DEVELOPMENT OF THE SKULL IN THE CROCODILIA. 295 
trabecule (ér), that thicken again at the coping of the wall, and then spring upwards 
and outwards to form the sides of the chamber for the fore brain(€!"). These diverging 
plates are the orbito-sphenoids (0.s); they narrow rapidly in front, and end in free 
points right and left of the olfactory lobes. The double chamber for these lobes (I) is 
cut across in the next section (fig. 3), and the vertical cartilage at this part is low, for 
there is a rounded gap in the wall here (Pl. LXIX. fig. 7), which is the perpendicular 
ethmoid (p.e). Right and left of this low part of wall the postero-inferior part of the 
olfactory capsule is cut across, and the hinder portion of the inferior turbinal (7.t) 
is shown. 
The next section (P]. LX XI. fig. 2) shows a higher septum (s.n), with the roof, walls, 
and floor of the nasal capsule; above, these cartilages are continuous, but, below, the 
upturned floor (n.f') is free; the curious tubular inferior turbinal (7.tb) is shown inside 
the bulging lower wall (n.w). 
Still further forwards (Pl. LX XI. fig. 1) the inferior turbinal is missed, and the 
sinuous walls are confluent with the septum both above and below. 
Close behind the ale nasi (Pl. LXX. fig. 13) the aliseptals (a/.s) form merely two 
round tubes, their dividing wall (s.n) being very low. But the narial valves, confluent 
with the olfactory capsule (Pl. LXX. figs. 2, 12, al.n), are thin coils of cartilage that 
belong to the “superficial” category, but early unite with the capsules; they lie over 
the prenasal spike (p.7). 
The partial vertical section (Pl. LXIX. fig. 7) is more than half the skull; in another 
figure (Pl. LXX. fig. 9) Jess than half is shown, and thus the nasal cavity of the right 
side is laid open. The transverse sections of the half-ripe Alligator (Pl. LXVI. 
figs. 5-10) help us here, as they show the ethmoidal region better. 
The long bulging part in front (Pl. LXX. fig. 9) is a mere fold of the wall, the 
next is the “upper turbinal” (w.tb); it, however, is formed merely by a special 
infolding of the aliethmoidal wall (Pl. LXVI. fig. 9, w.tb), which in that section seems 
to be a distinct cartilage, midway from side to side and from top to bottom, and having 
its convex face looking inwards. This fold lies in front of the upper part of the 
oblique “pars plana” (Pl. LXVI. fig. 10, p.p) (the lateral ethmeidal antorbital wall), 
whilst the inferior turbinal (7.40), which is a single tube behind (Pl. LX XI. figs. 2, 3), 
and an imperfect double tube further forwards, lies in a postero-inferior position 
(Pl. LXX. fig. 9). This part is very strong directly in front of the pars plana 
(Pl. LXXT. fig. 3, 7.46, and Pl. LXVI. fig. 10, p.p). 
b. Visceral Arches. 
The lower jaw is now as long as the rest of the skull (Pl. LXIX. fig. 9), the facet on 
the quadrate (g.c) being far back, and the angle of the lower jaw well developed. The 
quadrate (q) is very large; it occupies most of the side of the hind skull, and is as broad 
as that part of the basis cranii against which it abuts. 
VOL. XI.—PArRT 1x. No. 5.—October, 1883. 22 
