Any of various primitive elongated freshwater or anadromous fishes of the family Petromyzontidae, characteristically having a jawless sucking mouth with rasping teeth.

• 七鳃鳗，八目鳗一种七鳃鳗科的原始细长淡水或溯河产卵鱼，特点是长有无颌的吮吸嘴，嘴内有锉牙