Bill longish, slender, straight, tapering to a very sharp point. Nostrils basal, oval, feet of ordinary length, slender; tarsus compressed, covered anteriorly with a few long scutella, sharp-edged behind, longer than the middle-toe; toes scutellate above, free; claws arched, slender, compressed, acute.
Plumage blended, the feathers soft and tufty. Wings rather short, the second and third quills longest. Tail slightly emarginate, of ordinary length, the twelve feathers rather narrow, and tapering broadly to a point.
Bill dusky above, pale greyish-blue beneath. Iris hazel. Feet and claws dusky. The general colour of the plumage above is dull brownish-green, the rump and tail-coverts light yellowish-green, the edge of the wing at the flexure yellow. On the crown is a spot of bright reddish-orange, more distinct when the feathers are raised. The under parts are of a dull olivaceous yellow, the lower tail-coverts bright yellow. The quills and tail-feathers dark brown, slightly margined with paler.
Length 5½ inches, extent of wings 7 11⁄12; bill along the ridge 5⁄12, along the edge ½; tarsus 9⁄12.
Adult Female. Plate CLXXVIII. Fig. 2.
Bill and feet of the same colour as in the male, the former inclined to yellowish-grey beneath. The female wants the orange spot on the crown, but in other respects resembles the male in colour, although the rump and upper tail-coverts are of a darker tint.
Length slightly less than that of the male.
This species appears to form the transition from the Sylviæ to the Reguli; or rather to be allied to the Reguli on the one hand, and to the Slender-billed Finches on the other.