The bitemporal diameter: this is the greatest width of the cranium between the verticals passing through the base of the tragus.
The biauricular diameter: the craniometrical points are in front of, and a little below, but very near to the upper insertion of the auricle. They are little depressions that can be felt, as we have already said, by applying the finger along the upper edge of the root of the zygomatic arch.
Height of forehead: from the ophryon to the roots of the hair.
Circumferences and Curves:
Anterior Semicircle.—The tape is applied from one supra-auricular point to the other, passing through the ophryon; it corresponds to the anterior part of the maximum circumference. Manouvrier measures it in correspondence to the verticals erected from the tragus.
Posterior Semicircle.—This is obtained by subtracting the anterior semicircle from the whole circumference.
Vertical Curve of the Head.—The tape passes through a plane that is vertical to the orientated head, starting from the supra-auricular points or from the tragus, according to different authorities.
Cephalic Index.—This is the proportion between the maximum transverse and longitudinal diameters. It is obtained by applying the familiar formula:
in which d represents the transverse diameter and D the longitudinal. The index represents the percentual relation between the two diameters, and is obtained from the formula by reducing the greater diameter to a scale of 100, as follows: