34 MK. w. p. PYCRAPT 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 

 C'orydon, 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 

 {i\\\VLii,Euryl(Bmus and Cymhirhynchus, in the Bidtish 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, Avhich 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 premaxillfe. In Eurylcemtis, Cymhirhynchus, 

 and especially in Corydon, this septum becomes greatly swollen 

 and grooved on its under surface. 



The Cranial Cavity. — The mesencephalic fossa is capacious. 

 Its floor sweeps rapidly upwards to form a strongly 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 Eurylfemidre appear to agree with all the other 

 Passeriformes. The vagus foramen lies at the bottom of a deep 



The cerebellar fossa is small, relatively to the cerebral, shai-ply 

 defined, and has the supra-occipital region marked with prominent 

 horizontal ridges. The foccular 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 veitical ridge 

 above, and an equally prominent ridge formed by the pro-otic 

 below. 



The 2^'i'tuitary fossa takes the form of a narrow tube rising 

 vertically from tlie floor of the skull. The dorsum sellce is reduced 

 to a knife-like edge. The pre-pituitary region is produced into a 

 moderately Avell-defined optic j^latform, triangidar in shape. 



