Which animal has a circular and sucking mouth located on the anteroventral side?

Assertion: Cyclostomates are marine but migrate for spawning to fresh water.
Reason: After spawning, within a few days they die. Their larvae after metamorphosis return to the ocean.

The lamprey $(Petromyzon)$ is included in the same taxonomic class as the

Write the characteristics of class $Cyclostomata$.

Statement $- I :-$ All living members of class $Cyclostomata$ are ectoparasites on some fishes.
Statement $- II :-$ $Cyclostomata$ have a sucking and circular mouth without jaws.

Petromyzon is a connecting link between