The Formicariidæ, or Ant-birds, are another very important constituent of the Neotropical Avifauna, but are less generally diffused than the Dendrocolaptidæ, the greater number of the forms being restricted to the hot forests of South and Central America. In the Argentine Republic we meet with only four species of the widely-spread genus _Thamnophilus_, and of them only one appears to extend as far south as Buenos Ayres. 222. THAMNOPHILUS LEACHI (Such). (LEACH'S BUSH-BIRD.) +Thamnophilus leachi+, _Scl. et Salv. Nomencl._ p. 69; _White, P. Z. S._ 1882, p. 614 (Misiones). _Description._--Black, thickly and conspicuously spotted above with white or pale yellowish; on the wings the spots occur on the outer webs of the feathers; upper tail-coverts faintly edged with grey; tail black, unspotted; feathers on the lower breast and belly slightly edged with grey; bill and feet black: whole length 10·5 inches, wing 3·4, tail 5·0. _Female_: spots larger and yellow, on the crown lengthening to stripes and tinged with rufous; inner webs of the wing-feathers also spotted on their margins; whole under surface thickly spotted with pale yellow. _Hab._ Brazil and N. Argentina. White met with a single individual of this fine Bush-bird at Concepcion, Misiones. It was observed on the ground feeding on a swarm of black ants. 223. THAMNOPHILUS MAJOR, Vieill. (LARGER BUSH-BIRD.) +Thamnophilus major+, _Scl. et Salv. Nomencl._ p. 69; _White, P. Z. S._ 1882, p. 614 (Salta); _Salvin, Ibis_. 1880, p. 359 (Salta). +Thamnophilus stagurus+, _Burm. La-Plata Reise_, ii. p. 471 (Paraná, Tucuman). _Description._--Above black, upper wing-coverts crossed by a row of white spots; the outer rectrix on each side tipped and barred with white, the other rectrices, excepting the middle pair, spotted with white on their inner webs; beneath pure white; bill black, feet grey: whole length 8·0 inches, wing 3·6, tail 2·8. _Female_ above rufous, beneath white, lower flanks and under tail-coverts tinged with ochraceous; tail wholly rufous. _Hab._ Paraguay and N. Argentina. White found this species common in the gardens round the town of Oran. He noted the iris as "crimson."