Shell very solid, heavy, globose, equivalve, roundish in form, with an umbo prominent and bent anteriorly, valves adorned by about 20 big radial ribs wider than the interspaces, crossed by concentric lines that often make some nudules on the ribs. The internal margin of the valves is denticulated. The ground colouring pattern is dark brown with irregular, dirty white spots. The periostracum is dark yellow in colour. Some varieties in form such as: trapezoidea, elata. sulcata and other ones, have no taxonomic value, as well as some varieties in colour as: pallidior. turgida and so on. The maximum measures reach 30 mm in diametre. The very young shells (up to 1 mm) can be confused with R jozinae juvenile shells, but making a comparison, it can be noted a different solidity of the radial ribs and a more prominent umbo in jozinae.

Habitat: it lives in rocky bottoms, sometimes fixed by its byssus, even at some tens of metres depth.
Distribution: common all over the Mediterranean, missing in the Black Sea. In some localities it can be found plentifully so that it is put up for sale on the markets (Taranto - Apulia - Italy).