154 
MR. W. K. PARKER OX THE STRUCTURE AXD 
ossified cribriform plate ( cr.p .) ; behind, it gets to be a low thick w 7 all between the 
retral recesses of the nasal labyrinth. The septum (s.n.) is moderately thick from 
above, where it gives off the aliseptal folds ( al.sp.) to the thick base ; that part shows 
its thickness as a solid rod with a flat crest, from the low hind part to the equally 
low foremost part of the septum nasi proper. There, the septum is notched, below, 
and right and left of the notch the base of the alinasal folds gives off the recurrent 
cartilages ( rc.c .), large spatulate processes, tubular, proximally. The palatine process 
of the premaxillary (p.px.) is seen in its thick part, the rest, separate, for some time, 
as a front vomer, is given in outline in the figure, showing that it is inside the 
cartilaginous process. The vomer ( v .) is seen supporting the thick intertrabecular 
base of the partition, and under this we see the thick inner edge of the palatine 
plate of the maxillary ( mx .) ; these bones are united by suture, and now we see why 
the median vomer should have its keel double (see Plate 19, fig. 7, v.), for it articii- 
lates with two plates beneath it, and these bones, doubly sutured together, divide 
the right and left nasal passages from each other. This division ceases where this 
suture ceases, and this is half-way between the external and posterior nasal openings ; 
the latter open out behind the soft palate, which is strengthened right and left by 
the descending plates of the palatine and pterygoid bones (pa., pg.). The cranial 
cavity is roofed, and largely walled in, by the frontals, parietals, and interparietals 
(/, p., i.p.), the ossified remains of the endocranium lying low down in the floor of 
the skull. A round notch makes the orbitosphenoid bilobate; above the front lobe 
is a thin ragged tract lining the orbital plate of the frontal. Where these join 
there the 1st branch of the 5th nerve (V 1 ., ophthalmic) has entered (see also Plate 20, 
figs. 3 and 5, V 1 .), it is seen in this section riding over the outside of the cribriform 
plate to gain the nasal cavity. The longer, more regular hinder lobe of the orbito¬ 
sphenoid ( o.s .), passes inside the alisphenoid (al.s.); these parts lie so low down that 
neither the optic foramen, nor the foramen lacerum anterius, or sphenoidal fissure, 
are seen in this directly lateral view. The parietal (p.) passes so well down the 
skull wall that the squamosal—as in the Ostrich—is not seen, or scarcely at all; in 
this inner view the elegant curve of the lateral sinus (l.s.) is seen near the lower edge 
of the parietal. 
The alisphenoid (al.s.) is here visible as a strong concave shell of bone, hidden, 
however, in front, by the orbitosphenoid, and below by its own large basal beam ( b.s .); 
its thick ear-shaped hind part rides over the front of the cochlea, and the great 
oval foramen (V 3 .) is seen opposite its front third ; behind this part of the base the 
sella turcica is seen as a shallow concavity, and the posterior clinoid wall as a mere 
thickening of the base ; behind that thickening the postclinoid region dips downwards 
—a normal state for this and the rest of the base ( b.o.). 
A solid tract of cartilage still exists between all the three basicranial bones, the 
first of these ( p.s .) is high, but it is not an independent presphenoid ; it is only 
formed, as bone, by the juncture and ankylosis of the right and left orbitosphenoids. 
