Hab. Throughout North America; Texas (Woodhouse); Oregon (U. S. Ex. Exp. Vincennes). Spec. in Mus. Acad., Philada. Obs. The American Osprey is very similar to that of the old continent (_P. haliaetus_), and specimens from Western America even more intimately resemble it. It is, however, larger, and retains in all the specimens that we have seen, differently-formed spots on the breast, being heart-shaped and circular, instead of narrow and lanceolate, as in the. European species. The Fish Hawk is abundant on the sea-coasts of the United States, and is one of the few rapacious birds of this country which are not molested. IV. GENUS POLYBORUS. Vieillot, Analyse, p. 22. (1816.) CARACARA. Cuvur. Reg. An., p. 316. (1817.) Size smaller than the preceding; bill long, compressed, wide laterally; cere large; wings long, pointed; tail moderate, or rather long; tarsi long, rather slender, covered in front with large hexagonal and irregular scales, and laterally and horizontally with smaller; claws long, slightly curved, rather weak; space in front of and below the eye naked. Two species only form this genus, both of which are abundant birds of South and Central America. 1. Polyborus tharus. (Molina.) The Caracara Eagle. The Mexican Eagle. Falco tharus. Molina, Sagg. Stor. Nat. del Chili. (1782.) Falco cheriway. Jacquin, Beytr. Gesch. der Vogel, p. 17. (1784.) Falco brasiliensis. Gmelin, Syst. Nat., I. p. 262. (1788.) Falco plancus. Miller, Cimelia Physica. Polyborus vulgaris. Vieill., Nouv. Dict., V. p. 257. (1816.) Jacq. Vog., pl. 4; Miller & Shaw, Cim. Phys., 2d ed., pl. 17; Vieill., Gal., I. pl. 7; Spix., B. of Bras., I. pl. 1, _a_; Aud., B. of Am., pl. 161; oct. ed., I. pl. 4; Swains. Zool. Ill., I. pl. 2; Gay’s Chili Orn., pl. 1. Legs long; occipital feathers somewhat elongated. Adult. Head above, back, rump, wings, broad abdominal belt and tibiæ brownish-black; neck before and behind, sides of the head behind the eye, breast, upper and under tail-coverts yellowish-white; on the breast and neck behind finely barred transversely with black; tail for about two-thirds of its length white, with numerous narrow bars of black, and widely tipped with black; bill at base bluish; tip yellowish-white; tarsi and toes yellow. Younger. Head above dark-brown; other upper parts pale-brown, with paler edgings to many feathers; under-parts dark-brown, nearly all the feathers having longitudinal central stripes of dull white; throat yellowish-white; tail for the greater part and its coverts above and below white, with numerous transverse bands of pale ashy-brown, and tipped with brownish-black. Dimensions. _Female_—total length (of skin), about 26 inches; wing, 17; tail, 10 inches. _Male_—larger? Hab. Southern North America; Florida (Audubon); Texas; Mexico (McCall). Abundant in South America. Spec. in Mus. Acad., Philada.