Animals in this phylum are characterized by radial symmetry as adults, with body parts that repeat around an axis. Many echinoderms have five of these similar body parts, giving them pentaradial ...

1b. Test composed of just 20 columns of plates; interambulacral and ambulacral zones each composed of two columns of plates Go to 2 2a. Test with bilateral symmetry superimposed over pentaradial plan; ...