NORTHERN THREE-TOED WOODPECKER. 321 
southern as no more than a variety, in which he was mistaken, 
since they are widely distinct ; but as he had no opportunity 
of seeing specimens, he is not to be censured, especially as he 
directed the attention of naturalists to the subject. The merit 
of firmly establishing the two species is, we believe, due to 
Vieillot. Besides several other traits, the northern bird is 
always to be distinguished in every state of plumage from its 
southern analogue by that curious character whence Vieillot 
took his highly characteristic name (Picus hirsutus, Pic a 
pieds vétus), the feathered tarsi, a peculiarity which this atone 
possesses to the same extent. The plumage is a uniform 
black above in the adult, with the top of the head yellow in 
the male, while the southern, whose tarsi are naked, is black 
undulated with white, the male having the sinciput red. It 
is worthy of remark that the three-toed group found in arctic 
and in tropical America should have no representative in the 
intermediate countries. 
Although these are the only three-toed woodpeckers noted 
as such in the books, several others are known to exist, some 
of which, long since discovered, have through inadvertence, or 
want of proper discrimination, been placed among the four-toed 
species. ‘The three-toed woodpeckers have been formed into 
a separate genus, a distinction to which they might indeed be 
considered entitled if they all possessed the other characters 
of the present ; but, besides that this character appears to be 
insulated, and of secondary importance (since all forms of the 
bill known among the four-toed species are met with among 
the three-toed, which ought, therefore, to make as many groups 
as there are forms, instead of a single one), the naturalist is 
perplexed by the anomalous species that inhabit India, of 
which one has only a stump destitute of nail, and another 
merely a very small nail without the toe; and, as if Nature took 
delight in such slow and gradual transitions, two others, fur- 
nished with both toe and nail, have the toe exceedingly short, 
and the nail extremely small! ‘This serves to demonstrate 
that Picus, like other natural groups, admits of subdivision. 
VOL. IIL. x 
