Fig. 70.—Sphenoid cranium.
VIII. Spheroid.—Seen vertically, it presents the appearance of a very broad ellipse; all the curves tend to become spherical. The forehead, however, is not notably vertical.
IX. Platycephalic.—The fundamental characteristic of this type of cranium is that it is flattened on top, or rather, since such flattening cannot be absolute, the arch of its vault is a segment of a circle of very large diameter (Sergi), with the result that this cranium has the appearance of being very low vertically and very broad laterally. When seen vertically it may present a wide variety of contours, ellipsoid, ovoid, pentagonoid, etc., but its distinguishing characteristic remains that of the flattened vault.
Fig. 71.—Spheroid cranium.
Sub-varieties.—Sphenoids trapezoids, or trapezoid cranium. Observed from the vertical norm, this form appears as a variety of the sphenoid; and when seen laterally it is characterised by the lines of its contour forming a trapezium. Starting from the vertex of the cranium one line slants toward the forehead and another toward the occiput, which is very massive. In the figure given below, the quadrangle drawn in solid lines serves to indicate the correct position of the cranium, while the trapezium formed of dotted lines gives us its characteristic form.
Fig. 72.—Trapezoid cranium.
Among the forms described by Sergi, are several which were formerly held to be abnormal, such, for instance, as the platycephalic cranium and the pentagonoid. Similarly, when the surfaces of the cranium showed a tendency toward flatness, or when there were cranial protuberances, even though these were destined to disappear, they were regarded as malformations. Before this high authority offered us his guidance, there were certain forms, frequently encountered, that it was difficult to define, for example, the trapezoid cranium, which often presents a notable vertico-occipital flattening, with the vertex notably higher than the forehead.