OF THE MARS1P0BRANCH FISHES. 
387 
Section 5 (fig. 5).—Here the pre-oral groove is deeper, and the front inter trabecula 
is here at its largest part. The true form of the prepalatine section ( pr.pa.) is seen 
here. In this section, and in the 7th and 8 th, we get a view of an important character 
in the nasal passage (' n.p .), namely, that it has a valvular fold in it, growing down 
from above, and making it heart-shaped in section. 
Section 6 (fig. 6).—This section is much larger than the last, and here we have the 
upper lip breaking into two large, sharp folds, and the palatal part of the oral 
I vestibule wrought into two rounded folds. The valvular process of the nasal passage 
was not clear in this section, but we see that here the annulus is not thickened below, 
and that it turns inwards right and left. The front intertrabecula ( a.i.tr .) is now long- 
oval in section, and the prepalatine (pr.pa.) oval. In the two folds of the upper lip 
(u.l.) we have the oral palpi ( o.bb .) cut through, the outer longitudinally, and the 
inner across. 
Section 7 (fig. 7).—In this section the two lobes of the upper lip ( u.l .) are confluent, 
but the palpi (o.bb.) still come into section in a similar manner to the last; there are 
now five folds of the prepalatal region above, and two below; these latter look 
upwards, the meaning of which will soon be seen (see figs. 8-11). The valvular 
fold in the roof of the nasal passage is here clearl} T shown, and also the lessened depth 
of the front intertrabecula (a.i.tr.). The true thickness of the prepalatines (pr.pai) is 
here shown, just at them base; and here also (see Plate 10, figs. 1-3) the ethmoidal 
region of the skull (eth.), with its attached conical yellow tooth (et.t.), is cut across.* 
The closed-in, or ethmoidal part of the skull is formed, as we saw, by the coalescence 
(or continuity) of the palatine bars outside, and the trabeculm within ; here, at the 
junction of these parts, the cartilage is high above, and gently convex below, where 
it carries the tooth. 
Section 8 (fig. 8).—The section through the dilated hind part of the front inter¬ 
trabecula (see Plate 10, fig. 2, a.i.tr.) was not figured ; here, in front of that part, it is 
nearly circular in section ; and because of the sinuous form of the hinder narial 
annuli, this section shows one cut into three pieces ( e.n.t.); the nasal tube still shows 
its valvular character up to the proper capsule. The ethmoidal region (eth.) is 
arched; the outer part is palatine, and the middle trabecular. A cushion of fibrous 
tissue fills the concavity, and to it is attached the great tooth (et.t.), which is here 
cut across obliquely near its apex, showing its internal cavity. The lining of the 
mouth is sinuous, and the floor of it is now complete ; this is the first section through 
the lower lip (l.l.), the ascending fold of which is the fore part of the supra-lingual 
apparatus. Right and left of these folds, not far from the mucous membrane of the 
mouth, two large hard cartilages have been caught by the razor ; these are the outer 
front basi-hyals (b.hy a .) (see also Plate 9, fig. 3). These bars turn upwards and out- 
* The specimen sectioned was older than the one which was dissected, and so the hard cartilage had 
extended further in the former; this will explain some slight discrepancies between the two sets of figures 
as to colour , and also as to the fineness or coarseness of the dotting. 
