[Proc. Roy. Soc. Victoria, 26 (N.S.), Part I., 1913]. 



Art. XV. — On the Estimation of the Position (ind Slope of 

 the Foramen Occipitale Magnum. 



By L. AV. U. BUCHNER 



(<jovernment Re.searcli Scholar in the Department of Anthropology, 

 Melbourne University). 



(With one Text Figure). 

 [Keacl 10th July, 1913]. 



Ill 190i) Bolk^ published a work concerning the estimation of the 

 displacement, position and slope of the foramen occipitale magnum. 



In describing its position he refers to the fact that in Mycetes 

 the foramen lies very near " the occipital pole of the skull, so that 

 the condition is found which is the rule Avith other mammals; some- 

 times, as in man, it lies about the middle of the cranial base." The 

 same writer^ also states that, " Together with the variations in 

 position the inclination of the plane of tlie Foramen nmr/niini also 

 generally changes." 



As the question of the earlier liistory of the foramen occipitale 

 magnum, and of the base lines from wliicli have been estimated its 

 position and slope has been already fully considered by Bolk, it 

 is mmecessary to jiursuo the (|uestion further in the present paper. 



In view, however, of the much more recent work accomplished 

 by this author, on the foramen occipitale magnum, it will be 

 necessary for me to examine his methods in some little detail, inas- 

 much as they form the basis of the present investigation. Bolk 

 introduces a new baseline estimated in the bisected skull. He says, 

 " As frontal point I chose the lowest point of the frontal wall of 

 the skull, where the interior surface . . . bends inwardly in a 

 more or less sliai)) curve, to be continued in tlu' roof of the nasal 

 cavity."" He further states that "the dfteniiiiiat ion of this point 

 presents no ditHculties as a iiilc, since in the niediaii plane the 

 interior surfaci' of all Primate skulls ])o.sscsscs a distiiut fi-ontal 

 wall, wliicli niav l)e nioi'e or less inclined, and may ])ass more or 

 less gradually into the cranial wall, lint whirli is still always 

 presi.-nt."' 



This authoi- then goes on to say that " in tlic median all Primate 

 skulls possess a front. On both sides of the median plane this 

 frontal wall disappears, since tlu' roof of the orbitae approaches 



