800 
ME. W. Iv. PAEKEE ON THE STEUCTTTEE AND 
A section through the fore part of the ethmoid (fig. 8, eth.,j>.e.), showing the sharp 
front edge of the perpendicular plate, gives a front view of the back wall of the nasal 
labyrinth : in this figure the outer bones are not given. 
This large back wall is the prefrontal plate, and much of it answers to the pars plana 
of anthropotomy. In this section the upper turbinal ( u.tb .) is seen to be, at its posterior 
end, an outgrowth from the posterior wall of the nasal labyrinth ; so that, although it 
is a mere swelling bag at its middle (figs. 7 & 10), yet it is a fixed outgrowth from the 
walls of the labyrinth at both ends. If the inner view of the left half of the cartilagi- 
nous labyrinth (fig. 10) be compared with the front view of its back wall, from which the 
turbinals have been cut away, leaving their roots, it will be seen that the inferior tur- 
binal (i.tb.) is an outgrowth of the pars plana, posteriorly, and that its root there is 
continuous with that of the upper turbinal {u.tb.). Here there is no differentiation of 
a middle turbinal, except a small lamina ( m.tb .) which grows upwards from the inner 
side of the root of the lower turbinal ; in this respect the Gallinse, like most other birds, 
are inferior to the Struthionidse (First Paper, Plates vm.-xiv. m.t.b.), which show a 
rudiment of those outgrowths which are so largely' developed from the front face of the 
Mammalian “ pars plana.” 
In this section the nasal nerves (fig. 8, n.n .) are seen entering the labyrinth close 
below the roots of the cartilaginous aliethmoid {al.e.) ; whilst the smaller olfactory crura 
(1) enter between the widening part of the perpendicular ethmoid (jp.e.) and the convex 
margin of the crescentic root of the upper turbinal ( u.tb .), close above a little horn-like 
process growing from the supero-internal angle of the pars plana (_p.jp.). 
The rostrum of the basisphenoid ( r.b.s .) reaches so far forwards as to underlie the 
cultrate fore edge of the perpendicular ethmoid. 
A section (fig. 9) made through the most solid part of the ethmoid displays much 
that is instructive. The nasal processes of the premaxillaries (n.px.) are reduced to 
delicate flat styles; the nasals (n.) are still of considerable breadth, and overlie the 
wedge-like fore ends of the frontals (/.). The lacrymals {l.) send out here their broad 
superorbital plate, and grow downwards into an imperforate styloid anteorbital process ; 
on the inside of each lacrymal, in the recess between this bone and the nasal labyrinth, 
is seen the pyriform nasal gland ( n.g .). The huge perpendicular ethmoid (jp.e.) has 
here grown out largely into the aliethmoidal wings (al.e.), only leaving the very edge soft, 
from which a narrow isthmus grows downwards, outside the nasal nerve, connecting the 
broad top of the ethmoid with the supero-external angle of the anteorbital (prefrontal) 
plate. This flat, smooth, subconvex sheet of cartilage, the anteorbital, is oblong in 
general form, and has sinuous edges, the inner of which, although quite distinct from, 
yet lies close to the perpendicular plate. In the Fowl, even to old age, it is soft; but 
in many birds it is ossified, and is extremely apt to form bony adhesion with the per- 
pendicular plate. Below the anteorbitals the median plate becomes suddenly thin, 
swelling a little below, where it lies in the grooved rostrum (r.b.s.). 
In this section the thick outer and the sharp orbital parts of the palatines are seen ; 
