The genus _Donacobius_ contains two species somewhat intermediate between the Mock-birds and the large Wrens of the genus _Campylorhynchus_. The well-known Brazilian _D. atricapillus_ extends through Paraguay, where Azara found it abundant, into Corrientes and the adjoining provinces of La Plata. It is met with among the reeds on lakes and streams. 12. TROGLODYTES FURVUS (Gm.). (BROWN HOUSE-WREN.) +Troglodytes furvus+, _Scl. et Salv. P. Z. S._ 1869, p. 158 (Conchitas); _iid. Nomencl._ p. 7; _Durnford, Ibis_, 1876, p. 157, 1877, p. 32 (Chupat), p. 167 (Buenos Ayres), 1878, p. 392 (Central Patagonia); _White, P. Z. S._ 1882, p. 593 (Buenos Ayres); _Döring, Exp. al Rio Negro, Zool._ p. 36 (Azul, R. Colorado, R. Negro). +Troglodytes platensis+, _Burm. La-Plata Reise_, ii. p. 476; _Barrows, Bull. Nutt. Orn. Cl._ viii. p. 86 (Concepcion). +Troglodytes musculus+, _Sharpe, Cat. B._ vi. p. 255. _Description._--Above brown; the tail-feathers and outer webs of wing-feathers pencilled with dark wavy lines; beneath very pale brown; bill and feet horn-colour; eye brown: total length 4·8 inches, wing 2·0, tail 1·7. _Female_ similar. _Hab._ South America. The common Argentine Wren is to all English residents the "House-Wren," and is considered to be identical with the species familiar to them in their own country. It is a sprightly little bird, of a uniform brown colour and a cheerful melodious voice; a tireless hunter after small spiders and caterpillars in hedges, gardens, and outhouses, where it explores every dark hole and cranny, hopping briskly about with tail erect, and dropping frequent little curtsies; always prompt to scold an intruder with great emphasis; a great hater of cats.