610 Proceedings of Royal Society of Edinburgh. [sess. 
indicating that the depth of cerebellum, with thickness of skull 
base near basion, is 3*2 per cent, greater in dolichocephali than 
in brachycephali. 
In the anthropoids, the steady diminution of the supra-zygo- 
matic segment, and the correspondingly steady increase in the 
infra-zygomatic segment, are equally noteworthy. 
Glabello-occipital Length . — The results obtained by segmenting 
this diameter in terms of the bregma and lambda are instructive, 
although probably less distinctive of the two extreme varieties of 
skull than might have been expected. 
(a) Brachycephali. — The glabello-occipital length averaged in 
the eleven skulls 175 '2 mm. 
(1) The prae-bregmatic segment varied from 62-88 mm., giving 
an average of 72 mm., or an average of 40*9 per cent, of the total 
length. 
(2) The parietal segment varied from 90-105 mm., giving an 
average of 97 ‘9 mm., or an average of 55*3 per cent, of the total 
length. 
(3) The post-lamhdoidal segment varied from 3-9 mm., giving 
an average of 6 '2 mm., or an average of 3 ‘5 per cent, of the total 
length. 
( b ) Dolichocephali.- — The average glabello-occipital length of the 
twelve skulls was 187 '4 mm. 
(1) The prae-bregmatic segment varied from 67-88 mm., giving 
an average of 74*9 mm., or an average of 39 - 8 percent, of the total 
length. 
(2) The parietal segment varied from 97-113 mm., giving an 
average of 104 mm., or an average of 55 - 5 per cent, of the total 
length. 
(3) The post-lambdoidal segment varied from 3-18 mm., giving 
an average of 8 '5 mm., or an average of 4*4 per cent, of the total 
length. 
Several points of interest arise in connection with these figures. 
Thus, taking into account the thickness of an ordinary skull, it 
must be evident that with a post-lambdoidal segment averaging 
6*2 mm. or 8*5 mm., very little, if any, of the cranial cavity can 
lie behind the lambda. The prae-bregmatic segment, subject to 
deduction for the thickness of the skull in the region of the 
