Marstonia
Marstonia is a genus of freshwater snails with a gill and an operculum, aquatic gastropod molluscs in the family Hydrobiidae.
Distribution
Species in the genus Marstonia are distributed in springs, streams and lakes in eastern North America. Most of these species have extremely narrow geographic ranges and consequently have become a focus of conservation activities; two are federally listed as endangered and others are variously listed by state wildlife agencies.Description
The freshwater gastropod genus Marstonia is composed of 15 small, ovate- to elongate-shelled species. Marstonia differs from the other eight North American nymphophiline genera in that the oviduct and bursal duct join well in front of the posterior wall of the pallial cavity. It has also been resolved as a well supported sub-clade within its subfamily based on mtDNA sequences.Species
Eastern North American species of Pyrgulopsis are considered to be in separate genus Marstonia according to Thompson & Hershler.Marstonia agarhecta - synonym: Pyrgulopsis agarhecta F. G. Thompson, 1969 - Ocmulgee marstoniaMarstonia arga - F. G. Thompson, 1977 - synonym: Pyrgulopsis arga - ghost marstoniaMarstonia castor F. G. Thompson, 1977 - synonym: Pyrgulopsis castor - beaverpond marstoniaMarstonia halcyon F. G. Thompson, 1977 - synonym: Pyrgulopsis halcyon - halcyon marstoniaMarstonia hershleri - synonym: Pyrgulopsis hershleri F. G. Thompson, 1995 - Coosa pyrgMarstonia letsoni - synonym: Pyrgulopsis letsoni - gravel pyrgMarstonia lustrica - synonym: Pyrgulopsis lustrica - boreal marstoniaMarstonia ogmorhaphe - synonym: Pyrgulopsis ogmoraphe - royal springsnailMarstonia olivacea - synonym: Pyrgulopsis olivacea - olive marstonia, it may be extinctMarstonia ozarkensis - synonym: Pyrgulopsis ozarkensis Hinkley, 1915 - Ozark pyrg, it may be extinctMarstonia pachyta F. G. Thompson, 1977 - synonym: Pyrgulopsis pachyta - armored marstoniaMarstonia scalariformis - synonym: Pyrgulopsis scalariformis - moss pyrgOther species of Marstonia include:Marstonia angulobasis F. G. Thompson, 2005 - angled marstoniaMarstonia comalensis - Comal siltsnailMarstonia gaddisorum F. G. Thompson, 2004 - Gaddis marstoniaMarstonia inflata H.-J. Wang, 1977
Although Marstonia has been reviewed four times since 1978, three of its congeners have been little studied beyond their original descriptions and their anatomy is unknown. Two of these — Marstonia olivacea, Marstonia ozarkensis — may be extinct and thus will likely remain incertae sedis.