Apart from the mantle dorsally, the whole animal is translucent white without tint of any other colour, apart from occasionally discernible viscera, or dorsal mantle marks visible through the translucent mantle from below. Small patches of opaque, pure white on the head and/or underside of the mantle are diagnostic of this species.
The mantle lobes extend beyond the shell to create a peripheral cavity which covers the head and foot, but the true respiratory mantle cavity containing a bipectinate osphradium and large, unipectinate ctenidium is hidden within the shell, above the head and close to the respiratory siphon with an opening restricted by the shell rim and mantle.
The straight-sided foot is rounded at both ends.
Length 10 mm. In Laminaria holdfast, LWS, Menai Strait, Wales. February 2011.

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