FALCON I DA'] - 'I'U E K A LC( )N A 3 1 ;•{ 



tions Very ilcop. Tail ratlior slioit, slij;lilly rouiidoil i>i' wcdi^'c-slmpcd. Dill .simii^aM- tliiiii 

 in tlio iprt'CL'dlii},' gciicrn, its oulliiios iiuiiily ]uuiiI1l'1, iiml '.lie li|) somuwiiat iiicliiifl liack- 

 waril at tlic point | coinniissiii'i,' wilii a nioiu i)r less pioniincnt H'titoon ; nostril narrowly 

 oval, vertical; >l<iii ol' the ucre very hard ami lirtu. SuiM'rriiiary .shii'lil very prominent. 

 Fi'et Very strong', llie nieiiilirane lulween tiie outer and niiddii! toes very well developed; 

 tni'siis less llian twice as lonj,' as the inidiUo tot;; outer toe eipml to, or longer than, the 

 inner; claws very lon^' and stroiij.'', very iniieli gra<luated in size; seiitellie of the toes 

 snudl except on the terminal joint, where tliey lorni liroad transverse plates; tarsi den-;ely 

 feathered all round down to the base of the tot's; tihial phnnes well developed, loose- 

 wchlied, their ends reaching down to or heyond the ba.se of the toes. Feathers of the 

 nape and occiput laneeolate, acute, and distinct, Ibrining a nuchal " capo " of dillerently 

 formed feathers. Third to lifth (|uill longest; first shorter than the .seventh ; outer five or 

 six with their iniiei' webs deeply emarginuted. 



Tlii.s genus i.s almost peculiar to the Old World, wiiere about seventeen 

 80-ealled species are known, while America has no meml)er of the genus 

 exclusively its own, the single North American .species being the same as 

 the European one. Though the details of external structure vary somewhat, 

 and the size ranges from that of a JJn/iv to that of a sea-eagle {Ifd/iid'lits), 

 the generic characters given in the lilmve diagnosis a))ply well to idl the 

 species. The species oi Jlctcrojins, Hodgson, 1842 (A. vutlayensis, I!i:ix. and 

 //. (jurneyi. Gray), I remove entirely from Aquilu, since tiiey differ so strik- 

 ingly in many important respects. With the general aspect of A(j)ti/(i, 

 HctrrojiHS has the outer toe disproi)ortioniitely shorter than the iinier (in- 

 stead of equal to it, or longer), whicli curious feature it shares only with 

 Gernnoi^piza of tropical America, and J'o/i/boroalvs of South Africa, — both 

 terrestrial Buti-onine forms of sjjecialized structure. An entirely peculiar 

 feature of Hetcropus is the great length and straightncss of the claws. Its 

 bill is more like that oi' Arch ibi/feo than like that oi Aqitila. 



The Xorth American and European races of the single species which oc- 

 curs on tiie former continent may be distinguished as follows : — 



Species and Races. 

 A. chryaaStuB. Win?, •.>.".,00 - 27.00 ; tail, 14.00 - 10.00 ; culmen, 1.50- 

 l.ilO ; tar.sns, 3.40-4.20 ; middle toe, 2.40 - 3.10. Third to fifth cpiill longest 

 first shorter than seventh or eighth. Coloi' blackish-brown, ornniber-))rown, 

 nearly uniform, except on the tail ; niiclml cape of lanceolate feathers, and 

 tarsi of a paler and more tawny tint. Adult. Tail transver.'sely clouded with 

 ashy, and not white at the l)aso; feathers of tin; body not distinctly white 

 beneath the surface. Yonncj. Tail with the basal half plain white, the ter- 

 minal portion plain blackish ; feathers of the body distinctly white beneath 

 the surface. If<ih. Xearctic and Pala.'arctic Realms. 



Tarsi of adult pale umber; of young, dirty whitish. Ili'h. Palrearctic 



Re.ilni \m: cliry sail Ins} 



Tarsi of adult deep umber; of young light brown, ilah. Nearctic 

 Realm var. can a delists. 



1 Aqiiiln rJiri/.iaefii.i, var. chrii.inetiin (FjNN.). Aquihi Valeria, Aldin, B, IT. 1)1. ii. Aquilii 

 chrijsaelus, Bliiss. Orn. I, 431, ct Aucr. Fako chrijsa&us, LiXN. S. N. 1760, 125. Aquihi 

 Vol,, m. 40 



