The Collaborative International Dictionary
Nematocalyx
Nematocalyx \Nem`a*to*ca"lyx\, n.; pl. Nematocalyces, E. Nematocalyxes. [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.
Wiktionary
nematocalyx
n. (context zoology English) A kind of cup or calicle containing nematocysts, found upon hydroids of the family Plumularidae.