Ectopleura L. Agassiz, 1862

Diagnosis. Hydroid solitary or colonial, hydrocaulus simple, with open lumen, without parenchymatic endoderm or longitudinal canals but weakly divided by two rarely up to five internal longitudinal endodermic ridges, perisarc thin, a collar on neck region that does not cover whole neck; hydranth vasiform with one whorl of filiform oral tentacles and a whorl of long, filiform aboral tentacles; gonophores borne above aboral tentacles producing either free medusae, eumedusoids or fixed sporosacs.