An eel-like marsipobranch of the genus Petromyzon, and allied genera. The lampreys have a round, sucking mouth, without jaws, but set with numerous minute teeth, and one to three larger teeth on the palate (see Illust. of Cyclostomi). There are seven small branchial openings on each side.
- Any of various primitive elongated freshwater or anadromous fishes of the family Petromyzontidae, characteristically having a jawless sucking mouth with rasping teeth. Also called lamper eel.