580 STRUCTURAL CHARACTERS 



IX 



ORDER : PRO CELL ARIIFORMES 



Palate schizognathous ; nostrils holorhinal ; a large laterally expanded vomer fused at its 

 base with the palatines; deep supra-orbital depressions; beak hooked; rhamphotheca com- 

 pound ; nostrils tubular ; oil-gland tufted ; wing diastataxic ; front toes webbed ; hind-toe 

 vestigial or wanting ; young nidicolous. 



1. FAMILY PROCELLARIIDJE PETRELS. 



Supra-orbital grooves without an external overhanging ledge ; temporal fossae when present 

 in the form of deep depressions approaching one another in the middle line ; nasal fossae 

 large, divided by a median septum ; length of upper jaw never much exceeding that of 

 the cranium ; basipterygoid processes more or less well developed ; palatines long, 

 sharply defined anteriorly at their junction with the maxillo-palatine processes, which 

 are small and plate-like lamellae never projecting downwards beyond the level of the 

 tomium. 



(a) Genus Hydrobates. Supra-orbital grooves very narrow, separated by a very 

 broad interor bit al ridge ; basipterygoid processes vestigial, lachrymal fused; tarso- 

 metatarsus longer than the middle toe and claw ; tail not forked. (Vol. iv. p. 380.) 



(b) Genus Oceanodroma. Tail forked ; tarsus not exceeding the length of the middle 



toe and claw. (Vol. iv. pp. 382, 552.) 



(c) Genus Oceanites. Claws flat ; wing-bones shorter than leg-bones ; keel of the 



sternum with a large fenestra ; tarso-metatarsus covered in front with a large 

 shield ; only ten secondaries ; tail very slightly forked. (Vol. iv. p. 553.) 



(d) Genus Pelagodroma. 1 Differs from Oceanites chiefly in the more flattened form 



of the claws ; and in the skeleton in having a conspicuous pair of " wings " behind 

 the supra-orbital grooves ; and the great width of the base of the coracoid, which 

 nearly equals the length of the shaft. (Vol. iv. p. 553.) 



(e) Genus (Estrelata. Nostrils with the tubular apertures united above the culmen ; 



beak shorter than the head ; tarso-metatarsus reticulated ; posterior border of 



sternum with four notches ; interorbital region of frontals much greater than the 



width of the supra-orbital grooves. (Vol. iv. p. 555.) 

 (/) Genus Bulweria. Tubular aperture of nostrils opening on the culmen, fleshy at 



the rim, with a median septum ; tail long and cuneate. (Vol. iv. p. 555.) 

 (g) Genus Puffinus. Nostrils opening on each side of the culmen ; tarso-metatarsus 



laterally compressed ; posterior border of sternum with four deep notches. 



(Vol. iv. pp. 383, 553.) 

 (h) Genus Fulmarus. Tubular aperture of nostrils single, opening above the culmen 



nasal septum within the tube ; outer pair of sternal notches obliterated ; tail 



feathers fourteen ; temporal fossa deep, nearly meeting in the mid-dorsal line. 



(Vol. iv. p. 387.) 

 (i) Genus Daption. Tubular aperture of nostrils single, opening on the culmen; 



inter-ramal space bare ; beak flattened, wider than high at the base ; temporal 



fossa shallow ; outer pair of sternal notches obsolete ; tail feathers fourteen. 



(Vol. iv. p. 556.) 



1 The genus Pelagodroma should be merged with that of Oceanites. 



