MONOGRAPH OF THE PETRELS. 



Adult male. General colour above sooty-black, r with a strongly indicated gloss 

 of leaden-grey ; the wing-coverts sooty-brown, and with faint evidences of hoary- 

 grey margins at the ends of the feathers ; lower rump and upper tail-coverts white, 

 forming a broad band ; primary-coverts, quills and tail black ; the outer tail-feathers 

 white at the extreme base, the base of the shaft also white ; crown of head and sides of 

 face as well as the throat sooty-black, distinctly shaded with plumbeous-grey, the 

 throat being slightly mottled with white, the lower throat and chest somewhat 

 sooty ; centre of the breast and abdomen also sooty-black, as also the under tail- 

 coverts, which have white bases, the lateral ones being white, with some black near 

 the ends of the inner webs ; sides of breast, sides of abdomen, and flanks, pure white ; 

 axillaries white ; lesser under wing-coverts and the coverts round the edge of the wing 

 sooty-black ; median and greater under- wing-coverts pure white ; quills dusky-black 

 below, the inner webs inclining to leaden grey ; " bill and feet black, as also the webs ; 

 iris dark brown " (N. Hanson). Total length, about 7.5 inches ; culmen, 0.5 ; wing, 

 6.4 ; tail, 2.7 ; tarsus, 1.5 ; middle toe and claw, 1.1. 



Adult female. Similar to the male. Total length, about 7.0 inches; culmen, 

 0.5 ; wing, 6.5 ; tail, 2.75 ; tarsus, 1.4 ; middle toe and claw, 0.95. 



Young birds have the chin more or less mottled with white, and have a few black- 

 tipped feathers on the breast and abdomen, as well as some greyish-white fringes to the 

 dorsal feathers. 



As Salvia remarks, the amount of white on the throat varies in extent. Most 

 specimens have the chin mottled with white, but in very old birds it is entirely 

 black, like the rest of the throat and chest. 



The series in the British Museum measures as follows : — 



$ ad. Wing, 6.4-6.7 inches; tarsus, 1.5-1.55; middle toe and claw, 1.1-1.15. 



? ad. Wing, 6.5-6.7 inches; tarsus, 1.45-1.7; middle toe and claw, 0.95-1.15. 



The descriptions of the adult male and female are taken from a pair of birds 

 collected by Nikolai Hanson during the voyage of the " Southern Cross," and the 

 figure is taken from a specimen from Port Essington in our own collection. 



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