dicyclic (di-cy'-clic). (a) Said of a crinoid having two circlets of plates proximal to the radial plates or (in some crinoids that lack radial plates) proximal to the oral plates. (b) Said of the apical system of an echinoid in which ocular and genital plates are arranged in two concentric circles, the genital plates alone in contact with the periproctal margin. Cf: monocyclic.