FAMILY LARIDZ. — GULLS AND TERNS. 39 
Section 2. Length, over 21; bill, over 2; underparts, 
not white. 
Outer webs of primaries, ash color (immature). Larus glaucus. Glaucous Gull. 
See No. 24. 
Outer webs of primaries, dark brown; wing, over 17.50; depth of bill at angle, over .90 
(immature). Larus marinus. Great Black-backed Gull. 
See No. 27. 
Outer webs of primaries, dark brown; depth of bill at angle, under .90; wing, under 17.50 
(immature). Larus argentatus smithsonianus. American Herring Gull. 
See No. 30. 
Section 3. Length, over 21; bill, under 2; underparts, white. 
Back, grayish blue, more or less black on primaries. 
Larus argentatus smithsonianus. American Herring Gull. 
See No. 30. 
Back, pale pearl color; pri- 
maries, whitish or pearl color, 
shading to white at tips. 
Larus leucopterus, 
Iceland Gull. 
See No. 25. 
ka ; Great Black backed Gull. 
ye “he > 
/ a ~~ ~ ; N 
Ring-billed Gull. “= . 
Back, pale pearl color; primaries 
marked with slaty gray. 
Larus kumlienit. Kumlien’s Gull. 
See No. 26. 
Herring Gull. 
