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Genus OCEANODROMA. 



Procellaria apud Gmelin (1788). 



Hydrobates apud Boie, Isis, 1822, p. 562. 



Pachyptila apud Steph. in Shaw's Gen. Zool. xiii. p. 255 (1826). 



Thalaasidroma apud Audub. Orn. Biogr. iii. p. 434 (1835). 



Oceanodroma, Reichenb. Natiirl. Syst. Vogel, p. iv. Type Procellaria furcata (1852). 



Cymochorea, Coues, Proc. Acad. Phil. 1864, p. 75. Type Oceanodroma leucorrhoa. 



The present genus comprises the Storm-Petrels which have the tail forked, and includes twelve 

 species, only two of which occur within the Palsearctic area, viz. 0. leucorrlioa and 0. crypto- 

 leucura. The range of the genus extends over the seas chiefly of the northern hemisphere, 

 southward to the coast of Peru and the island of St. Helena. 



In habits they agree closely with Procellaria, being chiefly pelagic, and seldom seen on or 

 close to land, excepting during the nesting-season, when they frequent islands and deposit a 

 single egg either in a burrow in the soil or amongst stones. 



Oceanodroma furcata, which inhabits the North Pacific Ocean, is the type of the genus, but 

 its Palaearctic representative, Oceanodroma leucorrhoa, has the bill rather stout, longer than 

 the head, compressed, much decurved at the tip, and acute ; nostrils open in front by two 

 approximated tubes ; wings long and narrow, the first primary rather longer than the fourth, 

 the second longest; tail long, rather deeply forked; legs slender; hind toe very small, anterio 

 toes long, slender ; interdigital membrane emarginate ; claws curved, compressed, moderatel 

 acute. 



In the ' Birds of Europe ' I included 0. leucorrhoa in the genus Procellaria, but have since 

 found that the Fork-tailed Petrels should be separated specifically. 



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