DEVELOPMENT OP THE SKULL IN THE BATRACHTA. 
209 
species; it becomes the nasal septum afterwards, the space between the cornua 
becoming filled up, and often a projecting prenasal spike grows forwards from it. 
Over the foramen magnum, the occipital ring is completed by the investing mass 
in the last, but not in this. On each side, save where the ear-balls are intruded, the 
trabeculae have developed a steep wall, with the rudiment of a roof (“tegmen cranii ’); 
the two rudiments run up to the short ethmoidal wall. 
Thus there is left one large fontanelle ( fo .), oblong for the most part, semicircular 
behind, and more pointed in front in the last, and unfinished behind in this. The 
nasal capsules are not cartilaginous yet; the eye-balls have been removed; the ear- 
capsules (fig. 9, au.) are fused partially with the chondrocranium ; they are losing the 
simple ovoidal form, and taking a shape in which the curves and swellings of the 
canals (fig. 9, a.s.c., h.s.c., jo.s.c.) are seen. 
Below (fig. 10, fo.), there has been dehiscence of the fruit-like capsule, and the 
spindle-shaped space is the new fenestra ovalis ; its occluding (indifferent) tissue 
will be the stapes. 
On each side of the orbits, in front, an oblique squarish lobe of cartilage grows out 
of the cranial wall; these two processes are the “wings” of the ethmoid ( al.e .), and 
answer to the “ antorbital” of Birds and the “pars plana” of Mammals; close to these 
we see the rudiment of the post-palatine ( pt.pci .). Under these a band, passes 
outwards—the pterygo-palatine, and in front of the ear-capsules a similar, but longer, 
band passes outwards to join (or become) the large facial bar or suspensorium 
(sj).) ; this is two-thirds the size of the whole basis cranii. 
This outer plate runs forwards, curving round the inner nostril ( i.n .), and ends 
opposite the middle of the cornu trabeculae ( o.tr.) ; each band ends in an oblong, 
emarginate, obliquely inturned condyle—the quadrate condyle (q.). 
The hinder conjugating bar curves and twists round the front of the ear-sac; its 
root is the pedicle ; its rounded elbow the “ otic process.” 
Half the upper edge of the side plate is occupied by a large, sessile, decurrent leaf 
of cartilage, which turns inwards and just touches the ethmoidal wing ( or.p ., al.e.). 
I cannot find that it has, as yet, become fused with it; under it, the conjugational 
band is the pterygo-palatine. 
Here the basal plate shows signs of sub-division ; the apices of the trabeculae (tr.), 
from which the notochord (nc.) is retreating, are obliquely marked off from the newer 
investing mass behind, which has not yet finished the occipital condyles nor even the 
occipital ring. Hence the fontanelle (fo.) reaches from the foramen magnum to the 
ethmoidal region, where the intertrabecular tract is not evidently raised at the 
mid-line. 
The auditory capsules (au.) are longer than in the last, and the interorbital region 
of the skull is narrower in the middle; the cornua trabeculae ( c.tr.) are not so 
pointed externally, nor so definitely decurved. 
The part taken by the intertrabecula in the mid skull is not half as great as in the 
MDCCCLXXXI. 2 E 
