Brewster on a Petrel new to North America. 
93 
have seen ; and there is this peculiarity in addition, that the under 
tail coverts remain pure white.” 
This specimen had been previously described by Peale (Zool. 
U. S'. Expl. Exped., 1848, p. 299) under the name of Procella- 
ria gularis , but Dr. Coues, after expressing his doubts as to its 
probable relationship, provisionally referred it to NE. mollis ,* 
and there the matter has rested, the type, up to the present time 
remaining unique. 
The above description proved so nearly satisfactory that upon 
first reading it I felt little doubt as to the relationship of the bird 
in hand : but all uncertainty on this point has since been removed, 
for through the kind offices of Mr. Ridgway, the Smithsonian 
specimen “No. 15,706” is now before me. A comparison of 
the two at once establishes their perfect specific identity. The 
differences that obtain are just those which would be expected 
when the relative ages of the specimens are considered. Peale’s 
example is a young bird, apparently in its first year ; while mine, 
if not an adult, is certainly much older and probably in nearly 
mature plumage. Generally speaking, it may be said to differ 
from the type in having the predominating areas above pure cin- 
ereous instead of plumbeous ; the crown and forehead much 
mixed with white ; the lores and a conspicuous superciliary stripe 
pure white, unmingled with darker color ; the transocular facias, 
though equally dark, much more restricted ; and the white areas 
below, - }' considerably more extended and of a purer character. 
Of the stages in NE. mollis . Dr. Coues says : “the older the bird 
the clearer and purer is the cinereous and the more trenchantly 
defined are the boundaries of the several differently colored areas ; 
the difference in this respect being especially notable in the fore- 
head and sides of the breast. Young birds are all over of a 
pretty uniform deep brownish ash or fuliginous cinereous ; in- 
clining to smoky brown on the wings and tail.” 
And now a word as to the relationship which these interesting 
specimens bear to NE. mollis. Of the latter I have only a single 
specimen, an adult, kindly furnished by my friend Mr. Allen, 
from the collection of the Cambridge Museum of Comparative 
Zoology. But the testimony which it affords, taken in connection 
* Upon looking more closely into the earlier history of the case I find that this ar- 
rangement was first instituted by Cassin, who, in the second edition of the U. S. Expl. 
Ex., places Peale’s specimen under Procellaria mollis. 
t The type of gularis has a pure white throat and light breast. 
