DIAGNOSES OF SOME NEW GENERA OF BIRDS 

 By ROBERT RIDGWAY 



CURATOR, DIVISION OF BIRDS, U. S. NATIONAL MUSEUM 



OROAETUS gen. nov. (Buteonidae) 

 Type: Falco isidori Des Murs. 



Similar to Spiza'etus Vieillot/ but rectrices much broader, the 

 width of middle pair equal to about one-fourth their length (from 

 point of insertion) ; feathers of legs longer, those of thighs plume- 

 like ; wing-tip relatively longer, the longest primary exceeding outer- 

 most (distal) secondary by more than one-fourth the length of wing; 

 tip of tail truncate ; occipital plumes shorter, subcuneate ; adults 

 with under parts striped, upper parts uniform black, and tail mottled 

 grayish with a broad terminal band of black ; size larger (wing more 

 than 500 mm.). 



("Opo?, mountain; af.T6<i, eagle.) 



Species: Oroa'etus isidori (Des Murs). 



The type and only known species of this genus has been referred 

 by Sharpe and others to Lophotriorchis Sharpe (type, Astur kienerii 

 Geofifroy-St. Hilaire), but it would be difficult to find two forms of 

 this group (Spizaeti) more conspicuously different in structural 

 details or even in appearance. Lophotriorchis differs in (i) the 

 very broad cere, its width on top nearly if not quite equal to its 

 length; (2) relatively very much smaller bill; (3) densely bristled 

 loral region; (4) five outer primaries with inner webs deeply and 

 abruptly emarginated (instead of six obliquely sinuated) ; (5) very 

 different relative length of anterior toes, the inner (without claw) 

 not extending beyond the penultimate articulation of the middle toe, 

 the outer very little longer, the middle toe (without claw) three- 

 fourths as long as tarsus instead of only about two-thirds as long; 

 (6) tip of tail distinctly rounded instead of truncate. In short, 

 practically the only character, apart from those common to the 

 whole group, possessed by the two genera consists in the unim- 

 portant ones of a similar crest and striped under parts of adults. 



^ With "Falco mauduyti Daudin " — F. ornatus Daudin as type (subsequent 

 designation by Gray, 1840). 



Smithsonian Miscellaneous Collections, Vol. 72, No. 4 



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