OCR Text |
Show 264 MR. W. P. PYCRAFT ON THE [Mar. 17, limb with the outer border of the palatine. Its further relations with the lachrymal will be discussed presently. The nasal septum is completely ossified, and the external nares are in consequence imperforate. The ectethmoidal region presents several points for comment. Bv the ossification of the alinasal wall, the form of the external nares is greatly changed in many of the Cuculi. In consequence of this ossification, the space between the premaxillary and descending processes of the nasal becomes obliterated. Thus in Geococcyx the nostrils take the form of an oval aperture lying just cephalad of the middle of the beak. In Rhamphococcyx this aperture is still further reduced, and consists only of an elongated slit lying at the base of the beak above the tomium. In Rhinococcyx the aperture is nearly circular at the base of the beak, and bounded by a deep groove in front. The alinasal ossification is, however, imperfect, inasmuch as a small round hole is left in the angle between the premaxillary and descending processes of the nasals. In Taccocoua this superior foramen and the aperture of the nostril have blended. In Coua the floor of the anterior region of the nasal fossa is raised up into a sharp longitudinal ridge. In the Musophagi the form of the external nostril differs conspicuously from that of the Cuculi. It is situated slightly distad, or proximad, of a line passing through the middle of the beak, and is reniform in shape. In Turacus it lies distad, in Schizorhis proximad of the middle line. In both genera, just within the mouth of the aperture, lies a well-developed concha vestibidum. This is especially large in Schizorhis. Furthermore, the genus is peculiar in that immediately distad of the concha the nasal septum is pierced by a minute foramen. The Cranial Cavity.-The nietencephalic fossa is somewhat shallower in the Musophagi than in the Cuculi. The internal auditory meatus in the Cuculi is sharply defined, strongly contrasting in this respect with the Musophagi, in which it is but ill-defined. The vagus foramen, which lies caudad and ventrad of the meatus, is small. The orbito-nasal foramen (v1) pierces the outer superior rim of the fossa near the outer angle of the dorsum sellce. The cerebellar fossa is relatively smaller in the Cuculi than in the Musophagi, and in both it is relatively smaller than in many other groups, e. g. Falconiformes. In the Cuculi the floccular fossa is very shallow, and lodges a deep slit-like vertical depression. In the Musophagi this fossa is reniform, deeper, and lodges a deep and wide depression which gives the reniform character to the whole. The mesencephalic fossa is fairly sharply defined in both groups. Among the Cuculi, this is especially noticeable in Geococcyx. Its floor, in both groups now under consideration, is pierced by the trigeminal foramen. The difference in position of this foramen is worth noticing. In the Falconiformes it lies, together with the orbito-nasal (v1), in a pit carved out of the superior border of |