Sea urchin shell.

For Tiny Tuesday hosted by Nickimags888.
I grabbed this tiny shell off the sea bed while on holiday in Turkey some years ago.
Not only did I get a couple more but as a special gift I got a discarded urchin spine stuck in my finger.
After a few beers, the owner of the place we were staying at, offered to dig it out with a knife.
It didn't work, so after soaking it in olive oil and wrapping it in a plastic bag overnight he managed to remove it.
One of the guests, an English doctor, said afterwards it would have been interesting to have left it in to see what would have happened.
There was a lot of laughter on that holiday.