THE EVOLUTION OF THE EYEBROW REGION OF THE FOREHEAD. 305 



this can be formed without its aid. As we have seen, the superciliary eminence 

 frequently appears as an isolated eminence, standing absolutely independent of, and 

 apart from, the other elements of the region. I suspect that this problem must remain, 

 for the meantime at least, unsolved. It may be that, by adding to the volume of the 

 supraorbital projection, the superciliary eminence increased the aspect of ferocity, which 

 is generally associated with projecting brows, and thus contributed to the face a feature 

 which would no doubt have been a decided advantage in those early struggling days. 

 Little gain, however, is to be acquired by following a line of thought so highly 

 speculative. 



As is well known, the torus supraorbitals in the gorilla and the chimpanzee is 

 chiefly composed of dense bone. The frontal air-sinuses are relatively small, and are 



... Superciliary eminence 

 just beginning to 

 show. 



Frontal air-sinus extend- 

 ing upwards from the 

 nasal chamber into the 

 superciliary region. 



Fig. 12. — Sngittal section through the frontal bone of a child, in the 

 region of the superciliary eminence. 



situated at the base of the torus, close up against the inner table of the cranial wall. 

 Further, they are chiefly confined to the glabellar region, and do not extend for any 

 distance outwards into the superciliary part of the torus. Much interest is therefore 

 attached to the observation of Professor Schwalbe (8) that in the Neanderthal cranium 

 the air-sinuses lie well back, and that a thick layer of condensed bone forms their anterior 

 wall. It is usual to find a similar pithecoid condition in the supraorbital region of 

 the native Australian. The frontal air-sinuses, in this race, are as a rule relatively 

 small, and they lie behind a mass of condensed bone. Thus Dr Logan Turner (14) was 

 only able to map out these sinuses by the illumination method in less than a third of 

 the Australian skulls he examined (in 20 out of 69 skulls), and in a very large number 

 (30*4 per cent.) he found both sinuses totally absent. Amongst the Maori skulls, which, 

 as we have noted, also show a tendency to Type III. of the eyebrow region, the same 

 observer states that both sinuses were absent in 37 per cent, of the specimens he examined. 

 These are striking facts, and undoubtedly point to an important affinity in this 



