The Fragile Surf Clam, Mactrotoma fragilis (Gmelin, 1791) is a local clam of the surf clam family Mactridae that may reach about 45 mm (about 1.8 inches) in length. Fragile Surf Clams, as its name indicates, has a thin, but relatively resilient shell, with characteristic ridges on the posterior end. The periostracum, or outer, dark shell layer, is more predominant on the posterior end, and the shell never completely closes in that area.
The Fragile Surf Clam, Mactrotoma fragilis, from Sanibel. Photo by José H. Leal.