SHARKS, DOGFISH(WHICH ARE actually small sharks.),skates, and rays belong to a class of fishes called Chondrichthyes ; which is a division of the upperclassmen Gnathostomata(meaning "jawed mouths") Sharks and their relatives have a skeleton made of Cartilage (hence their common name ,cartilaginous fish), a characteristics that distinguishes them from bony fishes .Other important features of cartilages fishes are extremely tough tooth-like scales , and lack of swim bladder .Jaw less fish -hag fish and lampreys - are primitive eel like fish that make up the order Cyclostomata(meaning ...