NATURAL SCIENCES OF PHILADELPHIA. 555 



llydrochelidon fissipes, G. R. Gray. Gen. Birds, iii. 1849, 660. 

 Sterna nigra, Brisson, and of authors. Not of Linn. 

 llydrochelidon nigra, Boie, Isis, 1822, p. 563. 

 Viralva nigra. Leach, Steph. Gen. Zool. 1826, xiii. p. 167. 

 Sterna mevia, Linnaeus, S. N. i. 1766, 228. Young. 

 Sterna plumbea, Wilson, Am. Orn. vii. 1813, 83, pi. lx. Young. 

 Hydrochelidon plumbea, Lawrence, Gen. Rep. 1858, 864. 



Habitat. Europe. North America generally, both on the sea-coast, and in the 

 interior. 



This species in all its changes of plumage is too well known to require any 

 descriptions. 



I have critically compared quite a series of European and American speci- 

 mens, in all stages of plumage, but have been entirely unable to detect the 

 slightest discrepancies between the birds of the two continents. The speci- 

 mens before me are all absolutely identical in size and relative proportions of 

 different parts ; and the colors of those of the same age correspond minutely. 

 There do not appear to exist the slighest characters upon which to base 

 specific distinction. 



The first distinctive name applied to the American bird was plumbea, of Wil- 

 son, based upon the immature bird, he probably, however, not recognizing it as 

 the young, or desiring to separate it from the European Bpeeies. The birds of 

 the two continents were first formally separated by Bonaparte, in 1838, in his 

 Comparative List, and his example has been followed by the majority of subse- 

 quent American authors. 



To G. R. Gray, I believe, is due the credit of elucidating the synonomy of 

 this, as well as of the other species of the genus, which was in a state of great 

 confusion. The proper name of the present species appears to he fissipes, Linn., 

 the name nigra, Linn., usually applied to it, really referring to the white-winged 

 black Tern of Eurojte, of which leucoptera is the most firmly established syno- 

 nym. Mr. Gray has also shown that the proper name of the whiskered Tera 

 usually given as leucopareia Natterer, is hybrida of Pallas. 



Genus HALIPLANA Wagler. 



Onychoprion, Wagler, Isis, 1832, p. 277, Type S. serrata, Forster. 

 Haliplana, Wagler, Isis, 1832, p. 1224. Type S. fuliginosa, Gm. 



Ch. Bill as long as the head, but little less than the tarsus and middle toe 

 together, perfectly straight, stout, especially at base, where it is nearly as broad 

 as high, tip rather acute. Culmen but very slightly convex ; gonys about 

 straight, so ascending as to make the commissure nearly straight; rami slightly 

 convex, the prominence between them and the gonys illy developed, not acute. 

 Nostrils somewhat more anterior than in Sterna, not nearly so much so as in 

 Anous, in a decided, but rather irregularly-defined sulcus, which terminates a 

 little beyond the middle of the bill in several longitudinal striae. Outline of 

 feathers at base of bill much as in Sterna. Wings exceedingly long, pointed, 

 but the first primary scarcely surpassing the second. Tail very long, deeply 

 forked, the feathers broader and stiffer than in Sterna, not so regularly tapering, 

 but still quite acuminate at their tips. Legs rather long for this subfamily : 

 the length chiefly apparent by a greater denudation of the tibia. Toes rather 

 short; the middle with its claw exceeding the tarsus but slightly. Size mode- 

 rate ; general form slender and graceful. Bicolor. 



A genus distinguished from Sterna by several important characters. In the 

 shape of the bill, position of nostrils, proportions of primaries, color to some ex- 

 tent, there is an evident approach to Anous. It is, however, decidedly to be re- 

 ferred to the typical Sternex, rather than to the Megalopterese. 



Wagler's Onychoprion is based upon the S. serrata of Forster ; while his Hali- 

 plana has as type S. fuliginosa, Gm. The former of these species 5. serrata 



1862.] 



