Sand dollar

08_07_27,
originally uploaded by Hongyee.

A rarely-seen denizen of the tank's sandbed, this is a sand dollar - a echinoderm, closely related to sea cucumbers, starfish and urchins. I saw him lurking around under the sand and dug him up just for the shot. I'm actually astounded that he survived for so long, sand dollars are rarely heard of in captivity.