When in full plumage, this is one of the handsomest of the Swallows of the United States. It is quite abundant everywhere in the States on the Atlantic during the summer. Specimens from California present some points of difference from the bird of Pennsylvania, being apparently more tinged with blue, and having the bill perhaps slightly large. We regard the two, however, as specifically the same. 4. Hirundo thalassina. Swains., Philos. Mag., 1827, p. 366. Aud., B. of Am., pl. 385, fig. 4, 5, Oct. ed. I. pl. 49. Wings long, exceeding the tail, which is rather short and emarginate; entire upper-parts rich grass-green, very glossy, and shaded with purple, especially on the head, and in some specimens approaching to carmine on the back, rump, and upper tail-coverts; entire under-parts silky-white, generally with a tinge of cinereous; bill and feet dark. Female, less glossy, and with the purple generally tinged with brown. Dimensions. Total length, male, 5 inches; wing, 4½; tail, 2 inches. Female, smaller. Hab. Western North America. Oregon (Townsend); California (Gambel); Mexico (Swainson); New Mexico (Woodhouse). This is the most beautiful of the North American birds of this family. It is exclusively an inhabitant of the countries west of the Rocky Mountains and of Mexico. II. GENUS PROGNE. Boie, Isis, 1826, p. 971. Form robust and compact; bill wide at base, compressed suddenly to the tip, rather strong; upper mandible overlapping the under; wings long, pointed; first and second primaries longest; tail moderate, rather wide, usually deeply emarginate; tarsi and feet larger and stronger than usual in this family. Size, largest of American birds of this family. This genus contains about five or six American species, several of which are nearly related to each other, and not well understood, and probably one other (_Hirundo borbonica_, Gm.), which is a native of Madagascar, and of the Island of Bourbon. All the species, except the last, considerably resemble each other, and are difficult to distinguish in some stages of plumage. 1. Progne purpurea. (Linn.) The Purple-Martin. The House Martin. Hirundo purpurea et subis. Linn., Syst. Nat. I. p. 344. (1766.) Hirundo violacea. Gm., Syst. Nat. I. p. 1026. (1788.) Hirundo cœrulea. Vieill., Ois. d’Am., Sept. 1, pl. 57. (1807.) Hirundo versicolor. Vieill., Nouv. Dict. XIV. p. 509. (1817.) Hirundo ludoviciana. Cuv., Reg. An. I. p. 374. (1817.) Catesby, Carolina I. pl. 51; Vieill., Ois. d’Am., Sept. 1, pl. 26, 27; Buff, Pl. Enl. 722; Wilson, Am. Orn. V. pl. 30, fig. 2, 3; Aud., B. of Am., pl. 22, Oct. ed. I. pl. 45; Nat. Hist. N. Y. Birds, pl. 28, fig. 61.