English: Photograph of commercially-sold Sydney rock oyster (Saccostrea glomerata) on a half shell (bottom valve) with two views of empty shells (also lower valves, inside and outside). Image shows three shells, top-down view on a matte white background. Inside of shell is white, with a wavy black margin. The external shell surface is encrusted with algae, barnacle shell remnants, and marine worm tubules.