Christmas morning I noticed one of my rocks shifted a little. So I went and moved it back, I picked the rock up and was looking at it when I seen this. Looks kinda like a clam shell, but dont think so, maybe even a scallop. It does'nt seem to like lights to much, it opens up at night. I have to sneak up to it befor it will close up, and as soon as I hit it with some light. Its connected to the rock also. Here is a few pics of it, first one its closed, and second one its opened a little.