LAKID^E. CXXVIII. 219 



329. STSRCORARIUS Brisson. (Lat., scavenger.) 



643. S. pomarinus (Temminck). POMARINE XEGER. Chiefly 

 blackish, colors varying with age; middle tail feathers broad to 

 the tip, projecting about 4 inches. L. 20. W. 15. T. 9. B. l. 

 Arctic, S. in winter to N. J. (Eu.) (770^0, flap ; pis, nose.) 



644. S. parasiticus (L.). PARASITIC JJEGER. Dark brown; 

 middle tail feathers acuminate, projecting 4 inches. L. 20. W. 

 13. T. 5. B. 1J. Arctic, S. in winter to N. Y. (Eu.) 



645. S. longicaudus (Vieillot). LONG-TAILED JAEGER. Sooty 

 black; tail feathers filamentous, projecting 8 or 10 inches. L. 22. 

 W. 12. T. 13. B. l. Arctic, S. in winter. (Eu.) 



FAMILY CXXVIII. LARIDuE. (THE GULLS.) 



Long-winged swimmers, with the nostrils not tubular. Bill usu- 

 ally long, horny, not serrate nor lamellate ; nostrils developed ; no 

 gular pouch. Feet palmate ; tibia feathered ; legs near centre of 

 equilibrium ; hind toe elevated, small, often wanting. Wings very 

 long and pointed. Tail well developed. General color usually 

 white, with a darker mantle of a pearly bluish tint, and commonly 

 with some black markings. Sexes alike in color, but the plumage 

 varying much with age and season. Genera about 12; species 90 ; 

 abounding about all large bodies of water, and of remarkable 

 power of flight. Altricial; food chiefly fishes. 



a. Bill more or less hooked ; (general color chiefly white, with a darker, 



bluish, grayish, or slaty mantle); gulls. (Larince.) 

 b. Tarsus rough or serrate behind ; tail even ..... PAGOPHILA, 330. 



bb. Tarsus nearly entire behind. 



c. Hind toe rudimentary or wanting, with minute claw or none; tail 

 slightly emarginate ............. RISSA, 331. 



cc. Hind toe small, but with a perfect claw. 

 d. Tail even ................ LARUS, 332. 



dd. Tail forked ............... XEMA, 333. 



aa. Bill not hooked, the mandibles even; tail deeply forked (in our species). 



(Sternince.) 



e. Tail much more than ^ wing, its outer feathers narrow and pointed; toes 

 well webbed. (Color chiefly white, with a black cap in full plumage, 

 and the quills dusky with a long white stripe.) 



f. Bill stout, its depth at base equal to culmen. GELOCHELIDON, 334. 

 ff. Bill slender, its depth at base not its length. . . . STERNA, 335. 



ee. Tail little more than wing, its outer feathers broad and rounded; 

 toes scant-webbed; colors dark ..... HYDROCHELIDON, 336. 



330. PAGOPHILA Kaup. 



646. P. alba (Gunner). IVORY GULL. Adults pure white ; 

 young spotted ; feet black. L. 16 to 20. W. 13. B. 1. Arctic, 

 rarely to U. S., in winter. (EuS) 



