Partulina variabilis (Lanai tree snail, pupu kani oe), a member of the family Achatinellidae and the endemic Hawaiian subfamily Achatinellinae, is known only from the island of Lanai (Pilsbry and Cooke 1912–1914, p. 86). The shell may coil to the right (dextral) or left (sinistral), and both types can be found within a single population. The oblong to ovate shells of the adult are 0.5 to 0.6 in (14 to 16 mm) long, have 5 to 7 whorls, and have a white base color with no bands or a variable number of spiral bands around the shells. The shell may coil to the right (dextral) or the left (sinistral), and both types of shells can be found in a single population. Only snails with the same coil type can mate. Partulina tree snails reach adult size in 4 to 7 years. Upon reaching adult size, the snails stop growing and form a thickened edge or lip along the opening of the shell. A tree snail may attain an age that exceeds 15 years.