The operculate land snail genus Dioryx (Gastropoda: Alycaeidae): Data for Vietnam and an up-to-date checklist of species in the world

The land area of Vietnam is composed of a large variety of undisturbed habitats, such as high mountainous areas, forests over limestone, limestone karsts, and especially the Truong Son mountain range. Therefore, Vietnam is expected to have a high species diversity, especially for the terrestrial snails. Species of Dioryx have been recognised as occurring from the southeastern Himalayan region to Taiwan (China) in the east, and down to the northern part of the Malay Peninsula. This genus is characterised by shell small to medium, globose; protoconch smooth, not spirally striated; Region 1 (R1) usually very finely reticulated due to fine radial ribs and fine spiral striation, or smooth; R2 short to long, usually without ribs. The Vietnamese members of the genus Dioryx are reviewed, and a checklist of all Dioryx species is provided. Eight species are recognised from Vietnam, in which, seven species were recorded from the Northern and North Central, and one species (Dioryx cochinensis) from the Southern.