554 
PROCEEDINGS OF THE ACADEMY OF 
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 
and 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. 
(1. c.) a Slernula 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 ; lower 
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 Terk. 
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 given 
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 Sternula melanorhyncha , Less., as a synonym of 
the present species. 
Genus IiYDROCHELIDON Boie. 
llydrochelidon , Boie, Isis, 1822. p. 563. Type S. nigra Linn. 
Viralva , Leach, Stephen’s Zool. 1826, xiii. p. 166. Same type. 
Pelodes, Kaup, Sk. Ent. Eur. Thierw. 1826, 107. Type Sterna leuropareia, Nat- 
terer. 
Ch. — B ill 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 : ihe 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 J times in 
the wings, only moderately emarginate, (much as in Geloclielidon ,) 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. plumbea, but which is in all probability identical with the well- 
known European H. fissipes. Other closely-allied species of Europe are the R. 
nigra , (of Linnaeus=^T. leucoptera of most authors), and H. hybrida (of Pallas 
= 11 . leucopareia of most authors.) 
The principal synonym of Hydrochelidon 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 pissipes G. R. Gr. ex Linn. 
Sterna fissipes, Linn. Syst. Nat. i. 1766, 228. Not of Pallas. 
- {-Dec. 
