These planktonic forms of schyphozoans and hydrozonas, which are two classes in the Phylum Cnidaria. Each is a large collection of species, and have radial symmetry. These soft-bodied creatures are often mangled in plankton collections, so identifying species might be difficult. To identifiy them, look for transparent bells, often with tentacles dangling from the bottom. Hydromedusae are smaller, with a thin velum extends inward from the lip of the bell toward the mouth, which is often on a long stalk called a 'manubrium'. Schyphomedusae are generally larger, with thicker bells and frilly oral arms around the mouth. You may also see small 'ephyra' stages of schyphozoans in the plankton.