Young. Entire upper-parts dark umber-brown, very slightly mixed with fulvous; upper tail-coverts white, spotted with brown; entire under-parts pure white, with a few narrow longitudinal lines and dashes of brown on the breast, and arrow-heads of the same color on the sides and abdomen, larger and more numerous on the flanks; tibiæ white; tarsi dark-brown, mixed with white; under wing-coverts and edges of wings white. Dimensions. _Female_—total length, about 23 to 25 inches; wing, 17 to 17½; tail, 9 inches. _Young_—smaller. Hab. California (Mr. E. M. Kern); Sacramento valley (Dr. Heermann). Spec. in Mus. Acad., Philada. Obs. This is one of the handsomest of the American Falconidæ. It is also one of the largest of the Buzzards, and easily distinguished from the preceding species. Of the recent American travellers, Mr. E. M. Kern was the first who brought home this fine species; since which adults, young birds, and eggs, have been collected by Dr. Heermann. It is not rare in California. IV. SUB-FAMILY MILVINÆ. THE KITES. Size various, usually medium or small. Bill short, weak, hooked, and acute; wings and tail usually long; tarsi and feet slender, frequently short. The birds of this sub-family habitually feed on reptiles and other small animals, and are deficient in the strength and courage of those of the other sub-families. About thirty-five species of all countries belong to this group. I. GENUS NAUCLERUS. Vigors, Zool. Jour., II. p. 386. (1825.) CHELIDOPTERYX. Kaup, Class., p. 112. (1844.) Bill short and weak; wings and tail very long, the former pointed, the latter deeply forked. Tarsi very short; toes short. Contains not more than three species, two of which are American, and the other African. 1. Nauclerus furcatus. (Linn.) The Swallow-tailed Hawk. Falco furcatus. Linn., Syst. Nat., I. p. 129. (1766.) Cat. Car, pl. 4; Buff., Pl. Enl., 72; Wilson, Am. Orn., VI., pl. 51, fig. 3; Aud., B. of Am., pl. 72, oct. ed. I. pl. 18; Gould, B. of Eur., 1. pl. 30; De Kay, Nat. Hist. N. Y., Birds, pl. 7, fig. 15. Wings and tail long, the latter deeply forked. Head and neck, inferior wing-coverts, secondary quills at their bases, and entire under-parts, white. Back, wings, and tail, black, with a metallic lustre, purple on the back and lesser wing-coverts, green and blue on other parts. Tarsi and feet greenish-blue; bill horn color. Dimensions. _Female_—total length, 23 to 25 inches; wing, 16 to 17½; tail, 14 inches. _Male_—rather smaller. Hab. Southern States on the Atlantic, and centrally northward to Wisconsin; Texas (Mr. Audubon); South Carolina (Prof. Gibbes); Wisconsin (Dr. Hoy); Pennsylvania (Mr. A. F. Darley); Jamaica (Mr. Gosse). Accidental in Europe. Spec. in Mus. Acad., Philada.