Its calcareous skeleton, called a test, is spherical in shape and flattened on the top and bottom. It resembles the hats once worn by Catholic priests.
It is called a "collector urchin" in English to illustrate its collector behaviour because it uses its podia (small sucker feet) to hold pieces of seaweed, shell fragments or pebbles on its skeleton. This acts as camouflage against predators (such as triggerfish) and protection against UV rays in very shallow waters.