THE SKULL THE CEANIUM 



263 



pterygoid is termed the vaginal l process. An imaginary line drawn 

 from this thin posterior margin to the posterior edge of the round 

 foramen marks the approximately outer posterior limit of the pterygoid 

 process. The outer border begins, behind, in the sharp, crescentic, 

 posterior margin of the round foramen, and runs forward, downward, 

 and slightly inward to end in the sharp anterior angle. It is thin, and 

 about half of its length is prolonged into a variable, external pterygoid 



FIG. 190. 



With Vomer. 



With Palatine. 

 Presphenoid. 



External Pterygoid Fossa. 

 External Pterygoid Process of 

 Alisphenoid. 



Hamular Process of Pterygoid. 



Foramen Rotundum. 



Foramen Ovale. 



Foramen for Vidian Nerve. 

 With Ectotympanic. 



Groove for Vidian Nerve. 

 With Entotympanic. 



Orbitosphenoid, with Frontal. 



-Pterygoid. 



With Squamosal of Temporal. 

 Alisphenoid. 

 Basisphenoid. 



With Petrous With Basioccipital. 

 of Temporal. 



THE SPHENOID BONE, EXTERNAL OR LOWER ASPECT. 



plate or process which, when well developed, points downward, back- 

 ward, and outward. The anterior margin is transverse and jagged ; 

 it joins the posterior part of the horizontal plate of the palatine. The 

 inferior surface of the pterygoid process is divided into two unequal 

 parts by the longitudinal internal pterygoid plate or process, which 

 projects downward. 



The internal pterygoid process is a thin plate, prolonged beneath 

 and behind into a hamular process. Its lower border begins on the 

 front margin just within the anterior external angle and runs back- 

 ward and downward to terminate in the tip of the hook. It is usually 

 sinuate, curving first outward, then inward, then outward again. The 

 posterior border begins behind where the lower border ends, and is 

 deeply emarginate. It curves upward and forward to a point opposite 



l From vagina, a sheath. 



