MONOGRAPH OF THE PETRELS. 



a 6 . Under tail-coverts white . . gavia, p. 120 



b 6 . Under tail-coverts white, 

 but the lateral ones sooty- 

 brown . . . . . . persicus, p. 124 



/ 5 . Axillaries white, or white with 

 a little brown or ashy 

 mottling. 



c 6 . Quills dusky-brown below, 

 not white or ashy-white. 



a 7 . Above black.. .. obscurus, p. 126 



b 7 . Above brown .. auduboni, p. 129 



d 6 . Quills white or hoary- 

 white below 



c 7 . Under tail-coverts 



pure white assimilis, p. 133 ; elegans, p. 136 



d 7 . Under tail-coverts 

 white, the lateral 

 ones more or less 

 distinctly edged with 

 black . . . . bailloni, p. 138 



Under-surface sooty-brown like the upper-surface. 



e". Under wing-coverts sooty-brown, or 



slightly ashy, but not white . . . . tenuirostris, p. 149 



/". Under wing-coverts more or less 

 white, with black shaft-stripes or 

 cross-bars. 



e"'. Under-surface sooty-brown ; throat 



grey . . . . . . . . griseus, p. 145 



/'". Under-surface whitish, with cross- 

 bars of ashy-grey . . creatopus (dark phase), p. 101 



g" . Under wing-coverts sooty-black. 



g'". Larger ; wing, 12 inches, or more ; 

 bill and feet flesh-coloured, the 

 tip of the bill black . . . . carneipes, p. 142 



h'". Smaller ; wing, not exceeding 10 



inches ; bill and feet black . . nativitatis, p. 153 



xlh 



