THE FACE OF FOSSIL MAN 495 
(see fig, 186) the basal axis reaches forwards to the 40-mm. 
vertical line ; this is also the case in the Gibraltar and 
both reconstructions of the Piltdown skull. In the 
native Australian — a representative of the modern type — 
the basal axis falls 5 mm. short of the 40-mm. line. In 
all the types of skulls represented in fig. 186, the basal 
axis commences immediately behind the zero line — the 
line of the external auditory meatus — in all save the 
lowest drawing, which represents the condition of parts in 
Dr Smith Woodward's reconstruction of the Piltdown 
skull. There the basi-cranial axis is contracted to a 
degree which would seriously incommode Eoanthropus 
in the acts of breathing and swallowing. 
The sections shown in fig. 186 bring out another 
change which has occurred during the evolution of the 
human skull, and also one of the features of Eoanthropus. 
This relates to the expansion of the human cranial cavity 
in a backward direction as the brain assumed a greatly 
increased volume. The occipital wall in the orang's 
skull (fig. 186) lies between 20 and 30 mm. behind the 
auricular vertical line ; in the Gibraltar and Australian 
skulls the occipital bone reaches the 40-mm. vertical line, 
but in the Piltdown reconstructions it falls short of that 
line. In the modern type of man, as represented by the 
native Australian, the brain, as it expands, tends to 
elongate or enlarge the skull in a post-auricular direction. 
In Eoanthropus the tendency was in an opposite direc- 
tion, to expand the skull in a pre-auricular or forward 
direction. Hence the high prominent bulging forehead 
of Eoanthropus. Attention is drawn to the curtailment 
or non-expansion of the post-auricular part of the head of 
Eoanthropus in fig. 185. A vertical line (E-F) is raised 
from the hinder and lower angle of the parietal bone. 
The posterior border of that bone forms an acute angle 
with the vertical line, somewhat similar to the condition 
in the orang's skull (fig. 183). In the Tasmanian and 
Neanderthal skulls (figs. 182, 184) the posterior border 
of the parietal bone slopes upwards and backwards, 
forming a more open angle with the vertical line. 
