Echinoderms do not have a brain. Instead, they have a chain of nerves extending from a central ring of nerve tissue. Most echinoderms live in salt water. Most echinoderms have arms or rays in multiples of fives. Many also have "suckers" on the end of these arms for locomotion.

There are currently about 6,000 species of echinoderms.

One example is the melon sea urchin, also known as Echinus melo. These can grow to be 7 inches in diameter.

Another example is the orange sea cucumber, also known as Cucumaria miniata. These organisms usually grow in crevices to anchor themselves down.

http://animaldiversity.ummz.umich.edu/accounts/Echinodermata/

http://www.mbgnet.net/salt/oceans/animals/echinod.htm