BIRDS OF NORTH AND MIDDLE AMERICA, 461 
toe, the gonys more than half as long as mandibular rami; nostril 
considerably anterior to latero-frontal antia, narrowly elliptical, 
longitudinal; latero-frontal antia nearer to vertical line from mental 
antia than to that from malar antia. Wing long and pointed,.the 
longest primary (outermost) exceeding distal secondaries by nearly 
twice the distance from tips of the latter to bend of wing. Tail a 
little more than one-third as long as wing, forked for between one- 
fourth and one-third its length, or even less, the rectrices (except 
middle pair) contracted terminally, especially the outermost pair, but 
not acuminate. ‘Tarsus longer than middle toe -with claw, nearly 
half as long as bill from rictus; anterior toes fully webbed. 
.Plumaje and coloration.—Occipital feathers distinctly but not con- 
spicuously elongated, soft and blended. Adults pale gray- above 
with black pileum, under parts immaculate white; inner webs of 
primaries unicolored, or at least not distinctly bicolored; bill red; 
downy young unspotted. 
Range.—Nearly cosmopolitan, but wanting in Central and Sou 
America, West Indies, and Pacific islands. (Monotypic.) 
HYDROPROGNE CASPIA (Pallas). 
CASPIAN TERN. 
Adults vn breeding plumage (sexes alike).—Enti r- pileum, including 
upper half of lores and auricular region and part of suborbital region, 
uniform deep black, the lower eyelid with a crescentic streak of white; 
rest of upper parts pallid neutral gray, fading into white on upper 
tail-coverts, the tail grayish white; inner webs of primaries uniform 
dark hoary gray or slate color; rest of plumage immaculate pure 
white; bill deep coral red, duller subterminally, the tip orange or 
yellowish; iris dark brown; legs and feet, black. 
Adults in post-nuptial plumage.—Similar to the breeding plumage 
but black on pileum more or less intermixed with white. 
Adults in winter.—Similar to the post-nuptial plumage but with 
pileum, etc., streaked with white; bill more orange-red. 
_ Young.—Upper parts pale grayish with a few roundish or more or 
less hastate spots of dusky, largest on tertials; pileum grayish white, 
the crown flecked with black, this increasing in extent posteriorly 
until nearly uniform dull black on occiput and nape; rectrices with 
a subterminal spot of dusky; under parts white; bill dull orange- 
reddish, more dusky terminally or subterminally. 
Downy young.—Upper parts grayish white, the down of pileum 
dusky gray beneath surface; back and rump finely and indistinctly 
mottled with grayish; throat and foreneck uniform pale grayish, the 
remaining under parts white. 
