Shingle urchin (Colobocentrotus atratus)
The shingle urchin is a species of sea urchin in the family Echinometridae. It is found on wave-swept intertidal shores in the Indo-West Pacific, particularly on the shores of Hawaii. This urchin is a deep maroon colour and shaped like a domed limpet. It can grow as big as a soft ball but is usually much smaller. The
upper surface is a mosaic of tiny polygonal plates formed from modified
spines to form a smooth mosaic. This is fringed by a ring of large,
flattened modified spines. On the underside there is another ring of
smaller flattened spines and a large number of tube feet. This urchin is usually found on substrates fully exposed to waves and their associated abrasive effect, often in groups. It feeds on periwinkles, other urchins and coralline algae.