278 PROF, W. K. PARKER ON THE STRUCTURE AND 
The single occipital condyle (0¢.c) is an elegant crescent, embracing the notochord (nc) ; 
much of that rod is naked behind on the lower surface, but is invested in front, and is 
only seen again at its apex in the back of the round pituitary space (py). ‘The whole 
of the hinder chondrocranial walls are very distinct from the larger lobulated auditory 
capsules (aw). Here the hypoglossal nerve (x11) passes through the “ posterior condy- 
loid foramen ” (Miall)'. 
The cochlear diverticula of the auditory capsules (ch/) have coalesced with the basal 
plate (iv); but laterally, and above, the occipital arch is quite distinct from them, and 
where the ninth and tenth nerves (Ix, x) emerge there is a large oval open space. 
Above, the supraoccipital cartilage roofs in three fourths of the hind skull, forms a 
flange on each side to the back of the auditory capsules, has concave lateral edges and 
then spreads out again, but to a lesser degree, in front of the capsules. The ascending 
fore end of the double basal plate is now a continuous slanting wall of cartilage 
leaning over the pituitary space behind (fig. 1, p.cl, py). From this wall a flying 
buttress is thrown across, right and left, and this buttress passes into the thickened 
coping of the alisphenoidal wall (a/.s). That thickening is developed behind into a 
crescentic horn, which embraces the front outer corner of the auditory capsule; this 
process is very thick and strong below (fig. 2), and the two hold, like opened tongs, the 
swollen front lobes which have the anterior ampulle (a.s.c) inside. The thick top of the 
alisphenoidal wall (a/.s) runs beyond that limited part, and curving round, passes into 
the hind corner of the orbitosphenoid (0.s); thus there is below a large “ orbito-alisphe- 
noidal fenestra” (0.a/.f). Below each flying buttress, sent out from the postclinoid 
wall, there is a large recess; it has the auditory capsule above and outside it, and the 
basal plate (¢v) bounding it below and towards the middle; this is the huge primary 
“foramen ovale” (v) for the trigeminal nerve and Gasserian ganglion. In front and 
below, the alisphenoid (a/.s) grows downwards, margining the pituitary cup above, and by 
a thick inturned process uniting with that cup as a partial rim. There is, then, infero- 
laterally, a lesser crescentic fenestra, the “lower or alisphenoidal fenestra” (al.f'); this 
transmits the lesser preauditory cranial nerves. The rest of the alisphenoid is a narrow 
convex band, which runs forwards and inwards, and is confluent with the postero- 
inferior angle of the orbitosphenoid (0.8) ; where these two bands converge to join the 
orbitosphenoids, there, on the upper surface, we see the foramina for the optic nerves 
(fig. 1, 11); these are separated by the sharp top of the intertrabecular bar (7.tr). 
‘The long rod-like structure which forms the base of the prepituitary region of the 
skull encloses the front and sides of the circular pituitary space, below, by its forks; 
these short forks are mamillated at their end, and project from the general surface 
of the cartilage. They converge rapidly to embrace the intertrabecular bar, which is 
' In my former papers on the skulls of the Sauropsida, led by the analogy of the Mammalia, I have con- 
sidered the anterior condyloid foramen as the passage for the hypoglossal nerve. 1 suppose that dissection 
would show that I have been in error, 
