XXX11 
DIV. I. — -VERTEBRATA. 
VERTEBRATA. 
CLASS IV.— PISCES. 
This class is divided into two great series, the Ossei and Chon- 
dropterygii ; in the former of which the skeleton is formed of true 
hone, while in the latter it always remains in the state of cartilage 
or gristle. The former is divided into six, the latter into two 
orders ; the principal characters being derived from the first gills, 
as the names of the orders will show. 
Class. Series. 
/ 
Pisces ' 
Ossei 
{Bony fishes) 
II. Chondropterygii 
(' Cartilaginous fishes) 
Order. 
( l . 
2 . 
4 , 
5 . 
\ 6 . 
Acanthopterygii 
Malacopterygii Abdo- 
minales 
Malacopterygii Sub- 
brachii 
Malacopterygii Apodes 
Lopbobranchii 
Plectognathi 
Eleutherobranchii 
(gills free) 
Pectobrancbii ( gills 
confined) 
SERIES I.— OSSEI. 
ORDER I. — -Acanthopterygii. 
The Acanthopterygians make three-fourths of all the fishes known, 
and are the most perfectly wrought type of the class. The families 
into which they are divided are in general very natural, but present 
so many varieties with respect to those characters on which it might 
be supposed they could be grouped into orders or other subdivi- 
sions, that it has been found expedient to leave them all together. 
