Fig. 9 in Muscle attachment scars in helcionelloids from Denmark cast light on mollusc evolution in the Cambrian

Fig. 9. Muscle scars on internal mould of the rostroconch Ribeiria Sharpe, 1853, in lateral view. Both the anterior and posterior median muscle scars lie across the median dorsal plane of symmetry, the former attached to the transverse pegma preserved as a deep cleft on the internal mould. The posterior scar is a uniform attachment area, often ornamented with transverse growth lines, unlike the multiple small scars of Eotebenna (based on Pojeta and Runnegar 1976; Polechova 2015).