placed low down on side of skull; maxillo-palatines long and slender processes, curved backward; vomer short, with long limbs; nares holorhinal; tensor patagii brevis masked passerine or quasi-picarian ; one pair of tracheo-bronchial muscles, the intrinsic muscles present; sterno-trachealis attached to processus vocales; palate ægithognathous (oscinine); mesorhinium compressed and arched, or expanded into a flattened oval shield; nostrils conspicuously operculate; tarsal envelope taxaspidean.
Externally, the Pteroptochidæ are characterized by their wren- like appearance (though with the bill relatively shorter and stouter than in the true wrens), large and strong feet (which are excessively developed in some genera), short, very concave, and much rounded wing (with 10 primaries), and, usually, short or very short tail, which is usually carried erect or thrown forward. Of terrestrial or semi- terrestrial habits they are well adapted to hopping or running on the ground; but their power of flight is very limited, the birds of this family being able to fly but a short distance. They are very active, inquisitive, and noisy birds, and their notes are varied and remarkable, but harsh and loud rather than musical.
The Pteroptochidæ are peculiar to the more southern portions of the Neotropical Region, the high mountains of Costa Rica, where a single representative occurs, being the northern limit; only seven of the thirty-one species and two of the eight known genera occur in the elevated districts of Colombia, the remainder occurring in the Andean district of Ecuador, Peru, and Chile, and thence to the Falkland Islands, Argentina, and southeastern Brazil, two of the Colombian species (belonging to separate genera) extending as far eastward as the higher mountains of Venezuela.
In Volume XV of the Catalogue of the Birds in the British Museum (1890, pp. 337-352) Dr. Sclater recognizes eight genera and twenty-one species; but Dr. Sharpe, in his Hand List of the Genera and Species of Birds (Vol. III, 1901, pp. 4-7), increases the number of species to thirty-one.
Genus SCYTALOPUS Gould.
- Scytalopus Gould, Proc. Zool. Soc. Lond., 1836, 89. (Type, S. fuscus Gould = Motacilla magellanica Gmelin.)
- Sylviaxis Lesson, Rev. Zool., 1840, 274. (Type, S. guttatus Lesson = unidentified species).
- Agathopus Sclater, Proc. Zool. Soc. Lond., 1858, 69. (Type, A. micropterus Sclater = Merulaxis analis Lafresnaye?)
Small wren-like Pteroptochidæ (length about 100 to 130 mm.) with the mesorhinium compressed and slightly arched, loral feathers short, tail much shorter than wing, tarsal envelope distinctly scutellate, and hind claw strongly curved and shorter than the digit.
