298 PROF. W. K. PARKER ON AGITHOGNATHOUS BIRDS. 
dition in the ordinary bird. That of the Fowl (Phil. Trans. 1869, plate Ixxxvi.) may 
be taken as a medium form; and a comparison of these together will reveal the ornithic 
shortcomings of the Hemipod. Seen from above (fig. 2) and from below (fig. 1) the 
whole labyrinth is large and tumid, the “‘alinasal” region (a/.n) occupying two thirds 
of the whole; and of the remainder much belongs, like the fore part, to the air-sifting 
region, that which is supplied merely by the nasal branches of the fifth nerve. 
A transversely vertical section through the first third of the long narial slits (fig. 3) 
shows the sharp fore end of the nasal septum (s. 7) and the “ale” given off by it, the 
alinasal roof. Near the septum a flap of cartilage is given off as a secondary growth, 
which turns its hollow face outwards and thickens below; this is the “‘alinasal turbinal” 
(a. th); it is very similar to what is seen in the Fowl (tom. cit. plate Ixxxvi. figs. 1 & 2, 
n. th). Letting the eye follow this series of sections it will be seen that the continuity 
of the various flaps has been destroyed by the first section, these divided cartilages being 
only apparently separate. If the whole labyrinth were separated out, and held with its 
fore end upwards, it would be seen to be two imperfectly closed tubes with three upper 
internal divisions, with the wnder surface split into four ribbons of cartilage, and having 
the base or the antorbital region closed in by a large sheet of cartilage, continuous with 
all but the infero-median flaps. The alinasal roof overlaps the wall; and at this part 
the wall is coped with a double outgrowth ; it is also coiled upon itself into three fourths 
of a cylinder, the inner edge coiling towards the turbinal (a. t): thus the wall becomes 
the floor. Over this section we have the thick root of the nasal portion of the pre- 
maxillaries (x.px); against it the dentary part (d.px), the apex of the maxillary (mz), 
and, below, the preepalatine spur (pr.pa). 
In the next section (fig. 4), within these bony bars we have a changed condition of 
the labyrinth; the septum has its basal, trabecular (¢7)-thickening (rudimentary “ sub- 
nasal lamine ”’), and the alinasal turbinal (a. tb) bent knee-like at its upper third and 
much expanded below. The upturned nasal floor has become separate from the down- 
turned nasal wall (x. f,7.w). In fig. 5 the fore part of the upper crus of the nasal (n) 
has been cut through, and the face has been severed where the skin of the forehead 
insheaths the skin of the beak, as we see in Ostriches and Tinamous. ‘This sheath is 
indicated by a dotted line in fig. 2. This section is through the double valley between 
the alinasal and aliseptal swellings (fig. 2, a/.n, al.s); and a branch of the nasal nerve 
(n. n) is seen piercing the thickness of the cartilage on each side of the septum, 
above. 
As the alinasal region overlaps the aliseptal below, it (with its turbinal) lies lower in 
this section; its outgrowth (a. tb) has become more angular, or genuflexed, towards the 
septum, and thicker and upcoiled below. The uptilted floor-flaps (n. f) are brought 
closer to the turbinals (a. ¢4) and to the septum, and much further from the wall, the 
section of which is now largely hammer-headed. This section (fig. 5) is a front view; 
and from the short aliseptal region (a/.s) we see a small ear-like process (outgrowth): 
