boring clam

There are two kinds of clams that bore into sedimentary rock, and I don't remember the names of either one. Plus, [broken record] No Book Access...

in shallow water. 1...

2...

3...

...and I touched the third one to make it withdraw so that I could safely excavate a little. I didn't know what they were, in fact. Now, I couldn't get the sand out of the way well enough for a decent picture, but there's the top of the shell protruding from rock. I was gentle with it because I know the shells of dead ones, at least, aren't very strong, but I got the impression that it had pulled the shell down into its rock so that no predator could pry it open without destroying the shell. How terribly clever!