BIRDS OF NORTH AND MIDDLE AMERICA 547 



dd. Tarsus much less than twice as long as middle toe (without claw), the 

 latter exceeding longest lateral toe by less than half the length 

 (curve) of culmen ; planta tarsi covered with small scales, or at least 

 without well-defined scutella; longest primaries exceeding distal 

 secondaries by much more than one-third (sometimes by more than 

 one-half) the length of wing; second primary much longer than 

 fourth (usually longer than third), the first longer than fifth (some- 

 times longer than third) ; inner webs of not more than two outer 

 primaries emarginated, the emargination subterminal; tail graduated 

 for less (usually much less) than one-fifth its length. -Falco (p. 614) 

 e. Tarsus covered (except on feathered upper portion) with small, 

 more-or-less hexagonal or roundish scales, without any transverse 

 scutellae on lower portion of acrotarsium or definite rows of larger 

 hexagonal scales elsewhere. 

 /. Inner toe, without claw, extending to or beyond penultimate 

 articulation of middle toe; second primary with inner web more 

 or less distinctly emarginated subterminally; first (outermost) 

 primary shorter than third, sometimes shorter than fourth; 

 longest primaries exceeding distal secondaries by little if any 

 more (sometimes less) than half the length of wing; emargina- 

 tion on inner web of first primary falling short of tip of fifth 

 primary (usually about opposite tip of sixth primary) ; tail more 

 than half as long as wing. 

 g. Tarsus with more than upper half densely feathered anteriorly 

 and laterally; size very large (wing 339-420 mm.). 



Falco, subgenus Hierofalco (p. 631) 

 gg. Tarsus with less than upper half feathered; smaller (wing usually 

 much less than 330 mm.) .-Falco, subgenus Qennaia (p. 621) 

 //. Inner toe, without claw, falling short of penultimate articulation 

 of middle toe; second primary without emargination on inner 

 web; first (outermost) primary much longer than third (some- 

 times as long as second), its emargination beyond tip of fifth 

 primary; longest primaries exceeding distal secondaries by more 

 than half the length of wing. 

 g. Nostril relatively much smaller; orbital region less extensively 

 bare; tip of tail truncate or slightly emarginate, the rectrices 

 relatively narrower proximally and broader distally (less 

 tapering) ; tarsus with less than one-third of anterior portion 

 feathered; young not materially different in coloration from 

 adults; smaller (wing 180-252 mm.). 



Falco, subgenus Neofalco (p. 670) 

 gg. Nostril relatively much larger; orbital region more extensively 

 (and more completely) bare; tip of tail distinctly rounded, the 

 rectrices relatively broader proximally and narrower distally 

 (more tapering) ; tarsus with more than upper third of ante- 

 rior portion feathered; young conspicuously different in 

 coloration from adults; larger (wing 2S.5-375 mm.).^^ 



Falco, subgenus Rhynchodon (p. 648) 

 ee. Tarsus covered with larger scales, the larger ones arranged in one 

 or more definite rows or longitudinal series. 



^* In American species only; an Old World species, probably referable to this 

 subgenus, is smaller, with wing sometimes as short as 231 mm. 

 839094—50 36 



