Class IV. CARTILAGINOUS FISH. 75 



Div.II. CARTILAGINOUS 

 FISH. 



THIS title is given to all filh whofe mufcles 

 are fupported by cartilages inftead of bones, • 

 and comprehends the fame genera of fifh to which 

 Linn^us 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 fiili are viviparous, 

 being excluded from an egg, which is hatched* 

 v/ithin them. The egg confifts of a white and a 

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

 tough fubllance, not unlike foftened horn : fuch 

 are the eggs of the Ray and Shark kinds. 



Some again differ in this rcfped, 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^ <kc, or on the top of the head, as in the 

 Pipe-jijh\ for they have not covers lo their gills 

 like the bony fifh. 



Slender 



