DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 
181 
cranium in the “ Hylide ” is very characteristic; the stoutness of the larval skull 
gives no promise of the delicacy of structure shown in that of the adult. The skull 
at this stage corresponds very closely with that already described (Plate 30, figs. 6, 7) 
in the larva of a narrow-backed Tree-frog, viz. : Acris Pickeringii, a type not very far 
removed from the Oxydactyle “ Cystignathidse.” 
Up to the quadrate condyles (Plate 30, figs. 8, 9, q.) this is a rather square skull, 
but those hinges are further back than in any other kind known to me, reaching very 
little in front of the inner nostrils (i.n.) ; the cornua trabeculae, on the other hand, are 
so long as to make this really one of the longest of the Tadpoles’ skulls. 
In this skull the occipital arch is fully formed, and the notochord (nc.) has become 
very small; the condyles ( oc.c .) are perfect, and the tegmen cranii (fig. 8.) runs forwards 
as far as to the exit of the 5th nerve (V.). 
The large auditory capsules (au.) reach as far back, nearly, as the condyles; and 
their breadth is about as great as that of the intermediate basal plate. Externally, 
they reach nearly as far outwards as the suspensoria, for the tegmen tympani ( t.ty .) is 
already developed outside the horizontal canal ( li.s.c .). In front of the tegminal lobe 
there is a smaller lobule of cartilage; here the formation of this tissue is spreading 
over the opercular region of the 1st cleft; that lobule will be detached as the 
“spiracular cartilage” (, sp.c .). The fenestra ovalis (fig. 9) is formed, but the stapes 
(st.) is not chondrified. The interorbital region is one-fourth longer than the inter- 
auditory ; apparently the basal plate is of the same width, but the wings that form the 
auditory floor are not evident at first. From the point where the notochord was, to the 
projection on each side in front of the inner nostrils {i.n.), the trabecula) (tr.) are very 
uniform in width. There is an evident tract of newer cartilage (intertrabecular) from 
the point where the notochord ended, to the most contracted part of the trabeculm 
(fig. 9, tr.) : and above (fig. 8) this median tract has risen in front of the great fon- 
tanelle (fo.) as a rudimentary “mesethmoid” (p.e.). 
The fontanelle (Jo.) is large and elegantly lanceolate; the walls are well developed, 
and the roof (tr.) exists as a marginal band from the hinder complete roof (above nc.) 
to the up-growing middle wall ( p.e .). 
The wings of the ethmoid (each side of p.e.) are very indeterminate at present, and 
there is no distinct elevation outside them forming a rudimentary post-palatine. The 
inner nostrils (i.n.) are wide apart—unusually so—and small; in front of them the 
trabeculae are lobate to catch the pre-narial ligament, which arises from the blunt pre¬ 
palatine spur (inside q.). The cornua (c.tr.) are very long, narrow, and sinuous; they 
each send out a sharp external angle. The suspensoria have a thick pedicle (fig. 9 ,pd.), 
a thick curved otic process (fig. 8, otp.) and a short and broad orbitar process ( or.p.). 
The ethmo-palatine band (p.pg. ) is wider than long, the suspensorium coming 
very close to the trabecula; beyond this band the quadrate region (q.) is one-third 
wider than it is long, and the pre-palatine spur is very blunt. The mandibles (mk.) 
are extremely large and massive; the angular process is short and thick. The lower 
