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Show 1S99."1 OSTEOLOGY O F T H E T U B I N A R E S . 391 below, presents an elongated tumid SAvelling immediately behind the maxillo-palatine process; immediately in front of this it rises suddenly dorsalwards, and curving forwards above the maxillo-palatine descends to the level of the palatines, between their extreme anterior ends, in the form of a long spine-like process. A median keel traverses the ventral surface from the region of the tumid SAvelling forwards. The vomer of the Diomedeidas is peculiar in that, though dorso-ventrally depressed, its edges are not upturned ; in that, about the middle of its length, it turns abruptly downwards, and then, at its tip, forwards. Furthermore, the ventral surface bears a deep median keel (Pl. XXIII. fig. 7). Seen from below, with the surrounding parts in situ, the vomer is discovered as a thin blade-tbe ventral keel-lying at the bottom of a deep, narroAv cleft, formed bv the palatines and maxillo-palatine processes. Immediately anterior to these last lies a short rod-the tip of the vomer (Pl. XXIII. fig. 8). The posterior dorsal surface of the vomer underlies the anterior end of the parasphenoidal rostrum. The junction of the vomer with the palatines is indicated by a notch on its posterior dorsal border. The palatine in its general form, and in the nature of its junction with the vomer, agrees very closely with that of the Storks and Herons. Seen ventraily, and traced from before backwards, the anterior end is strap-shaped and underlies the maxillo-palatine process ; more or less distant from the posterior free border of this, its inner border develops a strong keel, Avhilst the corresponding region of the outer border produces a similar, but smaller keel. Both terminate a short distance in front of the pterygoid articulation, the palatine in this region becoming suddenly rod-shaped. Dorsally, traced from the pterygoid forward, the palatine is more or less laterally compressed into a blade-like ridge, which, nearing the vomer, gives off from its outer border a thin, concavo-convex scroll of bone which runs gracefully forwards to terminate immediately behind the posterior maxillo-palatine border: meauAvhile the main body of the palatine runs forwards to become almost, if not quite, indistinguishably fused with the vomer. The scroll-like plate just mentioned, seen laterally, often forms a high vertical crest-e. g., Puffinus, Diomedea. In Bulweria the inner ventral keel is feebly developed, and the outer border rises upwards, scroll-wise, giving the whole palatine a tumid inflated appearance. In Oceanites and its near allies the ventral ridges of the palatine are but feebly developed. In Ossifraga the inner keel of the ventral surface is triangular. The palatine is pneumatic, the foramina opening at the foot of the dorsal crest. The pterygoid in Procellaria, Cymodroma, Oceanites, and Pelagodroma is rod-shaped, Avithout basipterygoidal facets or pneumatic apertures. Pelecanoides and Bulweria have also non-pneumatic pterygoids. The pterygoid of the remainder of the Procellariidas is more or less rod-shaped and carved into a strong dorsal crest. 26* |
