366 MR. J. H. GURNEY ON AQUILA DESMURSII. 



which the feathers have been also newly acquired, and which in this stage bear a con- 

 siderable general resemblance in point of colouring to the immature specimens o(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 

 neevioides, both adult and immature birds appear liable to have their plumage exceed- 

 ingly bleached by the action of the tropical sun ; but it is remarkable that the feathers 

 composing the occipital crest of 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 variety 

 from the ordinary darker colouring which cannot be accounted for by the effect of sun 

 and weather only. 



In conclusion, I will add the remarks on this species communicated to me by M. 

 Jules Verreaux, which are as follows : — " According 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 

 beitig well known to them as a very courageous bird, attacking even the small Gazelles 

 {Cepkalophorus maxwelli) which inhabit the same localities, and also preying on various 

 birds, and especially the Francolinus bicalcaratus." 



The figures in the accompanying plate, by Mr. Wolf (PI. LXXVII.), represent three 

 specimens of Aquila desmursii, from the collection of the Norwich Museum, in the three 

 different states of plumage above referred to. 



