Which class is not included in the superclass $Tetrapoda$?

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.

Ventral muscular heart,kidneys for excretion and osmoregulation,and paired appendages are found in all of the following $EXCEPT$:

Which group of chordates possess sucking and circular mouth without jaws?

Write a short note on class Cyclostomata.

All living members of the class Cyclostomata are: