DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 
163 
basisphenoid ( b.o .),* the tympanic wings of which are seen as projections, below. 
A small tract of each wing is seen above the internal carotid {i.c ) entering 
the skull, and the orbitosphenoidal band (o.s'.) is also seen at one-third of the height 
of the side-wall. The inner margin of the huge Gasserian ganglion (Y.)—here 
cut across its middle—lies in the bend of the artery, it reaches more than halfway 
outwards and upwards to the orbitosphenoidal band. 
The angle of the outer mandible {ran.) is cut through, and below, and further 
inwards, Meckel’s cartilage ( mk .). 
Over Meckel’s cartilage the curved section of a considerable tube is seen, and also 
under it and nearing outwards a much larger space ; the upper cavity is the beginning 
of the Eustachian tube, and the lower the tympanic cavity. Outside the latter 
a patch of cartilage is shown ; this is part of the meatus. Under the inner 
edge of the tympanic cavity the epihyal cartilage (e.hy) is cut oh close to its junction 
with the ceratoliyal ; and towards the mid-line the bypohyal {h.hy.) is severed near 
the larynx {lx.), part of the cartilage of which is laid bare. 
Sections 10 and 11 (Plate 23, figs. 9 and 10).—These two half sections show the 
pituitary body (py.) above and in front of the ascending postclinoid cartilage, in the 
upper surface of which we see the point of the notochord. The auditory capsules {chi.) 
are cut across; they lie a considerable distance from the basisphenoid {b.s.). The 
orbitosphenoidal band (o.s.) is present here, it soon becomes the supra-auditory crest. 
Over the auditory capsules the Gasserian ganglia (Y.) are seen cut across in their hind 
part, and below them the geniculate ganglia (YIL). 
In fig. 9, the tympanic cavity is cut across ; outside and below it the meatus 
cartilage is shown. The small upper piece is outside the head of the malleus {ml .),t 
below which the body of the incus is seen, whilst its long crus is shown as 
turning inwards towards the capsule ; the fenestra ovalis is cut across at its front 
margin in fig. 10, but the stapes is massed. 
Section 12 (Plate 23, fig. 11).—In this partial section we see the basilar artery {b a.) 
cut across obliquely over the hind part of the basioccipital {b.o.); here the large hind 
part of the cochlea {chi.) touches the basisphenoid, ready to coalesce with it. The 
orbitosphenoidal band {o.s'.) is now very deep, close in front of its supra-auditory 
continuation. 
The geniculate ganglion is still seen, and also under it the passage in the top 
of the auditory capsule for the facial nerve (YII.), which enters its canal at this place. 
The outer wall of the auditory capsule is deficient in two places here ; the upper 
deficiency is partly filled up by the base of the stapes (st.), it is the fenestra ovalis ; 
between its base and apex the stapedial artery {st.a.) is seen as it passes to the inside 
of the mandible. The other space, not stopped up by cartilage, is the fenestra rotunda ; 
the outer part of the capsule with its tegminal projection ( t.ty.) is seen external 
* The letters of reference should have been b.s., and only one line to i.c. 
t The line of reference to the figure is made too low down. 
Y 2 
