(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.
Size:
Up to 0.8 x 1.5 mm.
Colour:
Red-brown or pale horn coloured, with pale operculum.
Animal:
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.
Habitat:
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.
Distribution:
Widely distributed, from Azores to Arctic. On all suitable British shores; absent from eastern shores of North Sea and from Baltic (Distr. S. planorbis).