DEVELOPMENT OE THE SKULL IN THE BATEACHIA. 
661 
and beneath it ; this is, however, merely a part of the pterygoid (pg.). The exoccipital 
(, e.o .), jagged and somewhat bowed, touches the quadrate ( q .) outside ; the prootic region 
of the bone (pro.) stretches to the far-off tympanic apparatus. Wedged in between the 
inner edges of the exoccipitals, we see an elegant, convex tongue of the parasphenoid 
( pa.s ., its old spike, Plate 61. fig. 3). From thence, by step-like notches and projections, 
this under slab gains its full breadth under the 5th nerves, and retains it until it gains 
the palatine “wings.” Then it runs, with a rounded margin, rapidly inwards, and ends 
in the front spike, which runs a little under the septum nasi ; this spike is split at its 
end. Under this part in Dactylethra there is a vomer (Plate 59. fig. 2, v), but, with 
Professor Huxley, I have failed to find one in Pip a. 
At this part there are remaining tracts of cartilage, and the ethmoidal belt runs 
forwards, much narrowed at the septum nasi ( s.n .), which is thick and rounded below 
and above ; but not alate, except in front. The extreme flattening of the face has caused 
the septum nasi to be a very low Avail, especially in front ; in this type the depressed 
form attains its greatest degree in age, in Dactylethra in the embryo. 
The small alee of the septum (Plate 61. fig. 5, s.n.l.) are gone, but now there can be 
seen an azygous process projecting into the front wall, namely, the prenasal ( p.n .); it 
is a rounded spike. The depressed septum becomes altogether almost rounded in front, 
and the alinasal folds ( al.n .), as seen from beneath, might be supposed to grow from 
the lo\A r er margin of the septum ; but they are its roof, but are a very short distance 
from the floor (compare Plate 60. fig. 6, al.n., with Plate 62. figs. 7, 8, al.n.). Now, 
instead of showing a convex margin, emarginated slightly in the middle, the front is 
trifid, the middle projection being the spiked prenasal, and the lateral parts thick, 
cupped lobes, whose concave front face is beset with strong subcutaneous fibres. From 
this part they throw out, and run gently into the top of the septum within, whilst 
without they run backwards and outwards, as long, terete, nearly straight “ cornua 
trabeculae, ” Avhich end beyond the inside of the prepalatine lobe (figs. 7, 8, c.tr., pr.pa.). 
The manner in which these trabecular bars have retained their primary recurrent 
form, and yet have merely become attenuated, is noteworthy (Plate 60. figs. 3, 5, 6, and 
Plate 62. figs. 7, 8, c.tr.). They now form nearly a right angle with each other, and 
one of less than 45° with the septum. 
Here there is no “ girdle-bone,” the chondrocranium dies out a little behind the 
ethmoidal region, and the roof and floor meet at the sides (fig. 4). But the unossified 
cartilage binding the ethmoid with the palatine is guarded by a strong wing of bone, 
the palatine {pa.), which grows out from the angle of the parasphenoid. A vessel passes 
through the bone where this is given off, and there is an appearance of its former distinct- 
ness; this wing, we saw, Avas developed separately. The ethmo- and prepalatine [etli., 
pr.pa.) regions are present, but the postpalatine bar has been absorbed : if the ethmo- 
palatine had been segmented off from the ethmoid, as in the Common Toad, then we 
should have had the free antorbital cartilage of Menobranchus and Proteus (Plate 54 
figs. 3, 4, e.pa. ; and Huxley, “ On Menobranchus ,” op. cit. plates xxix. & xxx. A.o.). 
