Lampreys (PETROMYZONTIDA)

Family of cyclostome fishes, with seven external gill openings on each side of the neck, and a common internal pa age opening into the pharynx. Tke nasal sac does not open into the mouth. The mouth is circular, with fleshy toothed lips, with which it adheres to objects by suction. The Sea Lamprey ( Petromyzon mar in us ) grows to two feet in length: it ascends rivers with the shad in spring, to spawn. P. planer i, one of the River Lampreys, has Ammocœtes as its larva, which differs from the adult in being be without eyes or teeth, and in the form of its lips. The popular belief that lampreys are related to eels is erroneous.