Plectostoma wallacei busauense (Smith, 1893)
E.A. Smith (1894) original descriptions on Opisthostoma busanense – “Testa minuta, anguste perforata, plus minus rufescens; anfractus 5, perconvexi, sutura profunda sejuncti, apicales 1-2 Iaeves, sequentes oblique et distanter tenuiter lamellati, ultimus antice confertius lamellatus, vix solutus, retrorsum et sursum contortus, inferne subcristatus; apertura mediocriter magna; peristoma album, duplex, margine externo interno latius expanso.”
Kobelt (1902) descriptions on Opisthostoma (Plectostoma) busauense – “Schale eng durchbohrt, rötlich; Naht tief; 5 sehr gewölbte Windungen, die apikalen glatt, die folgenden mit weitläufigen, feinen, schrägen Lamellen, letzte vorn dichter gerippt, kaum abgelöst, nach hinten und oben gedreht, unten kammartig zusammengedrückt; Mündung massig gross; Mundrand weiss, doppelt, äusserer stärker ausgebreitet als der innere.”
By Vermeulen (1994)
"As the type subspecies but spire with flat to slightly concave sides. Apex not oblique. Whorls 4-5, convex; last whorl rounded. Constriction with or without an inconspicuous parietalis, without a longitudinal palatalis. Tuba free from the spire or touching it over its entire length. Radial ribs on the spire rather closely placed to widely spaced (3-7 ribs/0.5 mm on the penultimate whorl), (slightly) sinuous, sometimes with a slight, shallowly concave projection half-way, but those close to the tuba not or slightly sinuous; those on the tuba closely placed to moderately cpaced (4-9 ribs/0.5 mm halfway), below not or slightly sinuous, sometimes with a shallowly concave, short projection. Aperture hardly tilted with regard to the coiling axis, circular to subtriangular with widely rouned edges. Spire:height 1.2-1.6 mm; width 0.8-1.0 mm; index 1.4-1.6. Total width 1.6-1.9 mm. Height aperture 0.4-0.5 mm; width 0.5 mm."