Sea Urchin

This is a Pencil Sea Urchin. The body is a bit larger than a tennis ball, with 2 inch spikes. He mostly eats algae, and uses the pencils as protection (who would want to try to eat that?). Here he is from above:

Here he is from the side. The lighting is not all that good, but you can see his teeth a bit.

Dental closeup. A relative of the star fish, the urchin has five-way symmetry, and thus five teeth. He holds onto rocks and glass with suction cups on thin tentacles, a few of which you can see attached to the glass (upper middle and upper left). Those teeth make you wonder if he only likes algae. Still, a snail could out-run him...