Sea urchins or
urchins (/ˈɜːrtʃɪnz/), archaically called
sea hedgehogs, are small, spiny, globular animals that, with their close kin, such as sand dollars, constitute the class
Echinoidea of the echinoderm phylum. About 950 species of echinoids inhabit all oceans from the intertidal to 5,000 metres (16,000 ft; 2,700 fathoms) deep. The shell, or "test", of sea urchins is round and spiny, typically from 3 to 10 cm (1.2 to 3.9 in) across. Common colors include black and
(From Wikipedia)