Japonia ditropis Vermeulen & Junau, 2007
“Smaller than Japonia hyalina, and with two conspicuous spiral ridges on the last whorl instead of one. The peristome is also less distinctly protruding.” (Vermeulen & Junau, 2007)
Vermeulen & Junau (2007) original descriptions on Japonia ditropis – “Shell very small, conical with concave sides, slightly translucent pale corneous to white, somewhat shiny. Whorls 3 3/8-4 1/2, the first whorls convex, the last keeled slightly above and below the periphery, slightly convex above and below. Suture impressed. Sculpture protoconch: surface minutely verrucate. Radial sculpture teleoconch: the first whorls with fine, densely placed and regularly spaced riblets, later whorls with growth lines, partly and sometimes at more or less regular intervals grading into riblets. Spiral sculpture teleoconch: the first whorls with 4-6 about equally strong spiral ridges with a minutely erose crest; in the later whorls the lowermost developing into a supraperipheral keel, the other 3-5 continuing as much weaker threads, those closest to the periphery strongest but otherwise spread regularly from keel to suture; below this keel 3-6 spiral ridges: two distinct in subperipheral and basal position, the subperipheral slightly less protruding than the supraperipheral, 1-2 thin threads above, and 0.3 below the subperipheral. Umbilicus open, 0.4-0.7 mm diam. Aperture subcircular, but with 1-2 slight angles along the palatal side. Peristome double; the inner little reflected, a circular rim with a notch at the level of the suture; the outer moderately widened and reflected, flat, not or hardly widening towards the palatal side, deeply notched near the suture. Periostracum thin, pale brownish, with deciduous, small, semi-elliptic appendages over the spiral keels.”
Japonia ditropis – “Height 2-2.9 mm; width (excl. peristome) 2.4-3.3 mm. Apertural height 0.7-1.0 mm, width 0.9-1.1 mm.” (Vermeulen & Junau, 2007)
Type locality – “Malaysia, Sarawak, 2nd div.: Lower Bukit Lebik, ground level” (Vermeulen & Junau, 2007)
Other localities – “Malaysia, Sarawak, 2nd div.: Lower Tatau River valley, Bukit Sarang group, Bukit Anyi, NW. side” (Vermeulen & Junau, 2007); “Malaysia, Sarawak, 2nd div.: Lower Tatau River valley, Bukit Sarang group, Bukit Anyi, SE. side” (Vermeulen & Junau, 2007); “Malaysia, Sarawak, 2nd div.: Lower Bukit Lebik, sediment deposits c. 40 m above ground level” (Vermeulen & Junau, 2007)
Ecology – “Lowland rainforest on and near limestone bedrock.” (Vermeulen & Junau, 2007)