Clamshell

A clamshell is the two-part hinged shell of many bivalve mollusks, consisting of left and right valves connected by a hinge. Shells are secreted by the mantle and composed mainly of calcium carbonate, with an outer organic periostracum and an inner nacreous layer. When the adductor muscles contract, the valves close to protect the animal; when relaxed, they open for feeding and movement. Hinge teeth and muscle scars align the halves.

In life, clams and other bivalves use the shell for protection and to prevent desiccation. They feed by filtering water through their siphons. Shells grow in growth rings that indicate age and environmental conditions; shapes and ornamentation vary by species and habitat, ranging from smooth and rounded to elongated or sculptured.

Beyond biology, clamshell refers to hinged enclosures and devices with a two-piece design. Clamshell packaging uses two rigid plastic halves hinged together to enclose products for shipping and display. In electronics, the clamshell form factor describes devices with two rigid halves joined by a hinge, such as flip phones and some laptops, prized for portability and protection when closed.

Etymology: the term derives from the resemblance to a clam’s two-valved shell. In general usage, clamshell denotes both natural shells and manufactured hinged enclosures or devices that mimic this structure.