Priceless Paintings from W7

Serious questions – what are those?

(You can click the image for a larger version)

We found them attached to a log, sitting on a Welsh beach at low tide. At first glance, we thought mussels, but on second glance we were no longer so sure: First, each shell is attached to the log with a leathery, maybe 5mm thick, life line. Second, the shells open and some gill-like tentacles come out. It wasn’t clear wether these breathe – although they looked like gills, I find it more likely that they normally fish for microbes when submerged under water, and just kept moving out of some irresistible instinct.

Any intelligent guesses -or hard facts- will be most gratefully received.

Out and About Wales;