222 NORTHERN THREE-TOED WOODPECKER. 
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 Pzcws 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, cuneiform and 
obtuse at tip, and much depressed throughout, the ridge being 
very much flattened: both mandibles are perfectly straight, 
the upper pentagonal, the lower obtusely trigonal ; the tongue 
is somewhat shorter than that of other species of the genus ; 
the bristly feathers at the base of the bill are very thick and 
long, a provision which Nature has made for most arctic birds ; 
in this they measure half an inch, and are blackish, white at 
base, somewhat mixed with reddish white; the irides are bluish 
black ; the whole head and neck above and on the sides, back, 
rump, scapulars, smaller wing and tail coverts, constituting 
the whole upper surface of the bird, of an uniform, deep, glossy 
black, changing somewhat to green and purple, according to 
the incidence of light; the feathers of the front are tipt 
with white, producing elegant dots of that colour (which per- 
haps disappear with age); the crown of the head is ornamented 
with a beautiful oblong spot one inch in length, and more than 
half an inch broad, of a bright silky golden yellow, faintly 

