Mr. R. B. Sharpe’s Catalogue of Accipitres. 67 
scription of the adult; the slaty black of the breast without 
any whitish tips to the feathers, and extending down to the 
extremities of the under tail-coverts, and over all the inter- 
mediate parts except the thighs, but intermingled on the ab- 
domen with a few mottled feathers of two shades of grey, 
and with the under tail-coverts inconspicuously tipped with 
grey ; the thighs clothed with mottled grey feathers, which, 
for the most part, resemble those interspersed amongst the 
black plumage of the abdomen; but in some of them the mot- 
tlngs have already begun to assume the arrangement of the 
transverse markings with which, in the succeeding stage, all 
the tibial feathers are barred, in common with the remainder 
of the under surface except the chest. 
In the succeeding stage the bird bears a remarkable general 
resemblance in its coloration and markings to its somewhat 
more northern and much scarcer ally, Leucopternis princeps. 
In very old males of Geranoaétus melanoleucus (and pos- 
sibly in old females also; but of this I am not sure) the trans- 
verse bars of grey entirely disappear from the whole under 
surface, except the wing-linings, the flanks where covered by 
the wings, and the under tail-coverts ; in such specimens the 
portions of the plumage from which these bars have disap- 
peared are then pure white. 
I think that Mr. Sharpe is mistaken in stating that the 
white tips to the grey feathers of the breast are “ the remains 
of immaturity,” as I have met with them in very old indi- 
viduals, and do not recollect having ever seen an adult speci- - 
men in which they were absent ; in some adult examples these 
white tips are to be found on several of the interscapulary 
feathers as well as on the breast. 
I may add that those portions of the upper surface in the 
adult bird which Mr. Sharpe describes as black are all slightly 
tinged with slate-colour; so that they may perhaps be more 
correctly described as “‘ slaty black” than as “ black ” simply. 
To return to the genus Tachytriorchis, Mr. Sharpe, fol- 
lowing the late Dr. Kaup, separates under this title two species, 
Buteo albicaudatus. and B. abbreviatus ; but as I greatly doubt 
whether these two species really follow each other in natural 
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