The normal forms of the cranium may be grouped, according to Sergi, under nine primary varieties, each of which includes sub-varieties.
These nine varieties are named as follows:
I. Ellipsoid; II. Ovoid; III. Pentagonoid; IV. Rhomboid; V. Beloid; VI. Cuboid; VII. Sphenoid; VIII. Spheroid; IX. Platycephalic.
Fig. 57.—Ellipsoides depressus cranium.
I. Ellipsoid (Fig. 58).—This form is recognised by inspecting the cranium according to the vertical norm (see in the chapter on Technique the method of cranioscopy).
The cranial contour recalls an ellipse in which no trace of the nodules remains, and in which the occiput is not in the least flattened; while the anterior half of the cranium closely corresponds to the posterior half.
The sub-varieties are differentiated by their greater breadth and length, by the form and protrusion of the occiput, and also by the height of the cranium measured vertically.
Fig. 58.—Ellipsoid cranium.