Original taxon: Trochus dubius var. “spongiarum”. It differs from Call. zizyphinum by the size, or by the number of spiral cords, but firstly by the absence of granules on the apical whorls. Here is the original description:
 
« Test thin; first whorls smooth, without granulations, the other ones provided with a supersutural bead and three well marked decurrent furrows. The base of the last whorl is furrowed by numerous concentric cords. […] This variant, very characteristic, is found in the sponges of the Gulf of Gabès. […] Zone of Laminaria. Very rare at La Franqui. » – Bucquoy, Dautzenberg & Dollfus: Les mollusques marins du Roussillon Tome I, Paris 1885, p.353.