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 basaUy; 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 yeUow, the tip whitish, the mandible with a large 

 subterminal lateral spot of red. 



'"^.Young (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 ithe 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 cuhnen, 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 Bjjrrow, Sept. 5, 1897); British 

 Columbia (Vancouver Island, Dec. 20) ;?'^ Lower California (San 

 (San Geronimo Island, Mar. 18, 1897). 



[?J [Larus] chalcopterus Lichtenstein, Nom. Av. Mus. Berol., 1854, 99 (nomen 

 nudum; Polar re^ons; coll. Berlin Mus.). 



[?] [Leucus] chalcoptenis Bonaparte, Compt. Rend., xlii, 1856, 770; Consp. Av., 

 ii, 1857, 216, part (Bering Strait). 



[?] [Lm-us (Laroides)] chalcopterus Bruch, Journ. fiir Orn., 1855, 282 (monogr.). 



[Lams] glaucescens (not of Naumann, 1840) Gray, Hand-list, iii, 1871, 113, no. 

 10965, part. 



Larus nelsoni Henshaw, Auk, i, no. .3, July, 1884, 250 (St. Michaels, Alaska; 

 coll. U. S. Nat. Mus.); in Nelson, Rep. N. H. Coll. Alaska, 1887, 53.— Baird, 

 Brewer, and Ridgway, Water Birds N. Am., ii, 1884, 222. — American 

 Ornithologists' Union, Check List, 1886, and 2d ed., 1895, no. 46; 3d ed.. 

 1910, p. 37.— Nelson, Rep. Nat. Hist. Coll. Alaska, 1887, 53 (Point Barrow. 

 Alaska). — Saunders, Cat. Birds Brit. Mus., xxv, 1896, 287 (Alaska coast; 

 Vancouver Island, Dec. 20). — Dvaight, Auk, xxiii, 1906, 41 (crit.). — Cooke, 

 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. 

 ^ One specimen (the type). 

 c One specimen. 



<i Saunders, Cat, Birds Brit. Mus., xxv, 1896, 288. The specimen a young bird, 

 and the identification doubtful. 



