Apical System OF ECHINODERMS

Series of plates that lie around the center of the abactinal surface. In the center is a dor so-central plate, around which are five interradial ( basalia ), and five radial ( radialia ). In Starfishes, Ophiuroids, and Crinoids are five under basal plates, plates, placed radially within the circle of basalia (dicyclic arrangement). ement). In Starfishes, Ophiuroids and IMG:content-0203.png:[graphic] Pelma to zoa, there are also five primary inter radials (inter brachials), external to the circle of radials.