sea urchin

Spiny round-bodied marine animal, found on intertidal rocks and reefs worldwide; generally dark purple or black in color, but also brown, green, red, or white. Urchins are harmful to surfers, as the spines can break off and lodge into the skin. The common nonpoisonous purple urchins in California have small, blunt, solid spines. The spines on many tropical urchins, however, are longer—up to 12 inc...