Vor. II, Pr. IT) LOOMIS—A REVIEW OF THE TUBINARES 163 
pear to be absent. At the point of nearest approach the two 
species may be readily distinguished as follows: 
O. leucorhoa O. castro 
Tips of upper tail-coverts more Tips of upper tail-coverts black. 
or less dark gray, becoming white 
with wear. 
Lateral rectrices not definitely Lateral rectrices definitely white 
white at base for nearly an inch. at base for nearly an inch, or 
more. 
Eight “O. monorhis’ specimens from Los Coronados Islands 
(Nos. 5257-5264, coll. J. Grinnell, Aug. 6, 1902) and one 
from San Benito Islands (No. 22498 Carnegie Mus., July 14, 
1897) are in natal down. Most have reached the stage where 
the secondary down has emerged on the upper and lower parts 
of the body and posterior portions of the neck. In color the 
primary down is hair brown (darkest on the San Benito speci- 
men) and the secondary down chaetura drab. In a specimen 
from Humboldt County, California (No. 16718 Mus. Vertebr. 
Zool., Univ. Calif., Sept. 4, 1910), the breast and abdomen are 
still clothed with the dark secondary down, concealing the de- 
finitive feathers. On the upper parts of the body and on the 
occiput vestiges of the dark secondary down still remain. An- 
other specimen from the same locality (No. 16719 Mus. 
Vertebr. Zool., Sept. 4, 1910) retains the dark secondary down 
on the abdomen. In these two specimens the definitive feathers 
are not as brown as in the adults from the same locality, but 
are fairly matched by later autumn specimens taken at sea off 
the California coast. 
The material at hand exhibits no exceptional features in the 
moult. In July specimens from Humboldt County, California, 
there are no growing feathers, which is also true, with one ex- 
ception, in July “O. monorhis” specimens from the San Benito 
Islands. Feather growth is likewise in abeyance in the speci- 
men from Pigeon Point, California, May 7, and in five of the 
six June specimens from Southeast Farallon Island. The other 
Farallon specimen, June 18, is renewing upper tail-coverts and 
feathers of the breast. Three belated June specimens taken 
just below the Galapagos Islands are also moulting, one of 
them, at least, undergoing a complete rehabilitation of plum- 
