THE PARIETAL BONE. 35 



of the jugular process represents the paramastold process of many mammals : it may be so long 

 as to meet the transverse process of the atlas. In rare cases an additional articulation is 

 formed between the basilar process and the anterior arch of the atlas, or the tip of the odontoid 

 process. 



THE PARIETAL BONE. 



The parietal bones form a considerable part of the roof of the skull. They 

 have the shape of quadrilateral plates, convex externally, concave internally. They 

 are a little broader and thicker above than below ; the anterior inferior angle is the 



PACCHIONIAN 

 DEPRESSIONS 



LONGITUDINAL 



SULCUS 





TCRAL SULCUS 



Fig. 35. RIGHT PARIETAL BONE: INTERNAL SURFACE. (Drawn by D. Gunn.) 



most projecting. They articulate with each other in the middle line above, with the 

 frontal bone anteriorly, the occipital posteriorly, and the temporal and sphenoid 

 below. 



On the outer surface, near its middle, a more marked convexity exists, forming 

 the parietal eminence. Passing through or close below this are the superior 

 and inferior temporal lines, enclosing between them a narrow curved portion of 

 the surface, which is usually smoother and more polished than the rest. Below the 

 inferior temporal line is the temporal surface, somewhat flattened, forming part of the 

 temporal fossa, and giving origin to the temporal muscle. The surface above the 

 upper line is covered only by the scalp. Close to the upper border, and nearer 

 to the posterior angle, is the small parietal foramen. 



The inner surface is concave, the deepest part, opposite the parietal eminence, 

 being known as the parietal fossa ; it is marked by shallow depressions corresponding 

 with the convolutions of the brain, and by narrower furrows, branching upwards and 

 backwards from the lower border, for the meningeal vessels. The largest of these 



