476 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
Sterna elegans (not of Gambel) Lioraup, Ois. Trinidad, 1866, 542. 
(?) Sterna elegans Cory, Auk, x, 1893, 220 (Tobago). 
(2) [Phaéthusa] cayennensis (not Sterna cayennensis Gmelin) Heiner and REIcHENow, 
Nom. Mus. Hein. Orn., 1890, 355 (Brazil). 
[Phaéthusa] elegans Hutne and REICHENOW, Nom. Mus. Hein. Orn., 1890, 355, 
part (Brazil). 
THALASSEUS SANDVICENSIS ACUFLAVIDUS (Cabot). 
CABOT'’S TERN. 
Similar to T. s. sandvicensis® but white margin to inner webs of 
three or four outer primaries much narrower, usually falling short of 
the tip, which is occupied by a continuation of the inner dark gray 
stripe; wing and tail averaging decidedly shorter ? 
Adults in breeding (2) plumage (sexes alike) .—Pileum, including - 
occipital crest, nape, and upper half of lores uniform deep black; 
upper parts pallid neutral gray to nearly pale neutral gray, the outer 
webs of primaries slightly darker, with a silvery or hoary cast; inner 
webs of primaries mostly white, with a broad stripe of dark gray 
along shafts; hindneck, entire under parts (including axillars and 
under wing-coverts), rump, upper tail-coverts, and tail immaculate 
pure white; bill black tipped, more or less extensively, with yellow 
or whitish; iris dark brown; legs and feet black. 
Adults in post-nuptial (?) plumage.—Similar to the breeding (%) 
plumage but forehead and lores white, the crown streaked with 
black and white, and black occipital feathers faintly tipped with 
white. 
Young.—Pileum, nape, and upper half of lores dull blackish or 
dusky, irregularly intermixed with dull whitish, especially on crown, 
‘which is coarsely spotted; occipital feathers short and blended; 
rest of upper parts, including rump, upper tail-coverts, and tail pale 
gray, coarsely and irregularly spotted with dull blackish or brownish 
black; wings, except smaller coverts, as in adults; rectrices becoming 
darker gray terminally, where irregularly spotted, or with hastate 
spots, of dusky or blackish; under parts immaculate white; bill 
dusky or dull blackish, scarcely or at least not abruptly, paler at 
tip. 
Downy young.—Entirely white, the rump with a few minute flecks 
of blackish; bill pale dull grayish yellow or dull ivory white, with a 
sea fleck of dusky on maxilla and mandible; legs and feet 
usky. 
Adult male.—Wing, 259-302 (278.2); tail, 122-130 (126.2); exposed 
ace 52-54.5 (53.3); tarsus, 25-27 (26); middle toe, 19-20.5 
19.5).° 
a See p. 467. b Five specimens. 
