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Show 36 MR. W. P. PYCRAFT ON THE [May 2, Corydon, Eurylcemus, and Cymbirhynchus differ conspicuously from Calyptomena in this matter of the narial aperture, as may he seen by a comparison of figs. 2 5, 3 a, 4, PI. II. In all three genera the nasal is reduced to its smallest possible limits, little more than an arcuate bar being left. Of this, one half represents the descending process of the nasal, the other the body of the bone,-now merely a rod joined at its inner end to the nasal process of the premaxilla, and affording the means of articulation with the frontals. This, as I have remarked, takes the form of a nasal hinge. In Eurylcemus and Corydon the nasal fossa, as in Calyptomena, is open in the dried skull, the actual position of the nasal orifice in the living bird being indicated by semicircular grooves in the anterior border of the nasal fossa. The circle completing the rest of the fossa in the living bird was roofed by the alinasal wall. In Cymbirhynchus this wall almost completely ossifies, leaving an oval narial aperture, and a small semilunar space immediately in front of the nasal (fig. 3, PI. II.). In the Eurylsemidse the floor of the olfactory chamber is open behind, revealing in Calyptomena an ossified slieet-like nasal septum, which in Corydon becomes immensely swollen. In the Ooracife, certain Caprimulgi and Pici the floor of the olfactory chamber is more or less ossified. In Eurystomus and the Bucconidse there is a long palatal fissure, which at first sight appears to correspond to the huge palatal cavity of Eurylcemus. An examination shows, however, that this vacuity leads into a spacious cavity underlying the olfactory chamber and formed by the inflation and absorption of tissue of the nasal septum. In Podargus the palatal surface of the premaxilla is completely ossified, and the olfactory chamber is reduced to the smallest possible limits. In Corydon the nasal process of the premaxilla is immensely swollen and rises far above the level of the nasal hinge. The frontal is similarly swollen immediately above this hinge. The intermediate stages between this condition and that found in Calyptomena can be studied in Cymbirhynchus. Corydon, indeed, would appear to have reached the high-water mark of specialisation in the matter of the jaws, among the Eurylsemidte. The Maxillo-jugal Arch. The maxilla, as usual, is in the adult completely fused with the premaxilla. In Corydon the maxillary region of the jaw is highly developed and forms a large semicircular plate, the convexity forming its free edge and projecting downwards far beyond the level of the quadrato-jugal bar. The maxillo-palatine processes in Calyptomena take the form of a pair of delicate rods projecting backwards at a very marked angle from the body of the maxilla, which, at this point, is perforated by small pneumatic apertures. These rods, on each |
