This elegant bird, which is conspicuous amongst most land species by the whiteness of its plumage, is found, though not commonly, (in November) in Banda Oriental; whilst near Santa Fé, three degrees of latitude northward, it was common during the same time of year. It is rather shy, generally perches on the branches of bushes and low trees. 3. FLUVICOLA AZARÆ. _Gould._ PLATE X. _F. albâ; alis, caudâ caudæque tectricibus atris, his albo-marginatis; primariis flavescenti-albis, basibus apicibusque nigris; rostro pedibusque atris._ Long. tot. 8³⁄₁₂ unc.; _alæ_, 4⁹⁄₁₂; _caudæ_, 4³⁄₁₂; _tarsi_, 1; _rost._ 1. Head, all the upper and under surface white; wings and tail black; tail coverts black margined with white; primaries broad and crossed near their extremity with sulphur white, and tipped with brown; bill and legs black. Habitat, banks of the Plata. This bird is very common in the neighbourhood of Maldonado, where it frequents the open grassy plains. It sits on the top of a thistle, or on a twig, and catches the greater part of its food on the wing. It is generally quiet in its movements and silent. Mr. Gould remarks, that he finds “nearly all the species of this peculiar group to differ remarkably in the structure of their wings and tail, while in all other respects they closely resemble each other both in form and habit; I have, therefore, hesitated to separate them into so many genera. I have assigned the present species to Mr. Swainson’s sub-genus _Fluvicola_, considering that differences in the form of one organ alone would not be sufficient grounds for the institution of a new genus among such closely allied species; the present bird evidently leads off to _Tænioptera_, a genus proposed many years since, by the Prince of Musignano for the _Pepoazas_ of Azara. “This species is closely allied to, if not identical with the _Pepoaza Dominicana_ of Azara, but as there is a degree of obscurity in his description, which causes some doubt on this point, I have considered it better to pay a just tribute of respect to that zealous labourer in the field of natural science, by assigning his name to this very elegant bird.” 1. XOLMIS CORONATA. _G. R. Gray._ Tyranuus coronatus, _Vieill._ Eucy. Meth. p. 885. Muscicapa vittiger, _Licht._ Cat. p. 54. My specimen was obtained on the wooded banks of the Parana, near Santa Fé, in Lat. 31° S. Boie’s name of Xolmis is adopted by Mr. G. R. Gray, as it was proposed some five years anteriorly to that of the Prince of Musignano’s. 2. XOLMIS NENGETA. _G. R. Gray._