the Scyphozoa are an exclusively marine class of the phylum Cnidaria, sometimes referred to as the "jellyfish" (or sea
jellies - as they are not, in fact, fish).
The class name Scyphozoa comes from the Greek word skyphos (σκύφος), denoting a kind of drinking cup and alluding to the cup shape of the organism. Scyphozoans have existed, in geological time, from the Ediacaran period to the present.