Frequently met with, and remarkable for constructing its nest in a hole in the ground, usually by the side of a quarry or stream of water. This is one of the few American birds that appear to be absolutely identical with European species. On close comparison, we can discover no characters in the present sufficient to raise a probability of specific distinction. Specimens from California, that we have examined, present slight variations from those of the Eastern States. The bill appears to be smaller, and the tail not so deeply emarginated. 2. Cotyle serripennis. (Audubon.) The Rough-winged Swallow. Hirundo serripennis. Aud., Orn. IV. p. 593. (1838.) Aud., B. of Am., Oct. ed. I. pl. 51. Larger than the preceding; wing long; first primary longest; tail emarginate; legs short; outer edge of the first primary furnished throughout its length with a row of reversed hooked bristles, easily apparent to the touch; entire upper parts light ashy white, darker on the breast and flanks, lighter on the throat and middle of the abdomen; under-coverts of the tail white; under-coverts of the wing ashy brown; bill and feet dark. Female lighter in all the colors. Dimensions. Total length, male, 5½ inches; wing, 4½; tail, 2¼ inches. Female slightly smaller. Hab. Louisiana, South Carolina (Mr. Audubon); Pennsylvania (Prof. Baird); California (Dr. Heermann). This remarkable species is easily distinguished from any other North American Swallow by the recurved and stiff bristles of the outer edges of the first primary quills. There is a South American species which has, however, the same character (_Cotyle flavigastra_). The present bird considerably resembles that immediately preceding, but is larger, and is quite distinct. It was regarded as a rare southern species, until demonstrated by Professor Spencer F. Baird, then of Dickinson College, Carlisle, Pennsylvania, to be of frequent occurrence in the interior of that State. Dr. Heermann states that it is not uncommon in California. Ornithologists generally, however, have not noticed it, and in the vicinity of Philadelphia, it has been entirely overlooked, or does not inhabit this district. II. SUB-FAMILY CYPSELINÆ. THE SWIFTS. Bill less flattened than in the preceding sub-family, very wide at base, short, curved; wings very long, somewhat falcate, flattened; tail short; legs and toes short, strong; claws strong; general form adapted to very swift and vigorous flight, and the capture of insects on the wing. I. GENUS CYPSELUS. Illiger, Prodromus, p. 229. (1811.) APUS. Scopoli. MICROPUS. Wolf.