Burrowing urchin

Scientific name : Echinometra mathaei

Small urchin (test diameter about 5 cm). Dark colour, thick red-brown spines with a white ring at the basis.
Living in the back reef, also in the tidal zone. It burrows its hole in the carbonate rocks, using the teeths and the spines.
Easy to identify among the other urchins due to the white rings around the spines. The mantis shrimp Echinosquilla guerinii mimics it, showing only the spiny telson at the exit of its burrow. Another burrowing urchin, Echinostrephus sp., has long and thin spines.