General characters similar to the last genus, but with the shafts of the tail-feathers prolonged beyond the webs, and forming strong thorn-like points; tarsi and toes naked; bill small, curved, wide at base; wings long; tail usually short; legs short, rather slender; claws curved, strong; general form plump and robust. Of this genus there are about fifteen species, two only of which are known to inhabit the United States, though several are natives of South America. Like the birds of the preceding genus, they possess great rapidity of flight, and live in similar situations. 1. Acanthylis pelasgia. (Linn.) The Chimney Bird. The American Swift. Hirundo pelasgia. Linn., Syst. Nat. I. p. 345. (1766.) Hirundo cerdo. Bartram, Trav., p. 292. (1791.) Barton, Frag., p. 18. “Cypselus acutus. Temm., Mus. Lugd.” Bonap., Consp. Av., p. 64. Vieill., Ois. d’Am., Sept. 1, pl. 33; Wilson, Am. Orn., V. pl. 39, fig. 1; Aud., B. of Am., pl. 58, Oct. ed., I. pl. 44; Nat. Hist. N. Y. Birds, pl. 27, fig. 58. Wings very long, extending beyond the tail, flattened, somewhat falcate; shafts of primaries rigid; tail short; exserted spines sharp, elastic; tarsi and toes naked; entire plumage above and below fuliginous brown, darkest on the upper parts, and with a slight greenish lustre on the head and back (in mature specimens), much paler on the throat and neck before; quills dark fuliginous; tail lighter; spot in front of the eye black, a very narrow superciliary line ashy-white; shafts and spines of the tail-feathers black; bill and feet dark. Dimensions. Total length, male, from tip of bill to end of tail, 4¾ to 5 inches; wing, 5¼; tail, 1¾ inches. Female very nearly the same. Hab. Throughout North America. Canada (Dr. Hall); Florida (Mr. Williams); Indiana (Dr. Haymond); Indian Territory, Texas, New Mexico, California (Dr. Woodhouse). The Chimney bird is abundant in all the States on the Atlantic, and, according to Dr. Woodhouse, equally so in Texas. It possesses powers of sustaining protracted and rapid flight, perhaps not equalled by any other bird of North America, though characteristic in some measure of all the birds of this family. In Europe, birds of genera nearly allied to the present have received the name of “Swifts” from this fact. 2. Acanthylis Vauxii. (Townsend.) Vaux’s Swift. Cypselus Vauxii. Towns., Jour. Acad., Philada., VIII. p. 148. (1839.) Not figured.