NATURAL SCIENCES OF PHILADELPHIA. 295 



Sp. char. Length 24 inches, wing 16*75. Bill above 1*80, rectus 2-80, 

 depth at angle *65. Tarsus and middle toe and claw 2-26. 

 Hah. "Arctic seas; Baffin's Bay ; Labrador." (Lawr.) 



c. Color above pearl blue. Primaries about the color of the back to the 

 very tips, which have well-defined, rounded, white apical spots. 



4. Lakus glaucescens Lichtenstein. 



Larus glaucescens, Licht. Laroides glauc. Bruch, 1855 ; (nee Glaucus 

 glaucescens, Bruch, 1853, qui Larus chalcopterus.) Leucus glaucescens, 

 Bp. 1S56. Larus glaucopterus, Kittlitz, fide Bruch. Glaucus glaucop- 

 terus, Bruch, 1853. 



Sp. char. Bill long and rather weak, the upper mandible projecting con- 

 siderably beyond the lower, the convexity of the culmen comparatively slight. 

 Angle pretty well defined, the outline between it and the tip about straight. 

 Adult: Mantle pearl blue, much the same shade as in argentalus. Primaries 

 slightly deeper than the back, all with rounded, well-defined apical spots of 

 white. First, Base not appreciably lighter than the body of the feather, with 

 a well-defined white spot on both webs, near the end, separated from the 

 white apex by a transverse band of the color of the body of the feathers ; 

 second, third and fourth, basal portions notably lighter than the terminal, 

 fading into pure white at their junction with the latter, without spots except 

 the apical ones ; fifth, sixth, basal portions the color of the back, fading into 

 white near the end, separated from the white apices by a band (narrowest on 

 the sixth) of the color of the outer primaries. 



Young of the year. Bill black. Everywhere deep grayish, somewhat mot- 

 tled with whitish, the feathers of the back, wings and upper tail coverts edged, 

 tipped and crossed by more or less regular transverse bars of grayish white. 

 Length about 27 inches, wing 16"75. Bill above 2'25, gape 3-25, height at 

 angle -70 ; tarsus 2-60, middle toe and claw 2-50. 



Habitat. Pacific coast of North America. 



One of the later discoveries, and a very distinct and well-marked species. 



5. Lakus chalcopterus Licht. 



Glaucus glaucescens, ("Licht."), Bruch, 1853; (nee Laroides glaucescens, 

 (Licht.) Bruch, 1855. Laroides chalcopterus, Bruch, 1S55. Leucus 

 chalcopterus, Bp. 1856. Larus chalcopterus, Lawr. 1858. 



Sp. char. Adult: "Entirely similar to leucopterus, except in the primaries, 

 which are ashy gray, with rounded white apical spots." Young : "Dark gray, 

 as in glaucopterus," (of Kittlitz =< glaucescens, Licht.) 



Habitat. " American coast of Behring's Straits, and Greenland." 



A species I have never seen. The diagnosis is copied from Bruch's Mono- 

 graph. This author, in saying that the primaries of the bird are " ashy gray, 

 with rounded white apical spots," reduces the characters in this respect pre- 

 cisely to those of glaucescens, Licht. Then, the bird being "like leucopterus, 

 except on the primaries, " must be separated from glaucescens throwing out 

 of consideration the primaries, acknowledged to be identical by those points 

 in which leucopterus differs, viz.: smaller size, somewhat differently shaped 

 bill, and lighter mantle. In a word, chalcopterus is a leucopterus with the 

 wings of glaucescens. 



If the characters given are constant, the species is doubtless a valid one. If 

 so, it is the smaller analogue of glaucescens, and bears the same relation to 

 that species that leucopterus does to glaucus. 



Section B. Dominicanus Bruch. Very large and powerful ; color above 

 dark blackish slate ; primaries crossed with black near the end. 



6. Larus marinus Linnaeus. 



Larus marinus, Linn. 1776. Dominicanus marinus, Bruch, 1853 et 1S35. 



1862.] 



