Orobitella floridana (Dall, 1899) has an apparently contradictory vernacular name, as the shell rarely reaches beyond 16 mm (about 0.6 inch) in length. But all is relative in nature: the species belongs to the family Lasaeidae, a group of clams noted for their very small size, with many members of the family reaching only about a couple of millimeters (about 0.08 inch). The Giant Montacutid has an oval, inflated, white shell with a sculpture of concentric lines that become stronger on the anterior (narrower) end. The species is not commonly found on the beaches of Southwest Florida.
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The Giant Montacutid, Orobitella floridana, from Sanibel. Photos by José H. Leal.