European edible sea urchin

E. esculentus is approximately spherical but slightly flattened at both poles. It is reddish or purplish with white tubercles and grows to about ten centimetres in diameter. The brittle, limy test is rigid and divided into five ambulacral areas separated by five inter-ambulacral areas. There are two rows of plates in each of these areas, making twenty rows of plates in total. The test is covered in spines each articulating with a tubercle. There is a dense covering of secondary spines and a smaller number of longer, primary spines, carried on each second or third ambulacral plate. The spines are blunt ended and usually white with purplish tips. There is a radially symmetrical pattern of holes in the ambulacral areas through which the tube feet emerge. On the buccal plates round the mouth on the underside are pedicellariae, defensive organs like minute pincers, each with two lateral teeth and one terminal tooth. It typically reaches a diameter of 15–16 cm (5.9–6.3 in), but has been recorded to 17.6 cm (6.9 in).