The shell is small, conical and smooth or spirally lirate. The whorls are rounded or angulate, and there is a small umbilicus or chink. The aperture is simple, without a varix and thickening. Operculum thin, horny, paucispiral, simple. Radula with central teeth having a single pair of basal denticles. Mantle edge lacking pallial tentacle(s), snout with lateral pouches in female used for storing sand grains. Left cephalic tentacle with more pronounced ciliation than right. Penis with long accessory lobe containing duct of penial gland; penial gland located in basal part of penis. Pallial prostate gland and pallial oviduct open ventrally.
Ascorhis Ponder & Clark, 1988
Class Gastropoda
Infraclass Caenogastropoda
Order Littorinida
Suborder Rissoidina
Superfamily Truncatelloidea
Family Tateidae
Genus Ascorhis Ponder & Clark, 1988
Type species: Bythinia victoriae Tenison Woods, 1878.
Original reference: Ponder, W. F. & Clark, G. A. (1988). A morphological and electrophoretic examination of Hydrobia buccinoides, a variable brackish-water gastropod from temperate Australia (Mollusca: Hydrobiidae). Australian Journal of Zoology 36: 661-689.
Type locality: Lake Conneware, Victoria.
We follow the classification of Ponder & Clark (1988) and Ponder (1997).
Species of this genus are very small, and live on aquatic vegetation in the upper parts of estuaries and in coastal lagoons. They are commonly abundant. They feed by scraping bacteria and microalgae. The solitary hemispherical, sand-encrusted capsules contain a single egg, and are laid on virtually all substrata, including being frequently attached to the shell of Ascorhis and other co-occurring molluscs. Development is direct.
From Gladstone, Queensland, around southern Australia (including Tasmania) and westward to Geraldton, Western Australia.
This genus is distinguished from all other tateid genera in having open pallial genital ducts, an accessory penial lobe with a penial gland extending to the base of the penis, and lateral pouches on the snout in females. Ascorhis has a highly variable shell and a number of names occur in the literature. For example, spiral ribs may or may not be present, and the number of ribs and shell size are also variable.
Beesley, P. L., Ross, G. J. B. & Wells, A., Eds. (1998). Mollusca: The Southern Synthesis. Parts A & B. Melbourne, CSIRO Publishing.
Ponder, W. F. (1997). Nomenclatural rectifications in Australian Hydrobiidae. Molluscan Research 18: 67-68.
Ponder, W. (2019). Tateidae Thiele, 1925. Pp. 134-138 in C. Lydeard & Cummings, K. S. Freshwater Mollusks of the World: a Distribution Atlas. Baltimore, John Hopkins University Press.
Ponder, W. F. & Clark, G. A. (1988). A morphological and electrophoretic examination of Hydrobia buccinoides, a variable brackish-water gastropod from temperate Australia (Mollusca: Hydrobiidae). Australian Journal of Zoology 36: 661-689.
Ponder, W. F., Clark, S. A. & Dallwitz, M. J. (2000). Freshwater and estuarine molluscs: an interactive, illustrated key for New South Wales. Melbourne, CSIRO Publishing.
