“Compared with O. linterae, Sowb., to which it bears a close superficial resemblance, the present species is slightly smaller, the whorls are narrower and increase less quickly, and the last half-whorl (free portion) is more angular. The costae on last whorl of concinnum form narrow, almost complete, tubes, whereas in linterae the costae extend across the whorl as in O. pulchellum. The deflection at the constriction is also greater in linterae.” (Fulton, 1901)
Fulton (1901) original descriptions on Opisthostoma concinnum – “Shell conical, reddish above, shining golden colour below, lower part ornamented with oblique somewhat waved costae; whorls 6½, angularly convex, slowly increasing, last whorl slightly deflected at the constriction, becoming free at its termination; aperture circular; peristome thin, slightly expanded, margined by a moderately broad rim or flange.”
Fulton (1901) descriptions on syntype Opisthostoma smithi – “ “Shell pyramidal, narrowly perforate, red above, pale yellow below, ornamented with oblique costse, which are semitubular on lower portion of last half-whorl; whorls 7, angularly convex; aperture circular; peristome free, slightly thickened and expanded, and margined by a moderately wide rim. Alt. 3 millim.; diam. maj. 3¼ millim.”
Vermeulen (1994)'s description
"Spire conical with flat to concave sides. Apex not oblique. Whorls 5 1/2 - 6 3/8, moderately convex; last whorl (slightly) angular. Constriction with a parietalis, a longitudinal and a stransverse palatalis, a columellaris, with or without a basalis that is knob-shaped or a transverse ridge. Tuba gradually narrowed towards the constriction, (slightly) angular or with a ridge below. Radial ribs on the spire rather closely placed to widely spaced (2-6 ribs/0.5 mm on the penultimate whorl), with a (shallowly) concave to deeply trough-shaped projection half-way, often abraded to a sinuous or shallowly to deeply looped scar (projection of those close to the tuba often double-channeled either with both channels equally deep or with the upper channel much deeper than the lower, abrading to a scar with either a single or a double, deep or shallow loop when the shell is observed in front view); those on the tuba moderately to widely spaced (2-3 ribs/0.5 mm half-way the tuba), below with a deeply trough-shaped, slightly curved projection abrading to a scar with a deep, semi-circular loop. Spiral striation fine. Umbilicus open, 0.30-0.40 mm across. Aperture tilted up to 30 degree with regard to the coiling axis, circular. Peristome double; outer peristome spreading beyond the inner but gradually narrowed towards, and absent to narrow along the right side of the aperture, often somewhat widened along the the upper side; inner peristome hardly protruding from the outer, spreading. Spire: height 1.7-2.3 mm; width 1.3-1.5 mm; index 1.3-1.7. Total width 2.5-3.2 mm. Height and width aperture 0.6-0.7 mm."
Opisthostoma smithi – “Alt. 3 millim.; diam. maj. 3¼ millim.” (Fulton, 1901)
Shell height – 2.5 mm; Shell width – 3 mm. Aperture diameter– 0.67 mm.
Type locality – “Gomanton, N. Borneo” (Fulton, 1901); Opisthostoma smithi “Banguey island, Borneo” (Fulton, 1901)