Therasiella is a genus of land snails belonging to the family Charopidae. All known members of the genus are endemic to New Zealand.
In the original description, Powell described the genus as below:
The genus has a spirally lirate protoconch, and radial ribs that project into lamellae at the periphery at a sharp angle. Members of the genus have well-developed epiphallus on the penis.
The genus was first described by A. W. B. Powell in 1948, who named Nanina celinde (now known as Therasiella celinde) as the type species. The genus was transferred from Phenacohelicinae to Charopinae in 1973 by Frank Climo, based on anatomical differences. The holotypes of T. pectinifera, T. elevata, T. neozelanica and T. serrata are held by the Auckland War Memorial Museum.
Therasilla is endemic to New Zealand, found in the upper South Island, the North Island and on ManawatÃÂwhi / Three Kings Islands.
Species within the genus Therasiella include: