_Description._--Above black, very finely striated with white on the back; back of head and neck with a purplish tinge; secondaries of wings white with black ends, and covered with the black coverts, having a white speculum; primaries greyish white, the four outer ones on their outer webs and all on their extremities black; whole belly minutely vermiculated with grey and white; crissum white; bill rosy red, enlarged at the base; feet yellowish: whole length 19·0 inches, wing 9·4, tail 2·8. _Female._ Above brown, bend of wing and speculum white; beneath white, breast and flanks brownish; bill dark; feet horn-colour. _Hab._ Paraguay, Argentina, Chili, and Patagonia. The Rosy-billed Duck, usually called "Black Duck" in the Plata, inhabits the Argentine country from Paraguay to Patagonia, and also occurs in Uruguay and Chili, but does not extend to Brazil. A peculiar interest attaches to this species owing to the fact that it is the only freshwater Duck in the subfamily Fuligulinæ, in which it is classed. With the exception of the Loggerhead Duck (_Tachyeres cinereus_), found in the Falklands and the Magellan Straits, all the other sea-ducks of this division inhabit North and Central America; so that the Rosy-bill appears to have separated itself widely from its nearest relations geographically as well as in habits. In appearance it is a fine bird, the black plumage being frosted on the upper parts with white in a very delicate manner, while the rosy bill and large carmine caruncle and golden red iris contrast beautifully with the glossy purple head and neck. The speculum is white, the legs bright yellow. The plumage of the female is brown. In marshy places on the pampas the Rosy-billed Duck is very abundant, and they sometimes congregate in very large flocks. They obtain their food from floating weeds in the water, and are never seen, like the Pintails and other kinds, feeding on the dry land. They rise heavily, the wings being comparatively small, and have a rapid, straight, violent flight; they are nevertheless able to perform long journeys and travel in long lines and at a considerable elevation. Their only language is a deep, hoarse, prolonged, raven-like note, uttered by the male in the love-season. The nest is made on swampy ground near the water, of dry rushes, and is, for a duck, a deep well-made structure; the eggs are oval in form, cream-coloured, and twelve in number. 355. ERISMATURA FERRUGINEA, Eyton. (RUSTY LAKE-DUCK.) +Erismatura ferruginea+, _Scl. et Salv. Nomencl._ p. 131; _iid. P. Z. S._ 1876, p. 404; _Sclater, P. Z. S._ 1872, p. 549 (Rio Negro); _Burmeister, P. Z. S._ 1872, p. 368 (Buenos Ayres); _Durnford, Ibis_, 1877, p. 42 (Chupat), p. 192 (Buenos Ayres), et 1878, p. 401 (Central Patagonia).