In Table 18 are recorded a number of measurements of the Zinjanthropus cranium, especially metrical characters which have not been dealt with in the preceding sections. Most of these measurements relate to the calvaria alone, but several—such as nasion–basion length and basion–prosthion length—are, strictly speaking, cranial rather than calvarial measurements. To compare with the Zinjanthropus data, I have assembled as many measurements on the South African australopithecines as could be culled from Broom et al. (1950), Broom and Robinson (1952), Dart (1962b) or obtained by personal measurement; as well as some comparable measurements on Homo erectus.

Considerable difficulties arise when one attempts to apply measurements devised and defined for the description of modern human crania to ancient hominids, as well as to non-hominid Primates. These problems have been fully discussed by Davidson Black (1931), Washburn (1942) and Weidenreich (1943) among others. Among the most difficult termini of measurements are inion and euryon.

Cranial length and the toro-occipital index

In modern hominine crania, the inion and the opisthocranion (furthest occipital point) are different points, the former low and the latter high on the cranium. On the other hand, in some Neandertal crania, in H. erectus, in the australopithecines and in many pongid crania, the two points coincide to mark the posterior terminus of the maximum cranial length (glabella–opisthocranion).