NORTHERN THREE-TOED WOODPECKER. 263 



■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 furnished 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. These however 

 ought not to be separations ; and the genus has been left comparativelj' 

 untouched by the great innovators of our day, who have only established 

 three genera from it. The first of these, Oolaptes, 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 

 Ouculus ; 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 remarkably com- 

 pressed, 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-color, 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, z. 

 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 tipped 

 with white, producing elegant dots of that color (which perhaps disap- 

 pear 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 tinged with orange, and the feathers 



