There are a variety of fossil and Recent taxa in the Juliidae.  If known only from the shells, they are often misidentified as lepton clams.  Abbott (1974) lists four species for the U.S.

A few other gastropods may be loosely described as bivalved.  The most peculiar is probably Rothpletzia, originally described as an Oligocene rudist.  It was a capulid gastropod that secreted an extensive base.

    Dr. David Campbell
    "Old Seashells"
    Biology Department
    Saint Mary's College of Maryland
    18952 E. Fisher Road
    St. Mary's City, MD  20686-3001 USA
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"Mollusks murmured 'Morning!'.  And salmon chanted 'Evening!'."-Frank Muir, Oh My Word!