CRANIA FROM THE MOUNDS OF FLORIDA. 



431 



(12). The norma occipitalis. 



tian (No. 1,290) is shown. Two deep median depressions are noted on the line of 

 the sagitta, one at the postobelion and the other at the intertubera ; x two are seen 

 on either side of the sagitta, near the temporal ridges and two smaller ones on the 

 frontal bone on either side of the metopic line near the eminences. These depres- 

 sions being confined to the norma verticalis and found in a region in which indi- 

 vidual characters are often found, no doubt remains that they are anatomical variations 

 and not the results of disease. 



The various normse of the skull derive their 

 names from the positions assumed in their 

 delineation. But in the norma frontalis 

 and norma occipitalis names accepted in 

 other senses are introduced. In the norma 

 frontalis more than the front of the head 

 is seen, for a foreshortened view of nearly 

 all of the temporal fossa is possible. In 

 the norma occipitalis the occipital bone 

 does not yield even the most important 

 area. Most of the surface of the occipital 

 bone belongs to the norma basilaris. The 

 narrowest part of the occiput is nearest the 

 eye of the observer, and the anatomical 

 limitations of the occiput are not those parts 

 which are farthest from the eye, these being 

 part of the skull as far forward as the pari- 

 etal protuberance, the most convex parts of 

 the squamae, or even the line of the bregma. 

 In a word the norma occipitalis is not a view of parts seen nearly in the same plane 

 as are those of the other normge, but is a view in perspective of the entire brain case 

 as seen from behind. In brachycephalic skulls the parieto ecto-petrosal suture is 

 seen in the norma occipitalis, but in dolichocephalic it lies on the norma lateralis. 

 In a graphic sense the distinction between these two important types can be thus 

 discerned without other definition or measurement. Wilson used the term " in- 

 termastoid arch " for the limitations of the field of the norma occipitalis and repre- 

 sented it as the line formed between the mastoid processes. When the term pen- 

 tagonal is employed in describing the norma, it means that the entire contour is 

 resolved into five facet^like lines ; but two of these, namely, at the upper two-thirds, 

 are not part of the occiput at all, but are derived from the parietal bones. The 

 peculiarities of this norma occipitalis are so much more numerous and conspicuous 

 than those of the norma frontalis that special attention will be given them. 



1 For definitions for the terms " post-obelion" and " intertubera" see the author's Toner Lecture, 

 Smithsonian Institution, 1889. 



Fig. 25. — Norma occipitalis of an Egyptian skull (No. 

 1.290) showing great deformation the result of 

 absorptive processes going on in the porose inter- 

 temporal space (sconce). The abrupt interruption 

 in the curve of the lateral contour represents the 

 position of the temporal ridge. 



54 JOURN. A. N. S. PHILA., VOL. X. 



