182 MR. W. P. PYCRAFT ON THE MORPHOLOGY AND 
deep shelf. This is less marked in Rhea. In Dinornis and Crypturi it is but feebly 
developed. 
The cerebral fossee in Dinornithide do not taper forwards to finally pass into the 
infundibuliform olfactory fosse, but, on the contrary, are of great size and width in this 
region, reducing the olfactory fosse to the dimensions of shallow pits. 
The median bony falx, continued forwards from the tentorial ridge to the crista 
galli, is extremely well developed in Casuarius and Dromeus, less so in Rhea, 
and only feebly in Struthio and Dinornis and Tinamous. ‘There is no trace of it 
in Apteryz. 
In Casuarius and Dromeus the fosse bear distinct and deep impressions for the 
temporal and frontal lobes, a low ridge indicating an indistinct Sylvian fissure. 
The olfactory fosse in all, save Dinornis and Apteryx, are paired, more or less 
tubular, infundibuliform chambers, separated one from another by a erista galli. 
Anteriorly they are closed by a more or less perforated plate for the passage of the 
olfactory nerves. 
In Dinornis the olfactory fosse take the form of shallow pits lying at the anterior 
end of the large cerebral fossa. ‘The cribriform plate is large. 
In Apterya these fosse are of great size, and pass insensibly backwards into the 
cerebral fosse. They are not, in the dried skull, shut off anteriorly from the turbinals 
by a cribriform plate as in other Raditew, but continued forwards directly into the 
olfactory chamber. 
The Premaailla. 
The premaailia in all the Palwognathe is peculiar, in that the nasal process is 
median, and not paired as in all other birds (Pl. XLII. figs. 1-3). In all save 
Struthio there are well-developed palatine proceses. 
In Casuarius the beak is more or less laterally compressed. The body—that 
portion of the premaxilla from which the nasal, maxillary, and palatine processes are 
given off—is short, and more or less deeply grooved on either side, so that the distal 
end of the nasal process seems to be continued forwards into a strongly marked ridge. 
‘The maxillary processes extend backwards as a pair of slender splints to the level of 
the lachrymal on either side. The palatine processes are a pair of short narrow 
lamin extending backwards to a point corresponding with a vertical line passing 
upwards behind the top of the free end of the median nasal process. They enclose 
anteriorly a small chink-like palatine notch. In C. australis there is a small pre- 
narial septum, corresponding to that described by Parker in Dinornis, as the “ strong 
ascending keel, formed posteriorly of paired plates, but solid in front and gradually 
diminishing in height towards the top of the beak.” This keel is derived from the 
dorsal surface of the palatine processes. 
The nasal process is rod-like, its free end passes backwards into a tunnel-shapé 
in the inflated, mesethmoid mass forming the characteristic casque of these birds. 
