476 EIGHTH PACIFIC SCIENCE CONGRESS 



The place of the New Zealand gavia in this geographical pattern is 

 by no means clear. It is a brown-backed ally of P. pujfinus and Murphy 

 explains its origin [ibid., p. 7) by postulating a spread from the eastern 

 Mediterranean by way of the Mediterranean-Indian Ocean water gap. 

 If this is so the species group has invaded the Pacific basin from the 

 North Atlantic by two routes. 



The Puffinus kiiliUi group 



Alexander (1928, p. 61) and Murphy (1930, p. 11) refer to the 

 close affinity of kuhlii (syn. diomedea) and creatopus, and Murphy in 

 addition associates leucomelas in this assemblage. 



These forms are only secondarily units of the northern fauna, hav- 

 ing probably a southern ancestry, akin to the case of the preceding 

 species. 



The secondary cycle of dispersal of the north Atlantic kuhlii was 

 probably by way of the Panama water gap into the Pacific, Avhere 

 creatopus (breeding in the Juan Fernandez Island) and leucomelas 

 (breeding at the Bonins and Pescadores) were differentiated. 



STORM-PETRELS 



Oceanodroina spp. 



The members of this genus are essentially northern forms, which 

 have differentiated into a series of species and races in whose dissemina- 

 tion through the north Atlantic and Pacific, the Bering and Panama 

 water gaps have played essential roles, hence the colonising processes 

 must have begun in the pre-Pleistocene. The taxonomy of the group 

 has proved difficult, the latest revisor being Austin (1952, p. 394) who 

 has made certain parts of the geographical picture much clearer. 



O. leucorhoa is a widespread breeding species on both coasts of the 

 North Atlantic and North Pacific, the connection between the two 

 oceans being probably through the Bering water gap. 



O. castro is also a breeding form of both oceans, but of more 

 southern distribution, and it would appear that the Panama water gap 

 has contributed to the existing distribution pattern. The Pacific breed- 

 ing stations are at the Hawaiian, Cocos and Galapagos Islands. This 

 is the only Oceanodroma which is certainly known to have transgressed 

 the equatorial belt as a breeder, St. Helena in the south Atlantic being 

 a nesting station. 



The north Pacific is inhabited by a complex of related forms which 

 Austin considers all to have reached specific status, two of them being 

 now sympatric. These are O. melania (breeding in lower California), 

 O. matsudairae (breeding in the Bonins), O. tristra^ni (breeding in 

 the Bonins and Hawaiian Islands) and O. markhami, whose breeding 



