344 Mr. W. L. Sclater on ike [Ibis, 



The following key shows briefly the distinctions between 

 the various species and subspecies in adult dress : — 



a. Larger ; below uniform, unbarred. 



a\ With a white collar on the nape M. melanoleucus. 



b'. Without a white collar on the nape M. mirandoUei. 



b. Smaller ; under parts with transverse barring, 

 c'. Tail shorter ; only oue transverse white bar 



visible on the tail M. pliimbens. 



d'. Tail longer; two or more transverse white 



bars visible. 



c^. Throat and chest rich rufous or, at any rate, 



traces of a rufous wash on the chest ; 



barring becoming lighter towards the 



tail-coverts M. rufcoUis. 



d"^. Only the throat rufous-brown ; black bar- 

 ring continuing heavy to the tail-coverts . M. zonothorax. 

 e'-. Throat and chest not washed with rufous. 

 /^. Barring of abdomen heavy throughout ; 

 back rafous or slightly washed with 



rufous M. gilvicollis. 



(f. Barring becoming fainter or even obsolete 

 towards the under tail-coverts ; back 

 plumbeous M. guerilla. 



The four last-named forms appear to me to constitute a 

 compact geographical group, and I have therefore treated 

 them as subspecies. 



Micrastur melanoleucus. 



Sparvius melanoleucus Vieillot, N. Diet. d'Hist. Nat. x. 

 1817, p. 327 : Paraguay [ex Azara]. 



Falco leucomelas Licht. Verz. Doubl. 1823, p. 62 : Para- 

 guay [ex Azara] . 



Falco bracJiypterus Temm. PL Col. livr. 26, 1824, pi. 116 

 (juv.), pi. 141 (adult) : Brazil, Guiana, and Paraguay. 



Carnifex naso Lesson, Rev. Zool. 1842, p. 379 : South 

 America. 



Falco percontator Cabot, Boston Journ. N. H. iv. 1844, 

 p. 462 : Yucatan. 



Micrastur amaurus Gurney, Ibis, 1879, p. 173 : Panama 

 [founded on a melanistic variation]. 



