629 
DEVELOPMENT OF THE SKULL IN THE LACERTILIA. 
back part of the thalamencephalon, close behind the pituitary body, in front of the 
“ middle trabecula,’’ and through the Gasserian ganglia (py. V; see also fig. 3). 
Here the wide post-pituitary part of the halves of the basisphenoicl ( b.s .) are seen 
ascending to the ganglion on each side; the lower bar of the alisphenoid is above the 
ganglion, and the upper bar higher up (V, al.s.). 
The floor of the mouth is cut away, but on the sides, part of the quadrate cartilage 
is seen articulating with the mandible (q., ar.). 
The rest of the sections (Plate 40, figs. 1-6) are behind the thalamencephalon, the 
pituitary body, and. the middle trabecula. (See also Plate 39, fig. 3.) 
The 7 th section (fig. I) is through the most solid part of the mid and hind brain (C~, C 3 ); 
it is through the foremost part of the auditory capsules (an.) and in front of the 
notochord. 
The anterior “ampulla” (a.s.c.) is just caught, and above it the upper bar of the ali¬ 
sphenoid (al.s.), behind the end of the lower bar; here the basisphenoicl (b.s.) is at its 
widest part, and the open fontanel]e is between its unossified moieties. 
The shaft of the quadrate (q.) now comes into view above the mandible (mk.), and in 
the floor of the mouth (m.) come the common basal piece, the cerato-hyals, the cerato- 
and hypo-branchials ( c.hy ., br., h.br.). 
The 8 th section (fig. 2) shows the cavity of the mid-brain in two “horns,” and the 
beginning of the large cavity of the hind brain is shown (O', C 3 ) ; the basal cartilage 
(b.s.) is closing in towards the basioccipital region; and above, the upper bar of the 
alisphenoid (al.s.) is seen over the ear-sac (ecu.).. 
On each side, the quadrate (q.) still comes into view, for it is extended back in a 
cochleate form to make the cavity of the ear-drum. 
But in this section the parts are so many, and so important, that I have given the 
infero-lateral part of the right side in a more magnified figure (fig. 3), and part of 
the left side still more highly magnified (fig. 4). 
The arch of the anterior canal (a.s.c.) is cut through above, and the cavity of the 
vestibule is shown both above and below the entrance of the auditory nerve ( vb ., VIII). 
In this cavity otoconial masses are seen (ot.). 
Opposite the “meatus internus ” (VIII) we seethe fenestra ovalis ( f.o.) occupied by 
the stapedial base of the columella (st.); the “periotic” cartilage is fused with the 
basal plate (b.o.) ; this is seen both at its cut edge, and below. 
The periotic wall below the stapedial plate does not pass round below the ear-sac to 
reach the basal plate; here there is another equally large “fenestra” (f. rotunda, fr.). 
Correlated with this round window, we see the lower part of the vestibule under¬ 
going subdivision. The new bulb is the rudiment of the cochlea (chi.); it lies below 
the part from which it has budded, as we see also in the Snake (“Snake’s Skull,” 
Plate 31). 
Close below the “fenestra rotunda vel cochleae ” we see the styloid top of the cerato- 
hyal bar (st.h.), which is not a rudiment, as in the Snake, but a perfect bar. 
