This type attains its highest development in the Oscines, but it occurs also in many other orders.
Both types represent rather two divergent lines than successive stages, although that of the Clamatores remains at a lower level, possessing at the utmost three pairs of muscles, whilst these range in the Oscines from rarely two or three to five or seven.
Sharpe divided the Passeres respectively into Oscines, Oligomyodae, Tracheophonae and Pseudoscines (= Suboscines); Oligomyodae, Tracheophonae and Acromyodae; Oscines, Oligomyodae, Tracheophonae and Atrichiidae.
But the characteristic nature of the avifauna is more clearly brought out when we learn that of the 2000 species just mentioned only about 1070 belong to the higher suborder of Oscines, that means to say, nearly one-half belong to the lower suborder Clamatores.
This is a state of things which exists nowhere else; for except in Australia, where a few indigenous and peculiar low non-Oscines are found, and in the Nearctic country, whither one family of Clamatores, viz.
The HoLARCTIC Region, comprising North America and the extratropical mass of land of the Old World, may from an ornithological point of view be characterized by the Colymbi, Alcidae, Gallidae or Alectoropodous Galli, and the Oscines, which have here reached their highest development; while Ratitae, Tinami, Psittaci, and non-Oscine Passeres (with the exception of Tyrannidae extending into North America and Conurus carolinensis) are absent.
Euryceros of the Oscines, and Philepitta of the Clamatores, are remarkable enough to form the types of Passeriform families, and Mesites half-way between Galli and Gruiformes is of prime importance.
(2) Oscines, the true singing-birds, with more than 5000 recent species, are mostly divided into some thirty " families," few of which can be defined.
These are, again in an ascending direction, connected with the Coraciiformes, out of which have arisen the Passeriformes, and these have blossomed into the Oscines, which, as the apotheosis of bird life, have conquered the whole inhabitable world.
Aristotle seems to recognize eight principal groups: (1) Gampsonyches, approximately equivalent to the Accipitres of Linnaeus; (2) Scolecophaga, containing most of what would now be called Oscines, excepting indeed the (3) Acanthophaga, composed of the goldfinch, siskin and a few others; (4) Scnipophaga, the woodpeckers; (5) Peristeroide, or pigeons; (6) Schizopoda, (7) Steganopoda, and (8) Barea, nearly the same respectively as the Linnaean Grallae, Anseres and Gallinae.
At the same time Muller showed himself, his power of discrimination notwithstanding, to fall behind Nitzsch in one very crucial point, for he refused to the latter's Picariae the rank that had been claimed for them, and imagined that the groups associated under that name formed but a third " tribe" - Picarii - of a great order Insessores, the others being (1) the Oscines or Polymyodi - the singing birds by emphasis, whose inferior larynx was endowed with the full number of five pairs of song-muscles, and (2) the Tracheophones, composed of some South-American families.
In the Oscines or Polymyodi of Muller the number was either nine or ten - and if the latter the outermost of them was generally very small.
In two of the other groups of which Professor Cabanis, especially treated - groups which had been hitherto more or less confounded with the Oscines - the number of primaries was invariably ten, and the outermost of them was comparatively large.
Oscines, equal to Miiller's group of the same name; 2.
The Gymnopaedes are divided into two " orders " - Oscines and Volucres - the former intended to be identical with the group of the same name established by older authors, and, in accordance with the observations of Keyserling and Blasius already mentioned, divided into two " series " - Laminiplantares, having the hinder part of the " tarsus " covered with two horny plates, and Scutelliplantares, in which the same part is scutellated.