Initially, the apophysis follows the coiling of the shell but it projects ventrolaterally during the final ontogenetic stage of macroconch development. 33 ventrolateral ribs are present on the outermost whorl of microconchs corresponding to 42 mm diameter (CPC-1223), while macroconchs have 37 ventrolateral ribs at 38 mm diameter (CPC-1410).
Source: wiktionary