Mr. Hancock, whose opportunities were ample, fully demonstrates (as cited above) that the _Falco grœnlandicus_ of Greenland, which is the present species, and the _Falco islandicus_ of Iceland, are distinct, which appears to be assented to by all late writers. The bird, figured by Mr. Audubon as the adult of the species of which the young bird was obtained by him in Labrador, was an Iceland specimen, (Orn. Biog. IV. p. 476,) and therefore not correctly given as the American bird. We have never had the satisfaction of seeing the adult of this species; but for an opportunity of examining one of Mr. Audubon’s Labrador specimens, we are indebted to the Rev. John Bachman, D. D., of Charleston, S. C., who, with that disposition to advance the interests of Zoological Science which has always characterized him, most kindly forwarded it at our request. Turton’s description above cited, is copied by him from Pennant’s Greenland Falcon, Arctic Zoology, I. p. 257. III. GENUS HYPOTRIORCHIS. Boie Isis, p. 976. (1826.) DENDROFALCO. Gray list, p. 3. (1840.) Size small, tarsus lengthened and rather slender. In all other characters much like typical Falco. Toes long, slender and furnished with sharp, curved claws. This genus includes about ten or twelve small species found in various parts of the world, and for the greater part dark colored, like the species of typical _Falco_. 1. Hypotriorchis columbarius. (Linn.) The Pigeon Hawk. Falco columbarius. Linn. Syst. Nat. I. p. 128. (1766.) Falco intermixtus. Daudin, Traité d’Orn. II. p. 141. (1800.) Falco temerarius. Aud. B. of Am. I. p. 381. (1831, plate pub. 1829) “Falco æsalon. Temm.” Rich. and Sw. Faun. Bor. Am. Birds, p. 37. Cat. Car. pl. 3. Vieill. Ois. d’Am. Sept. pl. 11. Wils. Am. Orn. II. pl. 15, fig. 3. Faun. Bor. Am. Birds, pl. 25. Aud. B. of Am. pl. 75, 92. Oct. ed. I. pl. 21. De Kay, Nat. Hist. N. Y. pl. 4, fig. 9. Small, head and body broad and strong, bill short, wing pointed with the second and third quills longest, tail slightly rounded, tarsi and toes slender. Adult male. Entire plumage of the upper parts dusky slate color, inclining to bluish, every feather with a black longitudinal line. Forehead and throat white, other under parts pale yellowish or reddish white, every feather with a narrow longitudinal stripe of brownish black, plumage of the tibia, light rusty red, with narrow stripes of black. Quills black, with transverse bands of white on their inner webs, and narrowly tipped with ashy white, tail above light bluish cinereous tipped with white, and with a wide subterminal band of black, and with several other narrower bands of black, inner webs nearly white. Cere and feet yellow, bill blue.