382 ON THE PETEELS COLLECTED DURING 



Pagodroma resembles QSstrelata, but all the spines have become much 

 smaller and weaker, and this is still more the case in Daption, where they 

 have almost entirely disappeared save round the posterior nares. The 

 line of the interior margins of the premaxillae and of the palatines is 

 marked by a distinct raised ridge, and the edges of the upper mandible, 

 from the angle of the mouth as far forwards as the dertrum, are marked 

 by a series of slight, closely-set, raised ridges, oblique forwards and 

 outwards. It is by a great development of these that the peculiar fringed 

 bill of the genus Prion, reminding one of that of a duck, is produced. In 

 Prion (PI. XIV. fig. 5, Prion banJcsi) the palate is almost smooth through- 

 out, with the exception of a distinct prenarial ridge, and some indications 

 of the palatine series of spines posteriorly (not represented in the figure) : 

 the median fissure and narial opening are however, as usual, bounded by 

 small spines. From a point corresponding to the angle of the niouth 

 forwards to a little behind where the dertrum forms the cutting-edge of 

 the bill, the margins of the mouth are bounded by a well-developed fringe 

 of closely-set lamellae, reminding one much of the plates of a whale's 

 baleen. These lamellae are developed from the mucous membrane of the 

 mouth, and are probably entirely epidermic in origin ; in the cleaned 

 skull there is no trace of their presence (vide PL XXII. fig. 4). They are 

 best developed a little way in front of their posterior termination of the 

 fringe ; here the lamellae are nearly vertical thin plates, set on at right 

 angles to the axis of the beak, but curved both forwards and outwards. 

 Anteriorly they become more oblique forwards, and much shorter. 

 Outside of them the cutting-edge of the beak is produced downwards for 

 a little way, so that a groove is formed between the beak and the 

 pectinated fringe. 



When the lower bill is in position, the more posterior and strongest 

 of the lamellae completely occupy the slight space left between the 

 cutting-edge of the two jaws, lying with their free ends curved outwards 

 in a slight groove outside the lower mandible formed by the reflection 

 from it of the feather-covered skin. Anteriorly this groove disappears, 

 and the fringe simply lies against the outer surface which is quite 

 smooth, and not, like that of the duck or flamingo, correspondingly 

 grooved for the reception of the lamellae of the fringe of the lower jaw, 

 which in front it does not even reach. In the larger-billed Prion 

 vittatus these lamellae are even more developed, whilst in the smaller- 

 billed Prion desolatus they are less so: Prion banlcsi is so completely 

 intermediate in this respect that I see no reason for the adoption of 



Zool. Chall. Dr. Coues's genus Pseudoprion* '. The only other Petrel in which the 

 Exp. vol. iv. 

 pt. xi. p. 19. - 



* Proc. Ac. Nat. Sci. Phil, 1866, p. 164, where that writer has also described the 

 structure of these fringes at length. 



