The spines of the omnivorous pencil-spined urchin (Eucidaris thouarsii) extend outward from its body. There are some 700 species of sea urchins worldwide.

• 意译：海胆类：在自然界模式。这个脊骨的杂食的铅笔-有刺的海胆从它的身体延伸向外。全世界约有700种类的海胆。