BIRDS OF NORTH AND MIDDLE AMERICA. 479 
Chelochelidon (emendation) Brexm, Isis, 1842, 413. 
Geochelidon (emendation) Gunpacu, Journ. fiir Orn., 1861, 346. 
Laropis Waausr, Isis, 1832, 1225. (Type, Sterna anglica Montague=S. nilotica 
Linneeus.) 
Medium-sized Sternide (wing 275-338 mm.) with relatively short 
and stout bill, short and moderately forked tail, and long tarsus. 
Bill shorter than head, stout, its depth at base equal to nearly 
half the distance from anterior end of nostril to tip of maxilla, the 
exposed culmen shorter than combined length of tarsus and first 
phalanx of middle toe, rather strongly convex or decurved for distal 
half; gonys shorter than outer toe without claw, decidedly shorter 
than mandibular rami, nearly straight, strongly ascending terminally, 
its basal angle rather prominent; nostril close to but scarcely touching 
latero-frontal antia, rather broadly elliptical or narrowly oval, 
longitudinal; latero-frontal antia only slightly anterior to malar 
antia, the mental antia about on line (vertically) with middle of 
nostril. Wing long and pointed, the longest primary exceeding 
distal secondaries by twice the distance from tips of the latter to 
bend of wing. Tail less than half as long as wing, forked for about 
one-third its length, or less, the lateral rectrices contracted but not 
attenuated terminally. Tarsus decidedly longer than middle toe 
with claw; webs with anterior margin moderately excised. 
Plumage and coloration.—Feathers of occiput normal (short and 
blended). Summer adults with pileum and nape uniform black, 
the remaining upper parts pale gray, the under parts immaculate 
white, the inner webs of primaries distinctly bicolored; winter adults 
with head and neck white, the auricular region and spot in front 
of eye dusky; downy young mottled or marbled above. (Coloration, 
in all stages, essentially as in typical species of Sterna.) 
Range.—Europe, south of 55° north latitude, to northern Africa 
and Australia; Atlantic and Gulf coasts of United States, southward 
in winter to Patagonia, etc. (Monotypic.) 
GELOCHELIDON NILOTICA (Gmelin). 
GULL-BILLED TERN. 
Adults in breeding season (sexes alike),—Pileum, nape, and upper 
half of lores uniform deep black; rest of upper parts, including rump, 
upper tail-coverts, and tail, uniform pale gray (between gull gray 
and pallid neutral gray) ; entire under parts, including sides of head up 
to and including auricular and suborbital regions and lower half of 
lores, together with ‘axillars and under wing-coverts, immaculate 
pure white; bill wholly deep black; inside of mouth flesh color (in 
life); iris dark brown; legs and feet dark reddish brown (dark walnut. 
brown) in life, the soles of toes pinkish brown. 
