an order of the phylum Coelenterata of the class Hydrozoa. Narcomedusae are primarily free-swimming, umbrella-shaped animals, reaching a size of 10 cm in diameter. Certain species, such as the Cunina, have parasitic larvae that host on other species of hydrozoan medusae and multiply by budding. The larvae are later transformed into free-swimming specimens. Very small members of the family Halommohydridae, which have lost the umbrella shape, dwell on the bottom and creep along the sand. There are a total of 64 species, with no fewer than six species found in the USSR in the northern and Far Eastern seas.