DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 
191 
The reasons for the great unlikeness of this skull to that of the type are not, at 
first, easy to find; the same elements are there, having the same relations, and the 
degree of ossification of the chondrocranium, and the form and size and density of the 
investing bones is very similar in both. The occipital condyles (Plate 34, figs. 1-4, oc.c.) 
are reniform, and posterior; they are of the average size, and are separated by an 
emarginate space more than equal to their own diameter. The post-auditory part of 
the skull is here unusually developed—there is thus a “ neck ” to the skull, if there is 
none to the body. The “ parotic wings ” stretch out to an unusual distance, are of a 
good breadth to their end, and are then dilated along the tympanic roof. 
Considerable super- and basioccipital tracts of cartilage remain wedge-like between 
the lateral bones ; those of the same side are perfectly confluent. 
Each occipito-otic bony tract reaches forwards from the condyle to the middle of the 
space between the openings for the 2nd and 5th nerves (II. V.) ; laterally, the bone 
is arrested a little beyond the horizontal canal ( li.s.c .). 
There is, beyond the bone, an otic tract two-tliirds the extent of the ossified part; 
this extended tegmen narrows gently, and then dilates over the ear-drum, sending 
outwards and downwards a pedate process, to which the hinder crus of the annulus is 
attached behind the squamosal (figs. 1, 3, 4, t.ty., a.ty., sq.). This postero-external 
process is the familiar “ pterotic ridge” of the Fish, and is well seen, again, in Ran a 
pipiens, and Cystignathus ocellatus. 
I find no secondary fontanelles, but in that region there is a considerable tract of 
cartilage, triangular in shape, but with its apex truncated over the foramen 
magnum. From that edge to the ossified tegmen in front, the roof, ossified laterally, 
reaches nearly half way ; the fore half is occupied by the long oval main fontanelle 
(fo.) which is small, relatively, but almost entirely uncovered by the fronto-parietals 
IfP-)- 
This space is rendered narrow by the marginal tract of endocranial roof, which also 
extends a good way back in the ethmoidal region. The mid skull has the hourglass 
outline, for there is a considerable expansion of both the post- and antorbital parts of 
the roof, and the skull is rather narrow where the girdle-bone (eth.) ends. 
Where the superorbital ( s.ob.) cartilage overhangs the orbit, there the breadth, 
above, is doubled ; but this is only where this ear-shaped flap projects ; it lessens 
again and then is continued, roof-like, into the etlimo-palatine, as in Rappia bicolor 
(Plate 19, figs. 6, 7). 
Above (fig. 1), the girclle-bone keeps to the narrow width of the mid skull; but 
below (fig. 2), it ossifies all but the superorbital flap, and takes up all the cartilage 
belonging to it, both in the middle, and into the wings, right and left. 
In the fore skull the nasal region is evenly rounded in front, and does not form a 
square snout, with the nostrils (e.n.) wide apart, and at the edge, as in the Poly- 
pedatidae ; but these passages are superior, and not very wide apart; they are also 
large, and have a strong rim of uncovered cartilage. 
