154 
GULLS 
2. Tail marked with black. 
A. Wing over 13*25. 
a. Primaries mostly white 39. Ivory Gull (Im.). 
b. Primaries black or mostly black . . 54. Ring-billed 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. 
b 1 . Tarsus 1*50 or over 58. Laughing Gull (Im.). 
c 1 . Tarsus under 1*50. 
c 2 . Secondaries pearl color, tail square. 
60. Bonaparte’s Gull (Im.). 
c 3 . Secondaries mostly white, tail rounded. 
61. Ross’s Gull (Im.) 
d 
/ ' / e 
Fig. 78. First primaries of adult Gulls, seen from below: (a) Herring Gull; ( b ) Ring- 
billed Gull; (c) Laughing Gull; ( d ) Franklin’s Gull; (e) Bonaparte’s Gull. 
39. Pagophila alba {Gunn.). Ivory Gull. Ads. — Entire plumage 
pure white; bill yellow, feet black. Im. — Similar to ad., but wing and tail- 
feathers, and sometimes wing-coverts, with a black spot at their tips. L., 
17*00; W., 13*25; T., 5*50; B., 1*35. 
Range. — Arctic seas. Breeds in high Arctic latitudes from Melville 
