189.9."' OSTEOLOGY Or THE TUUINAEES. 891 



below, presents an elongated tumid swelling immediately behind 

 the maxillo-palatine process ; immediately in front of this it rises 

 suddenly dorsalwards, and curving forwards above the maxilJo- 

 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 swelling forwards. 



The vomer of the Diomedeidfe is pecuHar 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 (PI. XXIII. fig. 7). Seen from below, with the surrounding 

 parts in situ, the vomer is discovered as a thin blade — the ventral 

 keel — lying at the bottom of a deep, narrow cleft, formed bv the 

 palatines and maxillo-palatine processes. Immediately anterior to 

 these last lies a short rod — the tip of the vomer (PI. 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 ventrally, 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, whilst the corresponding 

 region of the outer border produces a similar, but smaller keel. 

 Both terminate a short distance in front of the pterygoid articula- 

 tion, 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 immedi- 

 ately behind the posterior maxillo-palatine border : meanwhile 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., Pvffinus, 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 jjterygoid in ProcelJaria, Cymodroma, Oceanites, and Pelago- 

 droma is rod-shaped, without basipterygoidal facets or pneumatic 

 apertures. Pelecanoides and Bidiveria 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. 



9fi* 



