298 PKOF. W. K, PAEKEK ON ^GITHOGNATHOUS BIEDS. 



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 (al.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. n) and the " alee " given off by it, the 

 alinasal roof. Near the septum a flap of cartilage is given oif 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 (torn. cif. plate Ixxxvi. figs. 1 & 2, 

 n. tb). 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 under 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 cojjed with a double outgrowth ; it is also coiled upon itself into three fourths 

 of a cylinder, the inner edge coiling towards the turbinal («. tb): thus the tvall becomes 

 the _^oor- Over this section we have the thick root of the nasal portion of the prse- 

 maxillaries ()!.ji)x); against it the dentary part {d.px), the apex of the maxillary {mx), 

 and, below, the prsepalatine spur (jjr.jM). 



In the next section (fig. 4), within these bony bars we have a changed condition of 

 the labyrinth ; the septum has its basal, trabecular (tr) thickening (rudimentary " sub- 

 nasal laminffi "), and the alinasal turbinal (a. tb) bent knee-like at its upper third and 

 much expanded below. The upturned nasal floor has become separate fi'om the down- 

 turned nasal wall (n.f n. w). In fig. 5 the fore part of the upper crus of the nasal (w) 

 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, al.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 («. 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. tb) 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 {cil.s) we see a small ear-like process (outgrowth) ; 



