caption: The image shows a group of four different types of clams on a black background. At the top of the image, there is text that reads "Unio Flexuosa Raffinesque, 1820, Type USNM 84047". The clams are arranged in a collage-like formation, with each one having a unique shell shape and color. The shells are of various sizes and shapes, with some having a smooth, glossy finish and others having a more rounded shape. The colors range from light brown to dark brown, and the shells have a glossy sheen.