What is "petromyzon marinus"

Lamprey \Lam"prey\ (l[a^]m"pr[y^]), n.; pl. Lampreys (l[a^]m"pr[i^]z). [OE. lampreie, F. lamproie, LL. lampreda, lampetra, from L. lambere to lick + petra rock, stone. The lampreys are so called because they attach themselves with their circular mouths to rocks and stones, whence they are also called rocksuckers. See Lap to drink, Petrify.] (Zo["o]l.) An eel-like marsipobranch of the genus Petromyzon, and allied genera; called also lamprey eel and lamper eel. 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. [Written also lamprel, and lampron.]

Note: The common or sea lamprey of America and Europe ( Petromyzon marinus), which in spring ascends rivers to spawn, is considered excellent food by many, and is sold as a market fish in some localities. The smaller river lampreys mostly belong to the genus Ammoc[oe]les, or Lampetra, as Ammoc[oe]les fluviatilis, of Europe, and Ammoc[oe]les [ae]pypterus of America. All lampreys attach themselves to other fishes, as parasites, by means of the suckerlike mouth.