+Serpophaga subcristata+, _Burm. La-Plata Reise_, ii. p. 454 (Entrerios); _Scl. et Salv. Nomencl._ p. 47; _Durnford, Ibis_, 1877, p. 177 (Buenos Ayres); _White, P. Z. S._ 1882, p. 606 (Misiones); _Barrows, Bull. Nutt. Orn. Cl._ vol. viii. p. 199 (Entrerios). _Description._--Above cinereous, usually with a slight olivaceous tinge on the rump; crest-feathers white at their bases, tipped with cinereous, and slightly varied with black; wings blackish, wing-coverts tipped with whitish, forming two handsome bands; outer secondaries externally margined with the same colour; tail dark ashy; beneath ashy white, with more or less yellowish tinge on the belly and under wing-coverts; bill horn-colour; feet black: whole length 4·5 inches, wing 2·0, tail 2·1. _Female_ similar. _Hab._ S.E. Brazil, Paraguay, Northern La Plata, and Bolivia. This species is one of the smallest members of our _Tyrannidæ_, its total length being only four and a half inches. The sexes are alike; the upper plumage is grey, with a greenish tinge on the back; the breast paler grey, becoming pale yellow on the belly. There is a white concealed spot under the loose feathers of the crown. It is quite common in Buenos Ayres, and, probably, has a partial migration, as it is most abundant in summer. In its habits it closely resembles the species last described, being always found in pairs, living in thickets, where they hop incessantly about, exploring the leaves for small caterpillars, and always conversing in low, chirping, and twittering notes. They also sing together a little confused song. The nest is fastened to the slender twigs of a low bush, and is a deep, cup-shaped and beautiful structure, composed of a great variety of soft materials bound together with spiders' webs, the interior lined with feathers or vegetable down, and the outside with lichen. The eggs are two, bluntly pointed, and of a cream-colour. 147. SERPOPHAGA NIGRICANS (Vieill.). (BLACKISH TYRANT.) +Serpophaga nigricans+, _Burm. La-Plata Reise_, ii. 454 (Paraná); _Scl. et Salv. Nomencl._ p. 47; _Durnford, Ibis_, 1877, p. 177 (Buenos Ayres); _White, P. Z. S._ 1882, p. 606 (Misiones); _Barrows, Bull. Nutt. Orn. Cl._ vol. viii. p. 199 (Entrerios). _Description._--Above dull brownish cinereous; wings and tail blackish, the coverts and outer secondaries with slight edgings like the back; crest slight, with a well-marked white basal spot; beneath paler and rather purer cinereous; under wing-coverts pale cinereous; bill and feet dark horn-colour: whole length 4·7 inches, wing 2·3, tail 1·1. _Female_ similar, but vertical spot not so well marked. _Hab._ S.E. Brazil, Paraguay, La Plata, and N. Patagonia.