OCR Text |
Show 260 MR. W. P. PYCRAFT ON THE [Mar. 17, The Cranial Roof.-The cranial roof is never marked by supraorbital grooves. The parietal region, in certain genera of Cuculi, is marked by deep temporal depressions (temporal " fossae "), which may meet in the middle line so as to form a faint sagittal crest, e. g. Rhopodytes, Piaya, Rhinococcyx, and Rhamphococcyx; or they may be divided by a low broad ridge, as in Geococcyx, Taccocoua, Saurothera, Eudynamys, Guira, Centropus, and Crotophaga. In Coua, Coccystes, Cuculus, and Cacomantis the temporal fossa is either barely perceptible or confined entirely to the lateral aspect of the cranium. Geococcyx, it should be remarked, presents an intermediate stage in this character; the width of the ridge dividing the right and left fossae being extreme, so much so that they barely pass beyond the lateral aspect of the skull. The interorbital region is moderately wide in all the Cuculi, save in Saurothera, but even in this genus it is not conspicuously narrow. In the middle line the region may be marked with a distinct furrow as in Coua, or even by a low ridge as in Eudynamys. The interorbital region is bounded anteriorly by the lachrymals ; these do not develop outstanding supraorbital processes, and are not conspicuous from this aspect of the skull. There is 110 trace of the fusion of the frontal and nasal bones. In the Musophagi the temporal fossae are not strongly marked, and are confined to the lateral aspect of the skull. The parietal region is more rounded than in the Cuculi; and in Turacus is marked by a median furrow, so that the form of the cerebral hemispheres is distinctly indicated. In other respects this region of the skull resembles that of the Cuculi. The Base of the Skull. The basitemporal plate, in the Cuculi, is flattened and triangular in shape, and with the apex lying immediately beneath the Eustachian apertures. Posteriorly it is bounded by a precondylar fossa, which, though generally barely perceptible, in Eudynamys, Centropus, and Geococcyx is fairly deep. The lateral angles of the base are truncated, and, turning sharply downwards, cross the paroccipital notch to form the lower portion of the rim of the mouth of the tympanic cavity. In some genera, e. g. Coua, Guira, these downwardly-directed angles are very prominent and simulate mammillary processes. The two sides of this triangular plate have fused with the ossified connective tissue forming the anterior wall of the recessus tympanicus anterior. Consequently the Eustachian grooves have been converted into tubes opening directly above the apex of the triangle. The parasphenoidal rostrum bears slight vestiges of basi-pterygoid processes in Eudynamys only among the Cuculi. The rostrum is relatively long, and curves slightly upwards. In the Musophagi the basitemporal plate, like that of the |