(Hydractinia) (Hydractinia) is a biological genus in the family Hydractiniidae and order Anthoathecatae (Athecate Hydroids).
Hydractinia aggregata
Hydractinia allmani
Hydractinia americana
Hydractinia arge
Hydractinia armata
Hydractinia californica
Hydractinia carica
Hydractinia carnea
Hydractinia carolinae
Hydractinia dubia
Hydractinia fucicola
Hydractinia hooperii
Hydractinia laevispina
Hydractinia minima
Hydractinia minuta
Hydractinia monocarpa
Hydractinia multispina
Hydractinia parvispina
Hydractinia polycarpa
Hydractinia polyclina
Hydractinia prolifica
Hydractinia selena
Hydractinia symbiolongicarpus
Hydractinia symbiopollicaris
Hydractinia valens
Hydractinia milleri
Hydractinia echinata
Clava
Hydractinia
Hydrocorella
Janaria
Podocoryne
Polyhydra
Stylactis