_Falco atricapillus_, WILS. Am. Orn. 1808, pl. lii, f. 3.—BONAP. Nouv. Giorn. Pisa, XXV, pt. ii, p. 55. _Astur atricapillus_, BONAP. Os. Cuv. Règ. An. p. 33.—IB. List, 1838, 5; Consp. 31.—WILS. Am. Orn. II, 284.—KAUP, Monog. Falc. Jardine’s Contr. Orn. 1850, 66.—DE KAY, Zoöl. N. Y. II, 19, pl. ii, fig. 4 (ad.), f. 5 (♂ juv.).—NUTT. Man. 85.—STRICKL. Orn. Syn. I, 118.—NEWB. P. R. Rep. VI, iv, 74.—COOP. & SUCK. P. R. Rep. XII, ii, 144.—LORD, Pr. R. A. I. IV, 1860, 110.—BLAKISTON, Ibis, III, 1861, 316.—GRAY, Hand List, I, 1869, 29.—BREWER, Oölogy, 1857, 17. _Falco palumbarius_, SAB. Frankl. Exp. 670.—BONAP. Ann. N. Y. Lyc. II, 28.—AUD. Edinb. J. Nat. Geog. Sc. III, 145.—IB. B. Am. pl. cxli; Orn. Biog. II, 241.—GIRAUD, B. Long Isl’d, 18.—PEAB. B. Mass. III, 77. _Astur palumbarius_, SW. & RICH. F. B. A. II, pl. xxvi.—JAMES. WILS. Am. Orn. I, 63.—AUD. Syn. B. Am. 18.—BREWER, WILS. Am. Orn. 685, pl. i, fig. 5.—GRAY, List B. Brit. Mus. 63. SP. CHAR. _Adult male_ (44,940, Boston, Mass.; E. A. Samuels). Above continuous bluish-slate, shafts of the feather inconspicuously black; tail darker and less bluish, tipped with white (about .25 of an inch wide) and crossed by five broad, faintly defined bars of blackish, these most distinct on inner webs (the first concealed by the upper coverts, the second partially so; the last, or subterminal one, which is about twice as broad as the rest, measuring about one inch in width). Primaries darker than the tail (but not approaching black). Forehead, crown, occiput, and ear-coverts pure plumbeous-black; feathers snowy-white beneath the surface, much exposed on the occiput; a broad conspicuous supraoral stripe originating above the posterior angle of the eye, running back over the ear-coverts to the occiput, pure white, with fine streaks of black; lores and cheeks grayish-white. Lower parts white; the whole surface (except throat and lower tail-coverts) covered with numerous narrow transverse bars of slate; on the breast these are much broken and irregular, forming fine transverse zigzags; posteriorly they are more regular, and about .10 of an inch wide, the white a very little more. Chin, throat, and cheeks without transverse bars, but with very sharp shaft-lines of black; breast, sides, and abdomen, a medial longitudinal broad streak of slate on each feather, the shaft black; on the tibiæ, where the transverse bars are narrower and more regular, the shaft-streaks are also finer; anal region finely barred; lower tail-coverts immaculate pure white. Lining of the wing barred more coarsely and irregularly than the breast; under surface of primaries with white prevailing, this growing more silvery toward the ends; longest (fourth) with six oblique transverse patches of slate, the outlines of which are much broken. Wing-formula, 4, 5, 3–6–2; 1=10. Wing, 13.00; tail, 9.50; tarsus, 3.70, naked portion, 1.35; middle toe, 2.00; inner, 1.21; outer, 1.37; posterior, 1.00.