604 Proceedings of Royal Society of Edinburgh. [sess. 
been privileged to test the capabilities of this instrument upon a 
number of human skulls, all of which had already been described 
by himself in his “Challenger” Report. These consisted of eleven 
brachycephalic skulls of Sandwich Islanders, and of twelve 
dolichocephalic skulls of aboriginal Australians, and were 
selected because of their extremely typical differences. I have 
also examined a few skulls of anthropoid apes for purposes of 
contrast and comparison. 
Methods. — In obtaining the principal diameters of the skull, I 
have been careful to adhere to the methods adopted and approved 
by Sir William Turner for ascertaining these measurements, and 
their segmentation has been carried out in terms of well-marked 
and definite points upon the surface of the cranium. 
A. Transverse Diameters. 
1. Minimum Frontal Diameter. — The point selected for the 
segmentation of this chord was the frontal suture in such cases 
where it was still visible, but when it had entirely disappeared the 
upper end of the inter-nasal suture was taken instead. In this 
way we can represent the relative proportions of the frontal region 
on the right and left sides of the mesial plane, approximately at 
the level of the roof of the orbits. 
2. Stephanie Diameter. — The segmentation of this chord may be 
effected either from the same points as the preceding or from the 
bregma, which is the more convenient point. It ^ frequently 
happens, however, that the anterior end of the sagittal suture, i.e. 
the bregma, does not correspond to the highest point in the 
transverse arch of the vault. In other words, there is such a 
pronounced obliquity in the direction of the sagittal suture, be- 
tween its posterior and anterior ends, that it becomes difficult to 
regard it — the sagittal suture — as an accurate expression of the 
mesial plane, since it may not run in a true antero-posterior 
direction. At the same time, there is no reason to suppose that 
the falx cerebri does not correspond with the direction of the 
sagittal suture, and therefore the position of this suture may fairly 
be taken as representative of intra-cranial developments. 
3. Maximum Parieto-squamous Breadth. — This diameter is 
most readily segmented from the lambda, and it is the almost 
