oDTERNA, 89 
Genus STERNA Linnavs. (Page 24, pl. X., figs. 1-3; pl. XI., figs. 1, 2.) 
Species. 
a, Wing more than 9.00. 
b. Wing more than 12.00. 
c’, Tail much less than half as long as wing, forked for less than one-fifth 
its total length; feathers of occiput short, blended ; depth of bill at 
base equal to nearly one-third the exposed culmen; inner webs of 
quills entirely gray, or slaty. (Subgenus Thalasseus Bors.) 
Adult in spring: Above pale pearl-gray, becoming white on tail, 
and more silvery gray on quills; whole top of head, and nape, 
uniform glossy black ; rest of plumage pure white; bill coral- 
red (drying orange-red) with dusky tinge near tip; feet black. 
Adult immediately after pairing season: Similar to spring plu- 
mage, but black on top of head mixed with white. Winter 
adult: Similar to summer adult, but black of crown, ete., 
streaked, instead of speckled or flecked, with grayish white. 
Young: Above pale grayish, marked with a few roundish and 
more or less hastate spots of dusky, largest on tertials; top of 
head grayish white, the crown flecked with black, this color 
increasing in extent posteriorly, until nearly uniform on occi- 
put; tail-feathers marked with a dusky subterminal spot; rest 
of plumage white; bill dull orange-reddish. Downy young: 
Above grayish white, the down of the head dusky gray beneath 
the surface; back and rump finely and indistinctly mottled 
with grayish; throat and fore-neck uniform pale grayish, rest 
of lower parts white. Length 19.00-22.50, wing 15.00-17.40, 
tail 5.30-6.75 (forked for about .75-1.60), culmen 2.48-3.10, 
depth of bill through base .75-.95, tarsus 1.60-1.90, middle toe 
1.15-1.40. West (usually solitary) a depression in sand near 
sea-shore. Liggs 2-3, 2.66 X 1.77, ovate or elliptical-ovate, pale 
grayish buff, varying to olive-buff or dull whitish buff, more or 
less spotted with brown and stone-gray or lavender-gray. Hab. 
North America in general, but rare on Pacific coast; breeding 
in isolated and widely separated localities throughout its range. 
(Also occurs in various portions of eastern hemisphere, includ- 
ing Australia.)...... 64. S. tschegrava Lzpecn. Caspian Tern. 
c. Tail more than half as long as wing, forked for at least half its total 
length; feathers of occiput lengthened, lanceolate, forming a dis- 
tinct crest; depth of bill at base much less than one-third the length 
of the exposed culmen; inner webs of quills with inner margin ab- 
ruptly and broadly white. (Subgenus Actochelidon Kaur.) 
d', Bill deep orange, or orange-red. 
e. Depth of bill at base more than one-fourth the length of the 
exposed culmen. Adult in spring; Above pale pearl-gray, 
