404 BIRDS or AUSTRALIA. 



continent. One of the principal features which distinguishes 

 the Austrahan bird from its northern representative is its 

 hght and silvery coloured back and wings; it has also a 

 much stouter and longer bill, as well as longer and larger 

 legs. 



I have at this moment before rae, for the purpose of com- 

 parison, beautiful skins of the G. anc/lica, collected by Osbert 

 Salvin, Esq., in Algeria ; one from the continent of India, 

 and another from Java : all these are as nearly alike as possi- 

 ble in colour and admeasurements ; it is evident, therefore, 

 that the European and Indian birds are of the same species. 



In summer the crown of the head and back of the neck 

 are black ; all the upper surface and primaries are Hght 

 silvery grey ; the remainder of the plumage is white ; and 

 the bill and feet are black. 



In winter the black colouring of the head probably dis- 

 appears and is replaced by white. 



Total length 17 inches ; bill 2^ ; wing 13 j ; tail 6 ; tarsi If. 



Genus GYGIS, Wagler. 



One species of this genus of Terns is found in Australia- 

 Little is known respecting it or its allies, all of which frequent 

 the South Indian Ocean and the seas of Polynesia and 

 Australia. 



Mr. G. R. Gray remarks, in his * Catalogue of the Birds of 

 the Tropical Islands of the Pacific Ocean in the Collection of 

 theBritish Museum,' that "the late Prince Bonaparte gives three 

 species of this form in the ' Comptes Rendus de I'Academie 

 des Sciences' for 1856, p. 773, viz. Gygisalba, Sparrm., G. Can- 

 dida, Eorst., and G. napoleonis, Pr. B. ; but I have not met 

 with any characters by which he distinguishes them from 

 one another." 



The birds of this genus appear to deposit their single egg 

 on the branches of trees. 



