4DU ME. W. K. PARKER ON THE DEVELOPMENT 
proper is at present composed of two bands of cartilage, which run from the atlas to 
the large suctorial snout (s.d.) ; the lateral structures are the auditory capsules and the 
visceral arches. 
The basal pair of bands (Plate 30, fig. 3, iv., tr.) are thickest behind and at the fore end; 
for two-fifths of their length they embrace the notochord by their inner edge; they 
then diverge from each other so as to form a large spindle-shaped space (py) in front 
of which, for an eighth of their whole length, they approximate, but do not come into 
contact with each other. 
These dilated fore ends of the basal bands are as broad as the parachordal part 
behind (iv.), but are not so thick; they are conjugated by a tract of embryonic carti¬ 
lage, the rudiment of the “ intertrabecula ” (i.tr.) ; they themselves are the rudiments 
of the cornua trabeculae (c.tr.). The bowed interorbital part of the basal bands 
are the trabeculae (tr.), they are only half the width of the hind and fore parts ; 
these out-bent bars do not merely fence in the small pituitary body, they embrace the 
base of the fore-brain. 
The free, ascending, blunt end of the cranial notochord (no.) is twisted a little to the 
left—-it may curve either way, but the appearance is partly due to artificial pressure ; 
it is not invested by a large ascending “ posterior clinoid ” cartilage, as in the Amniota, 
for that tract is very small and very late in appearance in Lepidosteus. The pro-chordal 
part of the basal bands is bent somewhat upon the p am-chordal part. Behind the 
exit of the 9th and 10th nerves and the hind face of the auditory capsules the investing 
bars (iv.) thin out, and end in a sharp edge in front of the 1st vertebra. 
The auditory capsules (cm.) are of a short oval shape; they are largely chondrified, 
but the layer of cartilage is very thin; below, there is an oval fenestra, still membranous 
(au.f.) ; it is about two-fifths the length of the capsule. The capsules and the 
investing bars are only connected together by embryonic cartilage at present; the 
convexity of the capsules has produced a corresponding concavity in the side of each bar. 
The horizontal canal bulges over the lower convex part, which contains the otolith ; 
thus there is a rudimentary “ tegmen tympani.” Rudiments of all the framework of 
the visceral arches are now present, but the segmentation of these parts is imperfect. 
The skeleton of the first and second arches—mandibles and hyoid—is massive ; that of 
the branchial arches is very delicate. The pier of the mandibular arch (p.pg., q., pd.) 
is not a mere “ pterygo-quadrate, as in the Selachians, Teleostei, and Urodeles, but 
is a “ palato-quadrate,” as in the Anura. This arises from the primary continuity of 
the ethmo-palatine cartilage with the pterygoid fore-growth of the mandibular suspen- 
sorium; and this is not all, for the palatine region of the bar is also primarily continuous 
with the trabecula at its dilated fore end. 
The “ pedicle ” of this compound suspensorium is not fixed, as in the Tadpole, but 
free, as in the metamorphosed Frog ; as soon as it is sufficiently developed to articulate 
with the basal bar, it will then, at that part, correspond very accurately with what we 
find in the adult Frog. At present this palato-quadrate, or suspensorial cartilage is 
