OCR Text |
Show 1 9 0 3 .] OSTEOLOGY OF THE CUCULIFORMES. 2 6 7 In all the Cuculi, the palatines meet one another in the middle line immediately beneath the parasphenoidal rostrum, which they grasp laterally through their fusion with the liemipterygoids. In the Musophagi the palatines are relatively longer than in the Cuculi, from which they also differ in that they taper, instead of broaden, rapidly as they approach the {pterygoids. Furthermore, they do not meet below the parasphenoidal rostrum, but, on the contrary, are separated one from another by the whole width of this rostrum (PI. X X II. fig. 2). The dorsal surface of the pterygoid end sends up a long and deep, incurved keel, the antero-internal angles of which fuse with the vestigial vomer. The pterygoids, in the Cuculi, are moderately long and straight, and in some, e. g. Crotophaga, Rhinococcyx, Guira, Taccocoua, have the dorsal border raised up into a high, sharp crest, the palatine end of which embraces the parasphenoidal rostrum, whilst in Eudynamys, Coua, Geococcyx, and Piaya, for example, this crest is absent. The palato-pterygoid articulation is in the form of an obliquely transverse hinge-joint, permitting only a lateral motion. Basipterygoid facets are absent. The hemipterygoid element of the pterygoid is conspicuous only in Taccocoua and Geococcyx. Herein it forms a continuation of the dorsal crest of the shaft of the pterygoid, and rests on the palatine at a slight angle. Secondary fusion between the hemipterygoid and the main shaft of the pterygoid would reproduce exactly the conditions of the palato-pterygoid articulation which obtain in the Bucconidce and Momotidce. In the Musophagi the pterygoids are relatively short, somewhat twisted, rods, bearing vestiges of basipterygoid facets. They articulate with the palatines as in the Cuculi. The Mandibles. The mandible in the Cuculi has a short, blunt angular process, and a moderately long internal angular process. In Eudynamys, Cuculus, and Guira the rami are pierced by a long lateral vacuity, which is partly closed by a long and slender coronoid. In Coua the coronoid terminates midway across this vacuity; whilst in Taccocoua and Centropus this vacuity is quite open, the coronoid forming its ventral border. In Piaya, Rhino-coccyx, and Rhamphococcyx the ramal vacuity is absent. In Geococcyx it is partly closed anteriorly by the hinder end of the splenial. The mandible of Cucidus possesses one conspicuous feature in the presence of a triangular flange of bone formed by the deflection of the superior border of the ramus at the point corresponding, in the living bird, to the gape, in the skeleton to the region immediately behind the lachrymo-nasal fossa. The flange, especially conspicuous in Cuculus canorus, is also fairly distinct in Cacomantis, and is traceable in Piaya and Rhamphococcyx. The internal angular process is well marked in all the Cuckoos, but is especially so in Coua and Centropus. |