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40.<br />
index Z, (e) equal to 18.1 per 10 km 2 ; the series investigated thus<br />
constitutes about 5% <strong>of</strong> the population living in that area.<br />
When beginning<br />
the investigation, my object was to shed some light on the problem <strong>of</strong> the<br />
degree <strong>of</strong> individual variation, to examine the character <strong>of</strong> sexual dimorphism<br />
and,<br />
finally, to establish the character and degree <strong>of</strong> age variation<br />
in the cranialogical features <strong>of</strong> the ermine.<br />
On the basis <strong>of</strong> the data for<br />
age variation it was hoped to discover whether a reliable and easy diagnosis<br />
<strong>of</strong> age groups in an extensive series <strong>of</strong> craniological material would be<br />
a practical possibility.<br />
A biometric analysis was undertaken to<br />
elucidate this problem.<br />
The whole series <strong>of</strong>skulls was measured with respect to a large<br />
number (over 30) <strong>of</strong> characteristics.<br />
The extreme variants and the mean<br />
values with standard errors were then determined, and the standard<br />
deviations <strong>of</strong> each series and the coefficients <strong>of</strong> variation with their<br />
standard errors were calculated.<br />
Graphs <strong>of</strong> the variance curves <strong>of</strong> aach<br />
characteristic were also plotted, snd a series <strong>of</strong> correlation tables drawn<br />
up.<br />
The measurements were chosen in order to give a sufficiently complete<br />
description <strong>of</strong> the contours <strong>of</strong> the skull from all the principal points <strong>of</strong><br />
view (normee verticalis, leteralis, frontalis, occipitalis et basilaris).<br />
Of the total number <strong>of</strong> measurements usually adopted in craniometry,<br />
measurements <strong>of</strong> the nasal bones (nasale) and the greatest width <strong>of</strong> the hard<br />
palate were rejected, for the sutures bounding these bones unite relatively<br />
early and no differences whatever are found between adult (adultus) and<br />
senile (senex) individuals.<br />
To characterise the relationships between<br />
the bullae osseae, the shortest distance between them and the longest<br />
distance between the foramina lacera posteriora were taken.<br />
To<br />
characterise the skull from behind (norma occipitalis) the measurements<br />
taken were the greatest height and width <strong>of</strong> the foramen occipitale magnum,<br />
(a) No reference is given on how to calculate this interesting statistic - Ed.
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