146 MR. J. H. GURNEY ON AQUILA DESMURSII. [May 13, 



on tlie 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 Aquila ncevia. From the former it is readily distinguishable by 

 the greater length of all its measurements ; from the latter (as also 

 from Aquila ncevidides) 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 to 

 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 Aquila ncevio'ides 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 ncevio'ides, 

 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 

 desmursii 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 hicalcaratus" 



