Eleutheriidae

Cladus: Eukaryota
Supergroup: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Phylum: Cnidaria
Cladus: Medusozoa
Classis: Hydrozoa
Ordo: Capitata
Familia: Eleutheriidae
Genera: Eleutheria - Staurocladia

Eleutheriidae is a family of anthomedusan hydrozoans. These simple animals have a circular mouth surrounded by a variable number of tentacles, each with adhesive apparatus. The gonads are located in a dorsal brood pouch.

There are a mere 2 genera:

Eleutheria
Staurocladia

References

Eleutheriidae at GBIF
Zooplankton identification sheet