284 PROF. W. K. PARKER ON THE STRUCTURE AND 
(Pl. LXV. figs. 6-8, and Pl. LX VII. fig. 5) the three prochordal bands have united 
to form a rounded bar with a moderate crest; this is the part where the basi- and 
presphenoids pass into each other; the upper band (w.o.a/) and the lower (/.0.a/) are 
both seen in section at this part also. 
The composition of the “anterior sphenoid” is well seen both in the side view 
(Pl. LXV. figs. 6-8) and in section (Pl. LXVII. figs. 3, 4, 7.tr, tr, 0.8). Near the optic 
nerves (fig. 5, 11) the three elements are well fused together, but further forward 
(Pl. LXVII. fig. 3) they are seen more distinctly. The trabecule (tr) are very much 
flattened against the sides of the large, median, crested bar (7.7), but at its upper part 
they thicken, and pass upwards, and a little outwards as the two orbito-sphenoidal 
plates (0.8); these are convex inside, below, and outside, above, and form a trough for the 
rhinencephala (C”). Further forward (Pl. LX VII. fig. 2) the orbito-sphenoids (0.s) are 
separated from their root by a tract of membrane, and here the cornua trabecule (see 
fig. 1, ctr) begin. Still further forward (Pl. LXV. figs. 6-8, and Pl. LX VII. fig. 1, ¢, 7) 
we see the thick wedge-like ends of the cornua (c¢.tr); beyond these the whole bar is 
formed by the intertrabecula (7.tr); this section is through the low part of the wall, 
under the olfactory lobes, and through the fore part of the orbito-sphenoids (0.s). The 
ethmoidal, or true olfactory region of the nasal capsule, forms a pair of irregularly 
pyriform pouches (Pl. LXV. fig. 8, and Pl. LXVI. figs. 9, 10, al, e), which are covered 
only by membrane for some distance. I find no “ ethmo-palatine” rudiment upon the 
“pars plana” (p.p), or antorbital face of these pouches. Inside, both in the front of the 
ethmoidal region and in the back of the proper alinasal territory (Pl. LX VI. figs. 9, 8), 
there is an outgrowth of the cartilage which encloses, for some extent, two lesser 
spaces; this is the “inferior turbinal” (7.td) in a very rudimentary condition ; and the 
‘upper turbinal” is represented by a fold above this (fig. 9, w.tb). At this part and 
in the next section (Pl. LXVI. fig. 7) the floor of the nasal capsule is free from the 
base of the septum (s.z); but in the next (fig. 6), a short distance behind the outer 
nostrils, the nasal floor and septum (n.f, s.2) are confluent, like the nasal roof (a/.n); 
the wall here is incomplete. 
When the nostrils are cut through (fig. 5) we see an upper cartilage or alinasal (a/.n) 
confluent with the swelling floor in front of the septum ; here the prenasal rostrum (p.n) 
or sagittiform end of the intertrabecula is cut across; it is nearly circular in section. 
b. Visceral Arches. 
The quadrate or upper part of the first visceral arch (Pl. LXV. fig. 8, and Pl. LXVI. 
figs. 1, 3, g) is very large, and is partly ossified. 
The otic process (Pl. LXV. fig. 8, of.p) has a rounded anterior knob, and a falcate 
hinder lobe which overhangs the first cleft. The anterior limb or “ orbital process” 
has (in this species) scarcely any ascending process, but the pterygoid cartilage (pg.c) is 
long and pointed. The body is scooped behind, and a large semicircular notch is formed 
