LARID^. — LXIII. • 149 



del. Head dark — if dark below, head whitish (small or 

 slender species, with a black hood in the breeding 

 season, and the white under parts then pinkish or 

 rosy-tinted.) . . . CniicECOCEPHALUS, 5. 



&&. Tail forked; bill black, yellow-tipped. . Xema, 6. 



** Bill paragnathoiis (mandibles even) ; tail forked (in our species) ; 

 Terns. (Sternin^^e.) 



e. Toes full-webbed; colors chiefly white, with a black cap at 

 most seasons and the quills silvery dusky, with a long 

 white stripe. 



/. Feet black; forehead without white crescent. 



g. Kot crested ; bill stout, scarcely longer than tarsus. 



Gelochelidon, 7. 



gg. Crested ; bill slender, much longer than tarsus. 



Thalasseus, 8. 



ff. Feet not black; back pale, no crest. . . Sterna, 9. 



ee. Toes not full- webbed ; color quite dark. 



Hydrochelidon, 10. 



*** Bill hypognathous — the lower mandible much the longer, 

 compressed like a knife-blade. Skimmers. (Rhynchopin^.) 



Rhynchops, 11. 



/. STERCORARIUS, Brisson. J.egers. 



== Lestris^ Authors. 



1. S. pomatorhinus, (Temm.) Lawr. Pomarine 

 JjEGER. Chiefly blackish, colors varying with age; 

 middle tail feathers broad to the tip, projecting about 

 four inches; I.. 20; W. 15. Northern, U. S. in winter. 



2. 5. parasiticus, (Brunn.) Gray. Parasitic J.bger. 

 General color dark brown; middle tail feathers acuminate, 

 projecting 4 inches; L. 18; W. 13. Northern, U. S. in 

 winter. 



3. S. longicauda, (Vieill.) Long Tailed J^ger. 

 Similar, but still smaller; tail feathers filamentous, pro- 

 jecting 8 or 10 inches. Northern, U. S. in winter. 



