Relatively small, conical, thin but solid; whorls well rounded; yellowish to greenish brown, dark brown spiral band may be present
Shell: Small, relatively thin but solid. Shell conical in shape, the body whorl is comparatively large and inflated, while subsequent whorls taper considerably in size. Spire with up to six whorls, eroded. Sculpture consisting of faint growth lines and delicate regularly spaced spiral ridges, in some specimens these ridges become stronger at the base, inconspicuous axial ribs may be present too. Surface glossy, colour yellowish brown a spiral band of darker coloration may be present at the mid of the whorls. Aperture wide, oval and well rounded and produced at the base.

Central Thailand to Cambodia, only vague.

We were neither able to trace voucher material of Brandt from the Kaek River nor to find this species during our own field work. For this reason, we cannot confirm the occurrence in the Kaek River. Brandt (1974) described B. manningi, the shells of which are at best hard to distinguish from B. insolita. To complicate matters, B. insolita closely resembles some, but not all specimens of the type series of B. siamensis, among them the lectotype. The difficulties to reliably discriminate all these taxa will likely persist unless material suitable for studies on soft body morphology and molecular genetic is available. For the time being, we follow the treatment of Brandt (1974).