146 MR. J. H. GURNEY ON AQUILA DESMURSII. [May 13, 
on the western coast, and also in Nubia and Abyssinia, and on the 
banks of the White Nile. 
It is a small species, intermediate in size between Aquila pennata 
and Aguila nevia. From the former it is readily distinguishable by 
the greater length of all its measurements ; from the latter (as also 
from Aquila nevioides) it may, on the contrary, be distinguished by 
its less size and, as Dr. Hartlaub well remarks, “‘by the more deli- 
cately shaped bill, and by the greater length of the tail” as com- 
pared with that of the wings. 
Another well-marked distinction to which Dr. Hartlaub does not 
allude is to be found in the presence in Aquila desmursii of a well- 
defined, though small, occipital crest, consisting of from eight te 
nine pointed feathers, the longest of which are fully an inch and a 
half in length. 
The colouring of this Eagle, described in Dr. Hartlaub’s work, is 
that which characterizes what I believe to be the adult bird after it 
has newly moulted and has acquired its fresh plumage. In this dress 
the general colouring of Aquila desmursii closely resembles that of 
the adult of Aguila nevioides under similar conditions, being of a 
rufous brown, varying in intensity in different portions of the same 
feather. 
Other specimens of Aquila desmursii exhibit a plumage of an ex- 
tremely dark and almost uniform chocolate-colour. These indivi- 
duals I believe to be immature birds, in which the feathers have 
been also newly acquired. In this stage they bear a considerable 
general resemblance in point of colouring to the immature specimens 
of Aquila pennata, though I have never met with an immature 
Aquila pennata quite so dark as some specimens I have seen of 
Aquila desmursii. In Aquila desmursii, as also in Aquila nevioides, 
both adult and immature ‘birds appear liable to have their plumage 
exceedingly bleached by the action of the tropical sun; but it is 
remarkable that the feathers composing the occipital crest in Aquila 
desmursit appear to retain their original tint, notwithstanding the 
partial loss of colour from the above cause in the portions of the 
plumage immediately adjacent. It should also be remarked that, in 
some immature specimens, nearly the whole under surface is of a 
very pale whitish brown—a variation from the ordinary darker co- 
louring which cannot be accounted for by the effect of sun and 
weather only. 
In conclusion, I will add the remarks on this species communi- 
cated to me by M. Jules Verreaux, which are as follows :—* Ac- 
cording to the notes of the collectors, the irides of the adult birds 
are of a chestnut-brown tinged with yellow; whilst in the young 
birds the yellow tint is absent, and the brown is deeper, with but 
little tinge of chestnut. The natives (at Bissao) give the name of 
‘Socolas’ to this species only, it being well known to them as a very 
courageous bird, attacking even the small Gazelles (Cephalophorus 
maxwelli) which inhabit the same localities, and also preying on 
various birds, and especially the Francolinus bicalcaratus,” 
