516 MR. W. K. PARKER ON THE STRUCTURE AND 
frontals ( f.), the true olfactory region, and the zygomatic process of the maxillary (z.m.) ; 
above this is the overlapping malar or jugal (j.) The thick frontal slabs send inwards 
and downwards an ‘orbital plate,” which clamps the ethmoidal wall; this wall is seen 
to be separated by a very large space from the fore top of the septum or perpendicular 
ethmoid (p.¢.), on each side of which lie the olfactory crura (1), and above these the 
fore part of the hemispheres (C 1‘). Here we see that the comb-like floor of the 
olfactory crura (Plate XXXIV. figs. 5, 6, c7.p.) is connected with, and is the top of, a 
system of cartilaginous ingrowths, the upper and middle turbinals (w.tb., m.tb.), which, 
by repeated splitting, as it were, or rather by a process of foliation, is becoming more 
complex day by day. ‘This section is through the most solid part of the vomer (v.), 
where it is squared below to rest upon the “ hard palate” over its median suture; here 
the palatines are cut through their fore part, where they are thin bony scoops, protecting 
the outside of the posterior nostril passage. Large tooth-pulps (¢.p.) are seen above and 
below, and the lower are in relation to a large dentary groove, the outer wall of which 
is very massive and the inner a smaller rod: both of these sections are parts of a con- 
tinuous dentary (d.); below the inner bony bar is the Meckelian rod (ms.), on each side 
of the base of the tongue (¢7.). 
The seventh section (Plate XXXII. fig. 5) is through the fore part of the eyeballs 
(c.) and the sphenoidal sinuses (sp.s.), the hinder part of the backwardly projected nasal 
labyrinth. At this point the septum, ‘ perpendicular ethmoid,” ends; and the pyriform 
section seen here, at the posterior end of the large ‘‘rhinencephalic fossie”’ (see Plate 
XXXIV. fig. 6, o/., crp.), is no longer indebted to the inturmed nasal roofs for its height, 
which is due to the upgrowth of the trabecular crests*. ‘This section is through the 
most solid part of the palatines (pa.), and their interior edge is thickening and growing 
inwards ready to form their part of the hard palate. Only the malar (j.) is seen on 
the side and below, and mesiad of it is the coronoid process of the lower jaw (c7.). 
MecKeEL’s cartilage (m/'.) is now high up the inside of the jaw, which is here mainly 
composed of solid hyaline cartilage, the inner cells of which are rapidly proliferating as 
“osteoblasts.” In the root of the tongue (fq.) the ceratohyals are seen articulating with 
the basi- and thyrohyals (¢.hy., b.hy., th.h.), now one piece of cartilage. 
The eighth section (Plate XXXII. fig. 6) is one of the most instructive; it severs the 
orbito-sphenoids (0.s.) where they pass into the presphenoidal trabecular wall close at 
the back of the sphenoidal sinuses (see also in third stage, Plate XXXII. fig. 1). ‘This 
is the high part immediately in front of the optic foramina (Plate XXXIV. figs. 1, 4, 
6,2). ‘Phe orbito-sphenoids are overlapped above by the frontals (f:), and the presphenoid 
has the end of the vomer (v.) beneath it. Here the thin ascending plate of the pterygoid, 
and its thick **hamular” part, is cut through; the osseous matter is scarcely continuous 
in the ascending part, and every now and then a separate ‘* mesopterygoid” is developed. 
* If the reader wishes to see an exact counterpart of this structure displayed in the second facial arch or 
“ palato-pterygoid,” it is ready at hand in the skull of the Pelican, where both the preoral arches form a long 
and solid “commissure,” from which a high crest ascends. 
