How do teeth and sockets connect the shells of articulate lamp shells?

In articulate lamp shells, the two valves are connected by a specialized hinge mechanism consisting of teeth and sockets that allow the shell to open and close.

The articulating teeth are located at the angles of the delthyrium on the ventral valve and may be supported by vertical dental plates. These teeth function by fitting into corresponding hinge sockets, which are situated on the dorsal valve between the inside shell wall and a socket ridge.1

This mechanical connection serves as a pivot point for the valves. When the animal feeds, the contraction of diductor muscles pulls the dorsal beak forward, causing the shell to rotate on the line formed by these hinge teeth. Conversely, the adductor muscles work to close the valves.1