REPORT ON THE ANATOMY OF THE PETRELS. 17 



2. Alimentary Canal and its Appendages. 



The Tubinares as a group agree very closely together in the form of stomach and 

 intestines possessed by them, which have peculiarities not occurring in any other groups of 

 birds, and it is only in the variations in form and structure of the tongue, in the nature of 

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

 caeca 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 II. fig. 21, 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. From 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, Buhveria, and Majaqucus 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 Procellaria, 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. 



(ZOOL. CHALL. EXP. PART XI. — 1882.) L 3 



