Fig. 3

Distinguishing morphoanatomical characteristics of the shell and head-foot . External, species-specific, morphological features include: a the lengths and arrangement of primary (1°), secondary (2°) and tertiary (3°) periostracal bristles; b the architecture and diameter of the columella where arrowheads indicate the columellar fold (absent in A. boucheti) and; c head-foot coloration (arrowheads indicate neck furrows). Abbreviations: CT Cephalic tentacles; Ft Foot; Mo Mouth; PF Pallial fringe; Sn Snout