WHITE-TAILED HAWK. 279 
species, being white, or pale (bluish white, &c.), with more 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 have 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 subgenus Pandion.* This character, which we formerly 
attributed to all the Hlanz, 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 Nauclerus. 
The female white-tailed hawk is sixteen and a half inches 
long, and three feet five 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 grey, 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, margined 
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 third, the second longest; the two outer 
* In Pandion, however, it is the middle nail that is rounded ; in this 
species, it is the lateral and posterior only. 
