DEVELOPMENT OF THE SKULL IN STUKOEONS. 
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narrower, and more like a distinct beam; here also the outer bones do but fringe 
and enlarge the section. 
Section 7.—In. this (Plate 16, fig. 11) section the antorbital wall is exposed, behind 
the nasal sacs ; that wall is composed of the aliethmoids (al.e.) and the ethmo-palatines 
(i e.pa .). Here the paired cartilages are the trabeculae (tr.) for this section is behind the 
cornua; but the intertrabecula (i.tr.) is very large from top to bottom. The middle 
region of the intertrabecula is the perpendicular ethmoid (p.e.), on each side of which 
the olfactory nerves (I.) are escaping; 'its alae above are becoming the superorbital 
bands ( s.ob .), whilst below, its huge beam is burrowed by a vomerine bone ( v .). 
Section 8.— In this section (Plate 16, fig. 12) the eye-ball (e.) is just caught, and the 
cranial cavity laid open at the olfactory foramina, with their nerves (I.); the rest is very 
similar to the last section; in both, dermal bones defend the sides of the face, and 
above, the frontal scute is cut through. 
Section 9.—This (Plate 17, fig. 1) is through the middle of the orbit, where the 
superorbital band (s.ob.) narrows in; here the supercranial valley is very large and 
deep, and the section of the skull has the shape of an Ox’s face. In this young specimen 
the chondrocranium is very massive, and the pyriform cavity for the hemispheres (CP), 
is only one-fourth as large as the section itself, which is widest below, and rather 
pinched in the middle. The skull, below the cranial cavity, is as deep as the cavity, 
and is burrowed, below, by the splintery fore end of the huge parasphenoid ( pa.s .) ; 
the swelling cartilage on each side belongs to the trabeculae (tr.) the middle part 
to the intertrabecula (i.tr.). The orbital muscles (or.m.) are planted in chinks of the 
basal mass. 
This section is in front of the mouth and through the front of the upper lip (u.l .); 
there is, here, a crescentic cavity, with the horns below. 
Section 10.—In the next section (Plate 17, fig. 2) the small eye-ball is just missed, 
but the optic nerves (II.) are seen emerging from the brain (CP). Here the cavity is 
something like an hour-glass, being as wide below as above ; the tegmen cranii (t.cr.) 
is twice as thick as in the last, and the basal mass (tr., i.tr.) only half as thick, for this 
is behind the lobes that envelop the parasphenoid (see Plate 16, figs. 1-4). 
Here the superorbital bands are wider and more solid, and externally, a new plate 
of cartilage has come in, on each side from the eaves of the hind skull; this is the 
sphenotic (post-frontal) lamina (sp.o.). The solid basal plate is grooved sub-laterally 
and in the middle, and the parasphenoid (pa.s.) fitting to these sinuosities is, in section, 
like a stretched bow. 
Below the base of the skull there is a quantity of very lax tissue, permitting the 
greatest freedom to the movements of the protrusible oral apparatus, and below this 
we see the large arched mass of the “ adductor manclibulse ” muscle (ad.m.) on each 
side. Below the muscles, the fore part of the pterygo-quadrate cartilages (pg.([.) are 
cut through, and they are flanked by the maxillary and palatine bones (mx., pa.) 
the former outside, and the latter beneath. 
