Red slate pencil urchin (Heterocentrotus mamillatus)

   Most specimens are bright red, but brown and purple shades are also found. They often have a white ring at the base of the spines and alternating light and dark rings. The spines have a round or triangular cross-section. The main spines are very thick, heavy, smooth, and blunt at the tips. In addition to the main spines, there are smaller, sharper, and thinner spines used for defense and locomotion.