DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 
195 
the auditory capsules, is continuous bone. Above, the cartilage persists for a small 
extent behind the fontanelle ; and, outside, the tegmen (t.ty.) is unossified. This soft 
tract is less than half the huge parotic wing, which extends beyond the horizontal 
canal (. h.s.c.). The three canals ( ci.s.c., h.s.c., p.s.c.) are small, but well marked ; 
beyond them the parotic projects as far again from the middle of the skull, and 
increases in width so as to be equal in size to the hind skull. In this kind the 
tegmen is rounded behind, and sends outwards, and downwards, a, projection in front, 
like the process that appears, behind, in Pelodryas. The whole outline of this two¬ 
winged hind skull is strongly sinuous, behind and before. The fontanelle (fo.) is 
heart-shaped, and is open over a third of the cavity of the skull ; it has a considerable 
tegminal margin. The narrowing in front of the temporal region is followed by a 
continual increase in width up to the superorbital cartilages ; and the skull (figs. 7-9) 
is both wider and shallower than in Pelodryas. 
The prootic bony tract runs round the foramen ovale ( pr.o ., Y.) up to the optic 
fenestra (II.); this latter opening is very large, as in some of the lesser Australian 
Idylce. A definite margin of cartilage (o.s.) bounds that fenestra in front, and then 
the girdle-bone (eth.) begins; it does reach the edge of the skull-wall, but does not 
occupy the all proper ethmoidal territory either in front, or antero-laterally. Here, as 
in Pelodryas, the ethmoidal region has two pairs of wings, the front pair confluent 
with the nasal region, whilst the hind pair are the projecting superorbital eaves. 
Here we have, as in Alytes, a separate, but smaller, superorbital cartilage (s.ob 1 .) ; 
it is finger-shaped, and turns downwards (fig. 3). The outspread cranial roof runs 
forwards into the nasal roof, and outwards on to the ethmo-palatine bars ( e.pa .). The 
distance from the foramina ovalia (Y.) to the front of the girdle-bone is equalled by the 
cartilage in front of that bone. The trabecular floor (s.n.l.) is immense; the nasal roof 
is only a little smaller; but, from the narrowing of the snout, which is transverse, in 
front, the outer nostrils are only half as wide apart as the inner. These latter (i.n.) are 
as large as the Eustachian openings of Pelodryas; they are oval, and their direction is 
inwards and forwards. The openings for the nasal nerves (inside s.n.l.) are large, far 
backwards, and wide apart, the floor is narrowed between them and the inner nostrils ; 
it is definitely notched at its sudden narrowing. 
The pro-rhinals ( p.rh .) are well-developed, near together, and out-turned; but the 
angles of the nasal floor converge in a remarkable manner in front; they are bilobate 
(c.tr., s.n.l.), and the hinder lobes diverge. The septum nasi (s.n.) is moderately thick, 
and is rounded off in front, so that there is no definite rostrum. The nasal roof and 
wall (fig. 9, al.n.) are well developed, especially the latter, which is an unusually large, 
wide, ear-shaped band. The labials (u.l l .uP.) are normal, and are larger than in 
Pelodryas. 
The palato-suspensorial arch diverges outwards to the postorbital region ; it is of 
great breadth throughout, and so are the bones applied to it; these, however, do not 
greatly affect the cartilaginous pith, which is nowhere obliterated. 
2 C 2 
