When a relaxed and killed animal is removed from the shell, the translucent mantle is covered in black pigment which can be rubbed off.
Pigment does not cover the white, elongate left (1) and right (2) columellar muscles which approximate to the form and function of the encircling horseshoe shaped pedal-retractor muscles of limpets (Patellidae).
The mantle rim (3) is not covered in black pigment. Its thin upper layer is more yellowish than the thick lower layer of inflated connective tissue cells that block the entrance to the mantle cavity,

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