Please ID . ..is it a bivalve

[Critter]

I didn't know this was there until I turned this peice of base rock over. It wasn't there when I put the rock in, so must of came in as a hitchhiker.

 

[mbbuna]

i cant tell you exactly what it is but it look's to be ether a scallop or oyster

 

[Julio]

loks like an oyster.

 

[LeftCoast]

Definitely an oyster. Almost looks like a pearl bearing species.

 

[AngelReefer]

oyster

 

[Critter]

Thanks guys.