]G 
TERTIAET VEETEBEATA OF TJIE FAYCM. 
'I'he optic nerves leave the skull far forwards, perforating the orhitosphenoids by 
two diverging passages, the inner openings of which lie close together at the bottom 
of a fossa (text-fig. 5, ii.) hounded anteriorly by a transverse ridge. Immediately 
external to and slightly below the level of the openings of the optic nerves there is a 
Text-fig. 5. 
Cast of cranial cavity of Arsinoitherium zitteli : A, from above ; B, from below ; C, from left side. 
aud., auditory nerve-root ; ch., cerebellum ; f.l.a., nerves passing tbroiigb foramen lacerum anterius ; 
h., cerebral hemisphere ; l.l., lateral lobe of cerebellum ; oL, olfactory lobe ; s., sulcus ; u., optic chiasma. 
2 nat. size. 
large vertically elongated opening (represented by the ])rojcction marked f.l.a. in the 
cast), the anterior aperture of which { foramen lacerum anterins or foramen sphenoidale) 
is just over the alisphenoid canal, as described above (see text-tig. 4, ii. and f.l.a.). 
