Light (A, C) and scanning electron (B, D-I) micrographs of Argynnia dentistoma. (A, B) View of many specimens to illustrate variability in shape and size of the shell. (C, D) Broad lateral view. (E) Apertural view. (F) Narrow lateral view. (G) Broad lateral view of apertural region. (H) Close up view of aperture showing its oval outline. (I) Detail of shell surface showing shape and arrangement of shell-plates, and porous structure of the organic cement.