56 THE AUSTRAL AVIAN RECORD [Vol. H. 



is realized that the former occurs in the North Atlantic 

 and in the South Pacific, where it lives side by side with 

 the latter. In the same manner the difference in colora- 

 tion between P. leucogaster Boddaert and the others 

 in itself would justify generic separation, when it is 

 remembered that all the other genera and species have 

 a uniform style of coloration which is quite different 

 and one which is practically unchanged in the same 

 species with a North Atlantic, South Atlantic, and South 

 Pacific distribution. 



323. Sc^OPiL^THOisr, gen. nov. 



Differs from Phcethon Linne in its longer wing, stronger 

 legs and feet, shorter tail, though as powerful in the 

 bill. 



Type, Phcethon ruhricauda westralis Mathews. 



325. Leptoph^thon, gen nov. 



Differs from Phcethon Linne in its much smaller size 

 throughout, though having a comparatively longer tail. 

 Type, Phcetho7i lepturus dorotheae Mathews. 



Note. — ^The Tropic Birds have been referred to the 

 one genus Phcethon, though here again generic rank 

 is due to the differences observed. Phcethon and 

 Scceophcethon agree somwhat in size, but the latter has 

 discarded the plumage of the former, which is seen in 

 the juvenile, in favour of a uniform white one ; it has 

 also developed in size. Leptophwthon, on the other haiid, 

 has also achieved the beautiful adult - plumage of 

 Scceophcethon, but is sadly diminished in size. However 

 the evolution has proceeded, the birds are now sufficiently 

 distinct to warrant generic separation. 



367. NoTOEALCO, gen. nov. 



Differs from Rhynchodon Nitzsch in its much longer 

 wings, longer tail, and weaker feet. 

 Type, Falco subniger Gray. 



