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.
The Giant Montacutid, Orobitella floridana, from Sanibel. Photos by José H. Leal.