XXXll 



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 

 bone, 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. 



1. Acanthopterygii 



2. Malacopterygii Abdo- 



minales 



3. Malacopterygii Sub- 



brachii 



4. Malacopterygii Apodes 



5. Lophobranchii 

 \6. Plectognatlii 



7. Eleutherobranchii 



{gills free) 



8. Pectobranchii {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. 



