284 PEOF. W. K. PAEKER ON THE STEUCTUEE AND 



(PI. LXV. figs. 6-8, and PI. LXVII. 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 baud {u.o.al) and the lower {l.o.aJ) are 

 both seen in section at this p;irt also. 



The composition of the "anterior sphenoid" is well seen both in the side view 

 (PI. LXV. figs. 6-8) and in section (PI. LXVII. figs. 3, 4, i.tr, tr, o.s). Near the optic 

 nerves (fig. 5, ii) the three elements are well fused together, but further forward 

 (PI. LXVII. fig. 3) they are seen more distinctly. The trabeculse {tr) are very much 

 flattened against the sides of the large, median, crested bar {i.tr), but at its upper part 

 they thicken, and pass upwards, and a little outwards as the two orbito-sphenoidal 

 plates [o.s) ; these are convex inside, below, and outside, above, and form a trough for the 

 rhincncephala (C). Further forward (PI. LXVII. fig. 2) the orbito-sphenoids {o.s) are 

 separated from their root by a tract of membrane, and here the cornua trabeculee (see 

 fig. 1, c.tr) begin. Still further forward (PL LXV. figs. 6-8, and PI. LXVII. fig. 1, c, tr) 

 we see the thick wedge-like ends of the cornua {c.tr) ; beyond these the whole bar is 

 formed by the intertrabecula {i.tr) ; this section is through the low part of the wall, 

 under the olfactory lobes, and through the fore part of the orbito-sphenoids {o.s). The 

 ethmoidal, or true olfactory region of the nasal capsule, forms a pair of irregularly 

 pyriform pouches (PI. LXV. fig. 8, and PI. 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" {j^.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 (PI. LXVI. figs. 9, 8), 

 there is an ovitgrowth of the cartilage which encloses, for some extent, two lesser 

 spaces ; this is the " inferior turbinal " {i.th) in a very rudimentary condition ; and the 

 "upper turbinal" is represented by a fold above this (fig. 9, u.th). At this part and 

 in the next section (PI. LXVI. fig. 7) the floor of the nasal capsule is free from the 

 base of the septuiu {s.n) ; but in the next (fig. G), a short distance behind the outer 

 nostrils, the nasal floor and septum {n.f, s.n) are confluent, like the nasal roof {al.n) ; 

 the wall here is incomplete. 



When the nostrils are cut through (fig. 5) we see an upper cartilage or alinasal {al.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 (PI. LXV. fig. 8, and PI. LXVI. 

 figs. 1, 3, q) is very large, and is partly ossified. 



The otic process (PI. LXV. fig. 8, ot.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 



