found something new on live rock what is it.

[reefcrazy]

it looks like a clam it opens up and has two holes like a clam were it takes in food i guess it is like 1/2 of a inch long, so it's hard to tell if it's a real clam or something else i found two of them and they are stuck to the live rock. does any one know what they are. i tried getting pics but they are realy small and my cheap camera doesn't take good pics when i get close.

 

[reefcrazy]

well that's kind of what the shell looks like but from the front when they open they look like a clam except that they don't have the beateful colors of a clam they are only white.