1905-6.] 
Report on Two Crania. 
297 
In a table given by Schwalbe which deals with 352 skulls, there 
are no less than 66 specimens with a minimum frontal diameter 
below 91 mm., and included amongst the latter there are two 
modern European skulls. The majority of these instances in 
which this diameter attained so small a dimension occurred in such 
races as the Yeddahs and Australians, in some of which it reached 
the exceedingly low dimension of 81 mm. From his investigation 
into this character, Schwalbe comes to the conclusion that it is not 
always in the lowest races that the lowest postorbital breadth of 
cranium is found, nor yet is it in the highest races that the 
diameter attains its maximum. 
In the Brazil skull the minimum frontal diameter was even less 
than in the Rutland specimen. It measured 88 mm. In the 
Aberdeen skull, on the other hand, in conformity with its larger 
size, the minimum frontal diameter is 97 mm. 
With the view of pushing the comparison still further, outline 
tracings of the norma verticalis of the Rutland and Aberdeen 
crania were taken by means of the American periglyph ; these 
were then reduced to a common standard of size by photography 
and superimposed. The result was very instructive, because it 
became evident that the contour lines of the two specimens, not 
only in the postorbital region, but also throughout the entire extent 
of the tracings, were very similar. 
The fronto-parietal index has been employed to express the 
relative degree of postorbital constriction. In calculating this 
index the maximum breadth of the skull is taken as 100 and 
compared with the minimum frontal diameter. The calculation is 
made in the following manner : — 
Minimum frontal diameter x 100 
Maximum breadth 
Virchow had considerable faith in this index, and employed it 
in connection with his study of the cranium of Pithecanthropus,* 
but I am in complete agreement with Schwalbe in the view that it 
gives no true information regarding the point at issue. The more 
variable factor, viz. the parietal breadth, is taken as the standard 
of comparison, and it is not surprising, therefore, that in narrow- 
* “ Ueber Pithecanthropus erectus, Dub.,” Zeitschrift f. Ethnologic, October 
1895, Heft 6. 
