Fig. 7 in Muscle attachment scars in helcionelloids from Denmark cast light on mollusc evolution in the Cambrian

Fig. 7. Muscle scars on internal moulds of Palaeozoic bivalves. A. Left valve of Babinka Barrande, 1881, from the Lower Ordovician of Öland, Sweden (after Soot-Ryen 1969, length of specimen about 20 mm). B. Left valve of Palaeoneilo musculosa (Knod, 1908) from the Devonian of Bolivia (after Babin and Farjat 1994, length of specimens about 20 mm). C, D. Sketches in apical view showing asymmetry between pedal muscle scars (black) on internal molds of Palaeoneilo musculosa between left and right valves, and variation in pattern of pedal muscle between specimens (after Babin and Farjat 1994). Abbreviation: am, anterior adductor muscle scar.