DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 
217 
of the antorbital bar takes place. The passages for tlie emerging nasal nerves are 
large, and lie on each side the square end of the far-extended ethmoid bone. They 
lie close behind the facial edge of the snout, and on their outside the pro-rhinals 
spring ; these are hidden by the premaxillaries, and are small. 
The sinuously-transverse snout overhangs this part obliquely ; the large external 
nostrils (e.n.) are in its sides, and are wide apart. The roof is feebly developed, but 
there is a well-formed pouch in the outer wall (figs. 1, 3, al.n., n.wT) ; in front of the 
nostril there is the large, oval, hollow second labial (u.T.); below it, inside the vertical 
nasal process of the premaxillary, the small, lenticular first labial (Plate 36, fig. 8, u.l 1 .). 
The palato-suspensorial cartilage is broken up into an adze-shaped ethmo-palatine, to 
the under surface of which the large falcate bone (pa.) is grafted ; whilst the suspen- 
sorium has a remnant of the pterygoid cartilage. 
The pedicle (pd.) is completely covered with bone, and its original apex has been lost 
in the ossifying cartilage close to the foramen ovale (V.). The cartilage breaks out from 
beneath the inner foot-like ray of the pterygoid (pg.), which has used up nearly all 
the front process that was originally continuous with the palatine cartilage (fig. 3, sp.). 
The suspensorium, itself, or quadrate region (q.), is very large, and remains unossified 
(figs. 2, 3). The condyle (q.c.) is oblique, and reniform ; and above it a shell-like 
flange of cartilage grows from its outer edge, clamping the hind margin of the long, 
descending bar of the squamosal ; this crest of cartilage is the old “ orbital’ process,” 
(fig. 3, or.p .) once under the antorbital, and now beneath the auditory, region. The 
stylo-hyal ( st.h .), carried back by the retreating suspensorium, but loosened from it, now 
has grown inwards, and caught hold of the tympanic floor of the vestibule (vb.) on which 
it is grafted. The front fork of the pterygoid bone (pg ) is a sharp style ; the hind 
bar is flat and vertical, binding the inner face of the quadrate ; between it and the 
large inner process (pd.) the Eustachian opening ( eu.) is seen to be large and circular. 
The articular region of the mandible (fig. 3) is hollowed out for the reniform 
trochlea of the quadrate (mk.) ; the cartilage is but little ossified by the articulare 
(ar.) ; the dentary (d.) is three-fifths the length of the ramus, and the mento-Meckelian 
(m.mk.) is of the normal size. The “ annulus ” (a.ty.) is large and perfect. 
The stapes (Plate 36, fig. 10, st.) is large and sub-oval ; it has an ear-shaped boss 
and some ossified cells; the inter-stapedial (i.st.) is oval and semi-osseous; it fits in 
like a wedge between the stapes and the next segment—the medio-stapedial shaft 
(m.st.). This part is pistol-shaped and large, it is especially thick, proximally ; joined 
on to it is the broadly-spatulate extra-stapedial (e.st.) with its fastened, strap-like 
process, the supra-stapedial (s.st.). 
The hyo-branchial structures (Plate 37, fig. 4) show that this lesser Neotropical 
Toad is approaching its small, “ glandless ” relatives of the same region, viz. : the 
“ Phryniscidse ” (Plates 40 and 41), which of all the Anura have the narrowest basal 
plate. I shall return to this comparison when I come to that genus. Here the 
* The lower u.l 2 . in fig. 2 should be n.w. 
2 F 
MDCCCLXXXI. 
