1898 - 99 .] Dr Hepburn on Improved Form of Craniometer. 605 
constant discrepancy between the result obtained from the bregma 
and that obtained from the lambda, which emphasises the 
obliquity of the sagittal suture. 
4. Asterionic Diameter . — This measurement has reference to 
the region of the cerebellum, and for the segmentation of the 
chord a well-marked part of the external occipital crest near to 
the foramen magnum was selected. 
By the segmentation of these four transverse diameters, in terms 
of different points representing the mesial plane, my object was to 
indicate, if possible, the amount of divergence from true bilateral 
symmetry of the skull, and inferentially, of the cerebrum and 
cerebellum. 
B. Vertical Diameter. 
Basi-bregmatic Height . — The examination of a skull in vertical 
transverse section shows that the upper margin of the petrous bone 
(to which the tentorium cerebelli is attached), is practically upon 
the same horizontal plane as the posterior or supra-auditory root of 
the zygoma. Therefore by selecting the edge of this root imme- 
diately superior to the external meatus as a basis for segmenting 
the basi-bregmatic height, my intention was to express the 
approximate proportions of this chord which pertain to cerebrum 
and cerebellum respectively. 
C. Anteroposterior Diameter. 
Glabello-occipital Length . — This diameter, which expresses the 
length of the cerebrum between its anterior and posterior poles 
plus the thickness of the skull at each end, may be segmented 
in reference to several surface points. Thus, by selecting the 
bregma, we may ascertain the prse-bregmatic and post-bregmatic 
proportions of the total length. Again, by segmenting the chord 
in terms of the lambda, we may obtain not only the prse-lambdoidal 
and post-lambdoidal proportions, but by taking the sum of the 
prae-bregmatic and post-lambdoidal segments and deducting it from 
the total length, we may express, in the difference, the sagittal or 
parietal segment of the total length. In this way we may ascer- 
tain approximately how much of the total length is under cover of 
