Lanistes

Lanistes is a genus of freshwater snails which have a gill and an operculum, aquatic gastropod mollusks in the family Ampullariidae, the apple snails. The distribution of the genus Lanistes includes Africa and Madagascar. Lanistes has a unique anatomy among the Ampullariidae: it has a 'hyperstrophic' sinistral shell. This means that the body of the snail is dextral (as in all other ampullariids), but the shell appears to be sinistral. However the sinistral appearance stems from the fact that the rotation of the shell as it grows is in an upward direction rather than the usual downward direction. Three subgenera have been recognized, based on shell differences: Lanistes sensu stricto, Meladomus and Leroya. These subgenera are not used in recent works. Extant species within the genus Lanistes include: Fossil species within the genus Lanistes include: