260 
Observations on the Occipital Bone 
In one somewhat aged male skull, shown in Plate V. A, and presenting only a 
slight trace of the synchondrosis condylo-squamosa at the end abutting on the 
masto-occipital suture of the right side, the opisthial notch has a depth of 11 mm. 
with a maximum breadth of 10 mm. In another adult male skull, with a trace of 
the synchondrosis on the right side only, the foramen magnum is prolonged back- 
wards as a broad excavation which is not sharply defined laterally, but must be 
put into the same category. The antero-posterior diameter of the foramen magnum 
in this case measures 42 - 5 mm. and the greatest breadth is 305 mm. 
The opisthial notch evidently results from a defective development of the 
lower division of the occipital squama, which is formed by the supra-occipital 
element of the bone, and especially of the part which is derived from the so-called 
ossicle of Kerckring {manubrium squamae occipitis, Virchow). The existence of 
such a notch in the adult bone is not mentioned in Ledouble's Traitedes Variations 
des Os du Crane, Paris, 1903; but Hamy records a case of a microcephalic foetal 
skull in which there was a small posterior encephalocele resulting from absence of 
the ossicle of Kerckring (Bull, de la Soc. d' Anthropol. de Paris, 1867, p. 511). 
Hamy refers to this case again in his paper "Recherches sur les fontanelles anomales 
du crane humain," Journal de I'Anatomie, T. vii. 1870 — 71, pp. 591 — 601, and 
there uses the name fontanelle cerebelleuse for the membranous gap at the base of 
the occipital squama. This condition would appear to represent a persistence to 
a greater or less extent of Hannover's spinoso-occipital membrane. Ledonble 
states (op. cit. p. 53) that there is a similar defect of ossification in some skulls of 
normal foetuses in the Museum d'histoire naturelle of Paris, as well as in the skull 
of a hydrocephalic foetus in the Musee Dupuytren. 
In only one instance among the Egyptian crania under observation did the 
writer find any indication of the division of the pars basilaris, which leads to the 
separation of an anterior segment, first observed by Etienne Geoffroy Saint-Hilaire 
and named by him oto-sphenal, and subsequently designated by Albrecht basiotique. 
This occurs in a young specimen, about 12 years of age (Plate V. B, Cranium 
E 801), which also shows a slight indication of the synchondrosis condylo-squamosa. 
Here the basilar portion has on each side a cleft directed transversely inwards 
from the petro-occipital fissure for a distance of 9 mm. on the right side and 
4 - 5 mm. on the left. The intervening bridge of bone has a breadth on the surface 
of 15"5 mm. The division is more strongly marked on the endocranial aspect of 
the bone, where the fissures are only 12 mm. apart, and are connected by a shallow 
transverse furrow. An incomplete division of the basilar portion was found by 
Lucy 25 times in 496 skulls (5"04 per cent.). This skull also shows two well 
marked pressure facets at the hinder margin of the foramen magnum. 
Owing to the large number of crania under consideration and difficulties of 
access it has not yet been possible to examine the whole of this Egyptian series 
very carefully, but the writer has made a more cursory examination of the 
