Actinulida are an order of hydrozoans in the subclass Trachylinae. Very small, medusoid Hydrozoa without polyp phase, living in the sand interstitial, solitary, bell entirely or very much reduced, epidermis ciliated, 1-2 whorls of tentacles, statocysts present or not, club shaped and derived of ecto- and entodermal tissue; cnidome may include stenoteles.^[1]

Actinulida
Halammohydra octopodides
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Cnidaria
Class:	Hydrozoa
Subclass:	Trachylinae
Order:	ActinulidaSwedmark & Teissier, 1958[1]
Families
Halammohydridae Remane, 1927 Otohydridae Swedmark & Teissier, 1958