Bill short, wide at the base, much compressed toward the end; upper mandible with the dorsal line decurved from the base, the sides slightly convex, the edges with a slight festoon, the tip narrow and acute; lower mandible with the angle very wide, the dorsal line straightish, the tip rounded and declinate. Nostrils round, with a central papilla. Head rather large, roundish, flattened; neck short; body compact. Feet short; tarsus very short, thick, scaly all round; toes scutellate above, scabrous beneath, with pointed papillæ; claws rather long, curved, acuminate. Plumage blended, glossy. Wings extremely long, pointed, the third quill longest; secondaries short. Tail extremely long, very deeply forked. 18. 1. Nauclerus furcatus, Linn. Common Swallow-tailed Hawk. Plate LXXII. Male. Head, neck all round, and lower parts white; back, wings, and tail black, glossed with blue and purple; feet light blue, tinged with green; claws flesh-coloured. _Male_, 22, 47. _Female_, 25, 51-1/2. From Texas to North Carolina. Rather abundant. Up the Mississippi and Ohio to Louisville. Accidental in Pennsylvania. Migratory. Swallow-tailed Hawk, Falco furcatus, Wils. Amer. Orn. v. vi. p. 70. Falco furcatus, Bonap. Syn. p. 31. Swallow-tailed Hawk, Falco furcatus, Aud. Orn. Biog. v. i. p. 368. v. v. p. 371. GENUS IX. FALCO, Linn. FALCON. Bill short, robust; its upper outline decurved from the base; cere short, bare; edge of upper mandible with a festoon and a prominent angular process. Nostrils round, with an internal ridge, ending in a central tubercle. Feet strong; tarsi moderate, reticulate; toes long, broadly scutellate, the anterior webbed at the base; claws long, well curved, very acute. Wings long, pointed; second quill longest, first and third nearly equal; outer toe abruptly cut out on the inner web. Tail rather long, nearly even. 19. 1. Falco Islandicus, Lath. Iceland or Jer Falcon--Gyr Falcon. Labrador Falcon. Plate CCCLXVI. Adult Female. Plate CXCVI. Young Male and Female. Tooth-like process of the bill generally obsolete in old, festoon slight in young birds; tail from three to four inches longer than the wings. Adult white, with slate-grey sagittate spots above, the bill pale blue, the cere and feet yellow. Younger birds light grey, the feathers white on the edges; the bill and cere light blue, the feet greyish-blue. Young brownish-grey above, the feathers margined and spotted with reddish-white, the lower parts yellowish-white, longitudinally streaked with dusky. _Male_, 22-1/2, 49. _Female_, 23-1/2, 51-1/4. Breeds in the extreme north, and in Labrador. In winter, migrates southward as far as Maine. Falco Islandicus, Jer Falcon, Rich. & Swains. F. Bor. Amer. v. ii. p. 27. Gyr Falcon, Falco Islandicus, Nutt. Man. v. i. p. 51. Iceland or Jer Falcon, Falco Islandicus, Aud. Orn. Biog. v. iv. p. 466. Adult Female.