Georissa wallaceiana, from Stanisic et al. (2010).

Belongs within: Neritoidea.

The Hydrocenidae are a group of small operculate terrestrial snails with a scattered distribution in warmer regions of Eurasia, Africa and Australasia. Members include the genus Georissa, found in northern and eastern Australia and the southwest Pacific, usually on isolated limestone outgroups, with shells ornamented with variously fine to bold spiral cords (Stanisic et al. 2010). The genus Hydrocena is widespread throughout the Old World and may be either smooth or spirally sculpted (Knight et al. 1960).

Characters (from Stanisic et al. 2010): Shell small to minute (less than five millimetres), operculate, globosely turbinate with just a few whorls. Outer lip generally simple, not thickened. Shell whorls usually rounded, less commonly shouldered with strongly impressed sutures. Inner whorls absent, being dissolved or resorbed as shell increases in size. Aperture ovate to semi-circular with prominent columellar callus. Operculum calcareous, D-shaped, bearing a digit-like peg or apophysis on inner surface; nucleus paucispiral. Shell surface either smooth or sculptured to varying degrees with spiral ribs or lines, often bearing calcified accretions. Colour usually translucent yellow, pink or orange. Apical whorls bulb-like, prominent. Animal lacking true tentacles, with broad tentacle-like processes on sides of head; eyes large, mounted on raised papillae; dioecious.

Hydrocenidae [Hydrocaenacea, Hydrocenina, Hydrocenoidea]SS10
|--Acmella Blanford 1869S88
|--Monterissa Iredale 1944SS10
| `--*M. gowerensis Iredale 1944SS10
|--Hydrocena Küster 1844 [=Hydrocaena (l. c.); Hydroceninae]BR05
| | i. s.: H. niloticaB01
| | H. noticola [incl. Assiminea tyttha Melvill & Ponsonby 1897]PB27
| | H. saulae van Bentham Jutting 1966BC01
| | H. scalinella van Bentham Jutting 1966BC01
| | H. toili Schlickum 1978TTE93
| |--H. (Hydrocena)BR17
| | |--*H. (H.) sirkii (Küster 1844) [=Paludina sirkii]BR17
| | |--H. (H.) cattaroensis (Pfeiffer 1841) [=Cyclostoma cattaroense]KC60
| | `--H. (H.) dubrueillianaE99
| |--H. (Chondrella Pease 1871)KC60
| | `--H. (*C.) parva (Pease 1864) [=Cyclostoma parvum]KC60
| `--H. (Georissopsis Pilsbry & Hirase 1908)KC60
| `--H. (*G.) heudei (Pilsbry & Hirase 1908) [=Georissa (*G.) heudei]KC60
`--Georissa Blandford 1864 [incl. Omphalorissa Iredale 1937; Georissidae, Georissinae]SS10
|--*G. pyxis (Benson 1856) [=Hydrocena pyxis]SS10
|--G. angulata Stanisic in Stanisic, Shea et al. 2010SS10
|--G. atramontana Stanisic in Stanisic, Shea et al. 2010SS10
|--G. beerwah Stanisic in Stanisic, Shea et al. 2010SS10
|--G. chrysacme [=Hydrocena (Georissa) chrysacme]B01
|--G. enacoucomae Stanisic in Stanisic, Shea et al. 2010SS10
|--G. isseliana (Tapparone-Canefri 1883)S88
|--G. johnnetheryi Stanisic in Stanisic, Shea et al. 2010SS10
|--G. laseroni (Iredale 1937)SS10
|--G. levicordata Stanisic in Stanisic, Shea et al. 2010SS10
|--G. minuta (Odhner 1917)SS10
|--G. monterosatiana (Godwin-Austen & Nevill 1879)AA88
|--G. multilirata Brazier 1875SS10 [=*Omphalorissa multilirataP61]
|--G. nodilirata Stanisic in Stanisic, Shea et al. 2010SS10
|--G. obesa Solem 1989S97
|--G. palmerensis Stanisic in Stanisic, Shea et al. 2010SS10
|--G. postulata (Iredale 1937)SS10
|--‘Omphalorissa’ purchasi (Pfeiffer 1862)S88
|--G. quadricarinata (van Benthem Jutting 1963)S88
|--G. reticulata (van Benthem Jutting 1958)S88
|--G. rufescens (Moellendorff 1887)AA88
|--G. saritta [=Hydrocena (Georissa) saritta]B01
|--G. walkunder Stanisic in Stanisic, Shea et al. 2010SS10
|--G. wallaceiana Stanisic in Stanisic, Shea et al. 2010SS10
`--G. williamsi (Godwin Austen 1889) [=Hydrocena (Georissa) williamsi]B01

*Type species of generic name indicated


[AA88] Auffenberg, K., & T. Auffenberg. 1988. Density, spatial distribution, activity patterns, and biomass of the land snail, Geophorus bothropoma Moellendorff (Prosobranchia: Helicinidae). Nautilus 102 (1): 40–45.

[B01] Bandel, K. 2001. The history of Theodoxus and Neritina connected with description and systematic evaluation of related Neritimorpha (Gastropoda). Mitteilungen des Geologisch-Paläontologischen Institutes der Universität Hamburg 85: 65–164.

[BR05] Bouchet, P., & J.-P. Rocroi. 2005. Classification and nomenclator of gastropod families. Malacologia 47 (1–2): 1–397.

[BR17] Bouchet, P., J.-P. Rocroi, B. Hausdorf, A. Kaim, Y. Kano, A. Nützel, P. Parkhaev, M. Schrödl & E. E. Strong. 2017. Revised classification, nomenclator and typification of gastropod and monoplacophoran families. Malacologia 61 (1–2): 1–526.

[BC01] Boyko, C. B., & J. R. Cordeiro. 2001. Catalog of Recent type specimens in the Division of Invertebrate Zoology, American Museum of Natural History. V. Mollusca, part 2 (class Gastropoda [exclusive of Opisthobranchia and Pulmonata], with supplements to Gastropoda [Opisthobranchia], and Bivalvia). Bulletin of the American Museum of Natural History 262: 1–170.

[E99] Esu, D. 1999. Contribution to the knowledge of Neogene climate changes in western and central Europe by means of non-marine molluscs. In: J. Agustí, L. Rook & P. Andrews (eds) The Evolution of Neogene Terrestrial Ecosystems in Europe pp. 328–354. Cambridge University Press.

[KC60] Knight, J. B., L. R. Cox, A. M. Keen, R. L. Batten, E. L. Yochelson & R. Robertson. 1960. Gastropoda: systematic descriptions. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt I. Mollusca 1: Mollusca—General Features, Scaphopoda, Amphineura, Monoplacophora, Gastropoda—General Features, Archaeogastropoda and some (mainly Paleozoic) Caenogastropoda and Opisthobranchia pp. I169–I331. Geological Society of America, and University of Kansas Press.

[PB27] Pilsbry, H. A., & J. Bequaert. 1927. The aquatic mollusks of the Belgian Congo, with a geographical and ecological account of Congo malacology. Bulletin of the American Museum of Natural History 53 (2): 69–602, pls 10–77.

[P61] Powell, A. W. B. 1961. Shells of New Zealand: An illustrated handbook 4th ed. Whitcombe and Tombs Limited: Christchurch.

[S88] Solem, A. 1988. Non-camaenid land snails of the Kimberley and Northern Territory, Australia. I. Systematics, affinities and ranges. Invertebrate Taxonomy 4: 455–604.

[S97] Solem, A. 1997. Camaenid land snails from Western and central Australia (Mollusca: Pulmonata: Camaenidae). VII. Taxa from Dampierland through the Nullarbor. Records of the Western Australian Museum Supplement 50: 1461–1906.

[SS10] Stanisic, J., M. Shea, D. Potter & O. Griffiths. 2010. Australian Land Snails vol. 1. A. field guide to eastern Australian species. Bioculture Press: Mauritius.

[TTE93] Tracey, S., J. A. Todd & D. H. Erwin. 1993. Mollusca: Gastropoda. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 131–167. Chapman & Hall: London.

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