3^0 RiDGWAY 071 the Glaucus Gull of Bering's Sea. [July 



ON THE GLAUCOUS GULL OF BERING'S SEA 

 AND CONTIGUOUS WATERS. 



BY ROBERT RIDGWAY. 



The National Museum having accumulated a considerable 

 series of specimens of JLarus giauais from various North At- 

 lantic localities, and also an equal number of what appeared to be 

 the same species from the shores of Alaska and adjacent waters, 

 certain very obvious differences between specimens from the two 

 regions attracted attention, and eventually led to a careful compar- 

 ison. The result is that the so-called L. glauctis from Alaska, 

 etc., proves to be a quite distinct and easily recognized species, 

 which seems to \\xsn been hitherto unnamsd. I therefore pro- 

 pose to name and characterize it as follows : — 



Larus barrovianus, sp. nov. 



Sp. Char. — In phmiage resembling jL.^/rt/^cV/.s and ^. Iciicoptcrtis^ and in 

 size intermediate between these two species ; very different from the former, 

 however, in shape of the bill, which has the depth through the angle never 

 less, and usually decidedly greater, than through the base, instead of ex- 

 actly the reverse ; mantle averaging somewhat darker than in glaucus, 

 with an obvious or tolerably abrupt line of demarkation between the white 

 tips to the primaries and the pearl-blue of their basal portion. 



Males (four specimens) : Wing, 17.00-18.00 (average, 17-44) ; tail, 7.30- 

 7.50 (7.45) ; culmen, 2.00-2.30 (2.19) ; depth of bill through angle, .80-. 85 

 (.82) ; through base, .75-. So (.79) ; tarsus, 2. 55-2. 78 (2.64) ; middle toe (with 

 claw), 2.53-2.75 (2.64). 



Females (four specimens) : Wing, 16.25-17.25 (16.S1) ; tail, 7.00-7.20 

 (7. 11) ; culmen, 1.88-2.05 (1.98) ; depth of bill thi-ough angle, .72-. 80 (.75) ; 

 through base, .70-. 75 (.72) ; tarsus, 2.40-2.50 (2.45) ; middle toe (with claw), 

 2.35-2.50 (2.42). 



Habitat. Bering's Sea and contiguous waters, northeastward to Point 

 BaiTow, south westward to Japan (in winter). (Type, No. 88,913, U. S. 

 Nat. Mus., $ ad.. Point Barrow, Alaska, August 4, 18S2 ; Middleton 

 Smith, collector.) 



The specimens measured above are all adults, and are from the 

 two localities of St. Michaels and Point Barrow. An equal num- 

 ber of adults of Z. ^/a/^cz^j- (only two examples having the se.x 

 determined, however), measure as follows: 



Males (presumed, or ascertained; six specimens) : Wing, 17.60-18.75 

 (1S.20) ; tail, 7.70-S.50 (8.12); culmen, 2.42-2.70 (2.56); depth of bill at 

 angle, .86-.95 (.91), at base, .90-1.00 (.95) ; tarsus, 2.60-3.05 (2.91) ; middle 

 toe (with claw) 2.75-3.00 (2. 89). 



