Diadema antillarum , familiar in the Caribbean , has thin , potentially dangerous spines that can reach 10 to 30 cm ( 3.9 to 11.8 in ) long .
Diadema antillarum , familiar in the Caribbean , has thin , potentially dangerous spines that can reach 10 to 30 centimetres ( 3.9 to 11.8 in ) long .