554 PROCEEDINGS OF THE ACADEMY OP 



black ; tarsi orange. Lives on the banks of the Guadaloupe." Here, it will be 

 noticed, that though the characters are so brief, the peculiar features of bill 

 iind frontal lunula are given with such precision, that there can be no doubt of 

 the propriety of refening the description to the species now under considera- 

 tion. 



Immediately following the description of the S. antillarum, there is instituted 

 (I. c.) a Siernula melanorhyncha, Less., with substantially the following charac- 

 ters : " A little stouter than the preceding ; differs from it and S. minuta in 

 the straight and black bill. The white front of small extent. Black of head 

 above extends to middle of neck. Black of sinciput mixed with white; lowe: 

 neck white above, the gray of the upper part ,of the body washed with brown- 

 ish. Tail short, little forked ; the lateral feathers tipped with slender filaments. 

 Tail pale grayish white, the outer quills broadly margined with brown." It is 

 evident from almost every paragraph of this description, more particularly the 

 mention of the black bill, the sinciput mixed with white, and the upper parts 

 washed with brownish, that Lesson had in view an immature or winter Terr.. 

 The habitat given is the same as that of the preceding, antillarum, and I 

 have but little doubt that the description is that of the young bird of the spe- 

 cies now under consideration, in which the characters are almost exactly as givea 

 by Lesson. Indeed, a specimen before me agrees exactly with the description, 

 even to the lateral tail feathers tipped with slender filaments, said filaments 

 being the termination of the shaft of the feather, from which the web has been 

 worn away. I therefore quote Siernula melanorhyncha, Less., as a synonym of 

 the present species. 



Genus HYDROCHELIDON Boie. 



Hydrochelidon, Boie, Isis, 1822, p. 563. Type S. nigra Linn. 

 Viralva, Leach. Stephen's Zool. 182(3, xiii. p. 166. Same type. 

 Pelodes, Kaup, Sk. Ent. Eur. Thierw. 1826, 107. Type Sterna leuropareia. Nat- 

 terer. 



Ch. Bill a little shorter than the head, longer than the middle toe and claw ; 

 very delicate, slender, acute ; culmen and commissure decidedly declinato-con- 

 vex, the amount of curvature increasing towards the tip ; outline of rami and 

 gonys both concave, the former most so : the angle separating them prominent 

 and very acute. Wings exceedingly long, pointed, of same color as back, with- 

 out distinct markings on either web. Tail rather short, contained 2^ times in 

 the wings, only moderately emarginate, (much as in Gelochelidon,) the lateral 

 feathers but little exceeding the next, not tapering and acuminate ; all the 

 feathers broad and rounded. Feet slender and short ; tarsi much abbreviated, 

 rather less than the middle toe alone. Toes moderately long; the webs rather 

 narrow, and very deeply incised. Size small, general form delicate ; colors 

 mostly black, the wings and tail plumbeous. 



A genus distinguished from Sterna proper chiefly by its very slender attenu- 

 ated bill, with its decurved tip : its short tail, of a very different shape ; its 

 deeply incised interdigital webs and its very peculiar style of coloration. Other 

 differences, however, will be noted in the preceding diagnosis. North America 

 contains but a single representative, the young of which was described by 

 Wilson as S. plumb ea, but which is in all probability identical with the well- 

 known European //. fissipes. Other closely-allied species of Europe are the H. 

 nigra, (of Linnaeus^//, leucoptera of most authors), and H. hybrida (of Pallas 

 =H. leucopareia of most authors.) 



The principal synonym of I/i/ilrochelidon is Viralva of Leach, (1826,) based 

 upon the same type. Pelodes of Kaup, 1829, founded upon H. leucopareia, is 

 also strictly a synonym of Hydrochelidon. 



Hydrochelidon fissipes G. R. Gr. ex Linn. 

 Sterna fissipcs, Linn. Syst. Nat. i. U60, 228. Not of Pallas. 



[Dec. 



