31 BOARD OF AGRICULTURE. 



Order III. Malacopterygii Subbrachiati. Ventrals under the 



pectorals. 



Family Gadidte, (Cod fishes.) 



Pleuronectidae, (Halibuts and flounders.) 

 Discoboli, (ventrals formed into suckers.) 



Order IV. Malacoptertgii Apoda. Ventral fins wanting. 



Mursenidse. 



Order V, Lophobranchii. Tufted gills. 



Order VI. Plectognathi. Soldered jaws. 

 Family Gymnodontes, (naked teeth.) 



Sclerodermi, (rough skins.) , 



SECOND DIVISION— CARTILAGINOUS FISHES. 

 Chondropterygii. 

 This Division is divided into two orders. 

 Order I. Chondropterygii Branghiis Liberis. Free or open gills. 



Sturgeons. 



Order II. Chondropterygii Branchhs Fixis. Gills fixed with 

 separate openings for %i)ater to pass through. 



Family Selachii, (Sharks and Rays.) 



Cyclostomata, (Sucker-formed mouths.) 



Agassiz System. 



Agassiz, the eminent Professor of Natural History in Harvard 

 College, has given the following arrangement of fishes, which seems 

 to accord better than any other with that which geological re- 

 searches among fossil remains point out as the order of succession 

 in the formation or existence of fishes in early epochs of the world. 

 The distinctive characters are founded upon the structure of the 

 scales. 



1. Placoids. — Embracing those with cartilaginous skeletons or a 

 skin covered with enameled plates or scales, as the shagreen of 

 sharks. 



2. Ganoids. — Those, whether bony or cartilaginous, covered with 



