The Giant Bittersweet, Glycymeris americana (DeFrance, 1826), is the largest species of the Bittersweet family Glycymerididae found in the western Atlantic Ocean, attaining up to 5 inches in size. Shells of the species may be found along the beaches of Sanibel and Captiva after storms. Bittersweets feature a shell hinge that consist of a curved row of a large number of chevron-shaped “teeth” (top of left-hand photo). The hinge teeth in bivalves ensure that the two shell parts, or valves, do not slide past each other in opposite directions when a predator makes an attempt to gain access to the animal inside.
The Giant Bittersweet, Glycymeris americana (DeFrance, 1826).