220 AVES: LONGIPENNF.S. — XXXII. 



331. RISSA Lt-aoli. (loclandic name.) 

 6-17 R. tridactyla (I..). Kittiwaki; Gtll. Mantle bluish- 

 gray ; head, etc., white; hind chiw a minute knob, sometimes ab- 

 sent. L. 1<; to 18. ^\. 12. Arctie, S. in winter to N. Y. {Eu.) 

 (Lat., tres, three ; dactylus, digit.) 



332. LARUS Linna-us. (Xdpof, gull.) 



a. Ilend enfiri'ly wliitc in ••ulult in puinnier (young more or less dusky on 

 lioad, ttc); niantlf giayisli blue, or dusky ; lower part.'* wiiite. (Larw.) 

 b. Primaries, without any black, pearly-gray, wliitisli at tip. 



648. L. glaucua Briinnich. Ice (iuLL. Burgomaster. Bill 

 yellow with red spot on lower mandible; large. L. 30. W. 18. 

 T. 8. B. 2^. Arctie regions ; S. in winter to N. Y. {Eu.) 

 {yKavKOi. bluish.) 



64!>. Ij. leucopterus Faber. Iceland Gull. Similar but 

 smaller. L. 2b. W. 1.")^. I- O^- B. lij. Same region. {Eu.) 

 (XfVKos, white 5 nrepov, wing.) 



bb. I'rimaries with white and dusky (sometimes all black in yoimg). 

 c. Dark spaces on primaries gray. 



650. L. kumlieni Brewster. Similar to L. leucoptcrna. L. 24. 

 W. 16. B. 1|. Greenland to N. Y. (To Ludwig Kumlicn.) 



cc. Dark spaces on primaries black. 



<l. Shafts of primaries white throughout. 



651. L. marinua L. Great Black-backed Gull. Mantle 

 blackish slate color; largest of our gulls. L. 30. W. 18. B. 2^. 

 Feet llesh-colored. N. Atl., S. in winter to N. Y. (Eu.) 



dd. Shafts of primaries black in the black markings. 



652. L.argentatu3 Briinnich. Herring Gull. Common Gull. 

 Mantle pearly-gray ; bill i)lain. L. 25. W. 17. B. 2^. Feet flesh- 

 colored. Northern regions, abundant on all bodies of water. The 

 American form (var. smithsonianus Cones) has the white of outer 

 quill separated from the rest by a band of black. (Eu.) 



65.'?. L. dela'warensis Ord. Rixd-niLLED (iuLL. Mantle 

 pearly-gray ; ft'it yellowish ; bill yellowish, a black band at the 

 tip in adult; smaller. L. 20. W. 15. B. 1|. N. Am., abundant, 



5. to Mex. 



aa. Head black or dusky in adult in summer (more or less pale in young); 

 mantle gray; lower parts, etc., white, rosy in breeding season. {ChttB- 

 cncfphalus Kyton.) 

 e. Tarsus much longer than middle toe and claw. 



654. L. atricilla (L.). Black-headed or Laughing Gull. 

 Bill and feet dusky; reddish in summer. L. 15 to 17. W. \,\. T. 



6. B. Ij. E. U. S., coastwise. (Lat., a/er, black; cilia, tail.) 

 ee. Tarsus not longer than middle toe and claw. 



