Left: Live specimen in water, shows well the orange-red ground-colour with a bronze-like lustre caused by the interior nacre shining through the thin shell. Faint growth lines (1) are visible, and a few irregular, stronger ones (2) where a previous lip was damaged. A few very faint spiral striae are visible on the body whorl (3), and areas of slight greenish iridescence are present (4).
Right: Same specimen, vacant and dry. Many features are lost as the dry shell is less translucent and the periostracum damaged.
It is perhaps more than coincidence that another habitual utilizer of Laminaria, Patella pellucida flic.kr/s/aHsm91fKaF , also exhibits iridescence and, presumably, benefits from it in some way, perhaps by distraction or resembling iridescent algae.

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