526 BULLETIN 50, UNITED STATES NATIONAL MUSEUM 



margin slightly elevated or ridgelike, especially above. Wing long 

 and pointed, the longest primaries exceeding longest (proximal) 

 secondaries by nearly one-third the length of wing and extending 

 beyond tip of tail; second or third (usually thu-d) primary, from out- 

 side, longest, the first (outermost) longer than sixth, sometimes longer 

 than fifth; second, third, and foiu-th (sometimes also fifth) primaries 

 with outer webs sinuated, the three outermost with inner webs abruptly 

 and deeply emarginated, the fourth slightly sinuated; longer primaries 

 rigid, narrowed terminally, with tips subacuminate; primary coverts 

 hard, stifT, and subacuminate. Tail less than half as long as wing; 

 subtruncate or slightly double-rounded, the rectrices (12) rigid, but 

 with rounded tips. Legs and feet relatively large and exceedingly 

 strong, the very robust tarsus covered (except on upper anterior 

 portion, where feathered) with small, rough, somewhat imbricated or 

 projecting scales, those of the acrotarsium with lower edge projecting, 

 those of the planta tarsi the reverse; middle toe (without claw) de- 

 cidedly shorter than tarsus; lateral toes decidedly shorter than mid- 

 dle toe, the outer much longer than the inner; the hallux nearly as 

 long as inner toe; terminal phalanx and part of second phalanx of all 

 the toes with large transverse scutella, the remaining portion of upper 

 surface covered with small scales, their under surface covered with 

 prominent spicules; claws unusually long and very strongly curved 

 (the curve of each forming about one-third of a cu'cle) , and all, except 

 that of middle toe, as long as or longer than the digits, contracted in 

 transverse width toward their under surface, which is narrow and 

 smoothly rounded (in transverse section). ^^ 



Plumage and coloration. — Plumage exceedingly dense and compact, 

 imbricated and oily, the loral region densely clothed with short feathers 

 and without distinct bristles, the orbital region densely feathered up 

 to eyelids and without trace of superciliary shield ; anterior portion of 

 pileum and nape with feathers elongated, acuminate, when erected 

 forming short frontal and nuchal crests; feathers of thigh short, dense, 

 and compact, this feathering extending over upper portion of acrotar- 

 sium where terminating in an acute angle; remiges rigid, longer pri- 

 maries tapering terminally to their subacuminate tips, the primary 

 coverts similarly rigid and acuminate. Head mostly white with a 

 dusky lateral area; underparts white, the chest sometimes mottled or 

 spotted wdth brown; upperparts dark grayish brown. Sexes essen- 

 tially alike in coloration, and young differing mainly in having the 

 feathers of upperparts margined terminally \vith white and buffy. 

 Downy young with a conspicuous "pattern," thus differing from all 

 (?) other Falconiformes. 



•* In Pandion the form of the claws, and their uniform size, is wholly unique 

 among Falconiformes if not in the entire class Aves. 



