38 
THE VOYAGE OF H.M.S. CHALLENGER. 
Bay, which was only 119 mm. in its parietal diameter, had also a complete obliteration 
of the coronal and sagittal sutures; and a shape approximating to the scaphocephalic. 
The mean vertical index of thirty adult crania was 70*4 ; that of the twenty males 
was 70'G, that of ten females was 69*9, so that the difference between the two sexes 
was very slight. The mean basi-bregmatic height of twenty males was 135 mm. ; the 
minimum in two specimens was 130, the maximum in one 146 ; in two specimens only 
the maximum exceeded 140 mm. The mean basi-bregmatic height of ten females was 
124 mm. ; only two specimens reached 130 mm., and one was as low as 110 mm. The 
difference, therefore, between the height of the two sexes was very remarkable, andgreatly 
to the advantage of the males. In eight of the male crania the actual height was either 
equal to or within 2 mm. of the greatest breadth in the same skull ; in nine skulls the 
height was distinctly greater than the breadth, in two the height was less than the 
breadth. In the female skulls the height and breadth were almost equal in one specimen ; 
the height was greater than the breadth in three, but less than the breadth in six. 
Hence in the females it was not only the rule for the basi-bregmatic height to be less 
than the greatest breadth, but the mean altitudinal diameter was in relation to the 
length less than the transverse diameter. The skulls were tapeinocephalic. 
The mean gnathic index of twenty-nine skulls was 100*3 ; that of twenty males was 
100*6, that of nine females was 99*7 ; the average for each sex, as well as for both 
sexes collectively, brought this index into the mesognathous series according to the 
division employed by Prof. Flower. The maximum index in the males was 108, and 
seven specimens were 103 or upwards, i.e., had a decidedly prognathous index, whilst 
eight were mesognathous and five were orthognathous. The maximum index in the 
females was 105, and three specimens only were 103 and upwards. In the four youths' 
crania the mean gnathic index was 101*7, being somewhat higher than that of the adults. 
The mean nasal index of twenty-nine skulls was 53*4 ; that of twenty males was 53*47, 
that of nine females was 53*2. The average for each sex, as well as for the two sexes 
collectively, was platyrhine. The highest index in the male series was 60*5, and twelve 
specimens were 53 or upwards; one the Mudgee skull was 46, i.e., in the leptorhine 
series, whilst seven were mesorhine. The highest index in the female series was 59*5, 
and four were above 53, whilst the remaining five were mesorhine. The mean of the four 
youths was 52*9, i.e., on the verge of the platyrhine group. 
The mean orbital index was 84 ; that of twenty males 81*4, that of nine females 90. 
The average on the two sexes collectively was mesoseme; that of the males microseme, 
that of the females megaseme. In the males twelve were below 84, i.e., microseme; 
three were mesoseme, whilst five were megaseme. In the females the whole with one 
exception were megaseme. The mean orbital index in the youths' crania was 83*5. 
Journ., July 1865, the cephalic index of which, calculated on a parietal breadth of 4'3 inches, was only 53, but, 
calculated on a mastoid breadth of 4 - 8 inches, was 59. 
