Spermatozoa of the gastropodArchitectonica perspectiva Linné differ from those of other molluscs by having a long, transversely banded column interpolated between the base of the nucleus and the axoneme of the midpiece. The sperm head consists of a weakly helical nucleus (length 15µm) capped apically by a small, ovoid acrosome. Within the midpiece a cylindrical, mitochondrial sheath surrounds the banded column, and posteriorly, an axonemal complex (9+2 pattern axoneme associated with nine finely banded coarse fibres). Coarse fibres terminate near the annulus, leaving only the 9+2 axoneme to penetrate the glycogen piece. The posterior extremity of the end piece is paddle-shaped and contains only singlet microtubules. Total sperm length forA. perspectiva is 220 to 225µm. Available sperm data for the Architectonicidae indicate that some features may be diagnostic of the entire family (e.g. shape and substructure of the acrosome, coarse fibres and mitochondrial sheath), while others may prove useful at the subfamily or generic levels (morphology of midpiece, nucleus and annulus).