Steromphala divaricata (Linnaeus, 1767)
Algarve to Mediterranean, Black Sea.
Grazer and deposit feeder in the very shallow infralittoral.
Original taxon: Trochus divaricatus.
Synonyms: lessoni, marginatus, specialis, varians…
 
« Shell imperforate or narrowly perforate, conoidal, very thick and solid, cinereous, yellowish or green, longitudinally marked with rose-red lines, often oblique or broken into square dots ; spire more or less elevated, its outlines rather convex ; whorls about 6, encircled by numerous lirulae, the upper ones flattened, sutures slightly impressed, but scalariform specimens with deep sutures are frequent ; last whorl rounded at the periphery and on the base ; aperture rounded-quadrate ; outer lip bevelled to an edge, very thick and smooth within ; columella straightened in the middle, pearly ; umbilicus narrow or concealed. » – H. A. Pilsbry: Manual of conchology, structural and systematic vol. XI, Philadelphia 1889, p.207.

Above: the species in L. C. Kiener: Species général et iconographie des coquilles vivantes vol. XII, Paris 1880, plate XLVII.
On beach, south of the river mouth, Le Grau du Roi, Occitania, S. France. 16-19mm. Two differences with rarilineata: the purple blotches are more elongated, quadrangular and close-set, while they are more squared and insterspersed in rarilineata; the basis is flat to convex.
Shape variation.
Left: on breakwater, Skala Sikaminias, Lesvos, eastern Aegean, 12mm. Right: on rocks, Karfas, Chios, eastern Aegean, 14mm. Original pictures provided by J. Trausel & F. Slieker, Natural History Museum Rotterdam, for WoRMS – (CC BY-NC-SA).
Specimens in natural conditions: on rocks under the cliff, La Franqui, Occitania. 13-17mm.
On shallow reef at Ormos Point, Agios Nikolaos, Lasithi, N. Crete. 11mm.
Specimen, photographed in aquarium, collected in tide pool, Xylofágou, east of Larnaca Bay, SE. Cyprus. Original picture provided by D. Kolokotrónis (CY) – (CC BY-NC-SA).
A young specimen from Croatia. 7,5mm.
Original picture provided by P. Ugarković (HR).
– (CC BY-NC-SA) –
Adult on rock just below the surface, Tiha Bay, Cavtat, Dubrovnik-Neretva Comitat, S. Croatia.

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