Length 26 mm. Dorset, England. April 2017.
Two images of same specimen.
Left
Foot, head and hood expanded; colour saturation diminished.
Pallial cavity/groove closed by mantle-fold and foot; gills concealed.

Right:
Foot, head and hood contracted; colour saturation increased.
Pallial cavity/groove and gills exposed.
Narrow mantle-cavity/groove runs around the whole animal. It contains about fifteen gills on each side in the posterior two thirds only (merobranch arrangement).

KEY ID FEATURES : 01 Acanthochitona fascicularis