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(Pennant, 1777)

Common Heart Urchin

Description
Test
Test somewhat sloping anteriorly, the greatest height about midway between the apical system and the posterior end, up to 90 mm, usually yellowish in colour.

Ambulacrum
Frontal ambulacrum rather deeply sunk, the furrow continuing from the anterior end to the apical system. Besides the subanal fasciole an inner fasciole is present, surrounding only the frontal ambulacrum and the apical system. No dental apparatus. There are no gills or gill-cuts at the peristomial edge of the test. Sphaeridia present, not in grooves.

Tube-feet
Tube-feet confined to the ambulacra (E. cordatum test dorsal, E. cordatum test ventral).

Spines
Spines of various length, with longer spines above the ambitus and small spines forming the fascioles.

Pedicellariae
Globiferous pedicellariae have only been found in specimens from the Mediterranean. They have a thick brownish head and a thick stalk with a whorl of freely projecting rods. The blades have 5-6 teeth along each side of the terminal opening. The tridentate pedicellariae have leaf-shaped blades, with the edges of the lower part irregularly serrated. The triphyllous pedicellariae have a series of broad teeth inside the edge (E. cordatum pedicellariae).

Habitat
The species lives mainly on sandy bottoms, buried ca., 15-20 cm deep in the substratum. A channel leads from the hole to the surface of the ground. The channel is strengthened by slime, secreted by the spines glues. It is found from the low tide mark down to ca. 230 m.

Distribution
The species is very common in the whole North Sea. Elsewhere its distribution is very wide, the forms living at S. Africa, Australia, New Zealand, Japan etc. being scarcely distinguishable from the European form. In the European seas it occurs from Tromsö to the Sound on the Scandinavian coasts, and from the British seas to the Mediterranean. It is not known from Iceland or Greenland.

Common Heart Urchin (Echinocardium cordatum)