THE ENT1EE SKULL 477 



into the temporal fossa. The zygomatic fossa is filled by the coronoid 

 process of the lower jaw and by the pterygoid muscles. 



THE TEMPORAL FOSSAE. 



Each Temporal Fossa lies above and behind the zygomatic fossa. 

 Its upper limit is a line known as the temporal ridge, which begins 

 at the root of the postorbital process of the frontal, curves upward 

 and inward on the frontal and parietal bones, and fades away near 

 the median line above and behind the middle of the parietal bone. 

 It has no well-defined posterior limit, and may be said to end with the 

 greatest lateral convexity of the skull. The temporal fossa does not 

 extend below the level of the zygoma. It passes into the orbit in 

 front, and is separated externally from it only by the postorbital pro- 

 cesses. It is filled by the tip of the coronoid process of the mandible 

 and by the large temporal muscle. 



POSTERIOR ASPECT OF THE SKULL. 



The outline of the skull when viewed from behind is dome-shaped, 

 and does not include the projections caused by the zygomatic processes 

 and the auditory bullse. Above, and at the sides, the posterior outline 

 is the outline of the greatest transverse convexity of the vault of the 

 cranium, and is produced by the parietals and the temporals. The 

 lower outline is formed by the lower edges of the mastoid portions of 

 the temporals and the vertical plate of the occipital. 



The true posterior surface of the skull fills a part of the outline 

 of the posterior aspect. It is triangular, the base of the triangle 

 identical with the lower outline, except for the swellings produced by 

 the auditory bullse further forward on the base of the cranium. The 

 apex of the triangle is situated at about the middle of the area, from 

 which point the sides run downward, outward, and forward to the 

 lateral angles and form the lambdoidal crest. The region above the 

 lambdoidal crest has already been studied in the consideration of the 

 superior aspect of the skull. 



The true posterior surface of the skull is the posterior surface of 

 the vertical plate of the occipital, composed of the supraoccipital above 

 and of the exoccipitals at the sides. To this plate is attached at 

 each lateral angle the mastoid portion of the temporal. Inasmuch as 

 these parts have been already fully considered, it is not necessary here 



