Key to the Species. 
A. Abdomen sooty-black ; rump white ; tarsus 
booted .. .. .. .. . . O.oceanicus exasperatus^p. W. 
Abdomen white; rump grey ; tarsus scutellated 0. nereis nereis, p. 15. 
Note. — As, in the Monograph of the Petrels, so in this volume the Petrels are given 
in conventional attitudes, and the figures can only be considered as showing the colora- 
tion of the species, and not as being life-like representations. It is now known that these 
birds cannot stand as usually figured except, perhaps, the Albatroses. 
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