Form. Robust and compact; bill, rather large; wings, long, with the third quills longest, all the primaries more or less incised on their inner webs near the end; tarsi feathered in front to the toes, naked and scaled behind; toes, short; claws, strong. Dimensions. Total length (of skin), female, about 22 inches; wing, 16½ to 17; tail, 9 inches. Color. _Adult._—Tibiae and tarsi bright ferruginous, with transverse stripes of brownish-black, irregular and indistinct on the latter. Entire upper parts with irregular longitudinal stripes of dark-brown and light ferruginous, the latter color predominating on the shoulders and rump. All the upper plumage white at the bases of the feathers, and on the back with concealed irregular transverse stripes of brownish-black. Quills, ashy-brown, lighter on the outer webs, and with a part of the inner webs white, and with obscure brown bands. Tail, above, ashy-white, tinged with pale ferruginous, and mottled obscurely with ashy-brown, in some specimens narrowly tipped with black; tail, beneath, yellowish-white, unspotted. Entire under parts of the body white, slightly tinged with yellowish, with narrow longitudinal lines and dashes of reddish-brown on the breast, and narrow irregular transverse lines of the same color, and others of black, on the sides, flanks, and abdomen; under tail coverts, white; axillary feathers and some of the inferior coverts of the wing, bright ferruginous; toes, yellow; bill and claws, dark. _Young._—Entire upper parts dark umber-brown, a few feathers edged and tipped with pale ferruginous; upper coverts of the tail white, spotted with dark-brown; entire under parts pure white, with a few longitudinal lines and dashes of dark brown on the breast, and arrow-heads or irregularly shaped spots of the same color on the sides and abdomen, larger and more numerous on the flanks. Tibiæ and tarsi white, irregularly spotted with dark-brown; axillary feathers, white, with large subterminal spots of brown; under wing coverts and edges of the wings white, with a few brown spots; under tail coverts, white. Hab. California. (Mr. Kern, Dr. Heermann.) Spec. in Mus. Acad., Philada. Obs. This very distinctly characterized species somewhat resembles some stages of plumage of the Rough-legged Hawk and of the Black Hawk (_Archibuteo lagopus_ and _sancti-johannis_) but not sufficiently to render it necessary to point out differences. It has, as yet, only been observed in California, but will, very probably, like many other species of Western birds, be found to inhabit also the northern regions of this continent. [Illustration: Plate 27 The Black-headed Gnat-catcher Culicivora atricapilla (_Weill_)] CULICIVORA MEXICANA.—Bonaparte. The Black-headed Gnat-catcher. PLATE XXVII.—Male and Female.