CLASSIFICATION OF BIRDS. 15 
Each order, it will be seen, possesses a peculiar 
formation of the bill, wings, or feet ; and it is by the 
close observance of them, as well as of differences in 
their plumage, that the naturalist is enabled to dis- 
tinguish between the different species.* 
* With fuller anatomical information upon the subject, 
later zoologists have regarded the following arrangement as 
most nearly representing Nature: 
Of the class Aves there are three sub-classes, viz., Nata- 
tores, (principally aquatic), Cursores, (principally terres- 
trial), and Insessores, (principally arboreal). 
The sub-class, Natatores, embraces four orders, viz., 
the Pygopodes , (containing four families; grebe, loon, pen- 
guin, etc.); th e Longipennes, (two families; petrel, gull, 
etc.)]; the Steganopodes, (two families; pelican, etc.); and 
the Lamellirostres , (two families ; ducks, mergansers). 
The sub-class, Cursores, consists of three orders; first, 
Grallce , (containing six families, rails, herons, flamingo, 
snipe, plover, etc.); second, Brevipennes, (two families, 
ostrich, apteryx, etc.); third, Gallince , (four families, 
grouse, pheasant, turkey, etc.) 
The sub-class, Insessores, is a union of five orders. 
First, Pullastrce, (four families, brush turkey, dodo, pigeon, 
etc.) ; second, Accipitres , (three families, the birds of prey) ; 
third, Syndachyli, (seven families, hornbill, kingfisher, 
humming bird, swift, whip-poor-will, etc.) ; fourth, Zygo - 
dactyli , (seven families, trogons, cuckoos, woodpeckers, 
parrots, etc.); fifth, Passeres, (twenty families, sparrows, 
thrushes, tanagers, crows, etc.) The third of these orders 
is of uncertain limits ; very good authorities refer it to the 
fifth, (Passeres), forming from part of it a sub-order, (S tri- 
sores). In the system here sketched, the Passeres comprise 
two sub-orders, distinguished partly by the greater or less 
perfection of the vocal organs. They are the Clamatores 
