Bivalve ID?

[Phyl]

I have this bivalve that wanders my tank. I most recently found him hanging from the glass. The picture is taken through the glass on the front of my aquarium and the bivalve is attached to that front glass. You're looking at the 1/2 of his shell that is pressed up against the glass (he was laying flat against the glass).

http://www.schiavone.us/reef/p2171595.jpg

He's since moved off of the glass to a piece of rock that is sitting on the right hand side of my tank in a hole that is facing the left hand side of my tank so getting a new picture of him would have to wait until he's moved again since any picture I take now would put him about 3 1/2 feet away from the camera.

Any help would be greatly appreciated!

[rshimek]

Hi,

It is likely an ark shell, but it may not be, I can't tell for sure. :D One needs to see images of the hinge region of the shells to be able to identify them, and that is not visible in your image. Also, it it helps to get several different angles on the shell in different images.

Anyway, tentatively, it may be an Arca. These are relatively common hitch hikers as small animals on live rocks.