258 
Observations on the Occipital Bone 
there are 12 adult and 6 young specimens ; and, of these, 8 adult and 6 young 
specimens show the condition on both sides to a greater or less extent, while the 
remaining 4 adult (one a young adult) show it on the right side only. 
Of the rest, 48 adult and 20 young specimens show a fissure of less than 
15 mm. length — in some cases only a slight trace — and of these 29 adult and 
11 young show the condition on both sides, and the remaining 19 adult and 
9 young, on one side only. 
Thus, in the 1100 crania examined, the conditions found were : — 
Percentage showing 
Specimens 
Synchondrosis 
Fissure 
Less than 
persistent Synchon- 
Examined 
Obliterated 
15 mm. or more 
15 mm. 
drosis Condylo- 
squamosa 
1038 adult 
979 
12 
47 
5-7 
62 young 
36 
6 
20 
41-9 
The percentage of adult crania showing indications of the persistence of the 
synchondrosis condylo-squamosa agrees very closely with the figure (5"3) found 
by Zaaijer in the collection of adults examined by him, and similarly the con- 
dition has been found in a much higher percentage of young crania. The 
condition also appears to be of more frequent occurrence among the female crania, 
for of 322 adult female crania 30 show persistence of the synchondrosis condylo- 
squamosa (9'3 per cent.), while in 457 male crania the condition was found in only 
20 specimens (4 - 3 per cent.). 
It was thought worth while to examine the crania of other primates for com- 
parison, and the writer was enabled by the courtesy of Professor Keith to examine 
the collection at the Royal College of Surgeons. This collection includes a higher 
percentage of young specimens, and also a number of younger individuals than 
any in the collection of human crania under observation, and, as was therefore to 
be expected, a great number of the young specimens show the condition with the 
synchondrosis extending from the masto-occipital suture to the margin of the 
foramen magnum, but few adults show more than traces of the developmental 
condition. Owing to the very great range in size of the crania of the other 
primates a standard of 15 mm. length of fissure has not been adopted here as 
in the case of the human crania, and the cases have been grouped according to 
whether the fissure reaches the margin of the foramen magnum or stops short 
of it. 
Thus 13*3 per cent, of the adult anthropoid ape crania examined show some 
indication of the synchondrosis condylo-squamosa, while 21 - 8 per cent, of the 
young specimens show the whole length of the synchondrosis, and 54"5 per cent, 
show the condition in varying degrees. 
Of the Lemuroidea 17 specimens (14 adult and 3 young) were examined, and 
a single adult showed a trace of the synchondrosis while two young showed the 
