The mantle of this specimen has a lilac-grey ground colour (never found on Lamellaria latens). The dorsal surface of the mantle lobes, reflected and fused over the shell, has a dense, varied colour pattern which conceals almost all its ground colour.
The ventral surface of the mantle has just the ground colour with no pure white opaque marks like those found on L. latens.
The translucent head is coloured as the ground colour of the mantle with no pure white, opaque marks. When not in feeding position, the head is flat and rectangular with long, slender, smooth cephalic tentacles on the anterior corners, and no visible snout projecting between the tentacles. On the ventral face of the head there is an opening to a sac containing an inverted white proboscis, the straight, white, folded edge (1) of which may be visible when the translucent head is well extended. When ready to feed, the proboscis is engorged and everted from the opening (see images 18 & 19 ). The buccal mass and radula are within the proboscis. Length 19 mm. Llŷn Peninsula, Wales, March 2016.