OF THE MARSIPOBRANCH FISHES. 
437 
valvular entrance to the branchial canal (or “bronchus;” see also Plate 23, fig. 1). 
Here the cerato-hyals ( c.hy .) are seen to he obliquely-placed plates, sinuous in form, 
and bent upwards, both externally and within, where they are tied to the carinate 
basi-hyal ( b.hy .) (see also Plate IS, figs. 2, 6, 7). 
24 th Section (Plate 22, fig 3).—The cranial cavity is nearly surrounded by carti¬ 
lage in this part, for the alisphenoids nearly meet as a tegmen cranii (t. cr.) over 
the hind part of the mid brain (C 2 .). The hind brain (C 3 .) is also cut across in its fore 
part, and the hind part of the 5th nerve (V.) is still to be seen in the foramen ovale. The 
auditory capsules (cm.) have here an inner wall in front of the meatus interims. The 
section of the notochord (nc.) is larger; there is a fissure between the two parachordal 
plates (iv.) above; these plates pass, with but little thinning out, directly into 
the pedicles ( pd .) The section is made through them into the hyoid bar (e.hy), 
which is gently bowed outwards, enlarges, and again lessens before it is turned 
forwards and inwards, as the cerato-hyal. Just above its middle an elbow is seen; 
this is the back of the pterygoid bar ( pg .), whence the quadrate lobe and condyle 
shoidd have grown outwards and downwards. The cerato-hyal region is suddenly bent 
upwards with its convex face downwards ; each bar ends at a moderate distance from 
the median carinate rod (b.hy.). The posterior nasal canal (p.n.c.) is still larger than 
in the last section, and is sub-pentagonal in outline. Below it is the very narrow 
pharynx proper (food-pharynx, phx.), with its puckered, contracted lining, and below 
this is the body of the cartilage in the “intervelar shelf” (i.v.s.). The space below, 
right and left, is where the buccal cavities are passing into the branchial canal (see 
also Plate 23, fig. 1). 
25 th Section (Plate 22, fig. 4).—This is through the meatus' internus, and shows 
the 8th nerve and its ganglion (VIII.) The capsule (cm.) is continuous above, as in 
the last, with the alisphenoidal tegmen (t.cr.) over the hind brain (C 3 .), and also, 
below, with the thick parachordals (iv.), which have now a larger notochordal section 
(nc.) within them. The basal cartilage is cut through here, behind the pedicle, but 
the corresponding region of the hyoid arch is suppressed, for there is no hyomandibular 
tract, such as we see in the Myxinoids; beyond this point there is no more endo- 
skeletal cartilage in the side walls. The lower part of the epi-hyal and the cerato-hyal 
(e.hy., c.hy.) are cut through, and also the basi-hyal (b.hy.) Above the cerato-hyal we 
see the crura of the intervelar shelf (i.v.s.) cut across the pedate end, so that the toe 
and the foot are separate points of cartilage (see Plate 18, fig. 7, i.v.s.) The section 
of the posterior nasal canal (p.n.c.) is mutilobate and large; under it the food-pharynx 
(phx.) is very small, with its mucous lining corrugated, and in the space below it we 
have the beginning of the special branchial canal (see also fig. 5, br.c.). 
26 th Section (Plate 22, fig. 5).—This is behind the meatus internus and the ali¬ 
sphenoidal roof; the hind brain is seen to be very small as compared with the cranial 
cavity. As in the last, the notochord (nc.) is roofed by the investing cartilage (iv.), 
but the floor is imperfect. The fore part of the vagus, with its ganglion (X.), is 
MDCCCLXXXIir. 3 L 
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