Light (A) and scanning electron (B-I) micrographs of Tracheleuglypha acolla. (A, B) View of many specimens to illustrate variability in shape and size of the shell. (C-E) Broad lateral view of three specimens showing general shape and regular arrangement of shell-plates. (F) Apertural view. (G) Close up view of aperture to illustrate its shape, arrangement of apertural-plates and thin border of organic cement. (H) Lateral view of apertural region (I) Detail of shell surface to show overlapping shell-plates.