Class+Echinoidea+(Sea+Urchins)

=       = Echinoidea, or sea urchins, have radial symmetry, an external chitinous skeleton and a central jaw with teeth, known as Aristotle's lantern. The anus of sea urchins is located on the upper surface. Some sea urchins have a cloaca that extends out of the anus to excrete waste. Sea urchins move by using a tube foot that extends to pull the urchin along. Some urchins also use their spines to help with movement. 

**﻿Sources ** [] [|http://library.thinkquest.org/J001418/urchin.html] [|http://www.dailygalaxy.com/photos/uncategorized/urchins_1.jpg] 