Psammechinus miliaris

(Gmelin, 1778)

Shore Sea Urchin

Test rather depressed, often subpentagonal in circumference; up to 50 mm in horizontal diameter. Colour greenish, both the test and spines, but the point of the spines usually violet.

Apical system rather small. Buccal membrane usually closely packed with thick plates, which bear numerous pedicellariae, but no spines. Three pore pairs in each ambulacral plate (P. miliaris test).

Test closely set with spines of nearly equal size, the primary series not very conspicuous. On the naked test, however, the series of primary spines are fairly distinct. There is a primary spine on every ambulacral plate.

Globiferous pedicellariae small, usually very numerous, with outer parts of the blade rather broad and open. The edges thin and not connected by cross beams on the inside. A series of teeth along each side of the blade (P. miliaris pedicellaria). Tridentate pedicellariae rather coarse, with broad, leaf-shaped blades.

It is essentially a littoral form, but is found till depths of 100 m.

In the North Sea, the species is common around all coasts. Elsewhere it is distributed from Iceland to Morocco and the Azores, but it is not found in the Mediterranean. It does not occur at Greenland or at the Atlantic coast of America.

This species can form hybrids with Echinus esculentus. It can be confused with Paracentrotus lividus and Strongylocentrotus droebachiensis.