M. L. TiLDESLEY 229 
2. That it is approximately parallel to the plane of the foramen magnum. 
On the Moriori $ type contours it is actually parallel; for the males there is 
only a difference of 2°-5 between the two lines representing the planes, that of the 
foramen magnum being so tilted as to bring the opisthion slightly nearer to the 
N line than is the basion. 
The incUnation of these two lines to one another has been measured on our 
Burmese individual contours. In our type contours the positions of basion and 
opisthion were determined by other measurements and the angle as shown on the 
type is not bound to correspond exactly with the mean of individual contours. 
The following are our double values for this angle : 
Typos: 
Burmese (J 
Burmese $ 
A 
B 
C 
A 
B 
c 
Mean contour value 
From type contours 
7^-3 
6°-0 
8°-8 
7°-8 
7°-() 
7°-2 
8°-8 
7°-8 
8''-2 
7'-2 
and in all the above, the tilt of the basio-opisthion line was such as to bring the 
basion nearer to Ny. 
We see therefore that this second argument in support of Ny as base-line for 
comparison is much less potent in the case of the Burmese than in that of the 
Moriori. The Burmese basio-opisthionic line is in fact about equally inclined to the 
Ny and glabella-inion lines in our type contours, and would contribute nothing to 
a decision between these two. 
3. That the standard horizontal is approximately parallel to the maximum 
length, i.e. the glabella-occipital line. This is quite true for our series, in all six 
types. 
We will try each of these lines in turn as base-lines in comparing our own 
Group A and Group C type contours. Putting nasion on nasion and Ny over Ny, 
we get very markedly in the males and to a less extent in the females, an im- 
pression of flattened frontal in Group C: the ? type contour for the C's has an 
outhne which is decidedly more re-entrant at the nasion than that of the A's, so 
that the glabellar region of Group A ? seems more prominent — a feature not shown 
in the male contours, where in fact Group A shows slightly greater prominence. 
Now if we move our Group A ? contour further forward so that the glabellar 
regions are together — while still keeping Ny along Ny — we get a very similar con- 
trast between the two groups, in the two sexes; the forehead less sloping in Group A, 
and the back of the head descending more abruptly from the crown. In the males 
the occipital bone of Group C ends at a point some 5 mms. lower than that of 
Group A, but this is not so with the females, and we must remember that the range 
of variation in Group A males is nearly four times that of Benington's type con- 
tour for 100 skulls, so that even this divergence might be accounted for by the 
Biometrika xni 16 
