Vor. Ii, Pr. IT] LOOMIS—A REVIEW OF THE TUBINARES 161 
beali,’” and the accompanying table of measurements shows no 
notable superiority in dimensions in favor of the Alaskan birds. 
“O. beldingi,” therefore, has no claim to recognition. 
Compared with the northern specimens, the six Farallon 
specimens exhibit no marked disparity in size. They average 
decidedly larger, however, than the series of “O. kaedingi.” 
The breeding grounds of “O. kaedingi’’ have not been re- 
ported. The specimens, referred to above, were taken at sea 
off Lower California; twenty-five of them, including the type, 
in latitude 31° N., longitude 117° W., July 25, 1897, and 
three in latitude 28° 35’ N., longitude 118° 30° W., July 18, 
1897. The plumage of all has suffered from wear, and the 
depth of the fork of the tail has thereby been diminished, ren- 
dering that dimension unreliable. As shown by the tables of 
measurements, the various dimensions intergrade with the 
minimum dimensions of the northern birds, the alleged specific 
characters proving inconstant. Besides averaging smaller, the 
“O. kaedingi’” specimens seemingly average darker than the 
northern ones. The white of the upper tail-coverts is greatly 
restricted in several of them. In three it is reduced to two 
lateral traces. Two others are intermediate, and connect the 
two phases, which I believe exemplify dichromatism and not 
individual variation. A tendency to this bicoloration is mani- 
fested in some of the specimens from the other regions, the 
white being conspicuously interrupted by the dark central 
coverts. 
Of the forty-three Expedition specimens of “O. socorroen- 
sis” obtained on July 14, 15, 17, 1905, on San Benito Islands, 
not one has any indication of white on the upper tail-coverts. 
Mr. Adriaan Van Rossem states that on Los Coronados 
Islands, late in June, 1913, “the majority of birds showed at 
least a trace of white, while of those taken August 13 of the 
present year [1914] only about one in four showed the above 
mentioned character.”* Specimens with the upper tail-coverts 
extensively white intergrade with the darkest concolor speci- 
_ mens, and also are apparently indistinguishable from examples 
of O. leucorhoa from the north. As in the “O. kaedingv’ 
series, I attribute the dual style of coloration to dichromatism. 
The absence of a dark phase on the Atlantic indicates a geo- 
1 Condor, v. 17, p. 78. 
