416 ON THE PETRELS COLLECTED DURING 



fenestrated, pointing backwards, and with their inner edges appearing 

 but slightly internal to the palatine bones. They remain free from 

 each other in the middle line, and are also unconnected by ossifi- 

 cation with the vomer or nasal septum. Hence the Tubinares are 

 in this point strictly schizognathous birds. But in the Albatrosses, 

 where the maxillo-palatines are very large and nearly vertical in position, 

 the space between their inner edges is very narrow, and just in front of 

 them the decurved end of the vomer fills up the intervening chink, 

 Zool. Chall especially in Phcebetria fuliginosa, where it is firmly fixed to, though 

 Exp. vol. ir. apparently not anchylosed with, the maxillary plates. The transition 

 p . xi. p. . rom n j s f. Q a desmognathous type would therefore be but very slight. 



The palatines in the smaller forms are of generally flat form, with 

 their posterior angles rounded off, closely apposed together for a very 

 short way behind the posterior nares, and with fairly developed descending 

 and ascending plates, the latter being recurved posteriorly and anchy- 

 losed to the vomer. This latter bone (PI. XXI. figs. 4 and 5) is always 

 broad behind, of generally depressed form, and strongly bent downwards 

 in front, its pointed extremity appearing between the maxillo-palatine 

 processes at about their anterior edge. 



In the larger forms the vomer becomes enormously broad, and keeled 

 both above and below. The palatines meet for a much more considerable 

 distance posteriorly, greatest in Fulmarus, and their descending plate 

 becomes more pronounced ; at its anterior end the bones of opposite 

 sides nearly meet. The ascending plate, too, becomes very large, more 

 or less embracing the vomer at its base, and being separated, especially 

 in the Albatrosses, only by a narrow chink anteriorly from the posterior 

 end of the equally upturned maxillo-palatine. The posterior margin 

 of the palatines is more or less concave. The pterygoids are nearly 

 straight, slightly compressed, cylindrical bones, which articulate mesially 

 partly with the basisphenoidal rostrum, partly with the truncated pos- 

 terior ends of the palatines. Well-developed basipterygoid facets are 

 present in all the forms (vide PI. XXII. figs. 2 and 4), except the Diome- 

 deinae, the Oceanitidse, Procellaria and Cymoclwrea *. The quadrate, as 

 in most birds, is two-headed. Its distal end has two distinct articular 

 cartilage-coated areas, separated by a depression. The most external of 

 these is oblique from behind outwards, and is somewhat saddle-shaped, 

 being convex from side to side, arid concave antero-posteriorly. The 

 inner facet has its axis directed forwards and inwards, nearly parallel to 

 that of the pterygoid bone. It is divided by a prominent oblique trochlea 

 into an inner, nearly flat, surface, of triangular shape, and a more 

 external, deeply grooved one, also of saddle shape. As might be expected, 



* Ha 7 ocypfena has not yet been examined in this respect: it probably resembles the 

 last two genera named. 



