THE VOYAGE OP THE ' CHALLENGER/ 381 



mucous membrane of the mouth, and in the presence or absence of 

 CEeca that the various forms differ in any important degree from each 

 other. 



The mucous membrane of the palate usually presents, in the Tubinares, 

 several series of longitudinal rows of pointed, retroverted papillae, which 

 no doubt serve in the capture and retention of the prey by these birds. 

 The most ordinary arrangement of these may be understood from 

 Plate XIV. fig. 3, where the palate of (Estrelata lessoni is represented. 



The palate is cleft for about half its length by a narrow median fissure, 

 fringed on each side by a row of small spines, which dilates behind into 

 the opening of the posterior nares, which is similarly fringed. Behind 

 this, separated by a small interval, is the linear median aperture of the 

 Eustachian tubes. Prom the anterior extremity of the median fissure 

 runs forwards, to near the end of the beak, a sharp median ridge, with 

 four or five strong, conical spines developed on it posteriorly. This 

 ridge is separated by a deep groove on each side from the margins of the 

 beak. Along a line corresponding to that of the palatine bones, and 

 extending for an extent equal to that^ of the median fissure, there is 

 developed on each side a second longitudinal row of retroverted and 

 pointed spines, much longer and stronger than the more median series. 

 In front of the posterior-narial aperture there runs between the two 

 longitudinal series an oblique series of smaller spines, whilst behind 

 the Eustachian aperture is a second transverse series, concave anteriorly. 



In all the species of the genera (Estrelata, Bulweria, and Majaqueus 

 examined by me the same condition obtains, the larger species, however, 

 as that figured, frequently developing one or two rows of smaller spines 

 lying parallel to the external longitudinal row, one outside, and the other 

 between it and the median fissure. Puffinus is similar, but the anterior 

 median keel is smooth, and almost without spines, and the palate to the 

 sides of the Eustachian aperture becomes covered with small spines. 



In Cymochorea and Procellarla, as in Halocyptena, the palate is much 

 as in (Estrelata, but with all the spines smaller and feebler, particularly 

 those on the palatal ridge. In the first genus at least the prenarial 

 ridge is nearly smooth, and between the palatine row of spines only 

 developed posteriorly and the median a stronger row is developed, so 

 that there are here altogether three pairs of longitudinal spines above. 



In the Oceanitidse the palate is much the same, but the palatine row 

 becomes very weak and nearly obsolete, whilst the intermediate row is 

 the strongest, considerably, of all. The prenarial ridge may be slightly Zool. Chall. 

 toothed or nearly smooth : it always ends, however, at the commencement Exp. vol. iv. 

 of the median fissure, in a slightly raised prominence, divided into two 

 lateral parts, in a way not seen amongst the Procellariidge. (Vide 

 PI. XIV. fig. 6, giving an enlarged view of the palate of Oceanites 

 oceanicus.} 



