Light (A, B) and scanning electron (C-I) micrographs of Sphenoderia fissirostris. (A-C) View of many specimens to illustrate variability in shape and size of the shell. (D) Broad lateral view. (E) Narrow lateral view. (F) Apertural view to illustrate shape and arrangement of apertural-plates and structure of the collar. (G) Close up lateral view of aperture showing linear aperture and conical collar. (H) Detail of apertural part of the shell to show large, oval shell-plates in the first two rows. (H) Detail of aboral region to show smaller, oval or circular shell-plates on the shell apex.