AQUILA. 59 



Twenty-four or twenty-five remigcs in the wings : the first five graduated, the difference between 

 them being nearly equal, or very gradually becoming less ; the fifth the longest ; the first scarcely 

 so long as the eleventh, or first of the secondaries ; all up to the fifth with a diminution of the 

 inner half of the vane, which descends very low down, and is scarcely recognisable on the last of 

 them. Tail moderately long, rounded. Tarsus with scutes both before and behind. 1 



/3. No scattered contour-feathers beside the band-like dorsal portion of the spinal tract, 

 but either mere down-feathers, or two very sparse rows of single contour-feathers, 

 one on each side. 



The pterylographic differences presented by the numerous species of this group are gene- 

 rally small, and relate merely to the greater or less separation of the external branch of the inferior 

 tract from its main stem, or to the comparative lengths of the remiges ; but we may also employ 

 the absence or presence of a lumbar tract, and the occurrence of powder-down-tracts, for cha- 

 racterising a few species in which they occur. I have observed the latter in the Harriers ( Circus) 

 examined by me, as also in Falconcs plumbeus, bidentatus, melanoptsrus, lophotes, and uncinatus, and 

 in all in the form of two elliptical fields situated on the sides of the spinal tract, not far from the 

 tail. Externally the narrow lumbar tract runs close to these powder-down-patches ; I have 

 found it at least in the Harriers, and in F. bidentatus, plumbeus, and lophotes. I have also met 

 with a very distinct lumbar tract in Gypoyeranus serpentarius, the Eagles and the Buzzards ; it 

 is less distinct and weaker in the Hawks and Honey Buzzards, and in the subgenera allied to 

 them, in which, indeed, it is sometimes wanting. The separation of the external branch of the 

 inferior tract is most complete in the groups Circus, Gypogeranus, Milvus, Astur, and Morpknus ; 

 it is less complete, the interval between it and the main stem being neither so deep nor so broad, 

 in Aquila, Buteo, Polyborus, and Cymindis ; and I have found it to be quite incomplete, so that 

 only the apical half, or even the last third, appears to be separated, in F. lophotes, plumbeus, 

 and especially F. bidentatus. In all these cases, however, the external branch is very distinctly 

 marked out by the different direction of its rows of strong feathers. As I have already repeatedly 

 remarked, a hook-like branch, which passes into the liypopterum, very often originates from its 

 apex, especially in Circus, Gypogeranus, Astur, Polyborus, and Pernis. Hence the character 

 which must chiefly occupy us is the number and relative size of the remiges. 



1. AQUILA. 

 a. With feathered tarsi. 



1. F.fuhus. The form of the inferior tract of this bird, which may serve as the type for most 

 of the other Falcons, may be seen at a glance in Plate II, fig. 3. The only peculiarity of the Eagles 



1 Although this bird, which has not yet been figured, or perhaps even described, closely approaches 

 the Buzzards in its structure, it agrees best in the length of the tarsus with Falco urubitinga (TEMM., 

 PL Col., 55). It is entirely blackish -brown, except that the first four remiges are white at the base, 

 and the rest marked with lighter and darker bands. The tail has a median white band. The cere 

 and the feet are yellow. [This species is now usually called Urubitinga antJiracina (Nitzsch) the 

 present description of it being the earliest published. P. L. S.] 



