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SUB-KINGDOM V. VERTEBRATA. 

 CLASS I. PISCES. 



(FISHES.) 



OF that large division of animate beings which 

 are distinguished by an internal skeleton of bone, 

 and of which the most marked character is the 

 possession of a prolongation of the brain (known 

 as the spinal cord) , enclosed in a series of tubular 

 bones (the vertebrce), which unitedly constitute the 

 spine, the Class of Fishes is almost the only one 

 which falls within the province of the British 

 Marine Zoologist. It is the most populous in 

 species of all, and the marine kinds greatly exceed 

 in number (and in importance also) those which in- 

 habit fresh waters. 



The skeleton, of which a rudimentary sketch, if 

 I may so call it, appears first in the CEPHALOPODA, 

 is, in the lowest forms of the present Class, scarcely 

 advanced in structure. In the Myxine arid Am- 

 pliioxus, it is a simple tube of cartilage, of which 

 the divisions into joints are only indicated ; and it 

 is not until we arrive at the higher Orders that we 

 obtain true bone. 



The elements which enter into the vertebrae, or 

 joints of the spine, are the same in all Fishes. 

 They are as follows: 1, The central cylinder ; 

 2, the superior arch, formed by two sloping side 

 pieces, between which the spinal marrow passes ; 



