FIGURES 2A–G. Pisidium dorbignyi, anatomy. A. Siphonal and mantle edge musculature. B. Inner radial mantle muscles, lateral view. C in Anatomical characteristics of two enigmatic and two poorly known Pisidium species (Bivalvia: Sphaeriidae) from Southern South America

FIGURES 2A–G. Pisidium dorbignyi, anatomy. A. Siphonal and mantle edge musculature. B. Inner radial mantle muscles, lateral view. C. Distribution of scars of inner radial mantle muscles. D. Inner view of inner demibranch showing the upper position of brood sac. E–G. Nephridium (11, 13: dorsal view of left and right portions; 12: lateral view). (al: ascending lamellae; as: anal siphon; bs: brood sac; dl: descending lamellae; dln: dorsal lobe of nephridium; irm: inner radial mantle muscles; irms: inner radial mantle muscle scars; ll: lateral loop of nephridium; pa: posterior adductor muscle; pl: pallial line; pss: pre-siphonal; sr1: anal siphon retractor; sr2: retractor muscles corresponding to lacking inhalant opening).