[f. mod.L. cystis CYST + -ID.]
1. Geol. A member of the order Cystidea or Cystoidea of fossil echinoderms; a cystidean.
1862. Dana, Man. Geol., 162. The Cystids are the most anomalous of Radiates.
1877. Le Conte, Elem. Geol. (1879), 299. Stemmed Echinoderms or Crinoids, may be divided into three families, viz.: 1. Crinids, 2. Cystids, 3. Blastids.
2. Zool. The sac-like ciliated embryo of some of the Polyzoa (Syd. Soc. Lex.).
1877. Huxley, Anat. Inv. Anim., viii. 459. From one end of this cystid, one or more polypides are developed from thickenings of the wall of the sac.