Vol 'M)i9 XVI ] Dwight, Larus hyperboreus. 243 



If it were not for certain aspects of the matter I would merely 

 reaffirm my convictions of 1906; for it is a question whether Dr. 

 Oberholser has added anything new to the original claims made by 

 the describer, Mr. R. Ridgway (Auk, III, 1S86, p. 330). This 

 does not seem to be the case, for his diagnosis is virtually a restate- 

 ment of Mr. Ridgway's, except that a supposed character of the 

 bill is discarded on evidence I submitted in 1906. My measure- 

 ments had shown that this character, namely, " depth through the 

 angle never less and usually decidedly greater than through the 

 base," was not diagnostic, but this was not my only "evident 

 reason" then for rejecting " barrovianus" as Dr. Oberholser now 

 wrongly assumes. What I said was that this form "is scarcely 3% 

 smaller [than glaucus] in size and 4% smaller in bill" and further- 

 more, I said; "It is true that the largest specimens of barrovianus 

 never quite reach the dimensions of the largest glaucus, but over- 

 lapping of size is so considerable even when careful comparison 

 of sexes is made that without first reading the labels one cannot, 

 except in a very few cases, tell whether a bird is from Greenland 

 or Alaska. The variation in the size and shape of the bill in gulls 

 is very great and a few millimeters difference in wings that are as 

 long as one's arm is hardly ground on which to rest a subspecies, 

 much less a full species." 



These conclusions may be contrasted with Dr. Oberholser 's 

 recent diagnosis which reads, "Similar to Larus hyperboreus 

 hyperboreus, but smaller, the bill particularly so and relatively as 

 well as actually more slender; mantle decidedly darker; and the 

 line of demarcation between the white tips to the primaries and the 

 pale grayish basal portions usually more evident." I would here 

 call attention to the fact that the "line of demarcation" is not a 

 distinct character but a corollary of the preceding, for the color of 

 the mantle in the Glaucous Gull regularly runs over, so to speak, 

 into the wings, and a darker mantle would mean darker bases of 

 the primaries and therefore greater contrast as a matter of course. 

 Consequently, in the final analysis there are two characters and 

 only two on which "barrovianus" rests,— (1) darker mantle and 

 (2) smaller size, especially of the bill. I will invite attention to a 

 new estimate of the value of these characters. 



1. As for the color of the mantle, which Mr. Ridgway calls 



