HuTTON. — On the Geographical Relations of the N.Z. Fauna. 237 



Among the web-footed birds, the first thing that claims our attention is 

 the oceanic family of the petrels {Procellaridce), for although by no means 

 peculiar to New Zealand,* the great number of species in the southern oceans, 

 in comparison with the small number in the northern, is very noticeable. The 

 northern and tropical species have all closely allied forms in the southern 

 hemisphere, while many of the southern petrels, such as Ossifraga, Halodroma, 

 Majaqueus, Pterodroma, Daj)tion^ and Prion have no representatives in the 

 northern seas. This leads to the inference that the northern species have been 

 derived from stray southern birds, and that the southern hemisphere has been 

 the centre from which most oceanic birds have spread, while land birds, on 

 the contrary, have spread chiefly from northern areas, and this leads to the 

 further inference that the southern hemisphere has been for many ages more 

 oceanic in character than the northern. The next most remarkable point is 

 the great development of the cormorants, New Zealand possessing nine species, 

 four of which are found nowhere else. No other country in the world possesses 

 so many, and the phenomenon can only, I think, be accounted for in the same 

 way as the numerous species of moa, that is, by the former existence of several 

 small islands which have since been elevated to form the present New Zea- 

 land. The wide dispersion, however, of two of our cormorants is rather 

 against this view, one {G. carunculatus) being found at the Crozet Islands and 

 at Cape Horn, and the other {G. carho) in Australia, China, and Europe. I 

 must, however, remark that the identity of the first has not yet been perfectly 

 established, and that the second, although very closely resembling specimens 

 from Europe, shows at the same time some difference. It may also be useful 

 to remark here that our gannet [Dysporus serrator), although a far better 

 flying bird than the cormorants, is not found at the Chatham Islands, and 

 Dr. Finsch informs me that it is undoubtedly different from the species 

 {D. capensis) that occurs at the Cape of Good Hope. The occurrence of 

 G. brevirostris and G. melanoleucus in New Zealand presents a parallel case to 

 the two species of stilt-plover, with, however, this difference — that, judging 

 from the colours of the young bird, it is probable that G. melanoleucus has 

 been derived from G. brevirostris, owing to its having been isolated in 

 Australia, and that its descendants have migrated back again to New Zealand. 



Of the gulls we possess a species (X. pomare) which is found nowhere else, 

 a peculiarity of which few countries can boast, but which can perhaps be 

 accounted for by the fact that this gull only frequents fresh-water lakes, and 

 seldom comes down to the sea. Our other gulls are widely spread, but it is a 

 most remarkable fact, which at present appears to me to be quite inexplicable, 

 that neither gulls nor cormorants occur in any of the Polynesian Islands. 



Of ducks we possess nine species, four, or perhaps five of which are 

 * Procellaria parkinsoni is peculiar to New Zealand. 



