NORTH AMERICAN BIRDS. 
d', Wing 16.25 or more, and not more than 2.36 times as long as the 
tail; exposed culmen 1.88 or more. Adult in summer: Mantle 
very pale pearl-gray. Adult in winter: Similar, but head and 
neck streaked with pale brownish gray. Young: Grayish 
white, tinged with brownish gray on lower parts, the upper 
parts transversely mottled with same. Immature (second 
year?): Entirely white, including mantle and primaries. 
Downy young: Grayish white, paler below; head and neck 
irregularly marked with scattered large spots of dusky, the 
back, wings, and rump irregularly clouded with dark grayish. 
é. Length 26.00-32.00, wing 16.75-18.75 (17.99), tail 7.40-8.50 
(8.07), culmen 2.30-2.70 (2.52), depth of bill through angle 
.80-.95 (.88), through base .83-1.00 (.93), tarsus 2.60-3.05 
(2.85), middle toe (with claw) 2.68-3.00 (2.84). Eggs 
8.13 x 2.14. Hab. Coasts of the North Atlantic, and 
Arctic seas from Cumberland Gulf to Spitzbergen; south, 
in winter, to Long Island and the Great Lakes. 
42. L. glaucus Brinn. Glaucous Gull. 
é. Length about 25.00-28.00, wing 16.25-18.00 (17.12), tail 7.00- 
7.50 (7.28), culmen 1.88-2.30 (2.06), depth of bill through 
angle .72-.85 (.79), through base .70-.80 (.75), tarsus 2.40- 
2.78 (2.57), middle toe (with claw) 2.35-2.75 (2.55). Eggs 
3.05 xX 2.03. Hab. Bering’s Sea and adjacent waters, 
northeastward to Point Barrow, southwest (in winter) to 
Japan... 42.1. L. barrovianus Rivew. Point Barrow Gull. 
d@. Wing not more than 17.00 (usually less than 16.00), and nearly 
2.50 (averaging 2.41) times as long as the tail; exposed culmen 
not more than 1.70. In plumage exactly like Z. glaucus and 
LL. barrovianus. 
Length 24.00-26.00, wing 14.75-16.50 (15.41), tail 6.00-6.70 
(6.41), culmen 1.60-1.70 (1.67), depth of bill through angle 
.62, through base .55-.62 (.59), tarsus 2.10-2.40 (2.22), mid- 
dle toe (with claw) 2.10-2.35 (2.21). Eggs 2.79 « 1.89. 
Hab. Coasts of the North Atlantic; south, in winter, to 
Massachusetts and the Great Lakes. 
43. L. leucopterus Faser. Iceland Gull 
ce’. Primaries marked with distinct white tips and darker subterminal 
spaces. 
d'. Darker spaces of primaries gray. 
é. Second quill very pale pearl-gray, or bluish white, very broadly 
tipped with white, the outer web with an elongated space 
of gray, everywhere very sharply defined against the paler 
ground-color. 
1 Larus barrovianus Riwew., Auk, iii. July, 1886, 330. 
