OCEANODROMA. 429 
OCEANODROMA. 
Oceanodroma, Reichenb. Av. Syst. Nat. p. iv (1852); 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 O. homochroa, 
Coues, may also occur within our limits. 
1. Oceanodroma kedingi. 
Oceanodroma kedingi, Anthony, Auk, xv. pp. 37°, 314”, 316°, 317%; Rothsch. & Hart. Nov. 
Zool. ix. p. 415’. 
Fuliginoso-nigra: subtus paullo brunnescentior, capite colloque 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, 
ale 5°5, caude 2°45, culm. 0°55, tarsi 0°8, dig. medio cum ungue 0°9. (Deser. femine adulte ex 
mari, 13° N., 103° W. Mus. Rothschild.) 
Hab. Revittacicevo Is., San Benedicte, Socorro I., Clarion I. (Anthony 1~*); at SEA, 
lat. 13° N., long. 103° W. (Beck ®). 
0. kedingi, described from the Revillagigedo 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.4 
Mr. Anthony rightly compares 0. kedingi with Leach’s Petrel (O. 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 O. socorroensis. 
In his paper on the birds of the Revillagigedo group (‘ Auk,’ xv. pp. 311-318), 
Mr. Anthony says (J.¢. p. 314) that “A number [of 0. keedingi| were seen at sea off 
the island of San Benedicte as late as June lI. 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 
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