178 



HUMAN ANATOMY. 



six millimeties in the adult. A stiiall, sharp prominence, the spina siiprameatiim, is 

 found just behind the upper part of the meatus. It is an important landmark \\\ the 

 surii^ery of the region. Just posterior to it is usvially a minute venous foramen. 

 The inner side of ihe squamous portion, besides the large bevelled articular surface, 

 presents a smooth one, formini;; part of the wall and tioor of the cranial cavity. This 

 IS separated from the petrous portion by the petrosquamous suture, which is closed 

 early. Two grooves for branches of the middle m-Miingeal artery diverge from its 

 lower border, one running upward and the other backward. The front of the hori- 

 zontal part forming the 'floor is rough and thick, j >mmg the great wing of the 

 sphenoid. The zyi^omaiic process^ projects forward from the outer surface of the 

 squamosal to coinplete the zya^omatie arch with the malar, which it joins by a 

 serrated end. The free jxirt has an external and an internal surface, a rounded bor- 

 der below and a sharp edge above. The latter, which receives the insertion of the 

 temporal fascia, can be followed back to the origii\ of the process. The zygoma 

 has two roots. The posterior root passes direptly backward abo\e the auditory 



Fig. 197. 

 squamous portion 



GfX)ove for mcniii^al artery 



Internal audiiorx' meatus 

 Carotid canal 



PETROUS PORTION 

 Styloid process 



Aqufeducms ves- 

 tihuli 



uiove for lateral sinus 

 ASTOID PORTION 



A<i«ae<iuctus cochlea? 

 Risht temporal bone, internal aspect. 



meatus, crosses the squamous portion above the postauditory process, and. curving 

 slightly upward, is lost at the notch between the squamous and mastoid portions. 

 Its hind part is the sufyramastoid crest, which joins the inferior temporal ridge on 

 the parietal. The anterior root bends sharplv inward. It is grooved above for the 

 passage of the tibres of the temporal muscle. Its lower surface forms a semi- cylin- 

 drical transverse elevation, the emiueiUia artieu/aris,^ the front part of the articular 

 cavity of the lower jaw. Near its outer end is a tubercle for the external lateral 

 ligament. Just in front of the auditory meatus, on the under side of the bone, is 

 the smaller postglenoid tubercle, sometimes described as a third root. The glenoid 

 fossa^ is a deep hollow on the under side of the squamous portion, with its greatest 

 diameter ne.irlv transverse, but passing somewhat forward and outward, bounded 

 externally by the posterior root of the zygoma ; behind, by the fissure of G laser, ^ 

 wiiich separates it from the tympanic portion ; and extends forward and inward to 

 meet the inner end of the eminentia articularis. Both glenoid fossa and articular 

 eminence are covered with cartilage. The bone separating the glenoid fossa from 



' Proce.vsus jygom.itifu.* '- TubcrcuUim .irtioularc. ' Ftvswa iti.indibniaris. ' Fissnra pctrotympaniea. 



