ClasIV. CARTILAGINOUS FISH. 47 
Div. I. CARTILAGINOUS FISH. 
HIS title is given to all fifh whofe mufcles 
are fupported by cartilages inftead of bones, 
and comprehends the fame genera of fifh to which 
_ Linnzus has given the name of amphibia nantes: 
but the word amphibia, ought properly to be confined 
to fuch animals who inhabit both elements, and can 
live without any inconvenience for a confiderable 
fpace, either on land or under water. This defini- 
tion therefore excludes all that form this divifion. 
Many of the cartilaginous fifth are viviparous, 
being excluded from an egg, which is hatched within 
sham, The egg confifts of a white and a yolk, and 
is lodged in a re formed of a thick tough fub- 
ftance, not unlike foftened horn: fuch are the eggs 
of the Ray and Shark kinds. 
Some again differ in this refpect, and are ovipa- 
rous ; fuch is the Sturgeon, and others. 
/They breathe either thro’ certain apertures be- 
neath, as in the Rays; on their fides as in the 
Sharks, &c. or on the top of the head, as in the 
Pipe-fifh ; for they have not covers to their gills 
like the bony fith. 
Eo : Genus 
