caption: The image shows a group of four different types of oysters on a black background, with the text "Unio Microstictus Heude, 1877 USNM 472373" at the top. The oysters are arranged in a collage-like formation, with each oyster having its own unique shape and texture. The shells of the oysters vary in size and color, ranging from light brown to dark brown. The text is written in a bold, white font, making it stand out against the dark background.