192 PROCEEDINGS OF THE ANATOMICAL AND ANTHROPOLOGICAL 



fossse bulge downwards on each side of a median groove in the situa- 

 tion of the external occipital crest. 



Finally, I shall mention the condition of trigonocephaly, which I 

 have already described, and which is usually found associated with 

 premature union of the metopic or interfrontal suture. 



It may be of interest to note here that premature union of the 

 skull bones does not very materially influence the total capacity of the 

 skull ; the compensation in other directions resulting from arrest of 

 growth in one direction being almost complete. Thus in a skull of a 

 native Fijian, which exhibits a remarkable degree of scaphocephaly, 

 with complete parietal synostosis, the capacity is 1,620 cubic centi- 

 metres (No. 129, R.C.S. England). 



Passing now to the consideration of sutures which normally close 

 early, but sometimes persist in adult life, we find here that there is 

 an increase in the diameter of the skull at right angles to the line of 

 the abnormal suture. The most common of these sutures is the 

 metopic or interfrontal. 



In a series of 108 metopic skulls which I have measured at the 

 Royal College of Surgeons, England, and in other collections, I have 

 found the average minimum frontal diameter to be 104 mm., and the 

 average maximum frontal diameter to be 1 20 mm. ; the corresponding 

 average measurements of an equal number of normal skulls of cor- 

 responding nationality I found to be for the average minimum frontal 

 diameter 9(5 - 6 mm., and the average maximum frontal diameter 115 

 mm. The metopic skulls are thus wider than the normal skulls, the 

 difference in the minimum frontal diameter being 7'4 mm., and in the 

 maximum 5 mm. The fronto-parietal index also or the percentage 

 ratio that the minimum frontal diameter bears to the greatest trans- 

 verse diameter of the skull is also greater in metopic skulls than in 

 normal. The fronto-parietal index of the metopic skulls is 72, that of 

 the normal skulls (58, there thus being a difference of 4 per cent. 



Now the question arises, does this difference in the width of the 

 frontal region add to the total capacity of the metopic skulls or is the 

 increased width of the transverse diameters accompanied by a cor- 



