12 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 



form like the P. Brasiliensis, mingled with the other carrion-feeding hawks on the 

 banks of the Plata ; and there is now in the British Museum a specimen, which 

 may be considered as partly an albino. Spix, on the other hand, (Avium Species 

 Novec, p. 3.) has described some specimens from the coast of Brazil, as being 

 remarkable from the darkness of the plumage of their wings. 



Milvago, Spix. 



Several new genera have lately been established to receive certain species 

 of the sub-family of Polyborince, and consequently great confusion exists in 

 their arrangement. Mr. George R. Gray has been kind enough to give me the 

 following observations, by which it appears he has clearly made out, that Spix's 

 genus Milvago, is that which ought to be retained. M. D'Orbigny has made 

 two sections in the genus Polyborus, according as the craw is covered with 

 feathers, or is naked, and he states that the P. Brasiliensis is the only species 

 which comes within the latter division ; but we shall afterwards see that the 

 Falco Noves Zelandice, Auct. (the Milvago leucurus of this work) has a naked 

 craw, which is largely protruded after the bird has eaten. M. D'Orbigny 

 has also instituted the genus Phalcobcenus, to receive a bird of this sub-family, 

 with the following characters : 



" Bee fortement comprime, sans aucune dent ni sinus, a commissure tres- 

 arquee a son extremite ; cire alongee et droite ; un large espace nu entourant la 

 partie anterieure et inferieure de l'ceil, et s'etendant sur toute la mandibule 

 inferieure ; tarses emplumes sur un tiers de leur longueur, le reste reticule ; 

 doigts longs, semblables k ceux des gallinaces, termines par les ongles longs, 

 deprimes et elargis, tres-peu arques, toujours a extremite obtuse ou fortement 

 usee ; ailes de la famille, la troisieme penne plus longue que les autres." 



Mr. George R. Gray, however, has pointed out to me that Spix, (in his 

 Avium Species Novae) ten years since, made a division in this sub-family, from 

 the rounded form of the nostril of one of the species, namely, the M. ochroce- 

 phalus of his work, or the Chimachima of Azara. And Mr. Gray thinks, that all 

 the species may be grouped much more nearly in relation to their affinities by 

 this character, than by any other : he further adds ; — " The only difference 

 which I can discover between this latter genus {Milvago), and D'Orbigny's 

 (Phalcobcenus), is, that in the latter the bill is rather longer, and not quite so 

 elevated in the culmen as in the former ; and these characters must be considered 

 too trivial for the foundation of a generic division. I, therefore, propose to retain 

 Spix's genus, Milvago, for all those Polyborince which possess rounded nostrils with 



