DEVELOPMENT OE THE SKULL IN THE BATRACHIA. 
629 
it will be filled in with cartilage — two tubes, like drain-pipes, allowing the exit of the 
olfactory crura (1). Massive as the trabeculae seem, as seen from above (fig. 4), from 
below (fig. 5), the interorbital margins (the eye, e, is seen to be indicated by a dotted 
outline) are merely thin, arched leaves of cartilage. 
Besides the straight “ arms ” (ppg.) which pass from the trabeculae to the quadrate 
condyles, another pair of curved arms, in front of these, unite the trabeculae with the 
distal part of the mandibular piers. These are the middle pair of transverse arms, or 
wings, growing from the front of this remarkable chondrocranium. In our native 
Batrachia the trabecular cornua (in the tongued types generally) are gently bowed out- 
wards (Plate 55. fig. 4, c.tr.) ; but in the “ Aglossa,” as in the Sauropsida and Mammalia, 
they turn backwards, or, rather, they retain the retral condition they acquired during 
the “ mesocephalic flexure.” 
Here, breaking free from the closely cleaving labial band ( u.l .), on each side, the 
“ cornu trabeculae ” ( c.tr .) is seen to run outwards and then backwards, shutting in the 
nasal passage ( i.n .), and losing its free end in the pterygo-palatine plate behind 
{ppg-), and in the quadrate in front ( q .). In this case the end of the cornu and the 
tooth-like process at its side which gave attachment to the “ prenarial ligament ” in the 
Toad (Plate 55. fig. 4:,p.n.l.) have grown into one flat plate, and their cartilaginous sub- 
stance has converted the ligament into a lamina (figs. 4 & 5 ,p.n.l.). Inside the condyle 
of the quadrate (g.) a toothed process is seen ; this is for the insertion of the quadrate 
end of the ligament now chondrified. In Pseudis paradoxa the cartilaginous process 
from the quadrate runs across to the trabecula, but does not coalesce with it ; in Eana 
pipiens the tooth is short, and from it the ligament passes to the even outer edge ot 
the trabecula; in Bufo vulgaris (Plate 55. fig. 4, tr.,p.n.l.) the tooth is on the trabecula, 
and not on the quadrate. 
3. The mandibular arch. 
The origin of the next arch is best seen from below (fig. 5,pd.); and although the 
dorsal end of the mandibular arch is not equal to the trabecula, it is of great width. 
It runs winding itself in between the basis cranii and ear-capsnle. On the whole, it lies, 
from end to end, on a lower plane than the inner arch ; but even the quadrate, with its 
condyle on the antero-superior face, looks, in a bird’s-eye view, to be nearly as high as 
the upper labial and cornu trabeculae. 
We miss here that elbow of the pedicle seen in the sigmoid mandibular pier of the 
ordinary Tadpole (Plate 55. fig. 4) ; for the bar runs forwards and outwards, almost 
straight, to the orbitar process (fig. 4, or.p.) ; between that and the pedicle it has lessened 
in width. It attains its greatest width where the elegant orbitar process grows 
out. This process, like a sessile leaf, is not sensibly decurrent along the outer edge of 
the bar, yet its base is broad. Quite normally, the edge of the base of that process is 
concave, for beneath it (fig. 5, hy.c.) is the hyoidean facet, a crescentic scooping away of 
the substance of the bar. The bar is also scooped into another elegant hollow on its 
upper face at the end of the fixed part (q.). This convexo-concave facet is for the arti- 
