476 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 



Sterna elegans (not of Gambel) Leotaud, Ois. Trinidad, 1866, 542. 



(?) Sterna elegans Cory, Auk, x, 1893, 220 (Tobago). 



(?) [Phaethusa] cayennensis (not Sterna cayenncnsis Gmelin) Heine and Reichenow, 



Norn. Mus. Hein. Orn., 1890, 355 (Brazil). 

 [Phaethusa'\ elegans Heine and Reichenow, Nom. Miis. Hein. Orn., 1890, 355, 

 part (Brazil). 



THALASSEUS SANDVICENSIS ACUFLAVIDUS (Cabot). 



CABOT'S TERN. 



Similar to T. s. sandmcensis°- 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 (?) plumage (sexes ahke). — Pileum, including 

 occipital crest, nape, and upper haK of lores uniform deep black; 

 upper parts pallid neutral gray to nearly pale neutral gray, the outer 

 webs of primaries sUghtly 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 ijost-nuptidl (?) 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 blacldsh 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 

 subterminal fleck of dusky on maxilla and mandible; legs and feet 

 dusky. 



Adult male. ~Wmg, 259-302 (278.2) ; tail, 122-130 (126.2) ; exposed 

 culmen, 52-54.5 (53.3); tarsus, 25-27 (26); middle toe, 19-20.5 

 (19.5).^ 



o See p. 467. & Five specimens. 



