The Collaborative International Dictionary of English v.0.48:

Ctenocyst \Cte"no*cyst\ (t[=e]"n[-o]*s[i^]st), n. [Gr. ktei`s,
   kteno`s, comb + ky`stis bladder.] (Zool.)
   An organ of the Ctenophora, supposed to be sensory.
   [1913 Webster]