398 LAEID^. 



length. The pterylosis resembles that of the Snipes (Scolopacinae), and the tail is 

 more or less distinctly forked. 



Eleven genera of Terns are recognized by Mr. Howard Saunders, and four of them 

 are found in Central America. 



HYDROCHELIDON. 



Hydrochelidon, Boie, Isis, 1822, p. 563 ; Saunders, Cat. Birds Brit. Mus. xxv. p. 5 (1896). 



This genus includes four species of small size, with a blackish under surface in 

 summer, changing to white in winter, the young being also white below. The tail is 

 not very deeply forked, and is short, being less than half the length of the wing ; the 

 rectrices are rounded or slightly pointed. The bill is small, with the culmen less than 

 twice the length of the tarsus ; the feet are feeble, and the webs between the toes 

 considerably indented {cf. Saunders, I. c). 



Of the four species knovm, one is peculiar to the New World, and two of the 

 Eastern forms, viz. H. leucoptera and E. hybrida, have occurred incidentally in 

 American waters. 



1. Hydrochelidon surinamensis. 



Simnam Tern, Lath. Gen. Syn. iii. 2, p. 352 \ 



Sterna surinamensis, Gm. Syst. Nat. i. p. 604 ^ 



Hydrochelidon nigra surinamensis, Baird, Brewer, & Ridgway, "Water-Birds N. Amer. iii. p. 318' ; 



Ferrari-Perez, Pr. U. S. Nat. Mus. ix. p. 179 * ; Zeledon, An. Mus. Nac. Costa Rica, 1887, 



p. 133 = ; A. O. U. Check-l. N. Amer. Birds, 2nd ed. p. 26 ^ 

 Pelodes surinamensis, Heine & Reichenow, Nomencl. Mus. Hern. p. 356 '. 

 Hydrochelidon surinamensis, Saunders, Cat. Birds Brit. Mus. xxv. p. 20 ' ; Gates, Cat. Eggs Brit. 



Mus. i. p. 176, t. 13. fig. 5 \ 

 Sterna frenata, Scl. & Salv. Ibis, 1860, p. 278 ". 

 Hydrochelidon plumbea, Lawr. Ann. Lye. N. Y. vii. p. 479"; Scl. P. Z. S. 1864, p. 179'"; Sol. 



& Salv. P. Z. S. 1864, p. 373 ^\ 

 Hydrochelidon fissipes, Salv. Ibis, 1864, p. 385 '* ; 1866, p. 205 " ; Coues, Ibis, 1864, p. 391 " ; 



Scl. & Salv. P. Z. S. 1871, p. 573 "; Lawr. Mem. Bost. Soc. N. H. ii. p. 318 " ; Bull. U. S. 



Nat. Mus. no. 4, p. 52 " ; Sumichr. La Nat. v. p. 234 '°. 

 Sterna superciliaris, Lawr. Mem. Bost. Soc. N. H. ii. p. 318 " ; Sumichr. La Nat. v. p. 234 ". 

 Hydrochelidon lariformis, Streets, Bull. U. S. Nat. Mus. vii. p. 27 ". 



$ . PtU. cBstiv. Supra Bafcurate schistacea, alls dorso conooloribus, remigibus nigricantibus, primariis extns et 

 ad apicem cineraceis, rhachidibus albis, secundariis intunis omnino cineraceis : margine alari albo ; canda 

 cineracea ; pileo toto nigro, collo postico nigro adumbrato ; facie laterali et corpore snbtns toto famoso- 

 nigris ; tibiis, crisso et subcaudalibus albis ; subalaribns albidis, majoribus, axillaribus et remigibus intus 

 pallide cineraceis : rostro nigro ; pedibiia saturate brunneis ; iride saturate brunnea. Long, tota circa 9-0, 

 alse 7-9, caudae 2-8, culm. 1-25, tarsi 0-55. (Descr. feminse adultae ex Cay Dolores Channel. Mus. 

 nostr.) 



J . Ftil. hiem. Supra cinerea ; torque coUari albo ; pileo cineraceo, plumis medialiter nigris et cano adum- 

 bratis ; fronte, loris, regione oculari, facie laterali et corpore subtus toto albis, regione anteocnlari et 



