Protoconch corroded. Postnatal whorls four; five tubes and five varices on each whorl; tubes oval-subcircular, with a broadly rounded rib below extending to the suture; varices broadly rounded midway between tubes and growth lines, the profile evenly curved, not shouldered; peristome not quite continuous where the varix from the tube impinges upon it. Size 11 (including the corroded protoconch) bv 5.5 mm. White. From the comparison made by Barnard it appears that he felt that the possession by this species of an extra varix (five in all) and an extra anal tube (five in all) warrants its nomenclature! distinction from S. arcuatus. With five varices and tubes, S. pentaphasios would indeed appear to be unique within the subfamily.
Known only from the type locality (off Cape Point, South Africa).