LAIiiS. 29 



/' Two outer primaries with a distinct giaj* wcdi;e on inner web. 

 g^. Depth of bill through angle contained less than four 

 and a half times in the length of the tarsus; lower 

 mandible with a red subterminal spot. 

 7i'. Mantle deep plumbeous gray, inclining to slate- 

 color. 

 i\ Culraon 2.22 or more; dc])th of bill at angle 

 .75 or more ; third quill with a distinct 

 ■white " mirror" or large spot on inner 

 web between the black and the gray ; 

 mantle nearly the same color as in li. 

 Occident alls, but averaging a little darker; 

 rest of plumage (except primaries) pure 

 white ; feet dull purplish flesh-color in 

 life; length about 26.50, wing 16.75-19.00, 

 culmen 2.15-2.35, depth of bill through 

 angle .75-90, at base .75-.82, tarsus 2.60- 

 2.75, middle toe (without claw) 2.08-2.40. 

 Hab. Coast of northeastern Asia, from 

 Japan (?) to' Kamtschalka and north- 

 ward to Arctic Ocean north of Bering's 



Strait 48. L. schistisagus Stkjn. 



Slaty-backed Gull. 

 2". Culinon 2.15 or less; depth of bill at angle not 

 more than .65; third quill without white 

 spot on inner web between black and gray ; 

 mantle same color as in L. occldentalis, 

 but apparently averaging a little paler; 

 rest of plumage (excejit primaries) pure 

 white ; feet yellow in life ; length about 

 20.00, wing 16.50-17.25, culmen 2.00-2.15, 

 depth of bill at angle .62-.65, at base .65- 

 .70, tarsus 2.60-2.72, middle toe 1.78-2.10.' 

 Hab. Northern Asia ; accidental in south- 

 ern Greenland. 



50. L. affinis Eeinii. Siberian Gull. 

 h'. Mantle light plumbeous-gray, or lighter, 

 i'. Bill without black spots in adult. 



f. Mantle plumbeous-gray, or very deep 

 pearl-gray ; eyelids (in life) orauge- 

 red, and feet yellow ; otherwise ex- 

 actly like argejitatus and smithso- 

 nianus, with the markings of the 



^ The specimens measured arc all females. Males would somewhat exceed these dimensions. 



