Lyme 8j – Fragments of shale with holes made by seashore creatures, resting on bright green filamentous algae, at Lyme Regis in Dorset, England.
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Jessica's Nature Blog 
Do you know whether the seashore creatures made these holes while the shale was still forming, or whether they were made more recently? I’ve seen shale fragments with holes like this in the states, too, though I can’t remember whether that was in Michigan or Florida—quite different regions of the U.S.!
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These rock holes, in this photograph, were made in recent times by a marine boring mollusc called a piddock. They were not made when the sediments of the shale were accumulating prior to transformation into rock. Piddocks can still be found living in the rocks on this very same Monmouth Beach in Lyme Regis. It is also possible to find trace fossils (ichnofossils) in rocks of holes or burrows or tunnels made by marine worms, clams, and crabs – formed at the time the sediments were still soft. However, in these kinds of fossils, the spaces left by the activities of the burrowing animals are almost inevitably in-filled with sediment of a slightly different composition at a later date. You can find trace fossils like this on Monmouth beach too.
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This is amazing! Looks like a multipart tool for stripping down a motorcycle. Plus random washer. But why do the piddocks bore the holes, Jessica? For food or roughage? To get to the other side? RH
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Piddocks bore holes in rocks to custom-make a safe shelter in which to live – a place where predators cannot reach them. I’ve heard they can never leave their burrow because they start making it when they are small and make it bigger as they grow. Consequently the entrance hole tends to be narrower than the adult shell. They don’t eat the stone. They get all their nourishment by filtering the water they suck in. They blow out all the waste they create.
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