Freshwater Molluscan Shells / North American Pleuroceridae Burch (1982) provided the following breakdown for North American species, here tabulated. Please also see http://www.cofc.edu/~dillonr/28Sept04.html for a discussion on the use of the names Elimia and Goniobasis for the smaller high-spired snails (now superceded, see below).   Genus   Subgenus   number species   additional subspecies   Elimia       83   27   Gyrotoma*       6       Io       1 variable       Leptoxis   Leptoxix s.s. Athearnia* Mudalia   16 1 6       Lithasia   Lithasia s.s. Angitrema   3 7       Pleurocera   Pleurocera s.s. Strephobasis*   18 3   9 1   Juga   Juga s.s. Calibasis Oreobasis ___________   3 2 4 ________   1 2 0 _____   Totals   10   153   40 *Largely extinct due to dam construction. More recently, Dillon (2011) has continued a long trend in freshwater malacology in recognizing fewer species than former authors, but with wider ranges and more variable morphologies. DNA evidence shows many of the species listed by Burch may be synonyms, so the actual numbers will be substantially lower than shown here. In addition, also based based on DNA evidence, Elimia (or Goniobasis) can no longer be recognized as a valid genus, and its included species should be subsumed under a more inclusive genus Pleurocera. Nomenclature is in flux, and claiming to name these specimens with certainty would be inappropriate here. Dillon, R. T., Jr. (2011)  Robust shell phenotype is a local response to stream size in the genus Pleurocera (Rafinesque, 1818).  Malacologia 53: 265-277 Also note: the Juga snails of the Pacific Northwest (formerly also included in Goniobasis by many authors) have been reclassified with the east-Asian family Semisulcospiridae. See http://www3.interscience.wiley.com/journal/122198254/abstract?CRETRY=1&SRETRY=0#fn1 Tributaries of the Ohio Pleurocera canaliculatum (Say, 1821) (?) detail     Pleurocera canaliculatum (Say, 1821) (?) "Hornshell" Many species and varieties, or one variable species? Those in the upper Tennessee River, in Watts Bar and Chickamauga Lakes (upper images, left and right respectively) may be smooth, and/or nodular, and/or shouldered, to varying degrees. Those in Kentucky Lake, on the lower Tennessee River (left) are more uniformly conical and nodular, with spiral cords usually present on the base of the body whorl, and often lack a spiral color band.     Pleurocera canaliculatum(?) (Say, 1821) Form living in Duck River   Pleurocera parvum (Lea, 1862) highland tributaries of Tennessee River.       Pleurocera strigosa (Lea, 1841)* East Tennessee creeks. Has small vestigial operculum, more characteristic of the larger Pleurocera living in nearby reservoirs. *formerly "Elimia" or "Goniobasis"   Locally referred to as "periwinkles", species formerly assigned to the genus Elimia or Goniobasis) inhabit most creeks in the eastern half of the United States and southern Canada. According to Burch, the genus Pleurocera could be distinguished from Elimia by the presence of a short basal canal producing an auger-shaped base to the shells of the former. However, in the shells themselves, one can observe all gradations between straight-lipped, curved-lipped, and canaliculate apertures. However, Thompson, in http://www.flmnh.ufl.edu/malacology/fl-snail/snails1.htm indicates that shell characteristics are conservative indicators of genetic divergence, and that convergent shell features may make species identification question- able and their ranges dificult to determine. If this were generally true, there would be more species than cur- rently recognized.       A possible exterpation from Mossy Creek, Jefferson County, Tennessee In 1845, pioneering geologist Gerard Troost noticed these snails, and one endemic species in particular, of which he writes: Another singular fact is, that these shells (Melania of Naturalists) although taken from different creeks and of different species have generally a similarity to one another. Sometimes we find the same species in a great number;--but the species that exists in Mossy creek, and which has been described by Mr. Lea under the name of Melania Troostiana, is found only in this small creek, where it exists in great abundance. In April 2002, none could be found in this creek, its tributaries, or nearby, and the species is probably exterpated from this location. It now appears however that troostiana is conspecific with arachnoidea, and the name troostiana has precedence, which would make troostiana one of the more common and widespread species.         Pleurocera simplex (Say, 1825)* East TN creeks. Usually has a black sooty deposit on outer surface. Prefers fast moving water in small creeks, often crawling out well above the waterline.   Pleurocera ebenum (Lea, 1841)* Upper Cumberland River. *formerly "Elimia" or "Goniobasis"         Elimia aterina (Lea, 1836) Tributary creeks to Clinch and Powell, TN. Now regarded as synonymous with Pleurocera simplex.   Pleurocera laqueta, from small tributary to Duck River.         Pleurocera laqueta*, Nolin River, KY.   Pleurocera laqueta (Say, 1829)*, living in Chickamauga Lake, TN, atypical for snails formerly assigned to Elimia or Goniobasis.         Elimia interrupta (Haldeman, 1840) Hiwassee River and tributaries, East Tennessee.   Pleurocera troostiana. East Tennessee creeks. Like most species, varies in subtle ways from one creek to another. *formerly "Elimia" or "Goniobasis" arachnoidea.         Lithasia armigera (Say, 1821) Tributaries of the lower Ohio.   Lithasia duttoniana (Lea, 1841) Duck River and tributaries, Tennessee.         Lithasia geniculata geniculata (Haldeman, 1840), (left) and L. g. fuliginosa (Lea, 1841), (right) Duck and Buffalo Rivers, TN.   Lithasia verrucosa (Rafinesque, 1820) Ohio River tributaries, also in Arkansas.         Lithasia obovata (Say, 1829) Ohio River tributaries.   Leptoxis praerosa (Say, 1821) Tributaries of the Ohio, Tennessee, and Cumberland. Atlantic drainages   Pleurocera* virginica Say, 1817. Eastern rivers and creeks, widespread.   Pleurocera* catenaria postelli (Lea, 1858) Georgia rivers.         Pleurocera* catenaria dislocata (?) (Reeve, 1861) The left (striped) ones are from the Nottaway, and the plain ones (right) are from the Appomatox River, both in Virginia.   Pleurocera* catenaria var? South Carolina. *formerly "Elimia" or "Goniobasis"   Leptoxis carinata (Bruguiere, 1792) Eastern rivers. Note small projection on columella.   Leptoxis carinata (Bruguiere, 1792) (?) Burch refers a number of variable shells to this species. These came from (left to right) Roanoke River in western Virginia, Appomatox River in central Virginia, Buffalo Creek in central Virginia, and the Nottaway River in southeastern Virginia. Gulf Coast Rivers   Elimia catenaria vanhyningiana (Goodrich, 1921) Gulf Coast Florida.   Elimia vanuxemiana (Lea, 1834) Georgia and Alabama unimpounded rivers.           Elimia gerhardti (Lea, 1862) Coosa River basin of Alabama and Georgia.     Western Mississippi drainages     Pleurocera acuta acuta Rafinesque, 1831. Osage River, MO   Pleurocera acuta acuta Rafin- esque,1831. Gasconade River, MO   Pleurocera acuta acuta Rafinesque, 1831. Eleven point River, Arkansas               Elimia potosiensis (Lea, 1841) White River, MO   Elimia potosiensis (Lea, 1841) Weaubleau Creek, MO   Elimia potosiensis (Lea, 1841) Osage River, MO. Pacific drainages of the Far West (Family Semisulcospiridae)   Juga plicifera (Lea, 1838) Oregon and Washington rivers. The ones pictured are from near Portland, Oregon.   Juga silicula (Gould, 1847) Oregon and Washington creeks   In the rivers west of Seattle, all smaller shells are ribbed, while larger ones show that individuals have lost the ribbing at different times as they grow.   Typical Juga operculum, inner surface (left) and outer surface.       Burch lists twelve species and subspecies (nine nominal species) in three subgenera for Juga. Several are endemic to springs in the interior Great Basin. [Home Page[ | [Sitemap]