LARVS. 29 



/ 2 . Second primary with a distinct gray wedge on inner web. 

 g l . 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. 

 A 1 . Mantle deep plumbeous -gray, inclining to slate- 

 color. 



z 1 . Culmen 2.22 or more ; depth of bill at base 

 .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 L, 

 occidentalis^ but averaging a little darker ; 

 rest of plumage (except primaries) pure 

 white; feet dull purplish flesh-color in 

 life ; length about 26.50, wing 16.75-18.00, 

 culmen 2.15-2.35, depth of bill through 

 angle .75-.90, at base .7S-.82, tarsus 2.60- 

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

 Hob. Coast of northeastern Asia, from 

 Japan (?) to Kamtschatka and north- 

 ward to Arctic Ocean north of Bering's 



Strait 48. L. schistisagus STEJN. 



Slaty-backed Gull. 



?. Culmen 2.15 or less; depth of bill at angle 

 .65; third quill without white spot on 

 inner web between black and gray; 

 mantle same color as in L. Occident alis, 

 but apparently averaging a little paler ; 

 rest of plumage (except 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-.6S, at base .65- 

 .70, tarsus 2.60-2.72, middle toe 1.78-2.10. 1 

 Hab. Northern Asia ; accidental in south- 

 ern Greenland. 



50. L. affinis EEINH. Siberian Gull. 

 h 2 . Mantle light plumbeous-gray, or lighter. 

 i 1 . Bill without black spots in adult. 



/. Mantle plumbeous-gray, or very deep 

 pearl-gray ; eyelids (in life) orange- 

 red, and feet yellow; otherwise ex- 

 actly like argentatus and smithso- 

 nianus, with the markings of the 



1 The specimens measured are all females. Males would somewhat exceed these dimensions. 



