278 



MAMMALIAN ANATOMY 



postorbital process. Behind this process the superior surface is often 

 separated from the lateral surface by a curved temporal line, which 

 begins at the root of the postorbital process and curves upward, back- 

 ward, and inward to meet the end of the curved line on the parietal 

 at a point on the coronal suture known as the stepha'nion; 1 sometimes, 



FIG. 201. 



With Maxillary. 



Internal Angular Process. 



External Angular or Post- 

 orbital Process. 



Nasal Process. 



- With Opposite Frontal. 



With Parietal. 

 LEFT FRONTAL BONE, OUTER SURFACE. 



however, the lateral border becomes indistinct and the superior sur- 

 face rounds down into the vertical portion of the bone. The posterior 

 border is jagged, somewhat bevelled at the expense of the superior 

 surface, and passes at the side into the posterior border of the vertical 

 plate. It articulates with the anterior border of the parietal bone. 



The Vertical Plate presents an external and an internal surface. 



The external surface (Fig. 202) is divided into two parts, a large 

 anterior concave portion, entering into the formation of the inner wall 

 of the orbit, and a small posterior convex portion, contributing to the 

 temporal fossa. 



The orbital portion or plate is dome-shaped. The lower border is 



1 From (Gr.) Stephanos, a crown. 



