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(O.F. Müller, 1776)

Pea Urchin

Description
Colouration
Test elongated, often somewhat pointed at the anterior end, up to 15 mm in length. Mouth in the middle on the under side, anal opening posterior to the mouth. Colour greyish or greenish. On preservation or when hurt it turns green.

Ambulacrum
Ambulacral plates and sphaeridia
Ambulacral plates simple. On the upper side the ambulacra are usually widened ("petaloid"), forming a flower-like figure. Dental apparatus strongly developed. Sphaeridia present, but placed in grooves in the test so as not to be externally visible (E. pusillus test).

Spines
Spines quite small, forming a close, almost velvet-like coat. Spines of two sorts, somewhat longer, pointed ones, and smaller ones ending in a serrate crown.

Pedicellariae
Pedicellariae small and inconspicuous, mostly only tridentate, ophicephalous and triphyllous.

Habitat
This species prefers a bottom of coarse sand or gravel, from the lower tide limit to depths of 1250 m.

Distribution
In the North Sea, the species is common everywhere on a coarse sandy or gravelly bottom. Elsewhere it is distributed from Finmark to the Sound and the western Baltic, from Iceland to the Azores, Cape Bojador and the Mediterranean.

Pea Urchin (Echinocyamus pusillus)