DEVELOPMENT OE THE SETTLE OF THE COMMON FOWL. 
787 
a perfect floor to the “ anterior tympanic recess.” The basitemporal plate is notched on 
each side, where it forms a floor to the tympanic cavity, and all along its posterior margin, 
where it partly underlies the basioccipital ( b.o .). 
The side view (fig. 8) shows the high prepituitary part of the basisphenoid [b.o.) 
below the optic nerve (2), the rostrum ( r.b.s .), and the tympanic lip of the basitemporal 
(b.t.). 
The sectional view (fig. 7 ; the rostrum, r.b.s., and anterior pterygoid process, a.])., 
are not cut through) shows the rostrum, articular plate, prepituitary and postpituitary 
portions, the opening for the internal carotid (i.c.) in the fundus of the pituitary cup, 
and the thickness of the fast-growing basitemporals (b.t) where they underlie the equally 
thick shelving postpituitary part of the bone ; the declivity is caused by the height of 
the posterior clinoid wall (p.cl.). 
The end view (fig. 9) shows how the posterior margin of the basitemporals (b.t.) under- 
lies the anterior end of the basioccipital (b.o.) and the surrounding cartilage. 
The horizontal section (fig. 10) passes through the middle of the “'sella turcica,” cutting 
away much of the anterior and posterior walls, exposing the internal carotids, showing 
the basisphenoidal part of the cranial floor and the obliteration of the spheno-occipital 
synchondrosis at the mid line. Here the posterior or tympanic wings (p.r.p.) are seen 
to be thick and cellular, and to give attachment to the fore part of the membrana 
tympani (m.t.) in the long “ anterior recess ; ” the prootic (pro.) helps to wall-in this 
recess behind. 
The pedate tract of cartilage bounded by the basisphenoid, basioccipital, and prootic 
contains the cochlea, which is indebted to all these bones for its outer wall. The open 
fontanelle ( p.b.f. ) seen at the mid line in Plate LXXXIII. fig. 2, is here filled up by 
the rapidly growing basisphenoid ; a chink, however, remains for a long time. 
The windowed alisphenoids (Plate LXXXIY. fig. 8, a.s.) are now well ossified, all but 
the outstanding “ postfrontal” (p.f.) ; the suture between the alisphenoid and basisphe- 
noid remains long distinct. 
On each side a large postorbital fontanelle still exists, reaching down to the optic 
nerves (figs. 7 & 8, 2) below, and upwards to the frontal plate of the ethmoid (eth.), 
traversing the whole of the orbito-sphenoidal region, which is devoid of cartilage. The 
orbital plate of the frontal (f.) is gradually encroaching on this unwalled space. The 
whole of the presphenoid ( p.s .) and the hinder third and lower selvedge of the perpen- 
dicular ethmoid is still unossified ; but a large antero-superior tract of the latter is now 
ossified by a double (right and left) ectosteal plate (figs. 7 & 8, eth.), the cartilage within 
undergoing endostosis. 
The lower boundary of the cranio-facial cleft (fig. 7, c.f.o.) has been entirely absorbed, 
so that the ethmoid is now merely connected by an isthmus to the postero-superior 
angle of the septum nasi. Through this cleft (notch) the inferior turbinal coil (i.t.b.) can 
be seen ; and below this cleft the vomer (v.) lies, in a perfectly ornithic condition, in the ,, 
base of a plate of fibrous tissue, far away from the cranio-facial axis, and ready to lay 
hold on the fore spurs of the palatines (fig. 6, v.,pa.). 
5 m 2 
