286 LINNJEUS. 



The number of species described as belonging to 

 this class is 292. The specific characters are de- 

 rived from various circumstances connected with 

 the external conformation ; in the tortoises, from the 

 shell and feet ; in the snakes, from the number of 

 the abdominal and caudal plates ; in the swimming 

 amphibia, or, as they are now more properly called, 

 the cartilaginous fishes, from the form of the body, 

 the diflTerences of the fins, and other circumstances. 



The fourth class, that of Fishes, contains four 

 orders, founded upon the relative position of the 

 fins, which are compared to the feet of other ani- 

 mals. Thus, the ventral fins may be placed before, 

 beneath, or behind the pectoral, or they may be 

 wanting. 



I. Apodes, Apodal or Footless. Fishes destitute of 

 ventral fins ; such as the eel, the wolf-fish, and the sword- 

 fish. 



II. JuGULAREs, Jugular. Fishes having the ventral 

 fins placed before the pectoral ; as the dragonet, weever, 

 cod, haddock, and coal-fish. 



III. Thoracici, Thoracic. Fishes having the ven- 

 tral fins placed under the pectoral; as the goby, bull- 

 head, hohbut, gilt-head, perch, mackerel, &c. 



IV. Abdominales, Abdominal. Fishes having the 

 ventral fins placed on the abdomen behind the pectoral 

 fins ; as in the salmon, trout, pike, mullet, and herring. 



In this class there are 47 genera, and 400 spe- 

 cies. The specific characters are taken from the 

 number of rays in the fins, the form of the tail, the 

 cirri or filaments at the mouth, the colouring of the 

 body, the form of the scales, and other circum- 

 stances. 



