434 
ME. W. K. Px'lEKER ON THE SKELETON 
13 tli Section (Plate 21, fig. 1). —This is also through the outer nasal opening (e.n.) 
and the proximal part of the cornu ( c.tr.) ; the other sections are like the rest, except 
that the lateral distal mandibulars are no longer seen. 
l&th Section (Plate 21, fig. 2 ).-—The outer nasal passage (e.n.) is a flattened tube, 
vertically placed, here, for this is close in front of the nasal capsule, and through the 
junction of the cornu (c.tr.) with the solid pre-cranial plate or ethmoid; the cartilage 
lies over the large oral cavity (to.) as a thick beam, slightly arched upwards, and a 
little hollowed in the middle, above. The other points of cartilage are like the last. 
1 5th Section (Plate 21, fig. 3).—This section is through the front third of the nasal 
capsule (ol.), showing its nine pairs of radiating folds or lobes, each having its own 
fissure, and lined with mucous membrane; the interspaces of the folds are filled with 
black pigment. The lower folds are shorter than the upper and lateral, and the 
posterior nasal canal ( p.n.c .) is distinct; it is seen as a transversely oval space between 
the capsule and the ethmoid (eth.). The capsule itself (na.) is not so distinctly 
bilobed as in the young of P. marinus (Plate 18, fig. 3, na.), for its top is flat, 
and it is somewhat angulated at the sides. The cartilage of the capsule is of the 
softer kind, but approximates to the general hardness of the skeleton in the hind 
part; it does not meet below in the sections that cut through the folds,—only behind 
(fig. 6). It is not a mere grating as in the Myxinoids (Plates 10 and 17), but is a 
continuous sheet, dipping in towards the deeply pigmented interspaces of the folds. 
The cranium is cut through so as to show the continuity of the ethmoid (eth.) with 
the ethmo-prepalatine tract (e.pa.), running almost to the front spike. The whole 
of this arched, but flat-topped, tract is of nearly uniform thickness ; the palatine 
bars bend a little inwards above, and then outwards below, and are rounded 
at their edge. Under the oral cavity (to.) the only cartilages cut through are the 
basi-hyal (b.hy.) and the tip of the median distal mandibular (m.d.m.) 
1 6th Section (Plate 21, fig. 4).—This is through the middle of the nasal capsule 
(na., ol.) and the fore part of the eye-ball (<?.). The wheel-like appearance of this 
organ is most perfect here, the lower folds being larger; and the lower face of 
the capsule, which is membranous for a slight extent, is not pushed up by the 
posterior nasal canal (p.n.c.). On each side of the ethmoid (eth.) there is a low 
wall, the beginning of the orbito-sphenoidal region, and in the middle of the 
descending plate of cartilage there is a fissure,—this is the fore margin of the 
“subocular fenestra” (s.o.f.); the pterygo-palatine bar (pt.ga.) is thickened at its 
lower edge. The fining of the mouth (to. ) is quadrilobate; under it is the only 
other cartilage seen in this part—the basi-hyal (b.hy.). The third branch of the 5th 
nerve (V 3 .) is seen in section between the subocular fenestra and the oral cavity, 
17 th Section (Plate 21, fig. 5).—This is through the back of the nasal organ, 
and only two pairs of upper folds are laid open, the rest of these folds being covered 
here by the highly pigmented stroma ; the cartilaginous capsule (na.) reaches below 
to the lowest fold, right and left. The cranium at this part is four-winged, for the 
