''Borysthenia'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of small freshwater snails with an operculum, aquatic gastropod

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

s in the family

Valvatidae ''Valvatidae'', the valve snails, is a taxonomic family of very small freshwater snails with an operculum, aquatic gastropod mollusks. Taxonomy The family Valvatidae has no subfamilies (according to the taxonomy of the Gastropoda by Bouche ...

, the valve snails. The

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An ...

of ''Borysthenia'' is not circular."Genus summary for ''Borysthenia''"

AnimalBase AnimalBase is a project brought to life in 2004 and is maintained by the University of Göttingen, Germany. The goal of the AnimalBase project is to digitize early zoological literature, provide copyright-free open access to zoological works, and pr ...

, last modified 28 February 2009, accessed 22 May 2011. Animals are

ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...

Species

The genus ''Borysthenia'' contains the following species: * † '' Borysthenia goldfussiana'' (Wüst, 1901) * † '' Borysthenia intermedia'' Kondrashov, 2007 - from the Middle Pleistocene of

Oka Oka or OKA may refer to: Cars * Oka (automobile), a small car designed by AvtoVAZ and produced by ZMA and SeAZ * OKA 4wd, a large 4-wheel-drive vehicle made in Western Australia by OKA Military * 2B1 Oka, Soviet 420 mm self-propelled mor ...

Don Don, don or DON and variants may refer to: Places *County Donegal, Ireland, Chapman code DON *Don (river), a river in European Russia *Don River (disambiguation), several other rivers with the name *Don, Benin, a town in Benin *Don, Dang, a vill ...

PlainKondrashov P. E. (2007). "New gastropod species from the Pleistocene of the Upper Don basin". ''

Paleontological Journal ''Paleontological Journal'' (Russian: ''Paleontologicheskii Zhurnal'') is a monthly peer-reviewed Russian journal of paleontology established in 1959. It focuses on the paleontology and the fossil records of Eastern Europe and Asia. Articles are ...

'' 41(5): 513-519. . * '' Borysthenia menkeana'' (Jelski, 1863) * ''

Borysthenia naticina ''Borysthenia naticina'' is a species of small freshwater snail with a gill and an operculum, an aquatic gastropod mollusc in the family Valvatidae, the valve snails. Distribution This species occurs in the Pontic and Baltic regions as follow ...

'' (Menke, 1845) - type species as ''Valvata jelskii'' Crosse, 1863

References

{{Taxonbar, from=Q4946885 Valvatidae Taxa named by Wassili Adolfovitch Lindholm Gastropod genera Extant Middle Pleistocene first appearances