576 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
family), with well-developed, rather large, claw; claws of anterior 
toes large and strongly curved; bare portion of tibia very short, in- 
cluding only the extreme lower portion. 
Coloration.—Adults (at least in summer) entirely immaculate 
white; young (and winter adults?) white, sparsely spotted with 
dusky. 
Range.—Circumpolar regions, south in winter to British Islands, 
France, Long Island, Lake Ontario, British Columbia, etc. (Mono- 
typic.) 
PAGOPHILA ALBA (Gunnerus). 
IVORY GULL. 
Adults in summer (sexes alike).—Entirely immaculate white, the 
shafts of primaries yellowish; bill greenish gray or olivaceous (drying 
more dusky) basally (as far as anterior end of nostrils), the terminal 
portion yellow (sometimes tinged with red or orange), the tomia 
yellowish or horn color; isis dark brown; bare orbital ring brick red 
or vermilion; legs and feet black. 
Winter plumage.— (Undetermined or undescribed.) 
Young.—Similar to adults, but anterior portion of head-grayish 
brown or brownish gray, primary coverts, primaries, tertials, longer 
scapulars, and rectrices with a terminal or subterminal spot of dusky, 
and lesser wing-coverts with small central spots of the same; bill 
blackish, clouded with pale yellowish. 
Downy young.—Entirely pure white, even to the base of the down. 
Adult male.—Wing, 318-362 (833.6); tail, 128.5-156.5 (187.4); 
exposed culmen, 31-36 (34.9); tarsus, 33-38 (85.8); middle toe, 
29.5-36 (33.7).¢ 
Adult female—Wing, 300-327 (315.7); tail, 183-137 (185); ex- 
posed culmen, 33-34 (33.3); tarsus, 35-39 (86.3); middle toe, 31.5- 
34.5 (83)? . 
a Five specimens. b Three specimens. 
Ex- - 
Locality. Wing. | Tail. beet Tarsus. wets 
men. 
MALES, 
One adult male from southern Greenland.............2......- 318 128.5 31 33 29.5 
Two adult males from head of Cumberland Gulf.............. 332.5 | 136.5 36, 2 36.2 35 
One adult male from Quebec (Godbout, December)........... 323 129 35 35.5 34 
One adult male from Bering Island, Kamchatka.............. 362 156.5 36 38 35 
FEMALES. 
One adult female from off northeast Greenland............... 300 137 34 35 31.5 
Two adult females from head of Cumberland Gulf. ........... 323.5 | 134 33 37 33.7 
