OCEANODEOMA. 429 



OCEANODROMA. 



Oceanodroma, Reichenb. Af. Syst. Nat. p. iv (1853) ; Salvin, Cat. Birds Brit. Mus. xxv. p. 347 

 (1896). 



In Oceanodroma the tarsus is somewhat shorter than in the preceding genera, not 

 exceeding the middle toe and claw, and the tail is forked. From the last-named 

 character the species of this genus are often spoken of as the " Fork-tailed " Petrels. 



They are mostly sooty-black in colour, but, as a rule, somewhat larger than their 

 allies. 



The species of Oceanodroma are found in the subarctic zones of both hemispheres, 

 but several of the dusky forms are met with in tropical seas, and two have been 

 recorded from off the coast of Western Mexico. Besides those enumerated below, it is 

 quite possible that 0. castro (Harcourt, = 0. cryptoleucura, Ridgway), and 0. homochroa, 

 Coues, may also occur within our limits. 



1. Oceanodroma ksBdingi. 



Oceanodroma k<sdingi, Anthony, Auk, xv. pp. 37^, 314 ^ 316', 317 * ; Rothsch. & Hart. Nov. 

 Zool. ix. p. 415 ^ 



Fuliginoso-nigra : subtus paullo brunneseentior, oapite eolloque magis plumbescentibus ; tectricibus alarum 

 medianis et majoribus pallide fuliginoso-brunneis, plagam alarem indistinctam formantibus, supra- 

 caudalibus longioribus albis, rhachidibus nigris, nonnullis brunneo fimbriatis. Long, tota circa 6-5, 

 ala3 5'5, caudae 2-45, culm. 0*55, tarsi 0-8, dig. medio cum ungue 0'9. (Descr. feminse adultse ex 

 mari, 13° N., 103° "W. Mus. Eotbsohild.) 



Hab. Rbvillagigedo Is., San Benedicte, Socorro I., Clarion 1. {Anthoni/ ''■~*') ; at Sea, 

 lat. 13° N., long. 103° W. (Beck^). 



0. Jccedingi, described from the Eevillagigedo Islands ^, extends further south, as 

 Messrs. Rothschild and Hartert record the capture of three specimens by Mr. Beck 

 at sea, in lat. 13° N. and long. 103° W.^ 



Mr. Anthony rightly compares 0. Jccedingi with Leach's Petrel {0. leucorrhoa), but 

 points out that it is smaller and has a much less deeply forked tail. It belongs, 

 therefore, to the section in which the upper tail-coverts are more or less white 

 {cf. Salvin, Cat. Birds Brit. Mus. xxv. p. 347), but there appears to be a good deal 

 of variation in this respect. A few specimens had these coverts black, with whitish 

 patches on the sides, while one had them totally black, but was otherwise similar ^. 

 A parallel variation is to be noticed in 0. socorroensis. 



In his paper on the birds of the Revillagigedo group ('Auk,' xv. pp. 311-318), 

 Mr. Anthony says (l. c. p. 31 4) that " A number [of 0. koedingi'\ were seen at sea off 

 the island of San Benedicte as late as June 1. We found no evidence of the nesting of 

 small Petrels on any of the islands of this group, It is possibly accounted for by the 



