LARIDA — CXXVIII. 219 
329. STERCORARIUS Brisson. (Lat., scavenger.) 
643. S. pomarinus (Temminck). PomMARINE J@GER. Chiefly 
blackish, colors varying with age; middle tail feathers broad to 
the tip, projecting about 4 inches. L. 20. W.15. T.9. B. 1). 
Arctic, S. in winter to N. J. (Eu.) (aéua, flap; pis, nose.) 
644. S. parasiticus (L.). Parasitic Jm#Ger. Dark brown; 
middle tail feathers acuminate, projecting 4 inches. L. 20. W. 
i3. T.54. B.1}. Arctic, S.in wintertoN.Y. (Zu) 
645. S. longicaudus (Vieillot). Lone-rarLep JmGER. Sooty 
black; tail feathers filamentous, projecting 8 or 10 inches.  L. 22. 
Wei2)) Tas. B14: | Arete. im winter,, Clu.) 
Famity CXXVIII. LARIDA. (Tue GuLts.) 
Long-winged swimmers, with the nostrils not tubular. Bill usu- 
ally long, hor ny, not serrate nor lamellate; nostrils developed ; no 
gular neaahs Feet palmate ; tibia feathered ; legs near centre of 
equilibrium ; hind toe elevated, small, often ae 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. (Larine.) 
b. Tarsus rough or serrate behind; taileven. . . . . . GAvta, 330. 
bb. Tarsus nearly entire behind. 
c. Hind toe rudimentary or Nee with minute claw or none; tail 
slightly emarginate. . . . Sat si sn ata) SRE OSAY ioe ie 
cc. Hind toe small, but with a naan olin. 
Me Wa MPemel ee o(o/-d,-/'siiyaus) + pak Suen eye sli ia eid EU eee 
dq: Nail forked... ¢.«).« hgh eho) MAS aoe 
aa. Bill not hooked, the eanaiblen, even; aul eiesply forked (in our species). 
(Sternine.) 
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 fits length. . . . STERNA, 330. 
ee. Tail little more than } wing, its outer feathers broad and rounded; 
toes scant-webbed; colors dark. . . . . HyYDROCHELIDON, 336. 
330. GAVIA Boie. 
646. G. alba (Gunner). Ivory Guix. Adults pure white; 
young spotted; feet black, L.16 to 20. W.13. B.14. Arctic, 
rarely to U. S., in winter. (//u.) 
