flat-topped piddock

clam

Also known as: Penitella penita

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Last updated

June 26, 2026

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The flat-topped piddock (Penitella penita) is a marine bivalve mollusk belonging to the family Pholadidae. These mollusks are uniquely adapted for boring into hard materials such as rock, shells, and clay. The flat-topped piddock, found from the Arctic Ocean to Lower California, bores into materials like hard clay and sandstone, sometimes causing damage to man-made structures. Some species within the Penitella genus also bore into the shells of other mollusks, like oysters and abalone. Piddocks feed on microscopic organisms in the water, primarily phytoplankton.1

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piddock
The flat-topped piddock (Penitella penita), from the Arctic Ocean to Lower California, bores into hard clay, sandstone, and cement, sometimes damaging man-made structures. Some Penitella and Diplothyra species bore into the shells of other mollusks, particularly oysters and abalone.
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The flat-topped piddock (Penitella penita), from the Arctic Ocean to Lower California, bores into hard clay, sandstone, and cement, sometimes damaging man-made structures. Some Penitella and Diplothyra species bore into the shells of other mollusks, particularly oysters and abalone.
Read More