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(Linné, 1767)

Description (shell):
Shell thin and brittle, obliquely oval, both valves strongly convex; umbones anterior to midline, anterior margins obliquely truncate above a broad pedal gape; posterior gaping widely. Sculpture of fine concentric lines, raised as coarse ridges anteriorly, where they intersect with fine radiating ribs to form sharp tubercles. A median groove extending from umbones to ventral margin separates the two areas. Umbonal reflections broad, closely applied to, and extending just posterior to, the umbones; a small mesoplax present. Pallial line and adductor scars clear, pallial sinus deep, extending to beyond midline of shell. External median groove visible as a distinct ridge. Apophysis slender, slightly broadened distally, extending no more than one-third of distance to ventral margin (Z. crispata-drawing 2).

Up to 90 mm long.

Dull white, periostracum light yellowish brown. Inner surfaces white.

The animal is of red-brown colour. Long siphons, these have the orifices fringed with branched filaments. The siphons are united nearly to the openings and covered by a sheath; the animal is somewhat club-shaped. (Z. crispata-drawing).

Bores into peat, clay, and soft rocks, rarely into waterlogged wood, from the lower shore into the shallow sublittoral.

Distributed from Norway to the Bay of Biscay (Distr. Z. crispata).

Zirfaea crispata