Helmet Urchin (Colobocentrotus atratus)
Also called shingle urchin, the helmet urchin is a species of sea urchin in the family Echinometridae. They can be found on rocks nears shores of the Indo-West Pacific particularly in Hawaii. They look very different from other sea urchins as their spines have been modified to be flattened and smooth in order to better withstand the waves that crash against the rocks they live on in order to feed on periwinkles and algae. They are usually a maroon color and grow as big as a softball.