These yellowish shelled clams with long red tentacles live well back in cracks, crevices and small caves fairly deep on the steep seaward reef, most commonly at depths greater than 40m. They are commonly referred to as "electric clams," because when you shine a light at them back in their dark holes, it looks like repeated bright white electric arcs are being emitted by the clam. In fact, the arc is simply a white edging to the mantle cavity that waves back and forth and reflects light from the flashlight back when it is in the correct position.
The white edge to the body cavity that reflects back light and looks like an electric arc.
Created 13 February 2019