Steromphala cineraria (Linnaeus, 1758)
Barents Sea to Canarias, Azores to Mediterranean, Black Sea. Rare in the east, common in the north.
Grazer and deposit feeder on rocks and algae in the very shallow infralittoral, down to about 130m deep (MarLIN).
Original taxon: Trochus cinerarius.
Synonyms: electissimus, eltoniae, inflatus, strigosus…
 
Shell umbilicate, conoidal, very thick and solid, cinereous, yellowish to grey in colour, with a pattern of radial alignments of reddish-brown to purple dots. The five to six whorls are rather flat, the spire more or less elevated. Spiral sculpture always marked, crossed by minute prosocline growth marks. Last whorl angled at the periphery. Base hardly convex. Columella straight. Umbilicus narrow and deep.

Above: a specimen collected in Malága area, Andalucia, S. Spain. 9,2mm.
If the labial margin and the growth marks are very prosocline, the radial pattern usually changes inclination several times in the same specimen.
A specimen from the Oosterschelde, pictured on the shore south of Westkerke, Tholen, Zeeland, SW. Nederland. Original picture provided by v_s_ for iNaturalist – (CC BY-NC).
Ouessant Island, W. Brittany, NW. France. Original picture provided by F. Roche for iNaturalist – (CC BY-NC).

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