(a) The word Echinodermata means 'spiny skin' which is aptly used for group of animals represented by such common forms as starfishes, sea urchins, sea cucumbers, sea lilies.
(b) The skin forms a hard spiny protective skeleton covering.
(c) These are sluggish marine forms.
(d) Forms usually show a pentamerous radial symmetry.
(e) It is the only phylum in which adults are radially symmetrical while larval stages are bilaterally symmetrical.
(f) They have a coelom (coelomata) and water vascular system on ambulacral system.
(g) Locomotion takes place by means of numerous hollow tube feet.
(h) Excretion by diffusion through the body.
(i) Fertilization is open.
(j) Development includes free swimming diploneural larva. Examples : Asterias(Starfish), sea urchin (Echinus) and sea cucumber(Cucumaria) and Antedon.