A jawless fish, which lays eggs in fresh water and whose ammocoetes larvae after metamorphosis return to the ocean is :
Myxine
Neomyxine
Petromyzon
Eptatretus
As we learnt in
Class Cyclostomata -
All are ectoparasites on some fishes. Mouth is circular and jawless. Head and brain poorly developed.
- wherein
Eg. Petromyzon, Myxine.
Petromyzon(the lamprey) belongs to the section Agnatha of the sub-phylum-Vertebrata. They have long, greenish brown, cylindrical body with smooth scaleless, slimy skin, jawless mouth, etc. They lay eggs in freshwater but their ammocoete larvae(lower) after metamorphosis return to the ocean.