The endocranial surface of the frontal bone

Only a small part of the endocranial surface of the frontal bone is present. The angle between the squama and the floor of the anterior cranial fossa is difficult to determine, because only the rostral end of the floor is present; it seems, however, to be much nearer the angle in Homo erectus pekinensis (50°) than that of modern man (about a right angle–Weidenreich, 1943, p. 32). Laterally, the posterior turn or recurvation of the squama at the postorbital constriction is clear, giving an extremely narrow frontal region. From the mid-line, the chord to the line of recurvation is only 31·0 mm. The endocranial width between the left and right lines of recurvation is 59·4 mm.

There is a thin though strong frontal crest, as in Pekin Man and other hominines. In pongids, on the other hand, it is missing or, at most, is represented ‘by a low, insignificant ridge’ (Weidenreich, 1943, p. 32). The relationship of the frontal crest to the sulcus for the superior sagittal sinus is described in Section D of this chapter (p. 63). Weidenreich regarded the internal frontal crest as part of the sagittal reinforcing system of the cranial vault of Pekin Man; he drew attention to the fact that the frontal crest fades out just where the sagittal thickening (which he unfortunately designated ‘sagittal crest’) originates on the outer surface.