86 
SYSTEM OF NATURE. 
The saltant character might perhaps be traced, even in 
an eminent degree, in some of the genera belonging to 
this group; but this is foreign to my purpose. The 
preponderating use of legs throughout the group — while 
in the following group they are accompanied by wings, 
and in the remaining four are totally absent—is sufficient 
to establish the propriety of considering this group as 
equivalent to that of the Saltantia in minor divisions. 
2ndly. Volitantia . The winged insects — and such 
alone are comprised in this group — are preeminently dis¬ 
tinguished by brilliancy of colouring, rapidity of aerial 
progression, universally distributed respiration, and extra¬ 
ordinary development of instinct, so peculiarly displayed 
in nidification. These appear to me the characters whereby 
we should most readily distinguish birds. 
3rdly. Rapacia. The star-fishes and urchins are dis¬ 
tinguished by having their covering composed of those 
osseous or calcareous plates with which many of the car¬ 
tilaginous fish are so completely invested. They are ra¬ 
pacious animals, of great voracity, feeding on testaceous 
Mollusca and Crustacea. The mouth, particularly in 
Echinus, is one of the most formidable and powerful 
known to naturalists : its structure has long been the 
theme of admiration : it is described by Aristotle, Lamarck 
and Cuvier : it appears to be possessed of the power of 
masticating, and almost instantaneously converting into 
pulp the hardest shells. In these characters we must per¬ 
ceive a striking resemblance to the cartilaginous fishes. 
The extinct Pterichthys was almost an Echinus. 
4thly. Natantia. These are the lowest, most simple 
and most shapeless of all animals : they are all of them 
aquatic, most of them marine. The term Zoophyta or 
