THE SKULL THE CEANIUM 



279 



nearly straight, and jagged; it is articulated with the following bones: 

 in front, where it is directed somewhat upward for a short distance, with 

 the upper border of the lachrymal, and to a varying degree with the 

 os planum of the lateral ethmoid when present ; then with the ethmoidal 

 process of the palatine ; and for the posterior half with the edge of 

 the orbitosphenoid. Somewhat behind the middle of this border is a 

 notch converted by the orbitosphenoid into a canal which enters the 

 cranial cavity at the lower end of the articulation of the cribriform 

 plate of the ethmoid ; in many specimens in advance of this opening 



FIG. 202. 



With. Opposite Frontal. 



Nasal Process. 

 With Ifaxillary. 



With Parietal. 



With Lachrymal 



With Alisphenoid. 



With Palatine. With Orbitosphenoid. 



LEFT FRONTAL BONE, OUTER ASPECT. 



is a small foramen which enters the nasal cavity. The anterior and 

 upper borders of the external surface are formed by the sharp edges 

 of the internal angular process, the orbital arch, and the postorbital 

 process. The posterior border is not well defined. It curves down- 

 ward and backward from the postorbital process to the posterior lower 

 angle of the bone, separates the orbital and temporal surfaces, and is 

 continuous with the infratemporal crest on the alisphenoid. 



The postorbital process is a pyramidal prolongation of the supra- 

 orbital ridge. Its anterior surface faces downward and forward, is 

 smooth and concave, and is continuous with the upper part of the 

 orbital plate. Its superior surface is flat and convex, faces upward and 

 backward, and passes into the depressed portion of the superior sur- 

 face of the horizontal plate. The posterior surface is rounded, faces 

 downward and backward, and gives origin to fibres of the temporal 

 muscle. Near its base is an inconstant foramen leading into the can- 

 cellous tissue. 



