264 



MAMMALIAN ANATOMY 



the external pterygoid process ; here it turns abruptly and runs back- 

 ward, outward, and upward as a mere ridge parallel with the external 

 border of the whole pterygoid, and ends on the surface of the ali- 

 sphenoid opposite the oval foramen. The hamular process varies in 

 development and general direction ; the tendon of the tensor palati 

 winds about it. The inferior surface, between the internal pterygoid 

 process and this ridge within and the external border without, is con- 

 cave transversely and forms a long narrow fossa, the external ptery- 

 goid fossa (Fig. 192), which affords attachment to the internal ptery- 



FIG. 191. 



With Palatine. 



With Presphenoid. 



With Basisphenoid. 



Surface forming one-half of 

 Middle Pterygoid Fost-a. ' 



External Pterygoid Plate. 

 Hamular Process of Internal 

 Pterygoid Plate. 



- Foramen Ovale. 



With Temporal. 



Root of Tentorium.L 



LEFT ALISPHENOID, LOWER ASPECT. 



goid muscle. The inner portion of the inferior surface thus divided 

 is smooth, quadrate, longer than wide, and descends gradually from 

 the inner border to the lower border of the internal pterygoid and 

 hamular processes. The lower surfaces of the two pterygoids form the 

 roof and outer walls of the deep middle pterygoid fossa. 



The alisphenoidal part of the under surface of the posterior sphe- 

 noid (Fig. 192) has the general outline of the alisphenoidal part of 

 the upper surface, namely, that of a rude crescent, whereof the con- 

 cavity faces outward. The upper surface being concave from before 

 backward, this surface is of course convex from before backward. For 

 convenience of description it may be divided into four regions, an 

 upper or temporal, a middle or orbital, a zygomatic, and a posterior or 

 scaphoid. 



The temporal region comprises the anterior and superior promi- 

 nent horn of the crescent. It is sharply defined from the orbital 

 region by a longitudinal roughened line, the infratemporal ridge 



