“An internal constriction, which qualifies placement under the genus Opisthostoma, was detected in this species. All 38 specimens demonstrated four changes in the coiling direction and underwent similar detachment–reattachment phases, but displayed slight variations in the angles of each coiling axis (see electronic supplementary material). Intraspecific variation (n=6) among shell dimensions appeared to be low, with a mean (±s.d.) height and width of 1.5±0.1 and 0.9±0.1, respectively.” (Clements & Vermeulen, 2008)
Clements & Vermeulen (2008) original descriptions on Opisthostoma vermiculum – “Shell thin, cream or white, not transparent and slightly shiny. First whorl smooth; subsequent whorls sculptured with fine, white, regularly spaced radial ribs, becoming widely spaced and flared nearing aperture before being compressed; spiral striae absent. Whorls 4.5–5, convex, increasing in radius, uncoiling at the end of second whorl; detached third whorl returns to reattach to the base of second whorl, followed by a phase of detachment, reattachment and detachment; whorls deviate from primary teleoconch axis to coil around three additional axes. Suture deep. No umbilicus. Aperture round, vertical, without teeth. Peristome duplex, continuous, circular to rounded triangular.”
Type locality – “Gunung Rapat (4° 33’ N, 101° 7’ E), Perak, Peninsular Malaysia” (Clements & Vermeulen, 2008)
Only known from one locality: Gunung (Mount) Rapat, Perak, Malaysia.