256 BULLETIN 50, UNITED STATES KA.TIONAL MUSEUM. 



Small or medium-sized arboreal Icteridee with bill elongate-conical, 

 acute, not longer than head; nasal fossae well defined, broad and rounded 

 anteriorty, the nostrils overhung by a conspicuous semicorneous oper- 

 culum; tail more than three-fourths as long as wing (often as long as, 

 sometimes longer than wing), more or less rounded (sometimes gradu- 

 ated) ; tarsi rather short (never very much longer than culmen, some- 

 times shorter), and middle toe, with claw, never longer than tarsus 

 (usually shorter) ; colors usually black and orange or black and yellow, 

 in large strongly contrasted areas; if without orange or j'^ellow. chest- 

 nut or orange-brown replacing those colors. 



Bill much shorter than head to about as long, elongate-conical, acute, 

 with straight outlines or with the tip slightly decurved, its depth at 

 base usually less than half the length of commissure, sometimes (in 

 I. xanthorniis) nearly if not quite equal to length of gonys; culmen 

 straight or rather strongly (but gradually) decurved terminally, the 

 mesorhinium usually narrow and distinctly (sometimes almost sharply) 

 ridged, more rarely broader and rounded, or even somewhat flattened; 

 gonys straight or slightly decurved terminally; commissure straight to 

 behind nostril, or slightly arched, the rictal portion strongly and more 

 or less abruptty deflexed. Nostril longitudinal, narrow (linear or more 

 or less crescentic), overhung by a very distinct semicorneous operculum, 

 the anterior end of the nasal fossae broad and rounded . Wing moderate, 

 its tip moderately produced, rounded or subtruncate; outermost (ninth) 

 primary alwaj's shorter than sixth, sometimes shorter than third, the 

 eighth to seventh, eighth to fifth, or seventh to fifth longest; inner 

 webs of longer primaries very faintly or not appreciably sinuated. 

 Tail decidedly shorter than wing to longer than wing, slightly rounded 

 to strongly graduated (the graduation sometimes equal to more than 

 one-fourth the length of middle rectrices). Tarsus usually a little 

 longer than culmen, sometimes slightly shorter, the acrotarsal soutella 

 distinct; middle toe, with claw, shorter than tarsus (never conspic- 

 uoush' so), rarely (in I. icterus) equal to it; claws of lateral toes reach- 

 ing about to base of middle claw; hallux about as long as lateral toes, 

 much stouter, its claw decidedly shorter than the digit; all the claws 

 strongly curved, acute. 



Coloration. — Usually richly colored with sharply contrasted areas 

 of black and orange, black and yellow, or black and chestnut; never 

 entirely black; females (of some species) and young plainer, with olive- 

 greenish hues prevailing. 



Range. — The whole of temperate and tropical America (most devel- 

 oped in tropical portions). (More than fifty species and subspecies.) 



Notwithstanding the very great variation in relative length of wing 

 and tail, extent of graduation of the latter; relative length and thick- 

 ness of the bill and its degree of curvature; wing-formula, and all other 

 external characters, my best efforts to trenchantly subdivide the genus 



