DEVELOPMENT OF THE SKULL IN THE BATRACHTA. 
31 
occupied with a new (and rare) bony centre—the “ pro-parasphenoid ( pa.s .) 1 he 
endosteal tracts in front of and behind the auditory capsules ( pr.o., e.o.) are enlarging, 
and the “pedicles” ( jod .) in front of the former are becoming very attenuated, dhe 
rest of the hind part of the cranium is but little altered, but in front the nasal capsule 
is almost finished (fig. 4). 
The nasal roofs ( al.n.) are now completely confluent with the septum and the lateral 
wings of the ethmoid ; nevertheless the “cornua trabeculae ” ( c.tr .) that form the floor 
of the nasal cavities are undivided in front. The ear-shaped nasal roofs are seen to 
have curved down, round the external nostril ( e.n .), but the terminal halves of the 
trabecular cornua are interposed between the nasal capsules and the upper labials. 
These, however (figs. 4—6, u.l.), are seen to be breaking up into an inner and an 
outer pair : these will disappear ; the new labials and the newly formed premaxillaries 
have been removed. The inferior arches (Plate 3, figs. 5, 6, and Plate 9, fig. 1) are but 
little altered from what they were in the Second Stage. The drawing of the branchial 
arches was made from an outspread preparation which was figured from below; they 
are seen to turn obliquely backwards as they ascend to the sides of the basis cranii. 
Tooth-like processes of simple cartilage are interdigated with each other in the large 
clefts ; but the branchiae which grow on them, and which run inwards in rows, have 
been removed. 
But truly cartilaginous rays grow from the bars under these processes ; these are 
partly shown in Plate 9, fig. 3, br.r. 
The internal nostril (Plate 3, fig. 5 ; Plate 9, fig. 2, i.n.) is a curious oblong slit, 
diverging forwards, and protected by one or more papillae. 
A series of transversely vertical sections (Plate 3, figs. 7-13 ; and Plate 9, figs. 
4-6) show the solidity of this chondrocranium. 
The 1st section (Plate 3, fig. 7) is through the fore part of the nasal capsule, and 
catches the nasal roofs ( al.sp .) both above, and where they turn over to form the narial 
rim, or “alinasal” fold. They have coalesced with the intertrabecular wall, now the 
septum nasi ( s.n .). 
A branch of the orbito-nasal nerve (5 1 ) is seen emerging between the folds; the 
cavity between these folds externally is the outer nostril ; another space is seen 
below this and above the thick cornua trabeculae (c.tr.), which runs inwards to the 
inner nostril. At present the trabecular horns are not modified into the flat nasal 
floor, but are attached to the structure above by fibrous bands. 
The 2nd section (fig. 8) is close behind the nostril, and behind the second fold of 
cartilage ; on one side the wide part of the roof has been (obliquely) cut through ; the 
septum (s.n.) is still some distance from the cornua (c.tr.; the cross band is coloured, 
by mistake). 
The 3rd section (fig. 9) is similar; it is also oblique, and the hinder part of the 
capsule is partly severed. 
The 4 th section (fig. 10) is through the widest part of the nasal roof, where these 
