34 
SYSTEM OF NATURE. 
birds ; that in several characters, especially in possessing 
the marsupial bones, and in the peculiarities of other 
bones, they resemble the reptiles ; that they combine and 
as it were unite the characters of placentals, birds and rep¬ 
tiles; and seeing that the marsupials can be no longer con¬ 
sidered part of the true viviparous series, and that they are 
physiologically degraded to the oviparous series, we must 
either constitute for them a new and separate class, or else 
admit them among birds, reptiles or fishes, which would 
be as direct a departure from nature as to retain them 
among the placentals. 
2ndly. Tlieir divisibility or diversity. There appears to 
be a series of characters, principally dependent on food, 
very strikingly exhibited in the placental animals. We 
find a trace of this in the birds, not indeed confined to, or 
always indicated by, the divisions of birds in the various 
systems with which we are acquainted, but in those natural 
groups of birds which impress their differences forcibly 
upon us; neither are the differences in birds so strongly 
marked as in placentals, a circumstance to be inferred from 
the central position of the latter. The diversified charac¬ 
ters of the placentals, which strike me as peculiarly dis¬ 
tinctive of the divisions already alluded to, are these :— 
1st. The Primates are Scandentia or climbers, of which 
the monkeys are the obvious examples. 2ndly. The Ferae 
are Rapacia, hunters, or beasts of prey, of which a lion 
and tiger are examples. 3rdly. The Cheiroptera are 
Volitantia or flyers, of which bats are examples. 4thly. 
The Glires are Saltantia or leapers, animals whose fore 
legs are short, whose bellies touch the ground, whose pro¬ 
gressive motion consists of a series of leaps, as rabbits, 
&c. 5thly. The Bruta are Repentia or crawlers, whose 
