Mr. R. Ridgway ow the Genus Micrastur. 3 



termed by Pelzeln " erythrism/' and entirely analogous to 

 the condition of melanism . The condition is most exaggerated 

 in M. ruficollis, but it is plainly visible in M. guerilla. No 

 rufous specimens have been seen of M. concentricus , Ve\z., nor 

 M. pelzelni ; and^ on the other hand, I have seen no plumbeous 

 examples of M. zonothorax. But such probably occm-, and 

 should be borne in mind before any new form is described. 



Synopsis of the Species of Micrastur. 

 A, Outer toe decidedly longer than the inner. 

 a. Size large (wing more than 8 inches). 



1. Above black, with a nuchal collar of white or ochraceous. 



M. vielanoleucus* . 



2. Above plumbeous, without a nuchal collar . . M. mirandollii. 

 h. Size small (wing less than 8 inches). 



3. Wing 6-50-7-10, tail G-90-7-50. Tail crossed by 3-6 (terminal 



bar not counted) indistinct bars of white or pale greyish. Adult. 

 Tail-bars 3-4; above plumbeous, the dorsal region sometimes 

 chocolate; throat light grey; jugulum, breast, and entire lower 

 parts barred with white and dusky. Young. Above dark clove- 

 brown, plain or indistinctly spotted posteriorly ; beneath white 

 or buff, rarely immaculate, usually coarsely barred. 



M. fjiierilla. 



4. Wing 6-90-7-O0, tail 7-G0-8-40. Tail with 4-7 distinct white 



bars. Adult. Above, including neck and most of head, rusty 

 chocolate, less reddish anteriorly; throat light chocolate; jugu- 

 lum and entire lower parts everywhere ban-ed with white and 

 dusky. Tail-bands 4-5. Youmj. Above dark sooty brown, in- 

 distinctly barred with rusty ; cro'^vni and nape sooty black ; lower 

 parts white or buff, rarely immaculate, usually barred, and loitli- 

 out rufous tinge on the breast ; tail-bars Q-7. M. zonothorax. 



5. Wing 6-G0-7a0, tail 7 •30-7-80. Tail with 4-8 usually distinct 



white bars. Adult. Breast washed with rufous ; throat light 

 grey ; other lower parts everywhere barred with white and 

 dusky; crown plumbeous ; other upper parts varying from clear 

 light bluish plumbeous to rusty brown. Tail-bars 4. Young. 

 Above varying from greyish brown to dark rusty chocolate ; 

 throat and half-crescent behind the ear-coverts white, in abrupt 

 contrast ; beneath white, coarsely baiTed with dusky brown 



M. ruficollis. 



* I cannot identify Sparvius setnitorquatus, Vieill., with this species, 

 since that is said to have the top of the head white, ban-ed with black, 

 whereas it is always plain black in this bird, which, in the adult plumage 

 is S. melanoleucus, Yieill, 



B 2 



