Diagnostic description:
“This is a very minute species, and considerably smaller than any of those previously described. The lamellae are quite far apart, excepting upon the contorted portion of the body-whorl, where they become crowded.” (E. A. Smith, 1894)
Size:
Opisthostoma busauense – “Alt. 1.5 mm, diam. maj. 1.5 mm, min. 1 mm. Apertura cum peristoma 0.67 lata.” (E. A. Smith, 1894); Opisthostoma (Plectostoma) busauense – “H. & Durchm. 1.5 mm.” (Kobelt, 1902)
Distribution:
Type locality – “Busau, N. W. Borneo” (E. A. Smith, 1894)
Taxonomic name: