154 GULLS 
2. Tail marked with black. 
A. Wing over 13°25. 
a. Primaries mostly white ......... 39. Ivory GuLu (Im.). 
b. Primaries black or mostly black. . 54. Rine-Bintep Guut (Im.). 
B. Wing under 13°25. ; 
a. Hind-toe very small, without a nail... . 40. Kirrrwaxs (Im.). 
b. Hind-toe normal, with a nail. 
1. Tarsus 1°50 or over....... 58. LaucHine Guu (Im.). 
oc. Tarsus under 1°50. . 
c*, Secondaries pearl color, tail square. 
60. BoNAPARTE’s GULL (Im.). 
c3, Secondaries mostly white, tail rounded. 
61. Ross’s Guuu (Im.) 
Fia. 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 GuLu. Ads.—Entire plumage 
pure white; bill yellow, feet black. Jm.—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 
