Genus Obelia Péron & Lesueur, 1810

Colony erect, branched or unbranched, monosiphonic or polysiphonic, flexuose, internodes annulated proximally supporting a pedicellate hydrotheca on apophysis, hydrotheca campanulate, radially symmetrical, margin cusped or even, a true diaphragm, no sub-hydrothecal spherule, gonotheca inverted conical, gonophores as free swimming medusae