GEN. CHAR. General aspect somewhat vulturine, but bearing and manners almost gallinaceous. Neck and legs very long. Bill very high and much compressed, the commissure very straight and regular, and nearly parallel with the superior outline; cere very narrow, its anterior outline vertical and straight. Nostril very small, linear, obliquely vertical, its upper end being the posterior one; situated in the upper anterior corner of the cere. Lateral and under portions of the head naked and scantily haired, the skin bright-colored (reddish or yellow in life). Occipital feathers elongated. Wings and tail long, the latter rounded; five outer quills with inner webs sinuated; third to the fourth longest; first shorter than the sixth, sometimes shorter than the seventh. Feet almost gallinaceous, the tarsus nearly twice as long as the middle toe, but stout; outer toe longer than the inner; posterior toe much the shortest; claws long, but slender, weakly curved, and obtuse. Tarsus with a frontal series of large transverse scutellæ, the lower fourth to sixth forming a single row, the others disposed in two parallel series of alternating plates; the other parts covered by smaller hexagonal scales. [Illustration: =37871=, ♀. NAT. SIZE. =37871=, ♀. ¼ =37871=, ♀. ¼ =37871=, ♀. ¼ _Wing and tail._ _Polyborus auduboni._] This well-marked genus contains but a single species, the _P. tharus_, Mol., which extends its range over the whole of tropical and subtropical America, exclusive of some of the West India Islands. North and south of the Isthmus it is modified into geographical races, the southern of which is var. _tharus_, Mol., and the northern var. _auduboni_, Cass. The closely related genera _Phalcobænas_, _Milvago_, _Ibycter_, and _Daptrius_ are peculiar to South America and the southern portion of Middle America, most of them being represented by two or more species. They all form a well-marked and peculiarly American group, for which I shall retain Schlegel’s term _Polybori_. Their habits are quite different in many respects from those of other _Falconidæ_, for they combine in many respects the habits of the gallinaceous birds and those of the Vultures. They are terrestrial, running and walking gracefully, with the exception of the species of _Ibycter_ and _Daptrius_, which are more arboreal than the others, and are said also to feed chiefly upon insects, instead of carrion. Species and Races. =P. tharus.= Wing, 14.50–17.70; tail, 10.00–11.00; culmen, 1.20–1.48; tarsus, 3.20–4.20; middle toe, 1.75–2.30. _Adult._ Forehead, crown, occiput, back, rump, abdomen, sides, and tibiæ, and terminal zone of the tail, dull black. Neck, breast, tail-coverts, and tail, dingy whitish. Interscapulars, breast, and tail with transverse dusky bars. _Young._ Blackish areas replaced by dull brown; region of the transverse bars marked, instead, with longitudinal stripes.