"Vol. XXXI"! Nichols, Oceanodroma castro. do9 



1914 J 



one a heavier bill with stronger hook. The followmg table shows 

 the tail differences; the bill differences are perhaps better shown by 

 the figures. 



Whereas Atlantic and Pacific birds have little chance to inter- 

 breed, the differences are so slight that, intermediates would be 

 expected and the relationship is best expressed by considering 

 them subspecifically distinct. 



Oceanodroma castro bangsi ssp. nov. 



Type. No. 12413. Collection of E. A. and O. Bangs. 9 . Collected 

 1° N. 93° W., February 6, 1901, by R. H. Beck. 



Bill heavier and more strongly hooked than usual in the genus. Sooty 

 black, wing coverts sUghtly browner. Bases of tail feathers, except middle 

 pair 'broadly white, the shafts of the feathers pale. Upper tail coverts 

 are klmost all lacking in the type specimen, two or three remaining ones 

 white to the end. Probably the coverts were much as usual in the species, 

 and the remaining feathers very likely have had black tips worn off. Bill 

 and feet black. Length (skin) 7.1 in.; wing 6.2; tail 3.6; bill 0.6; tarsus 

 .95; middle toe and claw 1.0. 



The only other specimen at hand, from Cocos Island, has wings 

 moulting and not comparable. The tail and its coverts are also in 



0. c. bangsi. O. c. cryploleucura. 



poor condition. Some of the latter have sharp black tips as usual 

 in the species. Its bill is not dissimilar to that of the Galapagos 



bird. 



Named for Mr. Outram Bangs, of the Museum of Comparative 

 Zoology, Cambridge, to whose appreciation of slight differences 

 our knowledge of racial variation is indebted. 



