Size, large. Bill, short, thick, distinctly toothed, and with a slight festoon; wings rather shorter than in _Falco_; tarsi and toes shorter, the former covered with small circular scales. Color of adult usually white. Contains several species inhabiting the northern regions of both continents, nearly all of which where regarded with great favor for the purposes of Falconry. 1. Hierofalco sacer. (Forster.) The American Gyr Falcon. Falco sacer. Forster, Phil. Trans. London, LXII. p. 423. (1772.) Falco fusca. Fabricius Fauna Grœnlandica, p. 56, (1780,) not Gmelin, (1788.) Falco cinereus. Gmelin, Syst. Nat. I. p. 267. (1788.) Falco grœnlandicus. Turton, Syst. Nat. I. p. 147. (1806.) Falco labradora. Audubon, B. of Am. p. 196, (name on plate pub. about 1834.) “Falco candicans. Gmelin.” Bonap. Cons. Av. p. 23. “Falco grœnlandicus. Turton,” Hancock in Ann. and Mag., Nat. Hist. II. p. 249. “Falco islandicus. Lath.” Aud. Orn. Biog. II. p. 552. Edwards’ Birds, II. pl. 53, young. Aud. B. of Am. pl. 196, young, (but not pl. 366 which represents another species.) Schlegel, Traité de Fauconnerie, pl. (no number,) adult. Ann. & Mag. Nat. Hist. II. pl. 10, (feathers.) Form strong, and robust; second and third quills (in the young bird) longest and nearly equal. Adult, according to Hancock as cited above, “ground of the plumage pure white, upper parts elegantly marked with arrow shaped spots of a dark gray; under parts and head streaked with the same; wings reaching to within two inches of the end of the tail; second primary the longest.” Young. Entire plumage, brown, tinged with cinereous on the upper parts. Throat, dull white; all the plumage of the under parts edged with and having circular spots of dull yellowish white, the rounded spots more apparent on the tibia and under tail-coverts. Quills, mottled with the same white on their inner webs; tail, with numerous (about thirteen) irregular bars of the same. “Bill and cere, pale blue; iris, brownish black. Feet, grayish blue; the under parts of the toes greenish yellow; claws dusky.” (Audubon.) Hab. Northern America. Greenland, (Fabricius, Hancock,) Hudson’s Bay, (Richardson,) Labrador, (Audubon,) Louisville, Kentucky, (Mr. C. W. Webber.) Spec. in Mus. Nat. Hist. Soc. Charleston, S. C. Obs. The Gyrfalcon is of very rare occurrence in the United States, though not unfrequent in the northern regions of this continent.