The Green Sea Urchin, Psammechinus miliaris, is much smaller than its more familiar relative, the Edible Sea Urchin. Growing to about 4cms in diameter, it is more often found under stones than out in the open. The test (shell) is green when cleaned as are the spines although the latter have violet tips. With the beak-like mouth on the underside, it browses rock surfaces for food.
The foreground shows the spiny arms of the Common Brittlestar, Ophiothrix fragilis
North Sea. St. Abbs Marine Reserve