202 ZOOLOGY. 



The classification of Cuvier is the one more generally adopted. He 

 divides the entire class into bony and cartilaginous ; the former again into 

 spinous rayed and soft rayed ; the latter into those with free gills, and such 

 as have them fixed. We have here room only for the Orders and Families. 



I. AcANTHOPTERYGIA. Fill rmjS SpluOUS. 



Percidae. Chaetodontidae. Mugilidae, 



Triglidae. Scombridae. Gobidae. 



Sciaenidae. Teuthidae. Lophidae. 



Sparidae. Taenidae. Labridae. 



Maenida?. Atherinidae. Siluridae. 



II. Malacopteuygi* Abdominales. Fin rays soft. Ventrals behind the 



pectoral. 



Cyprinida;. Fistularidae. Clupeidae. 



Esocidae. Salmonidae. 



III. Malacopterygii Subbracihati. Fin rays soft. Ventrals beneath the 



pectoral. 



Gadidae. Cyclopteridae. Echineidas. 



Planidae. 



IV. Malacopterygii Apoda. Fin rays soft. Ventrals icanting. 



Anguillidae. 



V. LopiioBRANCHii. Gills in tufts ; not pectinate. 

 Syngnathidae. 



VI. Plectognathi. Bones of the head closely combined. 

 GymnodontidaB. Balistidae. Ostracionidae. 



VII. Chondropterygii Bkanchiis Liberis. Gills pectinate, free. A single 



gill opening. 



Sturionidae. 



VIII. Chondropterygii Branchiis Fixis. Gill apertures more than one 



on each side. Gills not free. 



Squalidae. Raiadae. Petromyzonidae. 



A highly philosophical classification is that of Prof. Agassiz, which is 

 especially applicable to the arrangement of fossil forms. This eminent 

 naturalist divides fishes into four Orders from characters derived from the 

 scales. They are as follows : 



I. Placoids. Characterized by having the skin provided with osseous 

 plates of various sizes and numbers, as in the sharks, rays, &c. The 

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