146 FALCONIFORMES CHAP. 
Fam. IV. Falconidae.—This group may be divided into the 
Sub-families (1) Gypaétinae for the Lammergeiers ; (2) Polyborinae 
for the “Carrion Hawks”; (3) Accipitrinae for the Hawks, with 
Circus, Polyboroides, and so forth; (4) Aquilinae for the Eagles ; 
(5) Buteoninae for the Buzzards and Kites; and (6) Falconinae 
for the Falcons. 
Though the skull is small in Crews and some other forms, it 
is usually large and broad, being considerably elongated in the 
Aquilinae. The short stout bill is strongly curved, and ter- 
minates in a hook, which is often nearly perpendicular, and is 
specially prominent in Lostrhamus, Leptodon, Harpyhaliaétus, 
Pithecophaga and Thrasaétus ; the basal third is straight in Eagles, 
while the edges of the maxilla are lobed or festooned to a variable 
extent, and in the Falconinae are distinctly toothed, or even biden- 
tate in the case of Spiziapteryx, Harpagus, and Baza. A bony 
ridge over the eye conduces to the fierce aspect, especially in the 
larger species. The feet are robust and well-fitted for grasping, 
and are enormously developed in 7hrasaétus ; the metatarsus is 
much flattened, and may be scutellated or reticulated, though the 
scales are usually smaller behind; the tibia generally exceeds it 
in measurement, but in Accipitrine forms is nearly equal, giving 
them a long-legged appearance. Elongated bare metatarsi are 
characteristic of Circus, Polyboroides, and the Polyborinae. The 
claws are sharp and curved, especially in Rostrhamus; a short 
membrane connects the middle and outer toes, and the inner also 
in the Polyborinae; while their under surface is more or less padded, 
and exhibits rugose spicules below in Busarellus, similar to those 
in Pandion. The powerful wings may be long and pointed, as in 
the Kites, Faleons, and Harriers ; moderate and somewhat rounded, 
as in the Eagles and Buzzards; or short and narrow, as in Hawks. 
Falconers term the long-winged forms “noble,” the short-winged 
“jenoble.” The tail, usually of medium size, but sometimes very 
short, as in Helotarsus and Gypohierax, is decidedly elongated in 
the Accipitrinae and Polyborus, and also in Afilvus, Lophoictinia, 
Elanoides, and Nauclerus, where it 1s forked—very deeply in the 
two last: it may be wedge-shaped, as in Uroaétus, Thalassaétus, 
Harpyhaliaétus, and Gypaétus ; rounded, as in Hanus and Hali- 
aétus ; nearly even, as in Buteo and Aquila; or emarginated, as in 
Lctinia and Rostrhamus. Normally there are twelve rectrices, but 
Thalassaétus has fourteen. The colour varies greatly with age, 
