DEVELOPMENT OF THE SKULL IN THE 13ATRACHIA. 
Fifth Stage. — 1 (continued). Advanced Tadpoles of liana clamata (C), all limbs free; 
3^ inches long; tail, lyh inch long. 
If this (Plate 4, figs. 5-7) be compared with the Third Stage, the second larva of R. 
clamata, (figs. 1, 2) we shall see what approach is made towards the adult condition. 
The angular and almost oblong form of the whole structure is changed for a short oval; 
and the facial outworks are only half the real and relative width they possessed then. 
The auditory capsules are of greater extent, antero-posteriorly, the ex-occipitals ( e.o.) 
are larger, and the prootics ( pr.o .) have begun on the outside of the foramen ovale (V.). 
The form of the cranial cavity is narrower in front compared with the hind part, and 
the whole ethmo-nasal structure in front of the cavity is shorter, and much modified. 
Besides the septum nasi (< s.n.) the whole intertrabecular space is filled in in front; 
the <c cornua ” ( c.tr .) are only half as long, and are bifurcated, the outer fork has become 
the large arcuate angle of the “ subnasal lamina,” and the lesser (inner) fork is the 
hooked “ pro-rhinal ” (p.rh.) which lies inside the premaxillary ( px .), and curves 
backwards. 
The internal nares (i.n.) are now relatively much forwarder, are more elongated, 
and are placed quite transversely. 
The front wall of the nose is completed by fusion of the roof with the septum, and 
a growth of cartilage over it to the lower face of the labyrinth. The external nostrils 
( e.n.) are now also much nearer the front of the head, for the large labial plate has 
been absorbed and two pairs of small new plates that form the outworks of the nose 
have appeared. The inner pair ( u.l h) are applied to the inner face of the apex of each 
nasal process of the premaxillaries (px.); whilst the outer forms a shell-like valve 
to the external margin of the nostril (u.l 2 ., e.n.). 
The nasal bones (a film over na.) have appeared like small shells. The condyle of the 
quadrate (cp) is now opposite the hinder margin of the nasal roof, instead of the front 
margin ; it is twice as far from the roof, and its condyle looks obliquely outwards, and 
not inwards as before. The elongated and oblique palato-pterygoid bar now has the 
“ post-palatine rudiment ” as a ridge looking outwards and backwards, and the “ pre¬ 
palatine spur ” (pr.pa.) nearly touches the tip of the horn of the trabecula (angle of 
“sub-nasal lamina,” c.tr.). 
Tracing the narrowing and retreating suspensorium backwards, we see that the 
orbitar process, and condyle for the hyoid (or.p., hy.fi) are now opposite, not the 
antorbital region, but the middle of the subocular fenestra. 
Further back, the true “otic process” is small and rounded (fig. 5, ot.p.), and the 
spiracular cartilage, now detached from the tegmen tympani, applies itself to the side 
of the otic process (sp.c,, ot.p., l.ty.); it is now a trifoliate rudiment of the “annulus.” 
Below (fig. 6, pd.), the pedicle is forming its condyle, to glide upon a pre-auditory 
process of the basal plate, whilst the dorsal part of the pier is now an attenuated 
thread of cartilage running under the prootic to the front of the foramen ovale (V.). 
MDCCCLXXXI. F 
