184 MAMMALIAN ANATOMY 



and is bevelled from above downward and forward. It is rough 

 for articulation with the anterior border of the upper part of the 

 occipital, and exhibits openings into the diploe, which are the ends 

 of vascular channels. 



The anterior surface (Fig. 121) presents a median portion, with 

 the outline of an erect triangle facing forward, and lateral parts, 

 bevelled at the expense of the upper surface, facing upward, outward, 

 and forward. The median portion has an angular or emarginate lower 

 margin and a prominent produced upper angle. It is concave from 

 above downward, and is frequently pierced on either side of the middle 



FIG. 120. 



Part of Sagittal Crest. FlG. 121. 



With Parietal. 



I ,~^< t A'" 1 ^ 



For Blood-vessels. 



With Occipital. With Parietals. 



INTERPARIETAL, OUTER SURFACE. INTERPARIETAL, ANTERIOR SURFACE. 



by large vascular foramina, whereof one is large and usually best 

 developed on the right side and appears to represent the continuation 

 into the skull of the longitudinal sinus in the dura of the brain. 

 The anterior surface is closely applied to the posterior borders of the 

 parietals. 



In skulls of advanced age the interparietal may be found firmly 

 united with the neighboring bones. 



Nomenclature. The term interparietal is from inter, between, 

 and parietal. The German term is das Zwisehenscheitelhe in ; the 

 French, I' interparietal. 



Ossification. The interparietal is developed from two centres 

 of ossification which early unite. 



Articulation. The interparietal articulates with the occipital 

 and the parietals. 



HUMAN PARIETAL BONES. 



Most of the features of the parietal of the cat can be easily 

 recognized on the human parietal. The tentorial process, however, 

 is absent, and the entire bone is more strongly curved. 



