« Tumid, thick, of a dark brown, with sometimes obscure radiations outside, paler (but still brown) within ; the concentric ridges are smooth, round, without interstitial spaces, but generally obsolete from the middle to the ventral margin. »   G. B. Sowerby: Thesaurus conchyliorum vol. II, London 1855, via BHL.
 
A difference with sulcata is given by the concentric sculpture: often absent or only present in the first stages of the shell, and vanishing towards the margin on adult specimens, this sculpture is composed of commarginal beads that become wider with the age, as it is shown on the drawing above.

« Testa cordato-trigona, inferne rotundata, compressa, lutea aut fusca, levi; costis concentricis frequentibus, obsoletis, margine acuto, integro. »   F. J. Cantraine’s description of Astarte affinis in “Diagnoses ou descriptions succinctes de quelques espèces nouvelles de mollusques”, Bulletins de l’Académie Royale des Sciences et Belles-Lettres de Bruxelles vol.2(11), Brussels 1835, p.399.