Lateral and dorsal views of tail valve viii under high magnification of Scanning Electron Microscope (SEM). Barents Sea, Arctic. © B. Sirenko.
The unobtrusive, antemedian mucro (1) is encircled by the concentric growth lines. The steep postmucronal slope is straight in lateral profile (2).
Chitons sense the environment through aesthetes (sensory tissue) exposed on small caps on the surface of the shell. On T. marmorea the caps are arranged in an offset grid pattern.

marinvert.senckenberg.science/image-browse/