762 MR FRANK J. COLE 
that the hard cartilage in the region of the bridges is either wholely or largely invaded 
by soft cartilage suggests precisely the opposite view that the hard cartilage replaces 
the soft. A careful examination of the sections of the 6°5 cm. and the 10 em. Hags 
undoubtedly reveals the presence of the bridges exactly as in the adult, and as they 
are also figured so by Neumayer, I cannot confirm ALLIs’s observation as far as Myxine 
is concerned. However, in the absence of information as to the size of his embryo, this 
is not conclusive. 
Hypophysial Plate (figs. 1 and 2, h. ».).—This occupies the median hypophysial 
fontanelle at the base of the skull, bounded by the palatine bars and their commissure, 
the trabeculee, auditory capsules, and parachordals. Its function is to provide a basal 
support for the hypophysial canal or naso-palatine duct. It consists of a central plate, 
fused with processes from the trabeculee and the nasal capsule, which sends out a rod in 
front and a wider process behind. The anterior half of the rod is sometimes formed of 
hard cartilage (as shown in fig. 2), thus differmg from the remainder of the plate, which 
is of soft cartilage. J. MULLER states that it is composed of hard cartilage in 
Bdellostoma, but Parker found no hard cartilage in it either in Bdellostoma or in 
Myxine. It commences under the nasal chamber, just behind the palatine commissure, 
as a circular deposit of cartilage in the stout membrane connecting the palatine bars. 
Where the hypophysial canal separates from the nasal chamber, and during its associa- 
tion with the hypophysial plate, it forms a tri-radiate tube, T-shaped in transverse 
section, and situated immediately below the floor of the membranous cranium, ventrally 
partly fitting for a time into a median groove in the roof of the pharynx. The 
hypophysial plate is situated at the base of the upright piece of the T. Itis at first 
slightly saucer-shaped, but further, posteriorly, it becomes bent up sharply at the sides 
of the hypophysial canal in the form of a V. At the external margin of its widest part 
it fuses first with the backwardly coursing rod of soft cartilage from the posterior 
transverse bar of the nasal capsule, and immediately afterwards with a forwardly 
coursing similar rod from the trabecula, as elsewhere described. PARKER does not 
describe either of these fusions in Myxime; but his fig. 3, pl. 10, seems to indicate 
that he saw something of the trabecular fusion, and this one is described and figured in 
dellostoma. Behind this region the hypophysial plate narrows down into the posterior 
process, which is bent upwards from below on each side of the vertical limb of the 
hypophysial canal in the shape of a U. This process expands at its posterior extremity, 
and is fenestrated to a greater extent than is shown in fig. 2. 
NEuMAYER’S figures of the preceding region agree with mine except that the 
parachordals are figured and described as completely fusing dorsally, and a fusion is 
described between the hypophysial plate and the subnasal bar. The latter statement 
is dealt with elsewhere ; and, as regards the former, | am quite unable to confirm it. 
The dorsal parachordal fissure is quite characteristic of Myaie. 
Superior Lateral Cartilage (figs. 1 and 2, s. l. c.).—Consists of soft cartilage, and in 
front fuses with the dorso-posterior border of the hyoid arch (hy.), there containing a 
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