This species differs from _Pyr. coronatus_ or _Musicapa coronata_, of authors, chiefly in its size; in other respects it is very similar. The admeasurements of the latter, for comparison (as given me by Mr. G. R. Gray), are: total length, 5 inches and 8 lines; bill, between 9 and 10 lines; wings, 3 inches and 2 lines; tail, 2 inches and 7 lines; tarsi, 7 or 8 lines. During the summer, this bird was common both near Buenos Ayres and Maldonado; but at the latter place, I did not see one in the months of May, June, July, (winter) and therefore, no doubt it is a bird of passage, migrating southward during the summer from Brazil. The birds of this and the allied genera, correspond very closely in their habits to certain of the Sylviadæ of Europe; some of the species frequenting bushes, like the black-cap, (_Sylvia atricapilla_); others more usually the ground, as the robin (_Sylvia rubecula_) or hedge-sparrow (_Accentor modularis_). Another group (_Synallaxis, &c._) represent those European Sylviæ, which frequent reeds. 2. PYROCEPHALUS OBSCURUS. _Gould._ _P. lividus rufotinctus; præcipuè in fronte ventreque._ Long. tot. 5⁹⁄₁₂ unc.; _alæ_, 3²⁄₁₂; _caudæ_, 2⁵⁄₁₂; _tarsi_, ⁷⁄₁₂; _rost._, ⁸⁄₁₂. All the plumage chocolate brown, tinged with red, the latter colour predominating on the forehead and lower part of the abdomen; bill and tarsi, black. A single specimen was obtained, and it would appear to be either an immature bird or a female. Habitat, Lima, Peru. (_August._) 3. PYROCEPHALUS NANUS. _Gould._ PLATE VII. _P. fuscus; rectricum exteriorum marginibus omniumque et sècundariorum apicibus nitidè griseo-brunneis._ _Femina, brunnea; gutture griseo-albo; corpore subtus pallidè flavescente; pectoris laterumque plumis in medio brunneo-striatis._ Long. tot. 4¹¹⁄₁₂ unc.; _alæ_, 2²⁄₁₆; _caudæ_, 2²⁄₁₂; _tarsi_, ⁸⁄₁₂; _rostri_, ⁸⁄₁₂. _Male._ Crown of the head, crest, and all the under surface, scarlet; back, wings, and tail, sooty brown; the external margin of the outer tail feathers, and the tips of all, light greyish brown; bill and tarsi, black. _Female._ All the upper surface, wings, and tail, brown; throat, greyish white; the remainder of under surface, pale buff, the feathers of the chest and flanks, with an obscure fine stripe of light brown down the centre. Habitat, Galapagos Archipelago. (_September._) There is nothing remarkable in the habits of this bird. It frequents both the arid and rocky districts near the coast, and the damp woods in the higher parts of several of the islands in the Galapagos Archipelago. 4. PYROCEPHALUS DUBIUS. _Gould._ _P. minor, lividus; fronte, superciliis corporeque subtus stramineis; tectricibus stramineo marginatis._