Help with Identification

[maggot]

I have what appears to be a clam or something. It is brown. It came from a rock that I have had a year now but I only found him recently. It has a white/Clear mouth like a thin or wavey lining of some sort. It looks like a clam shell except the shell is shaped more like a U in size, not a perfect circle. Like I said it is coming out of a rock and it is definately alive. About an inch in depth and half inch wide.
Thanks for any Help and please let me know if it is ok to keep in tank
Thanks
John :jumping:

 

[reefiness]

its fine you wont even know it is there and you dont need to care that it is there. all the Lr comes with critters like that and il bet that you have well over 1 of those clams in the Lr you have and everyone else had something like this as well, so dont worr about it. that is one of the reason your paying $5 a lb on a ROCK i mean you can get a nice steak cheaper then that. that is the "L" in LR.

 

[cain420]

i love free stuff!