356 ZOOLOGY. 



i l'.!. The sub-branehiated malacopterygii have the fins 

 formed in the same manner as in the last; but their abdominal 

 tins an- placi-d under the pectorals. This division comprises 

 the cod (Fig. :tt:i),themerlan, the remora (Fig. 313), and the 

 I'amilv of the pleuronectes or flat fish, as the plaice (Fig. 329), 

 the tiirbot (Fig. 314), the sole, &c. , 



500. Finally, the malacopterygii apodes are characterized 

 by the absence of ventral fins, and of spinous rays in the 

 dorsal fin. To this family belong the eels, the gymnotus 

 (Fig. 319), &c. 



Fig. 329. The Plaice. 



501. The cartilaginous fishes or chondropterygii have 

 the skeleton cartilaginous, and sometimes almost membranous, 

 never osseous, the calcareous matter hardening its surface 

 being deposited in little grains. There is even a resemblance 

 between it and that of the tadpole. The superior maxil- 

 lary and intermaxillary bones are rudimentary, and the upper 

 jaw is formed essentially by the palatine bones. Sometimes 

 the gills are free at their edge, and sometimes fixed, and this 

 difference serves as a basis for their division into two groups, 

 namely, the chondropterygii with free branchiae, and those 

 with fixed branchiae; and these latter are subdivided into two 

 others, the selaciens and the cyclostom.es. 



502. The order of chondropterygii with free gills are 

 also called sturiones, because they have for their type the 

 sturgeon (sfurio). It is composed of fishes in whose figure 

 there is nothing irregular (Fig. 330), and which have for the 

 most part the skin provided with large osseous plates dis- 

 posed in rows* and the moiith toothless. 



503. The cbondropterygii with fixed gills have a re- 

 markable common character, which has already been de- 



* In othor words, a dermoid skeleton. B. K. 



