606 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
tip, the extremity of this grayish portion obtusely wedge-shaped and 
fading into white at the apex; sixth primary without any distinct 
black area on inner web, which is white for about 45.5 mm. from tip 
(measured along shaft), the outer web white for about 15.5 mm., then 
slaty black for about 18 mm. (measured along edge), the anterior 
outline of the black deeply concave and partially inclosing a grayish 
white space; bill deep yellow, paler at tip, the mandible with a subter- 
minal lateral spot of red; rictus yellowish flesh-color; iris naples 
yellow or yellowish cream color; bare orbital ring purplish gray 
(in life); legs and feet pinkish flesh color (in life). 
Adults in winter.—Similar to summer adults, but head and neck 
(especially pileum and hindneck) streaked with dusky. 
Young.—‘ Clove-brown, with darker streaks on the head and neck, 
dark centers and, buffish-white margins to the feathers of the mantle; 
rectrices nearly uniform brown, with very little marbling at the bases 
and on the outermost; primaries brown, paler on their inner webs; 
edge of wing and coverts almost unmottled grayish brown; under 
surface brown, the tail-coverts striated; bill dark horn-color, paler 
at the base; tarsi and toes reddish brown.’ 
Adult male.—Wing, 445-470 (458.6); tail, 179-196 (189.2); ex- 
posed, culmen, 59-65.5 (61.9); tarsus, 64-72 (68.7); middle toe, 62— 
65.5 (64). 
Adult female.—Wing, 436; tail, 182; exposed culmen, 54; tarsus, 
59; middle toe, 55.5.°¢ 
Coasts and islands of eastern Siberia and Kamchatka and Okotsk 
Sea, breeding from eastern Siberia (Plover Bay; coast near Bering 
Strait; Gichiga) to Kuril Islands; migrating southward to northern 
Japan (Hakodate; Sakhalin Island; Samushi Island, and mouth of 
Amur River; casual or occasional in Alaska (Chernoffsky Bay, 
Unalaska, large flock, Oct.1, 1880; Port Clarence; Sitka), on Diomede 
Islands in Bering Strait (Sept., 1880), and on Herald Island, Arctic 
Ocean; accidental at Franklin Bay, Mackenzie (June 9, 1901). 
Larus argentatus (not of Pontoppidan, 1763) Mippenvorrr, Reis. Sibir., Zool., 
1851, 243, part (Okhotsk Sea).—Kuirriirz, Denkw. Reis., ii, 1858, 225, part. 
a Saunders, Cat. Birds Brit. Mus., xxv, 1896, 259, 260. 
b Five specimens. 
¢ One specimen (Kuril Islands, June). 
Ex- . 
Locality. Wing. | Tail. | posed | Tarsus.) Middle 
culmen 
MALES. 
One adult male from Bering Island, Kamchatka (May 5)...-.. 463 191 60 66 62 
Four adult males from Kuril Islands (June, August).....-..... 457.5 188 62.4 69.4 64.5 
