Cnidaria Hatschek, 1888 - cnidarians Class Hydrozoa Owen, 1843 Order Hydroida Johnston, 1836 - hydroids see Order Anthoathecatae 1 Family Plumulariidae McCrady, 1859 2 Family Aequoreidae Eschscholtz, 1829 3 Family Campanulariidae Hincks, 1868 4 Family Hydridae Dana, 1846