The Phylum Echinodermata is divided into five different classes. The three that will be focused on include: Echinoidea, Asteroida, and Holothuroidea. Organisms within these classes include sea urchins, sand dollars, seastars, and sea cucumbers. Collectively, the animals within this Phylum are called Echinoderms which means "spiny skinned" in reference to the spiny projections found on many species.