Medusae of the Amsterdam mid North Atlantic Plankton Expeditions (1980-1983) with Description of Two New Species

The medusa fauna of the mid North Atlantic Ocean between 24° and 55°N along approximately 30°W is studied. Two Hydromedusae new to science, Oceania tydemani and Annatiara lempersi , are described. The differences in fauna south and north of 42°N, and faunal borders near 50°, 48°, 45°, 35°, 30°, and 34°-37° N are discussed. The vertical distribution and for some species the diurnal migration and subtropical submergence are recorded.