150 Mr. J. H. Gurney on additional Species of Birds 



Of the African Spizaeti already known to science, three species 

 have been so frequently described, and differ so widely from the 

 bird now under our consideration, that it is hardly needful to 

 allude further to them here. These species are (1) Spizaetus 

 bellicosus (Daud.), which by its length of wing approaches very 

 closely to the genus Aquila-, (2) Spizaetus coronatus (Linn.), 

 which is the largest of the typical Spizaeti; and (3) Spizaetus 

 occipitalis (Daud.), which forms the type of Dr. Kaup's genus 

 Lophaetus. The fourth and rarest of the hitherto known African 

 Spizaeti is that described and figured by the Baron J. von Miiller 

 in his ' Description de Nouveaux Oiseaux d^Afrique,^ pi. 1, under 

 the title of Spizaetus zonurus, which had been previously de- 

 scribed by the same author in the ' Naumannia' for 1851, p. 27. 



It may be well also to mention that the name of Spizaetus 

 spilogaster has been given by M. le Vicomte Dubus to an African 

 Spizaetus, of which I believe neither figure nor description has 

 yet been published, but which is probably identical with Spizaetus 

 zonurus of v. Miiller, as it is stated by Prince C. L. Bonapai'te, in 

 the 'Revue de Zoologie^ for 1850, p. 487, to be destitute of a 

 crest, as is also the case in Spizaetus zonurus. At any rate, 

 the absence of a crest in Spizaetus spilogaster marks that bird as 

 being distinct from Spizaetus ayresii, in which the occipital crest 

 is a well-marked feature. 



The other points of difference between Spizaetus zonurus and 

 Spizaetus ayresii will appear by the following description and 

 accompanying plate of the latter, and especially by the subjoined 

 comparison of the dimensions of the two species. 



The Spizaetus ayresii may be described as follows : — 



Above, general colour nearly uniform chocolate-brown, with the 

 extremities of the feathers paler; head-feathers mai'gined with 

 yellowish rufous, especially on the sides ; occipital crest rather 

 broad (1*5 inch at the base), and about 1*75 in. in length, nearly 

 black, slightly paler at the termination ; front adjoining the 

 cere yellowish white; wing-coverts and secondaries like the 

 back; bend of the wing whitish; primaries uniform purplish 

 black, indistinctly barred with whitish on the concealed lower 

 parts of the inner webs, as is also the case with the secondaries, 

 though less distinctly; tail-feathers above greyish, with seven 



