DEVELOPMENT OP THE SKULL IN THE MAMMALIA. 
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rim. Outside the condyles a definite low convex paroccipital ridge is seen ( po.c .), 
outside this the cartilage is opisthotic (op.). Beyond and behind the condyles, there 
is a narrowish tract of cartilage, and there the lower edge of the bony supraoccipital 
(s.o.) is seen bulging backwards. 
The ovoidal cochlear region of the auditory capsule (chi.) lies each in its own 
oblique, well-made socket; the rest of the capsule seen in this aspect is the tegmen 
tympani outside, and the opisthotic region (op.) postero-externally. Outside the 
tegmen the large pneumatic foramen of the squamosal (tr.c.) is drawn in outline, 
and under the tegmen the facial nerve (VII.) is seen passing to its place of exit, 
the stylomastoid foramen. In front of the nerve the small stylohyal bone (st.h.) 
is seen, and inside it the epihyal cartilage (e.hy.) Further inwards, in the enlarged 
occipito-auditory “foramen lacerum posterius,” the 9th and 10th nerves (IX., X.) 
are emerging a little in front of the 12th (XII.). In front of this semicircular 
chink, the fenestra ovalis and fenestra rotunda (fs.o., fr.) are shown in the 
fundus of the nut-shapecl cochlea (chi.), the proximal or hinder part of which is 
more convex than the rest. 
The upper view (Plate 1 5, fig. 2) of the enclocranium shows what a long tract there 
is of the nasal labyrinth before we come to the dilated, and most complex, true 
olfactory region ; the cartilage roofing and walling all the regions in may still retain 
the old terms of alinasal, aliseptal, and aliethmoidal (al.n, al.sp., al.e.). The whole 
structure, as seen in this aspect, is more like the parts of a jlower than the fore end of a 
skull; the vestibular fluted part is very elegant, with its two pairs of semicylindrical 
tracts, gradually enlarging backwards, and then appearing to end, in each, in a point. 
Between these pointed ends, of which the submesial go furthest back, the roof (al.e.) 
is sinuously and gently concave, and then ends in a perforated triangular tongue— 
as in Birds—that tongue-like growth being the top of the moderately developed 
cartilaginous “crista galli ” (cr.g.). 
Bight and left of the crista galli—which is the concave free, posterior, mediastinal 
edge of the perpendicular ethmoid (see also fig. 3, p.e., cr.g.), the large, hollow, 
burrowing olfactory fossae are seen floored by the multiperforate cribriform plate (cr.p.). 
This porous roof over the “ middle turbinals” is itself the floor of the fore skull, and 
these two pre-cranial ovens are themselves roofed in front and at their sides by the 
arched edges of the upper turbinal regions of the olfactory capsule. The copious growths 
of the upper turbinal ( u.th.) are indicated right and left in the great pillow-shaped 
lobes of the ethmoid. On the inner edge of each of these there is a small angular tag 
of cartilage, and at a moderate distance behind the round swelling end of these upper 
turbinal masses, the round fore end of the cartilaginous, outer part of the orbito- 
sphenoid (o.s.) is seen; the tag is the remnant of the bond that did hold the much 
larger orbitosphenoid to the olfactory capsule. 
The cribriform plate is margined behind by a thick rim of cartilage—very thick 
inside and below the tag; but nearer the middle the cartilage is still more solid, form- 
MDCCCLXX X V. Q 
