58 THE AMERICAN BEAVER. 



curves forward to unite with the malar — posteriorly a 

 hooked process of the temporal winds around the 

 back part of the auditory tube to the base of the mas- 

 toid process. Anteriorly and inferiorly it joins the 

 ala of the post-sphenoid, and posteriorly it embraces 

 the tympanic bone; the sutures of this bone are squa- 

 mous. The glenoid cavity is a flattened groove of 

 greater width than length, its outer margin formed 

 by the abrupt termination of the malar, the inner 

 boundary being the vertical portion of the temporal; 

 the lower jaw moves freely, in a longitudinal direc- 

 tion, back into the space between the glenoid groove 

 and the auditory tube. 



The vertical portion of the occipital bone is much 

 roughened for muscular attachment. Its upper mar- 

 gin is a sharp ridge, in front of which is the trans- 

 verse suture. In young subjects the ridge is wanting. 

 The occipital foramen is subtriangular or rounded — 

 broader than its height. The condyles look down- 

 ward, outward, and backward. The basilar portion 

 lies between the tympanic bones, and is united in front 

 by ligament to the post-sphenoid. An oblong, deep 

 cavity in the basilar portion renders this bone very 

 thin. The mastoid processes of the occipital are 

 lateral to the condyles. In young subjects the bone 

 consists of four portions, viz.: the ujDper squamous 

 portion, the basilar portion, and the two lateral or 

 condyloid portions. 



The tympanic bone is very irregular in shape. It 

 forms a small part of the vertical extremity of the 

 skull, Jind its mastoid process joins that of the occipi- 

 tal. The bulla is thick and prominent. From the 

 posterior part of the auditory tube, a sharp prominent 



