Help IDing Please

[BPolyniak]

This little guy is embedded into a liverock that I bought. Could someone tell me what it is. Thanks in advance.

[MikeP]

Looks like some kind of small clam or oyster, likely a harmless filter feeder.

[malofish]

I've had two simmilar looking clams in my tank for about a year, ones about the size of a dime and the other's half the size, pretty cool to watch from time to time

[Instar]

Those are oysters. Great water filters! Good to have.