66 BULLETIN 5 0, UNITED STATES NATIONAL MUSEUM 



c. Size very large; wing over 500 mm. in length.'^ 

 d. Tarsus densely feathered, all around, down to base of toes. 



Aquila (p. 452) 

 dd. Tarsus naked, all around, for lower third or more. 



e. Wing much rounded (fifth to seventh primaries longest, the first 

 shortest), the secondaries very large and broad, reaching nearly 

 to tips of primaries; tail nearly as long as wing; occiput con- 

 spicuously crested; feet enormously developed Harpia (p. 430) 



ee. Wing pointed (third to fifth primary longest, the first longer than 

 ninth) , the secondaries only moderately developed, their ends fall- 

 ing far short of tips of primaries; tail not more than two-thirds as 

 long as wing; occiput not crested; feet moderately developed. 



/. Tail with 12 rectrices Haliaeetl^s (p. 472) 



//. Tail with 14 rectrices Thallasoaetus (p. 467) 



cc. Size small to moderately large; wing under 500 mm. in length. 



d. Maxilla sickle-shaped, slender; claw of middle toe with its inner edge 



produced and (if not worn away) pectinated. 



c. Longest primary exceeding distal secondary by two-fifths the length 



of wing; tarsus only one-seventh as long as wing and less than 



two-thirds as long as tail; tail nearly half as long as wing; its tip 



emarginate Rostrhamus (p. 130) 



ee. Longest primary exceeding distal secondary by less than one-third 

 the length of wing; tarsus more than one-sixth as long as wing 

 and more than half as long as tail; tail only two-fifths as long as 



wing, its tip truncate Hslicolestes (extralimital) ^^ 



dd. Maxilla not sickle-shaped, not slender; claw of middle toe not pro- 

 duced or pectinated on its inner edge. 

 e. Face encircled by a ruff of short, stiffened compact feathers, as in 



the owls Circus (p. 498) 



ee. Face not encircled by a ruff. 

 /. Tail relatively very long, at least two-thirds the length of the wing. 

 g. Tail almost as long as wing (85 percent) ___ Morphnvis (p. 421) 

 gg. Tail less than 85 percent as long as wing. 



h. Maxillary tomium doubly toothed Harpagus (p. 114) 



hh. Maxillary tomium smooth or sinuated, but not toothed. 

 i. Tarsus completely feathered to the toes. 



j. Five outermost primaries incised on their inner webs; the 

 distal portions of the feathers lying straight. 



Spizastur (p. 437) 



jj. Six outermost primaries incised on their inner webs; the 



distal portions of the feathers "bowed" or bent inward. 



Spizaetus (p. 441) 

 it. Tarsus naked for the lower two-thirds of its length. 



j. Toes relatively very short, the middle toe without claw 

 less than half the length of the tarsus. 



Geranospiza (p. 516) 



'* Some specimens of Aforphnus and Urubitornis have wings 500 mm. or more 

 in length, but the majority are under 500 mm. Also the southern South American 

 race of Buteo melanoleucus, a wholly extralimital form, has wings over 500 mm. 

 long. 



^^ Helicolestes Bangs and Penard, Bull. Mus. Comp. Zool., Ixii, April, 1918, 38 

 (type, by original designation, Falco hamatus lUiger). 



