‖n. pl. [ NL. See Siphon, and Stoma. ] (Zool.) (a) A tribe of parasitic copepod Crustacea including a large number of species that are parasites of fishes, as the lerneans. They have a mouth adapted to suck blood. (b) An artificial division of gastropods including those that have siphonostomatous shells. [ 1913 Webster ]