Class IV. CARTILAGINOUS FISH. 75 



Div.IL CARTILAGINOUS 

 FISH. 



JnrSHIS title is given to all nfh whofe mufcles 

 JL are fupported by cartilages inftead of bones, 

 and comprehends the fame genera of fifh to which 

 Linnaeus has given the name of amphibia nantes : 

 but the word amphibia, ought properly to be con- 

 fined to fuch animals who inhabit both elements, 

 and can live without any inconvenience for a con- 

 fiderable fpace, either in land or under water -, 

 fuch as tortoifes, frogs, and feveral fpecies of li- 

 zards-, and among the quadrupeds, hippopotami, 

 feals, &c. &c. This definition therefore excludes 

 all that form this divifion. 



Many of the cartilaginous nfh are viviparous, 

 being excluded from an egg, which is hatched 

 within them. The egg confiftsofa white and a 

 yolk, and is lodged in a cafe, formed of a thick 

 tough fubftance, not unlike foftened horn: fuch 

 are the eggs of the Ray and Shark kinds. 



Some again differ in this refpetft, and are ovi- 

 parous ; fuch is the Sturgeon, and others. 



They breathe either through certain apertures 

 beneath, as in the Rays \ on their fides as in the 

 Sharks, &c. or on the top of the head, as in the 

 Pipe~fijh; for they have not covers to their gills 

 like the bony fifh. 



Slender 



