462 OCEANITIDJE FEBGBTTA 



forked ; tarsus very long, exceeding the tibia and middle toe 

 considerably, covered in front by a single smooth plate ; phalanges 

 flattened, especially the basal one of the middle toe, which is equal 

 to or longer than the distal ones and claw ; outer and middle digits 

 subequal ; claws flattened, spade-like and pointed ; hind toe very 

 minute ; sternum entire, no ambiens muscle. 



Four species, found throughout the Oceans of the southern 

 Hemisphere, though wandering north of the equator from time 

 to time, make up this genus ; two of these inhabit the Cape seas. 



Fig. 144. — Left foot of Fregetta grallaria. x \ 



Key of the Species. 



A. Abdomen white with a centralline of black .. F.melanogaster, -pAGI. 



B. Abdomen whollj' white F. grallaria, p. i6S. 



780. Fregetta melanogaster. Black-bellied Petrel. 



Thalassidroma melanogaster, Gould, Aitn. Mag. N. H. xiii, p. 367 

 (1844) ; if?. B. Austr. vii, ^1. 62 (1847) ; Layard,Ibis, 1863, p. 249, 1867, 

 p. 459 ; id. B. 8. Afr. p. 358 (1867) ; Sperling, This, 1868, p. 292, 1872, 

 pp. 75, 76. 



Thalassidroma tropica, Gould, Ann. Mag. N. H. xiii, p. 866 (1844). 



Ooeanitis tropica, Sharpe, ed. Layard's B. 8. Afr. p. 764 (1884). 



