QE THE SKULL IK LEPIDOSTEUS OSSEUS, 
463 
The palato-quadrate cartilages (p-pgi) are lesser again, flattened obliquely, and are 
still further from the basal bars. Behind the angle of the mouth the mandible 
thickens rapidly; this part ( ar.c .) shows a section oblique and sub-reniform, close in 
front of the articular condyle. The large mouth-cavity (m.) is partly filled here with 
a transversely oval mass—the tongue ; it has a large double core of a soft spongy kind 
of cartilage ; this is the exceptionally symmetrical basi-hyal ( b.Jiy.). 
The same kind of surface bones are cut through above; the outer film is a super¬ 
orbital (s.ob.) —a continuation of the same chain as the preorbitals; and the inner 
piece' is the pointed fore end of the frontal (/.). The pterygoids (pgi) are still in 
section, but the mandible is cut through behind its splints. 
Section 6.—The next section (Plate 33, fig. 6) is through the middle of the eye-ball 
(e.), and through the hinder wide part of the hemispheres (C lft .). Here the cranium is 
largely membranous, for the only cartilages cut through are the superorbitals ( s.ob.c .), 
mere bands running superolaterally, and the trabeculae below. The latter (tr.) are just 
distinct at this point, and are brick-shaped—a little turned up at their outer ends. 
Thus at this part we have the fore end of the great fontanelle (see Plate 32, fig. I, Jo.), 
and the wide orbito-sphenoidal fenestra (fig. 2, os.f.). 
The quadrate region ( p.pg .) is cut through here, behind the hinge of the mandible ; 
this is still faced on the inside by the pterygoid (pg.), whilst another film of bone is 
cut through above, namely, the mesopterygoid ( ms.pg .). Above, the frontals (f) are 
seen in section, and below, the tongue and basi-hyal ( b.hy .). 
Section 7.—This (Plate 33, fig. 7) is post-orbital, and is through the mid brain (C 2 .), 
and the thalamencephalon (C 1 .), near the pituitary body. 
The trabeculae (tr.) are very small, nearly circular in section, and at their greatest 
distance apart. The flattened superorbital bands (s.ob.c.) are thrown to the side of the 
membrano-cranium, which is at its weakest point here. The quadrate (q.), which was 
thin above and thick below in the last, is now thick above and thin below ; the long 
pterygoid is still on its inside, and below its out-turned thin edge a small round rod 
of cartilage is seen : this is the symplectic (sy.). 
In the root of the tongue there are three cartilages cut through, the middle bar is 
nearly circular, the others are flattened ; these are the basi-branchial and the first 
hypo-branchials (b.br., Ji.br.). In a fold outside and below these, a thicker round rod 
is seen ; this is the cerato-hyal (cJiy.). Protecting the pituitary body, the parasphenoid 
(pa.s) has here widened out considerably ; for a short space, shown in this and the 
next section, the roof shows scarcely any osteoblasts. 
Section 8.— This section (Plate 33, fig. 8) is through the fore part of the auditory 
capsules and the widest part of the mid brain (C 2 .), where it turns down to join the 
hind brain. The anterior canal ( ci.s.c.) is cut through; here the capsule (cm.) is imperfect 
within, and is beginning to ossify as the prootic. The investing mass (iv.) is cut 
through where it is shooting out into the trabeculae, and the bands are wide apart. 
The superorbital band has now passed into the antero-superior angle of the auditory 
MDCCCLXXXII. 3 O 
