LABID^'-STERNIN^: TEBNS. 
765 
a moderate distance; tarsi exceedingly short, being less than middle toe without claw, or 
only equal to it; toes rather long for the size of the feet; the outer falls but little sliort of 
the middle one, while the tip of the claw of the inner hardly reaches beyond tlie third articula- 
tion of the middle one. The feet are a lighter tint of the color of bill, tending toward vermilion, 
or coral-red, but not so light as those of hirundo. Wings very long; primaries narnnv, 
tapering to their roundish but slender tips ; shafts white, with scarcely darker tips. Out(n- 
web of first primary grayish -black, lightening into silvery-gray at tip ; inner web white, 
with only a very narrow line of grayish-dusky along the shaft; this dusky space much 
narrower and lighter than in hirundo ; next four or five primaries silvery-gray, darkest 
toward their tips ; their inner webs mostly white (wholly so at their bases) ; but the white 
does not extend so far toward the tips of the feathers as on the first primary, and it runs up 
farther in the centre of the web than on the edge of it. Inner primaries of the color of 
the back, broadly tipped and margined internally with white. Tail exceedingly long, the 
exterior feather being as much lengthened, and as narrow, tapering and acute, as in S. dougalli. 
The tail-feathers reach beyond the tips of the folded wings. Tail pure white, the outer web 
of its exterior feather being grayish-black, lighter basally, and its inner web, and the outer 
webs of the next two rectrices, having a considerable wasli of pearl-blue. Cap pure, lustrous 
greenish-black, so broad on the cheeks as to leave only a slender line of white to extend along 
the edge of the feathers on the side of the upper mandible. Upper parts pearl-blue, of about 
the same shade as in hirundo ; this color, however, fading into white at tips of tertials and 
inner secondaries. Under parts but a little lighter shade of the color 'of the back, fading 
insensibly into whitish on the chin, throat, and edges of the black cap, and ending abruptly at 
the under tail-coverts, which are pure white, in marked contrast to the rest of the under parts ; 
lining of wings and axillars also pure white. Winter plumage of adult : Differs from the 
above chiefly in the color of the cap; forehead white; crown white, but marked with narrow 
shaft-lines of black, which increase from before backward until, on the nape, the black is 
nearly or quite pure. A lateral stripe, more or less pure and distinct, extends forward on 
sides of head over the auriculars, to just in front of eye, leaving, however, the eyelids white. 
Upper parts much as in summer, but under parts from chin to vent, much lighter. The 
carmine of bill and feet lighter and duller, but not the coral-red tint of the feet of hirundo or 
forsteri. Plumage of the young-of-the-year : Bill much smaller than in the adult, being 
only 1.08 inches long ; brownish-black toward tip ; gonys and sides of lower mandible toward 
the angle of the mouth dull orange ; feet only orange-colored on the soles, otherwise brownish- 
red. Tail much shorter than in adult, only 4.75 to 5.00 inches long, and the outer pair 
of rectrices broader and scarcely at all tapering in form. Forehead white; the crown 
streaked with narrow, longitudinal spots of white upon a black ground color, which extends 
as far as the eyes, and runs back over the temples and auriculars as far as the nape. Whole 
under parts from the chin, including under tail-coverts and under surfaces of wings, pure 
white. On the back there predominates everywhere a uniform, light bluish-gray (somewhat 
darker than in S. hirundo)^ all the feathers tipjied with yellowish -white or white, most of 
them with a blackish-brown streak or crescent-shaped spot near the end ; these spots darkest 
on the tertials and inner secondaries, and aggregated into a single, broad, slate-colored streak 
on the least wing-coverts. The ashen-blue primaries deepen into slate-color toward their 
tips ; their shafts white, their inner webs with a longitudinal space of white, the outer web 
of the first slaty-black. Inner tail-feathers white, as are their shafts ; their tips white, each 
with a subtermiual crescent- shaped spot of brownish-black. Dimensions of the adult : 
length (extremely variable from varying length of tail) 14.00-17.00 inches ; extent 29.00- 
33.00; wing 10.00-10.75; tail usually 7.00-8.00, sometimes 6.50-8.50; depth of fork 4.00- 
5.00; tibiae bare 0.45; tarsus 0.55-0.65; middle toe and claw 0.80-0.85; inner toe and 
claw 0.55; whole foot about 1.50; bill along culmen 1.20-1.40; height at base 0.30; 
