192 MAMMALIAN ANATOMY 



but the process is twisted on its own axis, at the bend which it makes 

 to turn forward, in such manner that the superior surface of the basal 

 portion becomes the internal surface of the extremity ; the inferior 

 surface becomes the external surface ; the posterior border, the supe- 

 rior ; and the anterior border, the inferior. 



The superior-internal surface (Fig. 130) begins as a dowmvard 

 and outward prolongation of the anterior lower part of the external 

 surface of the squamous. As the superior surface on the base of the 

 process, it is broad, convex from before backward, faintly concave from 

 side to side, and faces upward and forward. Its posterior part is 

 grooved in front of the elevated posterior border. The anterior 

 margin, which faces downward, is sharp and slightly emarginate 

 within the triangular, downwardly directed, anterior glenoid process. 

 It forms the anterior margin of the glenoid cavity. Beyond the 

 glenoid cavity the zygomatic process becomes suddenly thin and 

 narrow, and the superior-internal surface turns so as to face at first 

 forward and inward and then almost directly inward. Its upper 

 border is slightly arched, running upward and forward, but at a little 

 distance from the end it becomes emarginate, presenting at that point 

 a more or less prominent angle. The lower border follows in general 

 the course of the upper border, but is straighter. It is bevelled at 

 the expense of the outer surface and overlapped by the zygomatic 

 process of the malar. As the internal surface of the end of the 

 process, it is strongly concave from before backward and gently 

 concave from above downward. The masseter muscle has origin on 

 its lower anterior part. 



The inferior-external surface (Fig. 131) of the thick basal portion 

 of the process is a continuation outward and slightly forward of the 

 lower surface of the squamous. It is divided into anterior and 

 posterior parts by a transverse postglenoid process. 



The anterior part in the glenoid cavity is about three times as 

 wide as it is long from before backward ; it is concave from before 

 backward, and faces downward and largely forward. Its inner end is 

 flattened, and is continuous with the region of the alisphenoid just 

 external to the foramen ovale (Fig. 127). Its outer narrow end is 

 cut off obliquely behind by the forwardly arching posterior border. 

 Its anterior margin is well defined and slightly prominent at the 

 inner end, and produced downward at its outer end into a conspicuous 



