Clams, quahogs, oysters and mussels are probably the most well known bivalves, mollusks with two hinged shells, but there are many others. Another example is the jingle shell (Anomia simplex). Interestingly, despite having two hinged shells, it is often only the top shell that is found washed up on the beach. The bottom shell is less frequently discovered because it often remains attached to whatever substrate the animal was growing on. 

The upper shell is convex and is movable during filter feeding. The bottom shell, on the other hand, becomes fixed in place onto whatever the organism attaches and takes on the shape of whatever it’s growing on. If you were to find one of the bottom shells, however, you would notice that it tends to be smaller and flatter than the top shell, and has a hole near the hinge. It is through this hole that the animal passes its byssus, threadlike attachments that allow the jingle shell to cling securely to rocks and other hard surfaces. 

Contrasting with the thick, solidness of quahog shells, jingle shells are thin and translucent. Despite this, these shells are very strong and are capable of withstanding many environmental pressures. Jingle shells can also range in color from almost white to yellow to orange to a silvery black. 

Jingle shells are mainly found along the Atlantic coast of the United States from the Caribbean to Cape Cod, but have been found as far north as Nova Scotia. The origin of the nickname “jingle shell” refers to the sound a collection of these shells makes when carried in a container and mixed around, producing a “jingle.” This jingle sound can also be heard when waves wash over beaches strewn with these shells. Another common name for jingle shells is “Mermaid’s Toenails.” Despite the superficial resemblance that some of these shells have to large toenails, I’ve always been amused by this name since mermaids have fins instead of legs, feet and toes, and therefore have no toenails.