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lighter. Bases of primaries very different, the blue is much lighter, fades 
into nearly white at its juncture with the black; extends for a greater dis- 
tance, and runs up further in the centre than along the edges of the inner 
vane ; tarsus about equal to the middle toe and claw, while in canus the tarsus 
is a fourth longer, as in Delawarensis. The collections of Messrs. Kennicott 
and Boss would seem to indicate that this gull is extremely abundant in the 
interior of Arctic America. 
Genus II. Blasipus Bonaparte. 
Blasipus, Bp., 1852, fide Lawr. Bp., 1856, type Lams Heermani, Cass. 
Adelarus , Bruch, 1853. Id., 1855, p. 
12. Blasipus Heermani, Bon. ex Cass. 
? Larus Belcheri, Vig., 1829. ? Lencophacus Belcheri , Bp., 1856 ; (nec 
“ Adelarus Belcheri, Vig. ; fuliginosus Gould ” Bruch, 1853 et 1855). 
Larus Heermani, Cass., 1852. Blasipus Heerm., Bp.. 1856; Lawr., 1858. 
Adelarus Heerm. Bruch, 1853* et 1855, excl. synon. 
Sp. Char. — Bill bright Vermillion, black from angle to tip. Head all round 
white, gradually merging on the neck to a plumbeous ash, which extends 
over the whole under parts (considerably lighter on the abdomen and under 
tail coverts,) and also on the rump, but which on the back and wings deepens 
into a plumbeous slate color. Tips of secondaries and tertials broadly white. 
Primaries black, the tips of all but the three outer ones white. Tail black, 
narrowly tipped with white. ‘‘Length about 17*50 inches; wings 13*50; 
tail 5*50.” 
Habitat.— Pacific Coast of North America; Puget’s Sound; California; 
Mazatlan, Mex. 
Genus III. Rissa Leach. 
Larus, Linnaeus, 1758, (nec 1744, nec 1735, fide Gray.) 
Gavia, Boie, 1822, (nec Moehr. 1752.) 
Rissa, Leach, 1825, (typus Larus rissa, Briinn.) 
Cheimonea, Kaup, 1829, (typus idem.) 
Pulocondora Reichenbach, fide Bp. 
13. Rissa tridactyla Bon. ex Linn. 
Larus rissa Briinn, 1764. L. tridaetylus et rissa, Linn. 1766. L.torquatus, 
L. gavia, et L. canus, Pall., 1811. Rissa Brunnichii, Leach, 1825. 
R. cinerea, Eyton. R. tridactyla, Bon., 1838, etauct. Gavia tridactyla, 
Boie, 1822. Cheimonea tridactyla, Kaup, 1829. 
Sp. Char. — Bill rather longer than the tarsus, nearly equal to the middle 
toe without the claw, stout at the base, tapering somewhat towards the tip, 
which is rather acute and attenuated. Convexity of culmen regular and 
gradual. Angle at symphysis very moderately developed. Color of bill light 
yellow, clouded with olivaceous. Head and neck all round, under parts and 
tail pure white. Mantle rather dark bluish or cinereous gray, the tertiaries 
and secondaries of the same color nearly to their tips, which are white. 
Primaries : the first very light bluish white, without white apex, its outer 
web and its inner web for about two inches from the tip black ; second like 
the first, but without the black outer web, its tip being black for nearly the 
same distance as the first, its apex with a minute white spot ; on the third 
and fourth the black tips grow shorter, while the apices are more broadly 
white ; this lessening of the black on each feather is exactly proportional to 
the shortening of the successive quills, causing the bases of all the black 
tips to be in the same straight line. A subapical black spot is usually pres- 
ent on one'or both webs, but is sometimes absent. Legs and feet dusky olive. 
Young : Bill black. An anteocular lunula, and a postocular spot, dusky 
[June, 
