— acritarchous , adj.
/ak"ri tahrk'/ , n. Paleontol.
any of various microfossils, of unknown biological affinities, having a central cavity enclosed by a wall of chiefly organic composition.
[ 1963; Acritarcha (neut. pl.), irreg. ákrit ( os ) confused, doubtful (see A- 6 , CRITIC) + arché beginning, origin (cf. ARCHI-) ]