A class of the protozoan subphylum Cnidospora. Members of this class, which includes the orders Myxosporida, Actinomyxida, and Helicosporida, are parasites in fish, a few amphibians, and invertebrates. Actinomyxida with four families and Helicosporida with a single species (monotypic) do not contain subordinal categories. The Myxosporida, however, are divided into two suborders, the Unipolarina and Bipolarina.