ON CLASSIFICATION. 
9 
The next division is into Orders. 
We need only concern ourselves 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, §uch 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 
