34 MR. W. P, PYCRAFT ON THE [May 2, 
the mesethmoid by a horizontal plate of bone, almost rod-like 
in some species. “The vertical, hamulate portion of the plate, by 
its upper limb, considerably adds to the width across the frontal, 
the lower, descending, process turns outwards to reach the 
quadrato-jugal bar. In the extraordinarily wide-mouthed genus 
Corydon, however, the quadrato-jugal bar stands far from this 
descending process. 
The olfactory chamber, owing to the extremely reduced con- 
dition of the maxillo-palatines, in the macerated skull is without 
a floor, in the majority of the genera of this group; but in two 
skulls, Zurylemus and Cymbirhynchus, in the British Museum Col- 
lection, this is more or less filled up by the ossification of a pair of 
turbinals, one on either side of the septum nasi, which apparently 
answer to the concha media. Pyriform in shape, each extends 
from the narial aperture backwards to the anterior horn of the 
vomer, where it becomes attached. Above and behind this is an 
oat-shaped and laterally compressed turbinal answering to the 
concha posterior. 
The nasal septum, in Calyptomena, is formed by a thin sheet of 
bone running along the whole length of the under surface of the 
nasal process of the premaxille. In Hurylemus, Cymbirhynchus, 
and especially in Corydon, this septum becomes greatly swollen 
and grooved on its under surface. 
The Cranial Cavity.—The mesencephalic fossa is capacious. 
Tts floor sweeps rapidly upwards to form astrongly marked basin- 
shaped cavity. This upward rising of the floor is much more 
conspicuous than in some other genera, e. g. Menura or Corvus. 
The internal auditory meatus is represented only by a shallow 
depression. Immediately above and somewhat in front of this 
lies the trigeminal foramen. ‘This, opening under a strong ridge, 
leads immediately into a deep groove across the floor of the 
mesencephalic fossa and thence through the under wall of the 
skull. All the branches of v leave by this foramen. There is no 
separate foramen for the ophthalmic (v’) (orbito-nasal); and in 
this respect the Hurylemide appear to agree with all the other 
Passeriformes. The vagus foramen lies at the bottom of a deep 
fossa. 
The cerebellar fossa is small, relatively to the cerebral, sharply 
defined, and has the supra-occipital region marked with prominent 
horizontal ridges. The floccular fossa forms a conspicuous 
moderately deep and more or less pyriform depression, sharply 
bounded caudad by the anterior semicircular canal. 
The mesencephalic fossa is of considerable size and, as in other 
Passeriformes, extremely well defined by a strong vertical ridge 
above, and an equally prominent ridge formed by the pro-otic 
below. 
The pituitary fossa takes the form of a narrow tube rising 
vertically from the floor of the skull. The dorsum selle is reduced 
to a knife-like edge. The pre-pituitary region is produced into a 
moderately well-defined optic platform, triangular in shape, 
