400 
MB. W. K. PARKER OK THE SKELETON 
ending some distance behind the thick sheath; this appearance is due to the fact 
that the section was not quite in the middle : the proper structure of the notochord 
ends opposite the middle of the ear capsules. The capsule (au.) is shown in section 
near the meatus, so that its thickness appears greater than it is in reality, as the para¬ 
chordal cartilage thickens it on the inside. The folds of the nasal capsules (na., ol.) 
are brought into view, and the cartilages (na.), both of the capsule itself (ol.) and of 
the external nasal tube (e.n.t.) are cut through, very near the mid-line. A continuous 
passage is seen from the external opening (e.n.) of the nasal passage (n.p.) to the fringed 
lips of the naso-palatine canal (p.n.c.) which opens at the mid-line at the fore part of the 
velum (vl.), here shown in section, with a point of cartilage in it, here and there, caught 
by the razor. The size of the cavity and the character of the folds inside it, of the 
fore part of the naso-palatine canal (p.n.c.) are seen in this section, and also that these 
lie on the floor of the skull, between the hind intertrabecula (p.i.tr.) and the brain (C.) 
The opening out of the skull is behind that median cartilage, between the produced 
“bowl” of the “spoon ” (Plate 17, fig. 3, p.i.tr.) and the beginning of the trabeculae 
(tn\, iv.). Another cavity—a space between the hinder intertrabecula and the roof of the 
mouth—-is also seen. This is evidently artificial, and caused by the tearing away of the 
mucous membrane of the palate from the hinder intertrabecula. A curious coiled valve 
is seen behind these two openings, under the fore part of the velum, at the beginning 
of the pharynx ; a little in front of this fold, the proper oral cavity (lined with 
epiblast, the pharynx being lined with hypoblast) ends. At this part, the entrance 
of the proper pharynx, the passage is a series of slits or fissures (see the sections of 
the skull of Myxine, in Plate 13). Somewhat left of the mid-line, this section shows 
only part of the front intertrabecula ( a.i.tr.), and thus the whole of the great median 
tooth (et.t.), and the ethmoid ( eth.), a little to the left, is seen under it. Both the ethmoid 
and the base of the tooth are enclosed in a special fold of membrane over the oral 
entrance (ni). That space would be large, but two additional lingual masses, the paired 
rows of teeth (s.Z.L)ancl their membranous and cartilaginous settings (s.l.c.), fill the greater 
part of the space between the basi-hyal and the palatal membrane. This section 
being a little to left of the mid-line, shows the inner edge of the left bars of the basi- 
hval (b.hy.), and as the middle bars of the front or quadruple part are shorter than 
those outside, the cartilage is seen to stop short of the fore end of the under face 
(lower lip). These cartilages are enveloped in the muscular masses that move the 
tongue. The upper or ethmoidal tooth (et.t.) is seen to turn its point backwards ; 
in the figure it is in front of the paired rows of supra-lingual teeth (s.l.t.), but the 
powerful muscular apparatus works so as to make it antagonistic to the lower teeth, 
generally, which can be made to move backwards and forwards, and from side to 
side. This whole muscular mass, in my larger specimen, is sub-cylindrical, six inches 
long, and one inch in thickness. The reader is referred to Muller’s works for a 
description of the whole apparatus. 
