Nematocalyx \Nem`a*to*ca"lyx\, n.; pl. {Nematocalyces}, E. {Nematocalyxes}. [NL. See {Nemato-}, and {Calyx}.] (Zool.) One of a peculiar kind of cups, or calicles, found upon hydroids of the family {Plumularidae}. They contain nematocysts. See {Plumularia}. [1913 Webster]