Posted: Mar 3 2016, Rusty:  They are common to abundant on both sides of Florida, usually wash up with arks and other coarse and heavy bivalves. Sanbel island is only place I have seen that have both hinges attached. Easy to confuse with frond oyster and small jewel boxes especially when lower halves are attached to hard surfaces but some forms of young oysters can closely resembles kitten paws. Fossil forms are abaduant and once in a while I will find fossil ones that's bigger and thicker than modern species.