Length 16mm. Extracted tail valve (viii) at larger scale. Dorset, England. April 2017.
Intermediate valves have a protruding posterior beak visible from above (1) and laterally (2). On live specimens, when the white articulamentum is hidden by the girdle, the tail valve (3) looks tiny relative to the other valves, and its mucro (4), placed posterior of centre, barely protrudes.
The jugal area (5) of the tegmentum is often coloured distinctly different from the rest of the valve; black on this one with some red on it and adjacent area.

KEY ID FEATURES : 01 Acanthochitona fascicularis