Originally this great thickness of bone in the supraorbital region of the Neanderthal calotte was regarded as a proliferation of bony tissue caused by disease. Then it was proclaimed to be a characteristic by which one might distinguish the skulls of fossil from those of all living races. The subsequent recognition of true supraorbital ridges or tori in the Australian completely disproved both these hypotheses.
The feature is, so far as our present knowledge goes, essentially masculine, and, as such, suggests a secondary origin comparable to the tremendous supraorbital developments of bone in the skull of the male gorilla. Professor D. J. Cunningham, who investigated this subject thoroughly from a comparative anatomical point of view, found “superciliary and supraorbital elements” even more or less developed in the lower types of apes. A supraorbital prominence is rarely observed in the female ([Plate III], 2).
To return to the eye: the colour of the iris, in its normal condition, is practically without exception dark brown. The only exception to this rule, that has come under my personal observation, was a young, full-blooded gin of the Mulluk Mulluk tribe in the Daly River district, north Australia, whose iris was a deep bluish grey.
There is great variety in the shape of the cavities which hold the eye-balls of the Australian. The orbits are large, and their outer margins, as in the Neanderthal type, very nearly form a circle. According to Professor Klaatsch’s measurements, the ratio of the maximum vertical to the maximum horizontal diameter in the male Australian skull is as 39 millimeters is to 40. As a rule, the eye-cavities in children are slightly depressed horizontally, and occasionally this is also the case in the skulls of females.
The orbit’s upper edge is very strong; and what is known as the internal angular process of the frontal bone, in the inner wall of the cavity, is very prominent in the Australian. The last named characteristic is, however, also observed in the skulls of Veddahs and other primitive people, as well as in those of the anthropoids. But we must not forget, when dealing critically with a skull, that an internal angular process may not be so typical in the male as it is in the skulls of women and children.
The external angular processes are often well developed, the malar boundary being strong and broad, without the sharp edge usually noticed in European skulls.
The ethmoid bone in the inner wall of the orbit is, as in most of the primitive skulls, noticeably small.
The groove of the lachrymal bone, which intra vitam carries the tear duct connecting eye with nose, is usually very pronounced in the Australian.
In children’s skulls a supraorbital notch divides the upper margin of the orbital cavity into two almost equal parts, the outer of which has a well-defined edge.