7 t. 
29 
for the passage of blood-vessels and nerves. The two upper middle 
incisor teeth are absent, but their sockets show their size to have 
been nearly if not quite double the two outer ones. The two lower 
middle incisor teeth are narrower than the two outer. 
The female cranium is a full-grown one, but differing from the male 
in the prominence of the ridges, the two anterior corresponding to a, 
a in the male, and the central are rudimental only, except at the ex- 
