596 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
an indistinct spot of brownish gray about opposite the distal end of 
the darker area on outer web, the inner web being nearly white for 
about 35.5 mm. anterior to this spot but gradually deepening into 
pale gray basally; fifth primary with the pale gray color fading ~ 
gradually into white at about 45.5 mm. from tip, but the white ter- 
minal portion marked on both webs by a spot of brownish gray, that 
on outer web about 45.5 mm. broad on edge of the web, but less than 
half as wide next to shaft, that on inner web about 12.7 wide, and 
much more distinct than the corresponding spots on third and fourth 
primaries; bill deep yellow, the tip whitish, the mandible with a large 
subterminal lateral spot of red. 
“2Young (Vancouver I., 20th Dec.). This specimen is very simi- 
lar to the young of L. glaucescens, but the retrices are of a deeper brown 
and unmottled on the exterior webs of the outermost pair. In this 
respect the bird resembles the young of L. occidentalis, but some new 
gray feathers appearing on the mantle are far too pale for that 
species. The measurements suit L. nelsoni better than L. glau- 
cescens.’’* 
Adult male.—Wing, 468; tail, 194; exposed culmen, 57; tarsus, 69; 
middle toe, 64.° 
Adult female.—Wing, 417; tail, 172.5; exposed culmen, 51; tarsus, 
61; middle toe, 54.°¢ 
Breeding range unknown, and has been taken at few localities 
only, as follows: Alaska (St. Michael, June 20, 1880; Coast Bering 
Strait, date unrecorded; Point Barrow, Sept. 5, 1897); British 
Columbia (Vancouver Island, Dec. 20);2¢ Lower California (San 
(San Geronimo Island, Mar. 18, 1897). 
[?] [Larus] chalcopterus Licutenstein, Nom. Av. Mus.’ Berol., 1854, 99 (nomen 
nudum; Polar regions; coll. Berlin Mus.). 
[?] [Leucus] chalcopterus Bonaparte, Compt. Rend., xlii, 1856, 770; Consp. Av., 
ii, 1857, 216, part (Bering Strait). 
[?] [Larus (Laroides)] chalcopterus Brucs, Journ. fiir Orn., 1855, 282 (monogr.). 
[Larus] glaucescens (not of Naumann, 1840) Gray, Hand-list, iii, 1871, 113, no. 
10965, part. 
Larus nelsoni Hensuaw, Auk, i, no. 3, July, 1884, 250 (St. Michaels, Alaska; 
coll. U. S. Nat. Mus.); in Nelson, Rep. N. H. Coll. Alaska, 1887, 53.—Batrp, 
Brewer, and Rieway, Water Birds N. Am., ii, 1884, 222.—AMERICAN 
OrnitrHoxocists’ Union, Check List, 1886, and 2d ed., 1895, no. 46; 3d ed., 
1910, p. 37.—NezLson, Rep. Nat. Hist. Coll. Alaska, 1887, 53 (Point Barrow, 
Alaska)—Saunpers, Cat. Birds Brit. Mus., xxv, 1896, 287 (Alaska coast; 
Vancouver Island, Dec. 20).—Dwicut, Auk, xxiii, 1906, 41 (crit.).—CooxE, 
Bull. 292, U.S. Dept. Agric. (Biol. Surv.), 1915, 30, fig. 12 (range and migra- 
tion). 
a Saunders, Cat. Birds Brit. Mus., xxv, 1896, 288. 
5 One specimen (the type). 
¢ One specimen. 
@ Saunders, Cat. Birds Brit. Mus., xxv, 1896, 288. The specimen a young bird, 
and the identification doubtful. 
