16 Berthella plumula COMPARISON images of juvenile Trivia arctica (left, Macduff, Scotland. © C. Rickard) and T. monacha (right, North Wales).

16 Berthella plumula COMPARISON images of juvenile Trivia arctica (left, Macduff, Scotland. © C. Rickard) and T. monacha (right, North Wales).

Coffee bean-shaped shell almost as high as body length, covered by retractable whitish mantle with white or yellow papillae and varied dark marks. When active, mantle extends at anterior as an enrolled respiratory siphon.

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