Page:Birds of North and Middle America partV Ridgway.djvu/30

2 now considered in detail, and a new key to the families presented, based upon more extended or special study.

Mesomyodian Passeres with (usually) a single pair of syringeal muscles, attached to the middle portion of the bronchial semirings, the syrinx tracheal, the lower end of the trachea consisting of thin, membraneous walls, about six of the usual semirings extremely thin, sometimes obsolete, the bronchi with both outer and inner tympaniform membranes, vibratory tracheal membranes being also present, the few muscles (usually only one pair) wholly lateral (being thus specially modified as a vocal organ ;) feet schizopelmous; tensor patagii brevis passerine.

The Tracheophone Passeres are (excepting the small family Xenicidæ of New Zealand) a purely Neotropical group of birds, though, like many others, entirely absent from the Antillean Subregion. The various members bear a more or less close resemblance in external appearance as well as in habits to certain Oscinine families, though very distinct in their internal structure. Thus, among the Formicariidæ (Antbirds), some forms closely resemble Shrikes (Laniidæ), others Wrens (Troglodytidæ), and others again are strikingly similar to the Pittas (Pittidæ) in form, though lacking entirely the beautiful coloration of the latter. The Dendrocolaptidæ and Furnariidæ embrace species which, so far as external appearance goes, might pass readily for Tree Creepers (Certhiidæ), Thrushes (Turdidæ), or even Larks (Alaudidæ) ; the smaller Pteroptochidæ are conspicuously wrenlike, while some of the Conopophagidæ are not very unlike Pipits (Motacillidæ). While they vary greatly in size, form, and