426 
NORTHERN THREE-TOED WOODPECKER. 
into a separate genus, a distinction to which they might indeed 
be considered entitled, if they all possessed the other charac- 
ters 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, furnished with both toe and nail, have the toe exceed- 
ingly short, and the nail extremely small ! This serves to de- 
monstrate that Picus^ like other natural groups, admits of sub- 
division. These, however, ought not to be separations ; and 
the genus has been left comparatively untouched by the great 
innovators of our day, who have only established three genera 
from it. The first of these, Colaptes, of which P. auratus of 
North America may be considered the type, comprises the 
species that have four toes, and slightly curved bills, forming 
the passage to Cuculus ; another, for which the name of Picus 
is retained, includes the four-toed species with straight bills, 
and the third for the three-toed species indiscriminately. The 
only foreign three-toed species in our collection, the beautiful 
Picus Bengalensis of authors, [Picus tiga of Horsfield,) widely 
spread through tropical Asia and the adjacent islands, and, 
though long since known, always ranked as four-toed, has the 
bill precisely similar to the four-toed species, being even re- 
markably compressed, and very sharp on the ridge. 
The male northern three-toed woodpecker is ten inches 
long, and sixteen in extent ; the bill measures one inch and 
a quarter, is of a blackish lead colour, bluish white at the 
base of the lower mandible ; it is very broad at base, cunei- 
form and obtuse at tip, and much depressed throughout, the 
ridge being very much flattened : both mandibles are per- 
fectly straight; the upper pentagonal, the lower obtusely tri- 
