NATATORES. 481 



South Atlantic, which differed in being of a larger size, and in 

 having a patch of greyish white on the throat ; these differ- 

 ences will doubtless prove it to be a distinct species, and I 

 mention this in order that the two birds might not be con- 

 founded by subsequent voyagers or writers on the subject. 

 I have presented a specimen of the larger species, killed by 

 myself at the Equator, to the British Museum, where it is 

 always accessible for comparison and other scientific purposes. 



Like the F. melanogaster, the White-bellied Storm-Petrel is 

 a fine and powerful species, fluttering over the glassy surface 

 of the ocean during calms with an easy butterfly -like motion 

 of the wings, and buffeting and breasting with equal vigour 

 the crests of the loftiest waves of the storm ; at one moment 

 descending into their deep troughs, and at the next rising 

 with the utmost alertness to their highest points, apparently 

 from an impulse communicated as much by striking the 

 surface of the water with its webbed feet as by the action of 

 the wings. Like the other members of the genus, it feeds 

 on mollusca, the spawn of fish, and any kind of fatty matter 

 that may be floating on the surface of the ocean. 



I have not been able to trace the breeding-place of this or 

 of the preceding species ; information on this part of their 

 economy is therefore desirable. 



The sexes are so much alike that I could never distinguish 

 them by their outward appearance. 



Head and neck deep sooty black ; back greyish black, each 

 feather margined with white ; wings and tail black ; chest, 

 all the under surface, and the upper tail-coverts white ; bill 

 and feet jet-black. 



Some slight variation appears to exist in the extent of the 

 sooty colouring of the neck ; in some specimens it merely 

 descends to the base of the throat, w^hile in others it spreads 

 over the chest, but never down the centre of the abdomen. 



Total length 1\ inches ; bill f ; wing 6 ; tail 3 ; tarsi \\ \ 

 middle toe and nail 1. 



VOL. II. 2 I 



