Georissa


Georissa is a genus of minute land snails, terrestrial gastropod mollusks in the family Hydrocenidae.

Description

The shell is imperforate or scarcely perforate. It is very small, and conical, displaying an amber-colored or reddish hue. It is usually spirally grooved or striated.
The operculum appears semi-oval, lacking any trace of spiral structure, and presents eccentric striations. It is testaceous and transparent.
The animal is small and is equipped with hemispherical lobes in place of tentacles. Its eyes are normal, and its foot is short and rounded.

Distribution

Although the species are best known for living on the surface of limestone rocks, they are often also found in and on the vegetation and on non-calcareous rocks. One species, Georissa filiasaulae, is cavernicolous. It is only known from two caves in the Sepulut area of Sabah, Malaysian Borneo, where its above-ground sister species, Georissa saulae, inhabits the rocks outside of the cave, and is connected to the cave snail via narrow zones of hybridization at the cave entrances. Possibly, G. filiasaulae has evolved without ever having been fully separated from its ancestor, a process known as speciation-with-gene-flow.

Species

Species within the genus Georissa include:
  • Georissa anyiensis Khalik, Hendriks, Vermeulen & Schilthuizen, 2018Georissa bangueyensis E. A. Smith, 1895
  • Georissa bauensis Khalik, Hendriks, Vermeulen & Schilthuizen, 2018Georissa biangulata Quadras & Möllendorff, 1894Georissa borneensis E. A. Smith, 1895Georissa elegans Quadras & Möllendorff, 1894Georissa everetti E. A. Smith, 1895Georissa filiasaulae Haase & Schilthuizen, 2007Georissa gomantongensis E.A. Smith, 1894Georissa hadra Thompson & Dance, 1983Georissa hosei Godwin-Austen, 1889Georissa japonica Pilsbry, 1900
  • Georissa kinabatanganensis Khalik, Hendriks, Vermeulen & Schilthuizen, 2018Georissa kobelti Gredler, 1902Georissa laevigata Quadras & Möllendorff, 1894Georissa laseroni Georissa mawsmaiensis Das & Aravind, 2021 Georissa monterosatiana Godwin-Austen & Neville, 1879
  • Georissa muluensis Khalik, Hendriks, Vermeulen & Schilthuizen, 2018Georissa niahensis Godwin-Austen, 1889Georissa pachysoma Vermeulen & Junau, 2007Georissa purchasiGeorissa pyrrhoderma Thompson & Dance 1983Georissa pyxis - type species of the genus GeorissaGeorissa rufula von Möllendorf, 1900Georissa saulae Georissa scalinella Georissa semisculpta
  • Georissa sepulutensis Khalik, Hendriks, Vermeulen & Schilthuizen, 2018Georissa shikokuensis Amano, 1939Georissa silaburensis Khalik, Hendriks, Vermeulen & Schilthuizen, 2018Georissa similis E.A. Smith, 1894Georissa vesta Thompson & Dance, 1983Georissa williamsi Godwin-Austen, 1889