Description of shell (n=29 measured) B 15.7-17.8mm, mean 16.77mm, s.d. 0.61mm; H 10.5-13.4mm, mean 12.20mm, s.d. 0.83mm; mean H/ mean B 0.73; whorls 4.8-5.3, mean 4.98, s.d. 0.14. Depressed globose with rounded spire; whorls 1-3 of spire slightly convex with evident suture; body whorl rounded, separated from penultimate whorl by shallow suture. Aperture rounded to broadly oval except where interrupted by penultimate whorl, the lower margin less curved than upper. Peristome rather evenly thickened throughout, not reflected, upper edge without any obvious tooth or additional thickening, lower edge thicker at 5-6mm from the columellar margin where there is an obvious low tooth directed upwards into shell aperture. Shell thick and strong, slightly translucent, lustrous rather than glossy when fresh because of close microsculpture, except for glossy apex (whorls 0-2) and interior of aperture. Colour brown to dull brown, lighter inside aperture, with peristome pale brown to whitish (old shells often become extensively whitish on spire due to corrosion or wear). Protoconch smooth, lacking any sculpture; whorl 1 similar but with faint growth ridges. Teleoconch generally weakly sculptured, with continuous low spiral ribs intersecting weaker and rather irregular radial riblets. Underside with sculpture less prominent, mainly of very low and rather even spiral ribs, the spaces between these with microsculpture of elongate (straight or curved) papillae. Shell descriptions by Germain (1916: 209-210) presumably included the present species in his account of R. welwitschi. The epiphet sublaevis refers to the almost smooth shell, based on laevis (adj. B); a distinction from the other two species of the genus that have rougher shell sculpture.

External coloration of body Head, top of forepart of body, top of forepart of flanks and base of ommatophores light erev; foot and foot-fringe pale brown; mantlecollar brown-grey with pale outer edge; rest of exposed body whitish; exterior of mantle inside body-whorl whitish with blackish-grey spots and small blotches or streaks ~ throughout (the dark markings covering less than half of the total area); middle whorls of spire similar to body-whorl; uppermost whorls dull light brown with fine whitish reticulation. Generally, the body coloration of this species is lighter in tone with somewhat smaller dark markings than in R. hepatizon or R. welwitschi s. str.

Distribution and ecology Endemic on Sao Tome island, where our records (listed above) are only from the lowlands, at 68-236m alt., from edges of primary forest, secondary forest, and its edges including roadside banks bordering forest. The species is therefore known only from the Lower Rainforest zone which Exell (1944) defined as from sea-level to 800m, whereas R. welwitschi (q.v.) is characteristic of the Montane Forest above 800m (with a possible old record at 610m), although neither species now requires intact forest habitat. It will be interesting in future to ascertain whether the altitudinal ranges of the two species meet or overlap.