(Hydra) (Hydra) is a biological genus in the family Hydridae and order Anthoathecatae (Athecate Hydroids).
Hydra canadensis
Hydra oligactis
Hydra pseudoligactis
Hydra carnea
Hydra cauliculata
Hydra minima
Hydra rutgerensis
Hydra rutgersensis
Hydra hymanae
Hydra oregona
Hydra littoralis
Hydra utahensis
Hydra americana