Nematocalyx \Nem`a*to*ca"lyx\, n.; pl. {Nematocalyces}, E. -{calyxes}. [NL. See {Nemato-}, and {Calyx}.] (Zo["o]l.) One of a peculiar kind of cups, or calicles, found upon hydroids of the family {Plumularid[ae]}. They contain nematocysts. See {Plumularia}.