Skeneopsis planorbis

(Fabricius O., 1780)

Description (shell):
Shell very small, semi-transparent, glossy; a helicone of four tumid, rapidly expanding whorls; spire depressed; umbilicus deep, wide. Sculpture of irregular, sinuous growth lines, sometimes with fine spiral lines on upper surface of last whorl. Aperture almost circular, sinuous in profile; with a thickened peristome.

Up to 0.8 x 1.5 mm.

Red-brown or pale horn coloured, with pale operculum.

Snout short and bifid; cephalic tentacles long, cylindrical, bluntly rounded, finely setose at the tip. Mantle edges without pallial tentacles. Foot with a posterior mucus gland on sole; operculum horny, a concave spiral, with central nucleus.

On fine algae and in coralline pools from MTL to 70 m. Abundant in summer, rare in winter. Often found suspended from weeds or water surface by mucus.

Widely distributed, from Azores to Arctic. On all suitable British shores; absent from eastern shores of North Sea and from Baltic (Distr. S. planorbis).