Rough Piddock

Appearance

The anterior portion of the shell, while higher and more globose than the posterior portion, is not nearly globular. In this species, the anterior rasping portion comprises about half the shell and is separated from the posterior nonrasping portion by a oblique groove (photo). There is no protoplax but there is a mesoplax. Both valves have a myophore. The posterior shell tapers a bit but not to such an extent that it resembles a bird's beak. The white valves gape at the posterior end for the thick, united siphons. The siphons cannot be withdrawn into the shell. The valves have coarse concentric ridges; on the anterior end these ridges often have filelike projecting spines or teeth which are used for digging. The anterior end of the valves also often has projecting spines or teeth on the valve margin, and also has a gape through which the foot protrudes. This gape is not closed by a callum even in older individuals. the periostracum is brown and may be seen extending onto the base of the siphons. The siphons have small chitinous spots on the surface. The interior of the valves is chalky with well-defined muscle scars. Length up to 15 cm.

Naming

Zirphaea gabbi
Zirphaea pilsbryii