II. Securirostres. Neck not slender, and shorter. Nostrils concealed by bristles. Bill stout, cuneate, with the nasal ridges widely distant from each other.
III. Ligonirostres. Neck not slender. Nostrils covered, nasal ridges of bill placed near the culmen (or at least nearer it than the lower edge of the upper mandible), for the most part obsolete anteriorly.
IV. Nudinares. Nostrils open, uncovered by bristly hairs. Neck and bill various.
Of these series, the first and second correspond with Piceæ, as given below, while Centureæ and Colapteæ both belong to Ligonirostres. The Nudinares are not represented in North America, and by only one group, Celeus, in any portion of the continent.
In the following account of the Picinæ, we shall not pretend to discuss the relationship of the North American species to the Picinæ in general, referring to Sundevall’s work, and the monographs of Malherbe and Cassin, for information on the subject. For our present purposes they may be conveniently, even if artificially, arranged in the following sections:—
Piceæ. Bill variable in length; the outlines above and below nearly straight; the ends truncated; a prominent ridge on the side of the mandible springing from the middle of the base, or a little below, and running out either on the commissure, or extending parallel to and a little above it, to the end, sometimes obliterated or confluent with the lateral bevel of the bill. Nostrils considerably overhung by the lateral ridge, more or less linear, and concealed by thick bushy tufts of feathers at the base of the bill. Outer posterior toe generally longer than the anterior.
Centureæ. Bill rather long; the outlines, that of the culmen especially, decidedly curved. The lateral ridge much nearest the culmen, and, though quite distinct at the base, disappearing before coming to the lower edge of the mandible; not overhanging the nostrils, which are broadly oval, rounded anteriorly, and not concealed by the bristly feathers at the base. Outer pair of toes nearly equal; the anterior rather longer.
Colapteæ. Bill rather long, much depressed, and the upper outline
much curved to the acutely pointed (not truncate) tip. The commissure considerably curved. Bill without any ridges. The nostrils broadly oval, and much exposed. Anterior outer toe longest.
