The next table gives the percentage relations of the basion-nasion diameter to the mean diameter of the skull. The correlation of the two is even closer than in the case of the skull length, and the grouping, while in the main alike, seems in general even more in harmony with that in previous comparisons. The St. Lawrence Island females are very exceptional, as was also apparent in other connections. The unusual smallness of their skull (compare section on Cranial module) is evidently due to a poor development of its posterior half.

Eskimo Crania: Percentage Relation of the Basion-Nasion Diameter to Mean Cranial Diameter (Cranial Module)
BN×100
CM
BOTH SEXES TOGETHER IN ASCENDING ORDER
Southwestern and Midwestern
Pilot Station, Yukon65.6
Chukchee66.0
Little Diomede Island66.1
Hooper Bay66.4
Nelson Island66.7
Togiak66.9
Southwest Alaska67.3
Indian Point, Siberia67.4
Mumtrak67.4
Nunivak Island67.6
Pastolik67.6
St. Michael Island68.0
St. Lawrence Island:
Male67.2
Female(69.6)
Northwestern
Wales67.7
Point Barrow67.8
Point Hope68.1
Barrow68.4
Old Igloos69.0
Shishmaref69.2
Northern Arctic and northeastern
Baffin Land67.4
Hudson Bay67.6
Smith Sound (male)67.6
North Arctic68.1
Greenland68.5
Southampton Island68.7

PROGNATHISM

Since better understood, the subject of facial prognathism has lost much of its allure in anthropology; yet the matter is not wholly without interest.

Facial protrusion is as a rule secondary to and largely caused by alveolar protrusion, which in turn is caused by the size and shape of the dental arch; and the dental arch is generally proportional to the size of the teeth. The form of the arch is, however, quite influential. With the teeth identical in size a narrow arch will be more, a broad arch less protruding, and a narrow arch with small teeth may protrude more than a broad one with larger teeth. Another influence is that of the height of the upper face, the same arch protruding more in a low face than in a high one. And still another factor is the incline of the front teeth, though this affects merely the appearance of prognathism and not its measurements.

There are different ways of measuring facial prognathism, and with sufficient care all may be effective; I prefer, for practical reasons, linear measurements from the basion, which, together with the facial and subnasal heights, give triangles that can readily be reconstructed on paper and allow a direct measurement of both the facial and the alveolar angle. The three needed diameters from basion are taken, the first to the "prealveolar point," or the most anterior point on the upper dental arch above the incisors; the second to the "subnasal point," or the point on the left (for convenience) of the nasal aperture, where the outer part of its border passes into that which belongs to the subnasal portion of the maxilla (the point where the subnasal slant begins); and the third to nasion. The facial height is that from the alveolar point (lowest point of the upper alveolar border in the median line) to nasion; while for the subnasal height, which can not be measured directly, I utilize the difference between the facial and nasal heights, which is very close to the needed dimension.

The important basion-nasion diameter has already been considered. That to the subnasal point needs no comment. That to the prealveolar point shows in the western and other Eskimo as follows:

Eskimo Crania: Basion-Prealveolar Point Diameter
All Eskimo
Males:
Mean diametercentimeters10.54
Mean relation to length of skullper cent56.3
Females:
Diametercentimeters9.99
Relationper cent55.8
MALES
A = Basion prealveolar point diameter
B = Its relation to length of skull
Southwestern and midwesternNorthwesternNorthern Arctics and northeastern
ABABAB
10.38 56.410.58 56.410.65 56.2
Mean skull lengths
18.4118.7518.96
FEMALES
9.85 55.710.06 56.310.06 55.4
Mean skull lengths
17.6917.8618.15