Pigmentation layout on Mediterranean (on left) and Atlantic (on right) forms is virtually identical.
The whitish, translucent flesh is extensively covered by various shades of grey to brown-black pigment dorsally with opaque white spots.
Apart from the snout which is darkest laterally, the sides of the body are pigmented less intensely than the dorsum, and there is a translucent, whitish, slender triangle dorso-laterally (1) that tapers towards the posterior.
On darker specimens, such as these, the surface pigment may partially obscure the opaque, white anterior pedal gland (2) .
The whitish mantle is often brownish near its edge (3) and greyish where it forms the posterior of the mantle cavity roof (4) .
There is an opaque, white, dorsal patch behind each eye.
The foot on both forms can be translucent white with some opaque white spots and, dorsally, pale grey and/or pale-brown shading, but some Mediterranean specimens have distinctly yellow soles against which plentiful opaque spots show clearly; see images 40 Rissoa membranacea. and 41 Rissoa membranacea.
38 Rissoa membranacea.
