Source : Webster's Revised Unabridged Dictionary (1913)

Cyatholith \Cy*ath"olith\ (s?-?th"?-l?th), n. [Gr. ky`aqos a cup
   + -lith.] (Biol.)
   A kind of coccolith, which in shape resembles a minute cup
   widened at the top, and varies in size from 1/6000 to 1/8000
   of an inch.