286 PROF. OWEN ON THE ANATOMY 
side a process to join the lachrymal. In the Jbis the superior maxillary bones are 
in the form of slender round styles, having a wide interspace between them. In the 
Apteryx the small lachrymal bones are represented by two compressed plates of bone 
descending obliquely forwards from the anterior extremities of the frontals, and are ar- 
ticulated below to a small depression in the maxillary plate. ‘They are each pierced by 
a single small foramen. The frontal, nasal, and intermaxillary bones form one conti- 
nuous bony piece, too strong to admit of any elastic yielding movement between the 
upper jaw and cranium. The nasal and the upper or mesial portion of the intermaxillary 
bones form an elongated depressed narrow process, convex above, and with the outer 
margins bent inwards beneath the long nasal passages, of which they form the outer 
and part of the lower boundaries. 
The lower jaw’ presents all the usual ornithic characters with the Struthious modifi- 
cations traceable in the individual peculiarities. The transversely expanded angular 
and articular extremities offer the inwardly extended process for the attachment of the 
pterygoidei muscles: the superior transverse plate behind the articular surfaces is thin 
and concave towards the meatus auditorius externus, and is lined by the mucous mem- 
brane of that passage, of which it forms part of the bony parietes. There are two 
distinct narrow oblique articular surfaces, concave in the longitudinal and convex in 
the transverse directions ; the internal one is the largest, and behind this there is a small 
excavation’ into which a small process of the air-sac lining the tympanum is continued ; 
and this is the only part of the skeleton not immediately concerned in the formation of 
the organs of hearing or smelling into which air is admitted. The entry to the air-cells 
in the lower jaw of the Ostrich is situated in the part corresponding to the above de- 
pression or sinus in the jaw of the Apteryx. Traces of the compound structure of the 
lower jaw are very evident in that of the Apteryx, and the limits of the angular, arti- 
cular and coronoid pieces may be in part defined. There is a linear vacancy, bounded 
by the surangular and angular pieces behind, and by the bifurcate commencement of 
the mandibular or dentary piece in front: the surangular is compressed, and sends up- 
wards a very slightly elevated coronoid ridge. A second narrower fissure occurs be- 
tween the thick opercular or splenial element and the upper fork of the mandibular 
piece. The opercular piece reaches to the posterior part of the symphysis as in the 
Ostrich, and the rest of the lower jaw in front of this part is formed by the two anchylosed 
mandibulars. In the extent of this anchylosed symphysis the Rhea makes the nearest 
approach to the Apterya among the Struthionide, and the two impressions which diverge 
from the back part to the front of the symphysis are present in both the Rhea and 
Emeu as in the Apteryx. The lower jaw of the Apteryx differs from that of the Jbis in 
its greater posterior expanse, its more depressed form, the lower coronoid plate, the 
narrower fissure between the angular and surangular pieces, and the absence of the 
mesial furrow, extending in the Ibis to the end of the symphysis. 
1 Pl, LIIL. Figg. 6. & 7. 2 Pl, LIL. Fig. 6. a. 
