798 
ME. W. Iv. PAEKEE ON THE STEIJCTUEE AND 
stapedial,” or middle process ; a fenestra (f.) separates this oblique plate from the 
proximal part of the extrastapedial * 
This stage will be further illustrated by sections (principally transversely vertical, 
more highly magnified) (Plate LXXXVI.) ; these, for the most part, relate to the 
olfactory labyrinth, and complete what I partially described in the fourth stage (Plate 
LXXXIII.). 
A view of the nasal labyrinth from within (fig. 10) and from above (fig. 11) will help 
to explain the larger sectional figures, which are magnified 4 times ; the inner and upper 
views are one-half larger than the objects. 
A section through the most swollen part of the alinasal folds (Plate LXXXVI. fig. 
1) cuts through the thickest part of the nasal processes of the premaxillary (n.,px.) and 
through its sharp dentary edge (d.px.). The styloid end of the maxillary (ms.) and of 
the palatine (pa.) are seen below the palatine plate of the premaxillary (p.px.). Here 
the septum nasi ( s.n .) is deep and thin, thicker towards the top, where it spreads into 
the arched alinasal folds (al.n.) ; these end free opposite the middle of the septum. 
Halfway from their origin the alinasals give rise to the nasal turbinal (n.t.b.) ; the 
whole of this is seen in fig. 10, on its inner aspect. It first bends directly inwards, then 
passes downwards nearly parallel with the septum, and then curls outwards and upwards 
to its free edge. 
But the nasal passage (n.p.) is rendered doubly valvular by a forward constriction of 
the cartilaginous nasal wall (n.w.), which (see fig. 11, al.s., n.w .) is continued far forwards 
beyond the root of the inferior turbinal, or, properly speaking, beyond the aliseptal plate. 
The section of this wall of the nose is here elegantly S-shaped ; it ends as a thick free 
edge near the roof, and as a thin free edge below; and there it is only separated from 
the base of the septum by the nasal nerve (n.n.). 
A little further backwards (Plate LXXXVI. figs. 2 & 11) the section passes through 
the alinasal (al.n.) where it is dying out behind ; here the nasal wall (n.w.) is cut through 
obliquely, and it is seen to end (below) much further from the septum. Here the nasal 
turbinal (n.tb.) is further from the mid line, and diverges outwards to a greater extent 
below ; this section shows the thickest part of the dentary edge of the premaxillary (d.px.). 
The next section (fig. 3) shows a front view of the inferior turbinals (i.tb.) ; these are 
also seen from the inside in fig. 10 ; they are coiled outgrowths of the aliseptal plate 
(al.s.), which is seen to divide halfway down, giving rise to the nasal wall (n.w.). This 
section happily passes through the very important bridge for the nasal nerve (n.n.), 
* See also Professor Huxley’s figures and descriptions, Proc. Zool. Soc. 1869, p. 398, figs. 5, A, B ; and p. 406, 
fig. 8, C. These figures will be best understood by reference to wbat is seen in tbe Ouaran Lizard ( Psammosaurus ), 
where tbe bridge connecting tbe “extra-” and “suprastapedial” bars and tbe “fenestra” are absent: here tbe 
tensor muscle, which arises behind tbe “ parotic bar,” and above and behind tbe head of tbe quadrate, sends its 
tendon between tbe forks of tbe “ suprastapedial ” — which is bilobate as in tbe Eowl — to be inserted into tbe 
upper edge of tbe extrastapedial at its free end: tbe “infrastapedial” is shorter than in tbe Eowl. I here use 
these terms provisionally, as my researches into tbe structure of these parts in the Batrachia have satisfied me 
that these prefixes should have been set before tbe term “ incudal.” 
