12 
THE VOYAGE OF H.M.S. CHALLENGER. 
was broad and flattened in the norma facialis. The mean interorbital breadth was 
23*5 mm.; the maximum 27 mm.; the minimum 21 mm. 
The teeth were fully erupted in five crania, and in the adult from Drift, Calvinia, 
the sockets of the lower molars and upper incisors and canines were absorbed. In one 
skull the upper wisdoms were only partially erupted, and in the child's skull the denti- 
tion marked the 8 th or 9th year. Except in the child and one of the adults the teeth 
were much worn, even in the skull with imperfectly cut wisdoms, but there was no decay. 
The cranial sutures in B were simple in their denticulations, the sagittal immediately 
in front of the obelion was deflected to the right, and small Wormian bones were in the 
lambdoidal suture. In the other skulls the sutures were more deeply denticulated, and 
small Wormian bones were not unfrequent in the lambdoidal suture. In three the sutures 
were in course of senile obliteration. No skull was metopic, and the temporal squama 
did not articulate with the frontal. The temporal ridges were not strong. 
In two crania the ossa plana of the ethmoid were small. In one of these on both 
sides, and in the other on the right side only, the orbital plate of the superior maxillary 
sent a process between the os planum and the lachrymal to articulate with the frontal 
(PI. I. fig. 4) ; when a fronto-maxillary articulation occurs in the inner wall of the orbit, it 
marks a reversion to the pithecoid arrangement, and is a sign of degradation of the 
human cranium ; for in the Gorilla and other species of Troglodytes the os planum 
is triangular, and the frontal and superior maxilla articulate with each other between it 
and the lachrymal on the inner wall of the orbit. In two, faint indications of a maxillo- 
premaxillary suture were seen on the hard palate. The malar was not in any specimen 
divided either wholly or partially by a suture, and did not therefore conform to a charac- 
ter which Rolleston thought to be not unfrequent in Bush crania. One skull had a long 
right paramastoid which possessed a broad smooth articular surface at its lower free end 
for the transverse process of the atlas. 
The lower jaw was present in six crania. In all the chin was feeble and with but a 
slight forward projection ; the coronoid process was short, the sigmoid notch shallow, and 
the incisors almost vertical. The antero-posterior diameter of the ascending ramus, on a 
line with the alveolar border, was, as a rule, from 30 to 31 mm. In four adults the angle 
was everted at the insertion of the masseterics, very markedly so in two specimens, and 
there was only a slight hollowing on the inner surface of the ramus. In all the gonio- 
symphysial and intergomal diameters were either equal or almost equal. 
In the six adult crania the mean cephalic index was 75*9, and the range of variation 
from the minimum 75 to the maximum 76'5 was only 1*5; the skulls were therefore 
mesaticephalic. The mean vertical index was 71, and the range from 69 to 73 was 4. 
The mean height was therefore distinctly below the mean breadth, and in no specimen 
did the height equal the greatest breadth ; the skulls were tapeinocephalic. The mean 
gnathic index was 967, and the range from the minimum 92*6 to the maximum 102 was 
