A robust-looking regular sea-urchin. The test is somewhat flattened compared with Echinus and the spines are much thicker and very blunt. There are two distinct colour forms, purple all over and purple with white spines. The spines are very regular in size and arrangement giving a neat overall appearance. Up to 15cm. in diameter. This is a large urchin, comparable in size with Echinus esculentus, from which it is easily distinguished by the thick, neatly-arranged, spines.