262 PROF. OWEN ON THE ANATOMY 
If the beak of the Apteryr be compared with that of the Ibis and Rhea, it will be found 
that its plan of construction is precisely that of the Struthious Bird, and that the re- 
semblance to the grallatorial beak is confined to the elongated form and slenderness of 
its produced anterior part. In the Ibis, for example, the beak is compressed from its 
very commencement ; in the Apteryx it is depressed at its base, as in the Rhea. There 
is no production of integument, either plumed or naked, upon the base of the bill of 
the Ibis, while in the Rhea‘ we find precisely the same structure, but on a magnified 
scale, as that above described in the Apteryz ; the naked cere is deeply emarginate, both 
before and behind ; the plumed integument has many black sete, but shorter and finer 
than in the Apteryx, mingled with the short and stiff feathers. In the Jbis the external 
nostrils are pierced in the very base of the beak ; a groove is continued from each nos- 
tril to the end of the mandible ; the same grooves are seen in the Rhea, but here the 
nostrils open at the anterior angle of the lateral processes of plumed integument, which’ 
are extended along the sides of the base of the bill, as in the Apteryx. In another 
Struthious genus, the Cassowary, the nostrils are situated still more forwards, and are 
pierced, as in the Apteryz, in the horny sheath of the bill itself; there is no other Bird 
which approaches nearer to the Apteryz in the anterior position of the nostrils than does 
the Cassowary ; the peculiar modification of the base of the beak in this Bird obscures, 
as it were, the resemblance which we might otherwise have been able to trace in that 
part. The Emeu and Ostrich correspond with the Rhea and Apteryz in the modifications 
above noticed, in the base of the upper mandible. If we examine the lower mandible 
of the larger Struthionide, we perceive a modification of its inferior surface, which di- 
stinguishes it from that of any Gallinaceous or Grallatorial Bird ; in the Ostrich the tip 
is formed by a raised quadrate portion, separated by two lateral parallel grooves from 
the rest of the gnathotheca ; in the Rhea the corresponding raised median piece is longer 
and narrower than in the Ostrich, and the lateral boundary-lines converge backwards 
to the angle where the symphysis menti commences. In the Apteryx, notwithstanding 
the modification by which the bill is transformed from a granivorous to an insectivorous 
instrument, we find a middle piece marked out, as in the Rhea, by two grooves diverging 
forwards from the angle of confluence of the rami of the jaw*. The lower mandible of 
the Ibis offers no trace of this character, but is traversed longitudinally by a single mesial 
groove. 
In the Apteryx a narrow membranous fold or ridge is continued from each angle of 
the gape obliquely forwards and inwards upon the slightly convex under or palatal 
surface of the upper mandible, and these ridges are gradually lost about 8 lines in front 
of the posterior apertures of the nostrils’ ; these apertures present the form of two linear 
slits, 4 lines im length, situated close together, parallel with the axis of the beak, and 
4} inches from its extremity, in the male : the common opening of the Eustachian tubes‘ 
is situated two lines behind the posterior nares. From the anterior part of these aper- 
1 Pl. XLVII, Fig. 3. * Pl. LIII. Fig. 7. s Pl. XLVIII. a. Fig. 1. * Pl. XLVIII. 6. Fig. 1. 
