296 Proceedings of Royal Society of Edinburgh. [sess. 
of the frontal air-sinus, or to a large extent to a deposit of bone, as 
in the case of certain Australian skulls. In both the Rutland and 
the Aberdeen specimens the supraorbital projection is due to the 
former cause, and not to any massing of bone in this neighbour- 
hood, — the front wall of the sinus in both cases being not more 
than 4 mm. thick. 
Schwalbe has taught us to examine carefully and critically the 
contour of the supraciliary region and its relation to the margin of 
the orbital opening.* 
In some cases the supraciliary ridge is fused with the upper 
part of the orbital rim, and the result is an arcuate continuous 
projection overhanging the orbital opening. This is the case in 
the chimpanzee, gorilla, pithecanthropus, and Neanderthal skulls, 
and in the crania of certain Australian aborigines. In other cases 
the inner part of the supraciliary ridge is fused with the inner 
part of the upper portion of the orbital rim, whilst its outer part 
stands above and apart from the margin of the orbit, being borne 
upwards, as it were, by the supraorbital nerve, which seems to have 
some effect in producing this condition. There are many races 
which show this type of supraciliary projection, and it is not 
infrequent to meet with it in the modern European skull. Both 
the Rutland and the Aberdeen skulls fall within this group. 
Probably in the European skull it is most usual to find the 
supraciliary ridge standing quite apart, in its whole length, from 
the orbital margin. This may be regarded as a third type of 
supraciliary contour. 
The narrowing of the Cranium behind the Orbits . — The minimum 
frontal diameter of the Rutland skull, determined between the 
temporal ridges, measures 91 mm. It is a difficult matter to deal 
with this diameter in such a way as to arrive at a proper con- 
ception of its true worth from a comparative point of view, and 
yet the information gained by the eye is sufficient to show that 
it is a factor of considerable importance. The absolute measure- 
ment as well as the various indices which have been devised may 
altogether fail to give expression to its proper value and to convey 
to the mind its right significance. 
* “Studien iiber Pithecanthropus erectus, Dubois," by G. Schwalbe, Zeit- 
schrift fur Morphologie und Anthropologie, Band i. Heft 1. 
