Any ideas????
 

I was wondering if someone could give me an idea of what i have on my rock. I have no picture so i'll try to explain. Most are round shells and one peanut shaped, maybe the size of a dime or nickel, attatched to various pieces of rock. Last night i observed one shell opening up a little at the tip and there was this jet black thing inside. Although i have no idea what it was because you could only make out the dark balck color as the shell was only opened a bit and then later the shell closed. The shells have jagged edges to them. For the life of me i can't figure out what kind of creatures would appear so black. Any ideas????? In fact another shell is open most of the time with the same jagged edges and if i pick up the rock or disturb it, it will close. What could be in these shells?

do you notice any kind of webby substance coming from the shells? If you do they are probably annelid snails.

No webby substance............nothing. In fact on the black creature i could make out ribbed lines across it. It never came out of the shell but the shell was open slighty just for awhile.

Could be some kind of bivalve?

I'm with Beverly

Cheers
Tyler

It's very possible..........thanks. If only i could say for sure what it is. I have several of these shells in my tank which open and close. Interesting!!!