68 GULLS. 



ft*. Primaries pearl-gray, tipped with white, and with well-defined 

 gray spaces on the outer webs of the two outer primaries and on 

 both webs of the third and fourth primaries. 



45. KUMLIEN'S GULL. 



c 1 . Bill over 2-00 42. GLAUCOUS GULL. 



C. Bock grayish, whitish, or brownish, or mottled or spotted with gray- 

 ish or brownish. 



a. Tail black or blackish, with or without irregular white markings. 

 a 1 . Wing over 17'50 ; depth of bill at nostril over -70. 



47. BLACK-BACKED GULL (Im.). 

 a*. Wing under 17-50; depth of bill at nostril under -70. 



51a. AM. HEKKINU GULL (Im.). 51. HKKKIM; (iri.i. (Im.). 



b. Tail white or whitish or grayish brown, with or without black 

 markings. 



ft>. Bill under 2-00 43. ICELAND GULL (Im.). 



ft. Bill over 2-00 42. GLAUCOUS GULL (Im.). 



II. Wing under 15-00. 



1. Tail pure white. 



A. Head and throat slaty black. 



a. Outer primary block or mostly black. 



a 1 . Outer primary entirely black .... 58. LAUGHING GULL. 

 a*. Inner hulfot'inncr wel>s of iirst primary white. 



<',1. S.\I;IM-:'S GULL, 



b. Outer primary mostly white. 



A 1 . Tip of first primary white 69. FHANKI.IN'S GULL, 



4 1 . Tip of first primary black CO. BONAPARTE'* Gi "LL, 



J5. Head white, sometimes washed with pearl-gray, 



a. Wings white ,89, IVORY Ut'LL. 



b. Primaries with more or less black. 

 ft. Wing over 1100. 



4. Hind toe very small, without a nail . . . 40. KITTJWAKE. 



b*. Hind toe normal, with a nail ... 64. RINO-I'.II.I.KD Gi I.L. 



<>. Wing under 11-00 , , , 61. Ross's GULL. 



2. Tail marked with black. 



A. Wing over 18-25. 



a. Primaries mostly white 89. IVOKY GULL (Tm.). 



b. Primaries black or mostly black . 54. RINGTBILLEI> GULL (Im.). 



B. Wing under 13-25. 



a. Hind toe very small, without a nail ... 40. KITTIWAKE (Im.). 



b. Hind toe normal, with a nail. 



A 1 . Tarsus 1-50 or over 58. LAUGHING GULL (Im.). 



c 1 . Tarsus under 1-50. 

 <'. Secondaries pearl color, tail square. 



60. BONAPARTE'S GULL (Im.). 

 c*. Secondaries mostly white, tail rounded. 



61. Ross's GULL (Im.). 



39. Gavia alba < Ounn.}. IVORY GULL. Ad. Entire plumage puro 

 white; bill yellow, feet black. Im. Similar to ad., but the wing and tail 



