REPORT ON THE HUMAN CRANIA. 
123 
basi-occipito-sphenoid axis with the plane of the foramen magnum presented considerable 
variations in the different crania; in the Fuegian it was the lowest, 138°, and it reached 
its maximum in one of the Australians 157°, but amongst the three Australians it ranged 
from 139° to 157°. In each skull it was more open than the foramino-sellar angle in the 
same cranium. 
The sphenoido-ethmoid angle presented considerable variation in these crania. Prof. 
Huxley, in speaking of his corresponding angle, which he calls the basi-ethmoid angle, 
states that it diminishes in proportion to the downward rotation of the cribriform plate, 
i.e., in proportion to the departure of the human skull from the arrangement of that plate 
seen in the lower mammalia. But the cribriform axis is not the only factor in the 
formation of this angle, for the slope of the basi-occipito-sphenoid axis is not uniform in 
all crania, and the nearer that the latter axis approaches to the vertical the more would 
the sphenoido-ethmoid angle be diminished, just as if a downward rotation of the cribri- 
form plate had taken place. Table XIX. shows that this angle possessed a considerable 
range of variation. It was most open in the New Zealander and Chatham Islander, 
whilst in the three Australians and the Fuegian it was almost uniform at from 136° 
to 138V 
A line was also drawn from the spheno-ethmoid articulation to the most projecting 
point of the upper jaw-bone and named in the Table the spheno-maxillary line, and 
the spheno-maxillary angle, which it formed with the basi-occipito-sphenoid axis 
was measured. The spheno-maxillary line varied considerably in length in the several 
skulls. It was shortest, 69 mm., in the brachycephalic, mesognathic Hawaian, and it 
attained its maximum, 85 mm., in a dolichocephalic, prognathic Australian, the gnathic 
index of which was 105*8. It possessed also considerable length, 79 mm., in the Chatham 
Islander and Fuegian skulls, but in neither of these did the gnathic index exceed 98, so 
that these crania were not prognathic. There was comparatively little variation in the 
spheno-maxillary angle which, in the majority of the skulls measured, exceeded by a very 
little a right angle, though in the Fuegian A it sank to 89°, and in the prognathic Oahuan 
D it rose to 101°. The projection of the upper jaw is not the only factor which affects 
this angle. Undoubtedly when the forward projection of this bone is considerable the 
tendency of this angle is to become more open, but should the slope of the basi-occipito- 
sphenoid axis at the same time approach the vertical then the angle would be relatively 
diminished. Hence I cannot regard this angle as giving an accurate measure of the 
degree of prognathism. 
The base line from the back of the foramen magnum to the fronto-nasal suture, 
proposed by Prof. Cleland is also given in Table XIX., and as the total longitudinal arc 
1 Prof. Goodsir says that in man the cribriform side of this angle is, in well formed heads, horizontal. In the 
descending animal series this side rises so as at last to assume the rectangular position (see Lectures on the Dignity of 
the Human Body, in collected Anatomical Memoirs, vol. i. p. 258. Edinburgh, 1868). 
