BIRDS OF NORTH AND MIDDLE AMERICA. 575 
Alaska, 1886, 124 (Aleutians and Pribilof Islands; St. Michaels, 1 spec., Sept. 
18, 1876).— AMERICAN ORNITHOLOGISTS’ Union, Check List, 1886, and 2d ed., 
1895, no. 41; 8rd ed., 1910, p. 36.—TowNnsEnp, Cruise ‘Corwin’ in 1885 (1887), 
98 (Pribilof Islands; Otter Island).—Taczanowsx1, Mém. Ac. St. Peters. | 
xxxix, 1893, 1053 (e. Siberia). —CLarx (A. H.), Proc. U.S. Nat. Mus., xxxviii, 
1910, 35 (near Unalaska Island; western Aleutians; Commander Islandc).— 
Cooxg, Bull. 292, U. 8. Dept. Agric., (Biol. Surv.), 1915, 21, fig. 7 (range and 
mnigrations). 
Rissa] brevirostris Datu, Proc. Calif. Acad. Sci., v, 1873, 32 (Pribilof Islands).— 
Covzs, Key N. Am. Birds, 2d ed., 1884, 748.—Ripaway, Man. N. Am. Birds, 
1887, 25. 
{Larus (Laroides)] citrirostris ‘‘Schimper” Brucu, Journ. fiir Orn., 1855, 284 
(Kamchatka). 
[Rissa] kotzebuit Bonararte, Naumannia, 1854, 212 (western North America. 
California). 
Larus warnecki Coinpz, Rev. et Mag. de Zool., 1860, 401 (At. Paul Island, Dering 
Sea). 
Genus PAGOPHILA Kaup. 
Gavia (not of J. R. Forster, 1788) Borg, Isis, 1822, 563. (Type, Larus eburneus 
Phipps=L. albus Gunnerus.) 
Pagophila Kaur, Skizz. Entw.-Gesch. Eur. Thierw., 1829, 69. (Type, by mono- 
typy, Larus eburneus Phipps=L. albus Gunnerus.) 
Cetosparacies Maceituivray, Man. Brit. Orn., ii, 1842, 25!. (Type, Larus eburneus 
Phipps=JL. albus Gunnerus.) 
Medium-sized Laride (wing 300-362 mm.) with tarsus larger than 
middle toe without claw, roughly granulated or almost serrate behind, 
the scutella on front (as well as those of toes) large and prominent; 
webs of feet deeply incised; longer primaries attenuated and sub- 
falcate terminally, and color wholly pure white in adults, sparsely 
spotted with blackish in young. 
Bill much shorter than head (the exposed culmen usually a little 
shorter, rarely slightly longer, than tarsus), relatively stout, very 
slightly compressed; culmen nearly straight or even faintly concave 
basally, gradually decurved from above middle of nostril; gonys 
half as long as mandibular rami or slightly more, straight, ascending 
terminally, its basal angle prominent; nostril relatively large, its 
broader anterior end slightly posterior to gonydeal angle. Wing long 
and pointed, the longest primary (outermost) exceeding tertials by 
considerably more than half length of wing, the longer primaries 
attenuated and subfalcate terminally. Tail more than two-fifths as 
long as wing, truncate. Tarsus longer than middle toe without claw, 
about as long as exposed culmen (usually a little longer, rarely shghtly 
shorter),stout, the transverse scutella of acrotarsium large and prom- 
inent, the planta tarsi roughly granulated or almost serrate; anterior 
toes with thick and prominent transverse scutella, the lateral ones with 
roughly granulated outer edges, the connecting webs of anterior toes 
rather deeply incised; hallux well-developed (rather large for the 
