> Goniobasis ebenum (Lea 1841)
    ("Elimia ebenum")

> Habitat & Distribution
Goodrich (1940) restricted the distribution of G. ebenum to the Cumberland River and its tributaries in Kentucky and Tennessee, and Stewart & Dillon did not include the species in their (2004) Virginia review.  But the range of G. ebenum apparently extends into West Virginia and includes many other rivers and streams draining west off the Cumberland Plateau.  In 2007 we were surprised to discover a population inhabiting tributaries of the Big Sandy drainage in Dickenson County, VA.

> Ecology & Life history
This and other pleurocerids are grazers of epilithic periphyton (Harman 2000). Where they reach high densities, grazing by pleurocerid populations can have a significant effect on energy flow in streams (Dillon 2000: 86 - 91).

Like other pleurocerids, G. ebenum  is dioecious, eggs being deposited on hard substrates from spring to mid-summer. Eggs are spirally arranged in masses of 2-15 or more, with a tough, membranous outer covering (Smith 1980, Jokinen 1992). Although we are unaware of any study specifically directed toward the life history of G. ebenum, it seems reasonable to expect that two years will be required for maturity, and that several years of iteroparous reproduction can be expected thereafter, as is the case for pleurocerids generally (Dazo 1965). This is life cycle G of Dillon (2000: 156 - 162). 

> Taxonomy & Systematics
Burch (1989) and Turgeon et al. (1998) assigned this species to the genus Elimia. But Elimia (H. & A. Adams 1854) is a composite group, explicitly rejected by Tryon, Walker, Pilsbry and Goodrich (Dillon 1989).

> Essay
See my 28Sept04 post to the FWGNA web site for a review of the Goniobasis/Elimia taxonomic controversy.

>References
Burch, J.B. 1989. North American Freshwater Snails. Malacological Publications, Hamburg, Michigan. Dazo, B. C. 1965. The morphology and natural history of Pleurocera acuta and Goniobasis livescens (Gastropoda: Cerithiacea: Pleuroceridae). Malacologia 3: 1 - 80. Dillon, R., T. Jr. 1989. Karyotypic evolution in pleurocerid snails: I. Genomic DNA estimated by flow cytometry. Malacologia, 31: 197-203. Dillon, R.T., Jr. 2000. The Ecology of Freshwater Molluscs. Cambridge University Press, Cambridge, United Kingdom. Goodrich, C. (1940) The Pleuroceridae of the Ohio River drainage system.  Occas. Pprs. Mus. Zool. Univ. Mich., 417: 1-21.  Harman, W.N. 1972. Benthic substrates: their effect on fresh-water Mollusca. Ecology 53: 271-277. Harman, W.N. 2000. Diminishing species richness of mollusks in Oneida Lake, New York State, USA. Nautilus 114:120-126.   Jokinen, E.H. 1992. The Freshwater Snails (Mollusca: Gastropoda) of New York State. NY State Mus Bull 482, Albany, New York. Smith, D.G. 1980. Goniobasis virginica Gastropoda Pleuroceridae in the Connecticut River USA. Nautilus 94:50-54. Stewart, T.W., and R.T. Dillon, Jr. 2004. Species composition and geographic distribution of Virginia’s freshwater gastropod fauna: a review using historical records. Amer Malac Bull 19:79-91. Turgeon, D.D. et al. 1998. Common and Scientific Names of Aquatic Invertebrates from the United States and Canada: Mollusks. Amer Fish Soc Sp Pub 26, Bethesda, Maryland.