Came on a piece of live rock I bought from the LFS display tank. At first I thought it was just an old fossil, but it opens and closes often and appears to have tentacles inside it. I think I have a least 3 of these on the rock. :?:
It looks like some sort of clam to me. I had a shell that looked similar on my LR though it wasn't alive. If the top half moves indipendanlt of the bottom then it's probibly a clam. Do the tentacles look feathery or are they regular?
Well, if you take a look at the stats of your image, most of the pixels are black. It is an issue with the lighting and exposure setting of your camera.