Scyphozoa (class)

Class containing around 200 species of cup animals, including some jellyfish. Life histories commonly involve alternation of a very small polyp with a medusa that develops from an ephyra released by the polyp. They are divided by four longitudinal septa producing tetramerous radial symmetry; gonads are endodermal. They have marginal sensory structures (rhopalia) with statocysts and/or ocelli. They are most abundant in coastal waters, but oceanic species exist.