40 



KEl' TO THE BIRDS OF EASTERN NORTH AMERICA. 



Section 4. Length, over 21; bill, under 2; underparts, 



not white. 



Outer webs of iiriinaries, ilnvk brown ; bill, over 1.90 Cinimature). 



Lams nnientatits umithsonianMS. American Herring Qull. 



See No. 30. 



Outer webs of iiriiuaries, browuish; bill, under 1.90 immature) 



Outer webs of primaries, ash color (immature). 



Lams laimlieni. Kumlien's Gull. 



See No. 26. 



I^nms h'ncoptems. Iceland Qull. 



See No. 25. 



Section 5. Length, under 21. 



A baud .)f bb.ck (m the bill (adult), liill, dull yellow, tipped with black (immature). 



Lams delmmrensis. Ring-billed Gull. 

 See No. 31. 



Terns. 



Gulls. 



-X- 



Qroup 5, Wing, over 17 inches long. 



Primaries, marked with more or less lilack. Lams marhius. Great Black-backed GuII. 



See No. 27. 



No blMel< OIL prim.-iries. 



Lams <ihmrus. Glaucous Gull. 



See No. 24. 



For (lircctinns for ine.isurcment, sec paji^e 0. 



