Fish who are made of cartilage.

body is long eel-like

class cyclostomata are without jaws

there eg are :

petromyzon

myxine

Lampreys are in the superclass Agnatha, jawless fish. They are of the class Cyclostomata, which includes hagfish, as opposed to the extinct Ostracoderms.

Hagfish and lampreys are apart of Agnatha which means jawless fish. Hagfish are a parasite fish but can be free swimming. Both jawless fish will feed on carcasses on the bottom of the seafloor.