Highly turreted shell, thin but solid, smooth except for growth lines and fine, closely spaced spiral lirae; aperture wide, produced below; colour yellowish to olive-brown. Rachidian cusp relatively broad, upper rim well rounded.
Shell: Elongately turreted, thin but solid, six to ten convex and regularly rounded whorls; narrow suture. Sculpture of regularly spaced spiral ridges becoming more prominent at the base, fine axial growth lines; some shells completely smooth. Colour yellowish to light olive brown, glossy surface. Aperture wide, oval, angled, produced be¬low, pointed above, sharp to thin margin. Shell size: H = 21-63 mm, B = 9-22 mm.
Embryonic Shell: Smooth with faint growth and spiral lines; conspicuous subsutural depression; colour light greenish brown with broad chestnut brown spiral band.
Operculum: Round, up to eight regular whorls, almost central nucleus.
Radula: Central tooth relatively broad, basal margin well rounded. Central cusp flanked by three smaller denticles on each side. Inner marginals with two cusps, the outer one being broader. Outer marginals with mostly two, sometimes three cusps, outer one being broader.
External Anatomy: Animal dark grey with light grey patches. Columellar muscle well devel-oped, relatively short and broad.

From B. dautzenbergiana to be distinguished by its more conical shell, uneroded spire, in average fewer whorls, and lack of dark brown spiral band; or by statistical analysis of shell parameters. Types of M. citrina and M. citrinoides do only differ in average shell height but not in respect to other morphological or morphometrical characteristics. This feature is not considered sufficient to indicate separate status. For this reason, we agree with Brandt (1974) treating both taxa as synonyms.

Thailand: Prov. Kamphaeng Phet: Two lo-calities in vicinity of Mae Sot as only known records. Not recorded by Brandt (1974) oth-erwise giving an excellent overview of the gas¬tropod fauna of Thailand.
Habitat: Relatively cold, fast flowing, clear streams, well oxygenated, on limestone substratum. Buried in sand or mud, under rotten leaves or sunken wood presumably feeding on detritus.