Light (A, C) and scanning electron (B, D-I) micrographs of Difflugia lucida. (A-C) View of many specimens to illustrate variability in shape and size of the shell. (D) Broad lateral view illustrating smooth shell surface. (E) Apertural view to show elliptical aperture. (F) Lateral view to show compression of the shell. (G) Broad lateral view of aperture to show surrounding and irregularly arranged particles of quartz, giving to it a rough outline. (H) Portion of shell to show arrangement of flattish particles to give a smooth surface. (I) Detail of organic cement network.