Acoelomata
From ZooTerms (Dictionary of Invertebrate Zoology)
Acoelomata (noun; Greek a, without; koilos, hollow): A coined term denoting those lower phyla of zoological classification that lack a body cavity or coelom as Cnidaria (=Coelenterata), Nemertea, Platyhelminthes, Porifera, or Ctenophora.
