o04 PROCEEDINGS OF THE ACADEMY OP 



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 Ross would seem to indicate that this gull is extremely abundant in the 

 interior of Arctic America. 



Genus II. Blasipus Bonaparte. 



Blasijms, Bp., 1852, fide Lawr. Bp., 1856, type Larus Heermani, Cass. 

 Adelarus, Bruch, 1853. Id., 1855, p. 



12. Blasipps Heermani, Bon. ex Cass. 



? Larus Belcheri, Vig., 1829. ? Lencophacus Belcheri, Bp., 1856; I nee 

 11 Adelarus Belcheri, Vig. ; fuliginosus Gould " Bruch, 1853 et 1855). 

 Larus Heermani , Cass., 1852. Blasipus Heerm., Bp.. 1856; Lawr., 1858. 

 Adelarus Heeim. 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, Linnseus, 1758, (nee 1744, nee 1735, fide Gray.) 



Gavia, Boie, 1822, (nee Moehr. 1752.) 



Rissa, Leach, 1825, (typus Larus rixsa, Brunn.) 



Cheimonea, Kaup, 1829, (typus idem.) 



Putocondora Reichenbach, fide Bp. 



13. Rissa tridactyla Bon. ex Linn. 



Larus rissa Briinn, 1764. L.tridaetyhiset rissa, Linn. 1766. L.turquatus, 

 L. gavia, et L. canus, Pall., 1811. Rissa Briinnichii, 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, 



