e 
526 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
[Sterna] antillarum ScuatER and Satvin, Nom. Av. Neotr., 1873, 147, part.— 
Sarre, Hand-list, i, 1899, 137, part. 
S{terna] antillarum Ripeway, Man. N. Am. Birds, 1887, 46, part. 
[Sterna superciliaris var. antillarum] b. antillarum Covuzs, Birds Northwest, 
1874, 692, part (monogr.). 
Sterna superciliaris antillarum Covss, Check List, 2d ed., 1882, no. 801, part. 
Sterna] superciliaris antillarwm Couzs, Key N. Am. Birds, 2d ed., 1884, 766, part. 
Sterna superciliaris (not of Vieillot, 1819) Lawrence, Mem. Bost. Soc. N. H., ii, 
1874, 318 (Manzanillo, Colima). 
Sterna antillarum brownt Mearns, Proc. Biol. Soc. Wash., xxix, April 4, 1916, 71 
(near Monument no. 258, Mexican Boundary Line, edge of Pacific Ocean, 
San Diego Co., California; coll. U. S. Nat. Mus.). 
Sternula antillarum brownit OspRHOUsER, Auk, xxxiv, April, 1917, 199. 
Genus HYDROCHELIDON Boie. 
Hydrochelidon Bore, Isis, x, 1822, 563. (Type, as designated by Gray, 1841, 
Sterna nigra Linneeus.) 
Viralva StePuENs, Shaw’s Gen. Zool., xiii, pt. 1, 1826, 166. (Type, Sterna nigra 
Linnzus.) : 
Pelodes Kaur, Skizz. Entw.-Gesch. Eur. Thierw., 1829,107. (Type, by original 
designation, Sterna leucopareia Temminck.) 
Chlidonias (not Chlidonia Hiibner, 1816) Rarinesque, Kentucky Gazette, n.s.,i, 
no. 8, Feb. 21, 1822, [3], col.5. (Type, by original designation, C’. melanops 
Rafinesque=Sterna surinamensis Gmelin. See Rhoads, Auk, xxix, 1912. 197.) 
Small Sternide (wing 190-250 mm.) with incompletely webbed 
toes and short, slightly forked tail with outer rectrices broadly 
rounded terminally. 
Bill relatively small (little if any longer chen head, usually shorter), 
its depth at base less than one-fourth (H. nigra) to more than one- 
fourth (HZ. leucopareia) as long as exposed culmen, the latter slightly 
convex distally; gonys about as long as mandibular rami (H. nigra) 
to decidedly shorter (7. leucopareia), its basal angle not prominent; 
nostril elliptical, longitudinal, well separated from latero-frontal 
antia, the latter broad. Wing rather long and pointed, the longest 
primary (outermost) exceeding distal secondaries by very much less 
than twice the distance from tips of the latter to bend of wing. 
Tail much less than half (very little more than one-third). as long as 
wing, slightly forked, all the rectrices broad and rounded at tips. 
Tarsus as long as or longer than middle toe without claw; webs 
small, very deeply incised, occupying less than half of interdigital 
spaces. 
Plumage and coloration.—Plumage of head, neck, and under parts 
blended. Summer adults with head and neck, all round, uniform 
black, or else (H. lewcopareia) with sides of head (beneath eyes), chin, 
and throat white; under parts white only on anal region and under 
tail-coverts, otherwise gray or black. 
Range.—Temperate portions of Europe, Asia, and North America; 
in winter southward to New Zealand, Australia, Africa, and South 
America. (Three species.) 
