Land snail surveys conducted in northern Laos between 2013 and 2014 have led to the discovery of a living population of Trichelix horrida (Pfeiffer, 1863). This species has never been recorded from specimens other than the types, and its distribution and anatomy have remained essentially unknown. The genitalia and radula morphology are documented here for the first time and employed to re-assess the systematic position of this species: the unique morphological characters of T. horrida are a penis similar in length to the vagina, a small and triangular penial verge, gametolytic organs extending as far as the albumen gland, head wart present, and unicuspid triangular radula teeth. The type locality of this species was believed to be from "Lao Mountains, Camboja," and is restricted herein to be Luang Phrabang Province, northern Laos. The assignment of species to either of three genera, Trichelix Ancey, 1887, Moellendorffia Ancey, 1887, and Moellendorffiella Pilsbry, 1905, based solely on information provided in their original descriptions is difficult. The type specimens of all nominal species presently placed in either of these three genera are examined and illustrated herein. Comparison with the primary type specimens will assist future revisions aiming to resolve the systematics of these taxa. In addition, we transfer Moellendorffia faberiana (Möllendorff, 1888) to the genus Moellendorffiella.
Keywords: Biodiversity; Indochina; Japan; land snail; limestone; systematics; type specimen.
Chirasak Sutcharit, Khamla Inkhavilay, Somsak Panha.