the posterior inferior angle of the parietal meets the occipital 

 bone and mastoid portion of the temporal is named the asterion. 



The Zygomatic Fossa. 



The Zygomatic Fossa is an irregularly shaped cavity, situated below and on the 

 inner side of the zygoma ; bounded, in front, by the zygomatic surface of the 

 superior maxillary bone and the ridge which descends from its mlar process ; 

 behind, by the posterior border of the external pterygoid plate and the eminentia 

 articularis ; above, by the pterygoid ridge on the outer surface of the great wing 



E.rt. auditory 

 meatns. 



process 



FIG. 74. Zygomatic fossa. 



of the sphenoid and the under part of the squamous portion of the temporal ; 

 below, by the alveolar border of the superior maxilla ; internally, by the external 

 pterygoid plate ; and externally, by the zygomatic arch and ramus' of the lower 

 jaw (Fig. 74). It contains the lower part of the Temporal, the External and In- 

 ternal pterygoid muscles, the internal maxillary artery and vein, and inferior max- 



