122 Transactions. — Zoology. 



and presenting no trace of the beautiful buff-yellow so con- 

 spicuous in Sula serrator. It is also rather smaller, and the 

 shape and colour of the bare skin at the base of the bill are 

 different. In the masked gannet the bare skin extends a 

 little beyond the corners of the mouth, and then crosses the 

 throat in an almost straight line, while its colour in the adult 

 bird is a deej) blackish-blue. This dark colour contrasts 

 vividly with the snow-white feathers of the head and neck, 

 and is doubtless the reason why the bird has received the 

 common name of the "masked gannet." In Szila serrator 

 the bare skin is continued under the throat for a considerable 

 distance in the shape of a narrow triangular stripe, and its 

 colour is a pale leaden-blue. 



Like our species, it forms no true nest. On Curtis Island 

 its single egg was placed in a slight depression among the 

 scanty tufts of short grass which form the chief vegetation on 

 the top of the island. The females are quite exposed while 

 sitting on the nest, and from their white plumage form very 

 conspicuous objects ; but, as they are strong and powerful 

 birds, well able to defend themselves from all enemies, their 

 exposed position is probably no real disadvantage to them. 



Few birds have a wider geographical range. Drs. Fiusch 

 and Hartlaub, in their well-known book on the avifauna of 

 Central Polynesia, state that it has been found in the follow- 

 ing localities : The Atlantic Ocean, near Ascension Island ; 

 the Eed Sea ; Cocos Island ; the Straits of Sunda ; Torres 

 Straits and North Australia; Polynesia, from the Sandwich 

 Islands southwards to Samoa, and westwards from the Pau- 

 motu group to the New Hebrides. It seems probable that it 

 also exists on the coasts of both North and South America. 



2. Gygis Candida (Silky White Tern). 



"While conversing with Mr. Bell respecting the birds of 

 Sunday Island he alluded to a small white tern which visits 

 the island every November to breed. From his description of 

 the plumage, &c., and account of its breeding-habits, I con- 

 cluded that it would probably prove to be this species. Dur- 

 ing the last breeding-season Mr. Bell made further notes on 

 it, and has now sent me these, together with specimens of the 

 egg. As his notes, and the shape, size, and colour of the egg 

 agree exactly with the published accounts of Gygis Candida, I 

 have now no hesitation in considering it to be that species. 

 The bird, which is a most beautiful one, is rather smaller than 

 our common tern {Sterna frontalis). It has a slender body, 

 long wings, and deeply-excised tail. The whole of the plum- 

 age is pure-white, and of silky softness. The bill is long and 

 curved slightly upwards, dark-blue at the base, shading off 

 into black at the tip. Its breeding-habits are peculiar. Mr. 



