Light (A) and scanning electron (B-I) micrographs of Corythion dubium. (A, B) View of many specimens to illustrate variability in shape and size of the shell. (C, D) Apertural view of two individuals showing general shape and haphazardly arranged shell-plates. (E) Dorsal view. (F) Lateral view showing shell compression and oblique aperture. (G, H) Close up view of aperture to show its oval shape and surrounding apertural-plates, each of them with sharp, median tooth. (I) Detail of shell surface showing arrangement of shell-plates.