In earlier posts I have talked about some of the types of holes made by sea creatures in rocks, stones, shells, and wood on the seashore. Here are some photographs of holes made by the rock-boring species of bivalve mollusc known as the piddock (Pholas probably dactylus) in freshly revealed beds of clay dating from around 10,000 years ago, and hitherto buried beneath peat and sand at Broughton Bay on the Gower Peninsula in South Wales.

Fragile empty shells are visible in many of the burrows. It is difficult to tell whether the shells are ancient or modern but I found no evidence of living specimens. It is tempting to speculate that the holes were made prior to the clay being buried by the overlying peat. The peat was formed when sea levels dropped and the shoreline receded many thousands of years ago. The pictures show the holes exposed in both horizontal and vertical surfaces of the clay.

Some of these images may have been featured in earlier posts.

15 Replies to “Piddock holes & shells in clay”

  1. Thank you, Hamish. The last time I saw any living piddocks in their burrows was at Lyme Regis some years ago. I mostly see just the remnants of their existence and activities, as in these pictures.


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