ON CLASSIFICATION. 



The next division is into Orders. 



We need only concern onrselves here with the first 

 sub-class or Teleostei. These are divided into six 

 Orders. 



1. First come those fishes of which the perch may- 

 be taken as a type. They have usually a number of 

 sharp spines forming part of the fin on the back, and 

 some of the other fins. 



They are termed Acanthopterygii, (spiny-finned.) 



2. The second order contains fishes much resembling 

 the first, differing from them only by an anatomical 

 peculiarity of the lower bones of the throat, which is 

 not to be wondered at when we learn that they call 

 themselves Acanthopterygii pharyngognathi. 



3. The third order have all their fin rays soft and 

 flexible, such as the cod-fish and the soles, they are 

 termed Anacanthini, " without spines." 



4. The fourth order contains the greater number 

 of fresh-water fishes, and is the one with which we 

 shall be chiefly concerned. The fishes of this order 

 have frequently one strong bony ray in front of the 

 back fin, but the remaining rays of that fin are soft 

 and branched. They are termed Physostomi. 



5. The fifth order Lophobranchii ) 



> are unimportant. 



6. The sixth order Plectognathi ) 



The next division to be considered is that of 

 Families, and these form perhaps the most important 

 and natural of the groups into which fishes can be 

 divided ; each family forms generally a well defined 



