16 
FALCO DISPAR. 
or less of black. The comparatively even tail of the 
two allied species of which we are treating*, eminently 
distinguishes them from the others of the subgenus, 
which hare the tail exceedingly forked. They are 
remarkable also for another characteristic, that of 
having the nails rounded beneath, and not canaliculate, 
a circumstance that occurs besides only in the sub- 
genus Pandion .* This character, which we formerly 
attributed to all the Elani , and which we believe we 
first observed not to exist in the fork-tailed species, 
has induced Mr Vigors, the English ornithologist, to 
separate the latter as a new genus, under the name 
of Nquclerus. 
The female white-tailed hawk, is sixteen and a half 
inches long, and three feet live and a half inches in 
extent. The bill is black, and measures from the 
corners of the mouth one inch and a half, the sides of 
the mouth, posterior portion of the lower mandible, 
and cere, bright yellow orange; bristles on the cere 
white, as well as those first on the lores ; those nearest 
the eye, black ; irides, brownish red ; eyelids, white ; 
cilia, long and black ; orbits, black, wider before the 
eye ; front line over the orbits, sides of the head, neck, 
and body, and whole inferior surface of the bird, together 
with the thighs, pure white ; head, pearl gray, becoming 
gradually darker from the pure white front towards 
the neck and back, which are entirely bluish ash, as 
well as the rump, scapulars, secondaries, and greater 
wing-coverts; smaller and middle wing-coverts, deep 
glossy black ; spurious wing, blackish ; lining of the 
wing, and inferior coverts, pure white, the latter with 
a wide black patch ; primaries on both surfaces, slate 
colour, the shafts, black, and, the first excepted, mar- 
gined exteriorly, and slightly at tip, with dusky, and 
interiorly, with whitish ; the margin of the inner web 
is of a remarkably close texture, with a very soft 
surface; the first primary is a little shorter than the 
* In Pandion , however, it is the middle nail that is rounded; 
in this species, it is the lateral and posterior only. 
2 
