This small bird is only four and a half inches long; in both sexes the colour on the upper parts is dull grey, on the throat and breast ash-coloured; the belly pale yellow. It has the distinction of a slender curling Lapwing-like crest, composed of a few narrow, long, black feathers. The eye is white. It is found in the thorny thickets on the dry plains of Mendoza, and is also common in Patagonia. In its habits it closely resembles _Serpophaga subcristata_; lives always in pairs, perpetually moves about in a singularly deliberate manner while searching through the bush for small insects, the two birds always talking together in little chirping notes, and occasionally bursting out into a little shrill duet. It builds a deep, neat nest of fine dry grass and lined with feathers, in a low thorn, and lays two white eggs. 149. ANÆRETES FLAVIROSTRIS, Scl. et Salv. (YELLOW-BILLED TIT-TYRANT.) +Anæretes flavirostris+, _Scl. et Salv. P. Z. S._ 1876, p. 355; 1879, p. 613. _Description._--Above brownish olive; head black, mixed with white and surmounted by narrow elongated black crest-feathers; wings blackish, outer web of external rectrix whitish; beneath pale stramineous, throat and breast white, densely striated with black; under wing-coverts white; bill yellowish, with a black tip; feet black: whole length 4·2 inches, wing 2·1, tail 2·0. _Hab._ Bolivia and N. Argentina. A specimen of this species was procured, at Cosquin, near Cordova, by White. 150. CYANOTIS AZARÆ, Naum. (MANY-COLOURED TYRANT.) +Cyanotis azaræ+, _Scl. et Salv. Nomencl._ p. 47; _Durnford, Ibis_, 1877, p. 177 (Buenos Ayres, Centr. Patagonia); _Gibson, Ibis_, 1880, p. 32 (Buenos Ayres); _Döring, Exp. al Rio Negro, Zool._ p. 43 (R. Colorado, R. Negro); _Barrows, Nutt. Bull. Orn. Cl._ viii. p. 200 (Entrerios, Carhué, Pampas). _Description._--Above dark bronzy green; head black; superciliaries yellow; vertical spot crimson; wings black; broad tips of the lesser wing-coverts and broad edgings of some of the secondaries white, forming a large white bar on the wing; tail black, greater part of outer pair of rectrices and outer web and broad tip of next pair and narrow tips of third pair white; beneath bright ochreous yellow; chin whitish; crissum crimson; incomplete band across the lower breast black; under wing-coverts white; bill black; feet dark flesh-colour: whole length 4·2 inches, wing 2·1, tail 1·7. _Female_ similar. _Hab._ La Plata, Chili, and Western Peru.