PisciCLLTURE WITH Referknce TO Farming. 397 



tinctly, what species of pleasure can they derive from such 

 combinations ? " 



Following the example of Cuvier, the acknowledged 

 authority in Natural History, most authors have adopted his 

 system of classification. He divides osseous fishes (fishes 

 that have a bony skeleton,) into two classes : those which 

 have the upper jaw movable, and those which have the 

 upper jaw solidly fixed to the cranium. The first of these 

 classes he again divides into those having the branchiae or gills 

 in the form of a comb, and those which have their branchiae 

 arrano;ed in round tufts. The first of these sub-classes he 

 again divides into those which have their fin rays bony, and 

 those which have soft fin rays. This distinction is com- 

 monly known by the bony or spine rayed and soft rayed 

 fishes, and it is one that is easily recognized by those who 

 are only slightly familiar with the subject of Ichthyology. 

 The soft rayed fishes are divided into two or three classes, 

 which it is unnecessary to notice here. Agassiz attempted 

 to classify all fishes, both the varieties long since extinct, as 

 well as the living species, by the structure of their scales. 

 Those having scales consisting of enamel only, he called Pla- 

 coidians. Sharks and Rays belong to this class. Those having 

 scales composed of a bony substance and covered with 

 enamel he called Ganoids, embracing among its living spe 

 cies the Sturgeon and Gar Pike of North America. These 

 two orders, he says, " were numerous at the remote geolog- 

 ical epoch before reptiles were created, and consisted of 

 many genera with species of great size, and that the types 

 of these ancient fishes were reduced to a very few genera." 



