526 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 



[Sterna] antillarum Sclatek and Salvin, Nom. Av. Neotr., 1873, 147, part. — 



Sharps, Hand-list, i, 1899, 137, part. 

 S[terna\ antillaruvi Kidgway, Man. N. Am. Bii'ds, 1887, 46, part. 

 [Sterna superciliaris var. antillarum] b. antillarum CouES, Birds Northwest, 



1874, 692, part (monogr.). 

 Sterna superciliaris antillarum. Coues, Clieck List, 2d ed., 1882, no. 801, part. 

 S[terna\ superciliaris antillarum Coues, 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 antillaru7n 6rc>w?2i Mearns, Proc. Biol. Soc. Wash., xxix, April 4, 1916, 7J 



^near Monument no. 258, Mexican Boundary Line,, edge of Pacific Ocean, 



San Diego Co., California; coll. U. S. Nat. Mus.). 

 Sternula antillarum hrowni Oberholser, Auk, xxxiv. April, 1917, 199. 



Genus H YDROCHELIDO N Boie. 



Hydrochelidqn Boie, Isis, x, 1S22, 563. (T}T)e, as designated by Gray, 1841, 



Sterna nigra Linnaeus.) 

 Viralva Stephens, Shaw's Cxen. Zool., xiii, pt. 1, 1826, 166. (Type, Stemanigra 



Linnaeus.) 

 Pelodes Kaup, Skizz. Entw.-Gesch. Eur. Thierw., 1829, 107. (Type, by original 



designation. Sterna leucopareia Temminck.) 

 Chlidonias (not Chlidonia Hiibner, 1816) Rafinesque, Kentucky Gazette, n. s., i, 



no. 8, Feb. 21, 1822, [3], col. 5. (Type, by original designation, C. melanops 



Rafinesque =iS'/erna surinamensis Gmelin. See Rhoads, Auk, xxix, 1912. 197.) 



Small Sternidai (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 than head, usually shorter), 

 its depth at base less than one-fourth {H. nigra) to more than one- 

 fourth (77. leucopareia) as long as exposed culmen, the latter slightly 

 convex distally; gonys about as long as mandibular rami {H. nigra) 

 to decidedly shorter {H. 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 tlian 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. leucopareia) 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.) 



