“This species is about the same size as P. wallacei, but is more pupiform, redder, more distantly lamellated; the body-whorl has no basal crest, and the aperture and peristome are smaller.” (E. A. Smith, 1894)
E.A. Smith (1894) original descriptions Opisthostoma baritense – “Testa elata, ovato-conica, rufescens, angustissime perforata; anfractus 6, perconvexi, sutura profunda sejuncti, primus Iaevis, caeteri oblique subconferte tenuissime lamellati, ultimus retrorsum et sursum contortus, breviter solutus; peristoma leviter expansum.”
Vermeulen 1994 description:
"Spire conical with (slightly) convex sides. Apex oblique. Whorls 5 3/4, convex; last whorl rounded. Constriction with a parietalis, a longitudinal and a transverse palatalis, a dinstinct columellaris. Tuba gradually narrowed towards the constriction, rounded below. Radial ribs rather closely placed to moderately spaced (4-8 ribs/0.5 mm on the penultimate whorl, 4-7 ribs/0.5 mm half-way on the tuba), not or hardly sinuous. Spiral striation fine. Umbilicus open, 0.15-1.20 mm across. Aperture hardly tilted with regard to the coiling axis, circular to elliptic. Peristome somewhat distant from the spire, double; outer peristome slightly spreading beyond the inner, but gradually narrowed towards, and absent along the right side of the aperture, sometimes slightly widened along the upper side and/or along the lower side; inner peristome slightly protruding from the outer, spreading. SPire: height 2.0-2.3 mm; width 1.4-1.5 mm; index 1.3-1.5. Total width 2.2-2.4 mm. Height and width aperture 0.5-0.6 mm."
Opisthostoma baritense – “Alt. 2 1/3 millim., diam. maj. 2 1/3, min. 1½. Apertura 2/3 lata.” (E. A. Smith, 1894)
Type locality – “Barit Mountain, N. W. Borneo” (E. A. Smith, 1894) (i.e. Mulu, Sarawak)
Other localities – “Bakong, Sarawak” (Gredler, 1902)
Barit Mountain illustration and an old map from Sir Spenser St. John 1862 Life in the forests of the Far East: Travels in northern Borneo, Volume 2