NATATORES. 



485 



procured indicated that they had hitely been engaged in the 

 task of incubation. 



It is a large and powerful bird, the male being scarcely a 

 third less in size than the B. cxulans ; is rapid and vigorous 

 on the wing, and takes immense sweeps over the surface of 

 the ocean. It will be interesting to learn the extent of the 

 range of this species. A head in the possession of Sir William 

 Jardine was said to have been procured at the Cape of Good 

 Hope, but I believe this was by no means certain. 



When fully adult the sexes differ but little in colour ; the 

 female may, however, at all times be distinguished by her 

 diminutive size, and the young by the bill being clouded with 

 dark grey. 



Besides being larger than the three succeeding species (to 

 which and the present the generic appellation of Thalassarche 

 has been given), the beautiful grey on the sides of the man- 

 dibles, and the yellow mark at the base of tlie lower mandible 

 will at all times distinguish this bird from the other members 

 of the genus. 



The stomachs of those I obtained in Recherche Bay con- 

 tained blubber, the remains of large fish, barnacles, and other 

 crustaceans. 



Crown of the head, back of the neck, throat, all the under 

 surface, rump, and upper tail-coverts pure white ; lores and 

 line over the eye greyish black, gradually passing into the 

 delicate pearl-grey which extends over the face ; back, wings, 

 and tail greyish brown ; irides dark vinous orange ; bill hght 

 vinous grey or bluish horn-colour, except on the culmen, 

 where it is more yellow, particularly at the base ; the upper 

 mandible surrounded at the base by a narrow belt of black, 

 which also extends on each side the culmen to the nostrils ; 

 base of the lower mandible surrounded by a belt of rich 

 orange, which extends to the corners of the mouth ; feet 

 bluish white ; irides brown. 



Total length 31 inches ; bill 4^ ; wing 21| ; tail 9 ; tarsi 3. 



2 F 2 



