Light (A) and scanning electron (B-I) micrographs of Arcella rotundata. (A, B) View of several specimens to illustrate variability in shape and size of the shell. (C-D) Apertural view of two specimens. (E) Latero-apertural view. (F) Dorsal view. (G) Lateral view. (H) Close up view of aperture showing the bordering lip. (I) Portion of shell surface to show arrangement of organic alveoli and numerous small pores.