Neithea from the Mt. Laurel Formation

While some internal molds of Pelecypods are tough to figure out what genera made them, this one was easy for me to identify. It's an internal mold of a Neithea shell. It is easy to recognize because of the inequal valve sizes and the strong radial ribs that are visible. It reminds me a little of a scallop and is indeed a member of the Pectinidae.

Right valve

Left Valve

Anterior

Left profile

Posterior

Right profile

I have specimens of Neithea from Texas that are of the external shell but I haven't yet got around to posting them. For now, enjoy this Google images search for Neithea.