OF THE MARS1POBRANCH FISHES. 
389 
The two upper fissures are crescentic, and the form of the median space is a blunted 
wedge; the floor has two ridges. These sections show that the horny teeth are folds 
of a continuous epithelium ; they are huge papillce with a common horny base, and, 
distally, have their own cavity. 
Under the folds of the mid-line the median part of the supra-lingual skeleton ( s.l.c.) 
is cut through; this lies on the fused middle pair of front basi-hyals, which plate is 
concave under the lesser upper cartilage. 
The lateral pairs of the front basi-hyals ( b.hy a .) are solid, oval in section, and are 
further apart from the middle pair than they seem to be in the bird’s-eye view\ 
(Plate 9, fig. 3; and Plate 12, fig. 7.) 
Section 12 (Plate 12, fig. 1).—This section is through the hind bar of the nasal 
capsule {ol.), and the longitudinal rods of the grating are seen cut across close to the 
transverse bar. This section is close in front of the membranous cribriform plate, 
which will be described in my account of Bdellostoma, in which (and in Myxine) the 
olfactory nerves, as shown by Muller (II., plate 2, figs. 8-12), pass into the capsule by 
jive roots on each side, each root breaking into a pencil of fibres as it enters the capsule; 
a Mammalian anticipation. The palato-trabecular bands ( p.tr .), and the handle of 
the hinder intertrabecular spoon {p.i.tr.), are cut through, and are similar to what we 
saw in the last section. So also are the basi-hyal bars; but, here, the median supra- 
lingual plate is wider, and the side wings now come into view, to support the cheek¬ 
teeth, now showing their distinctness in section. 
Section 13 (Plate 12, fig. 2).—This section is very similar to the last, but it is behind 
the nasal capsule, and through the fore brain (C 1 .); a large space is seen between the 
fore brain and the feeble floor of the skull; this is the posterior nasal (or naso¬ 
palatine) canal. 
Section 14 (Plate 12, fig. 3).—Here the cranial cavity is at its widest part; the 
palato-trabecular bands are wider and less tilted at this part, which is in front of the 
small optic nerves (see Plate 13, fig. 1, e., II.). The hinder intertrabecula {p.i.tr.) is 
cut across in three places, the edges of the spoon being caught, laterally. The supra- 
lingual cartilage (see fig. 8) is here continuous from side to side, being cut through 
in front of the foremost fissures; it forms a deep trough for the bed of the paired 
rows of cheek-teeth. Here (see Plate 9, fig. 3) the four front bars of the basi-hyal 
{b.hy a .) are all distinct again, the section being made through the basi-hyal fontanelle. 
In the last four sections, the two median bars have been confluent. 
Section 15 (Plate 12, fig. 4).—This section is through the fore margin of the subocular 
fenestra (Plate 10, figs. 1-3, s.o.f), where some soft cartilage divides the palatine from 
the pterygoid regions (Plate 9, figs. 1, 2; and Plate 10, figs. 1-3), so that the hard 
cartilage {pa.) here is near the pterygoid ; the inner is trabecular (tr .). Here the 
spoon of the hind intertrabecula {p.i.tr.) is cut across in front of its lateral attachment 
to the trabeculae {tr.). The area on each side of the naso-palatine canal {p.n.c.) is the 
tissue through which the small optic nerves pass, but they were not caught in this 
MDCCCLXXXIII. 3 E 
