DEVELOPMENT OE THE SKULL IN THE BATRACHIA. 
659 
for the external nostril ( e.n .). Their round hinder edge is overlapped by the frontals, and 
their outer edge, in turn, overlaps the marginal bones externally and the ethmo-palatine 
bar (a little) behind. The large anterior sinuous narial notch is of great interest, as it 
makes the nasal bone of Pipa the prototype of that of a “ Carinate ” bird. The hinder 
of the marginal bones is a “preorbital” (Plate 61. figs. 2, 3, 4,^>.o.). It is not common 
in the Batrachia, but exists in Bana pipiens, and is well seen in Clarias capensis, a 
“ Siluroid ” fish ; here it is a thin bony scale, broadest behind, and having its thin inner 
edge deficient at places, forming teeth and hooks ; it helps to set bounds to the outer 
nostril. But the outside of the nostril (e.n.) is finished by a much smaller bone, the 
septo-maxillary ( s.mx .) ; it is set on the narrow end of the last, and is a sigmoid rod, 
bending first outwards and then inwards ; it ends in the front wall of the face in a blunt 
point ; this is the bony element of the curious nostril-valve. Below, the chondro cranial 
framework, in front (Plate 60. fig. 6), is strengthened by flat bony splints, the premaxil- 
laries and maxillaries (Plate 61. fig. 3, px., mx.) ; these are extremely embryonic and 
simple, for they only lie on the under face of the chondrocranium. Their free surface is 
gently rounded ; altogether they are thin and fibrous. The premaxillaries do not meet, 
yet, beneath the septum nasi, the form of each is an arcuate lobe, rounded within and 
sharp externally and behind; the outer edge has a round notch. 
The convex edge of the premaxillary is overlapped by the projecting end of the maxil- 
lary. This latter bone is falcate, with distant serrations on its sharp inner edge, and it 
ends behind as a sharp point, a little in front of a similar point, the fore end of the 
pterygoid. The pterygo-palatine cartilage bows out beyond these styles. Below 
(figs. 3 & 7 , pa.), the palatine style looks like a prop standing out between the para- 
sphenoid and the maxillary. 
The squamosals and the dentaries are the other investing bones. These have already 
been described ; there is no quadrato-jugal. 
The peculiar valves that protect the external nostrils are strengthened by cartilages 
within ; these are the “ upper labials,” now at their highest development. They are 
best seen from above (Plate 61. figs. 4 & 5 ; Plate 60. fig. 8, a section). The most massive 
of these (u.l a .) lies in the floor of the outer nostril ; it is pedate and flattish in front and 
bulbous behind ; the pedate expansion is largest externally. To the hinder bulbous 
part of this a second (u.P.) is articulated ; it is larger and thinner than the first. Where 
it articulates with the bulb by a concave margin, there it is squared on its opposite edge. 
From thence it runs outwards as a narrow, somewhat decurved band, which ends on the 
upper lip in a point, from which point a sharp hook runs inwards towards the first carti- 
lage. That is its outer end ; its inner end runs forward from the squared part, and 
dilates into a bilobate process that lies against the fore front of the septum nasi. Also 
on the subnasal laminse (s.n.l.) of the septum, where the trabeculae retain somewhat of 
their primordial flatness, there is a small, seed-shaped, third labial (u.l 0 .). Others than 
these I have not been able to find ; and these are fullest at the ripeness of the embryo, 
and then waste away by the time the Pipa is adult. 
4 y 2 
