Aquatic Snails - Identification
Aquatic Snail Identification
This section gives a quick key to identify major groups of aquatic snails and points to sources of more specific information.
Part 1. Major Features of Aquatic Snails
The major characters to observe in aquatic snails are the type of coiling (elevated, flat, or absent), the handedness of the aperture (left or right), and the presence or absence an operculum.
Type of Coil and Spire – this is an easily seen character.
The winding of the snails coil (whorls) rises to the apex as in the snails (left or 1st)
FLAT (planospiral or discoidal)
The winding of the coil stays in the same plane, like a cinnamon roll. Some Planorbid snails, including Planorbella trivolus, are examples. The “spire” is actually sunken below the upper edge of the body whorl. Image center or 2nd.
Limpets have no coil at all, the shell is one piece with a slight peak, or apex. Last image
Handedness – hold the snail with the spire upwards and observe the location of the aperture. If the aperture is on the left, it's left-handed and if the aperture is on the right, it's right-handed.
Note that Planorbid snails are not usually evaluated as to handedness, but they are left-handed as in Planorbella above.
left-handed: aperture on the left side of the spire
right-handed: aperture on the right side of the spire
Operculum – The operculum is a horny plate that closes the aperture (the opening of the shell) with the animal withdrawn inside and can be seen on a live specimen. The operculum also comes in types, to be presented later in context.
Part 2. The Major Groups of Aquatic Snails
Variability in shell type of the prosobranchs. Not to scale
Sources of Keys and/or More Information
There are a few sources to help with species identification.
The Ohio Division of Wildlife's picture key: Freshwater Snails of Ohio Field Guide is from a next-door state and great for iNaturalist ids. The link opens as a pdf. Not all species are covered.
Dillon and colleagues (2019) The Freshwater Gastropods of North America project includes The Freshwater Gastropods of the Ohio. This a great reference and has a key to the regional freshwater gastropods. The key is easy to use except for the genus Physa (or Physella) and a few other taxa which require dissection.
Key to Wisconsin Freshwater Snails (Perez, K. and G. Sandland) is also good to use.
For more information on freshwater snails, use Freshwater Mollusk Conservation Society's Freshwater Snails.
The species list below combines all the species from the sources - so it is not necessarily the truth. Their are degrees of certainty involved that I do not judge. Consider it an attempt to list the potentially possible. Note also that the scientific names of some species varies among these sources and those used to generate the other species list. The list below is annotated parenthetically with the name of the source of the species to the list: P = Pyron list, NS = Nature Serve list, AFS = AFS publication list, O = Ohio guide (only those that are identified there), and F = FWGNA list and keys (only those in the their delineation of the Ohio River Valley).
Amnicola limosa (Say, 1817) - Mud Amnicola (P, NS, AFS, O, F)
Antroselates spiralis Hubricht, 1963 - Shaggy Cavesnail (NS, AFS, F)
Birgella subglobosus (Say, 1825) - Globe Siltsnail (P, NS, AFS, F)
Cincinnatia integra (Say, 1821) - Midland Siltsnail (P, NS, AFS, O, F)
Fontigens cryptica Hubricht, 1963 - Hidden Springsnail (F)
Fontigens nickliniana (Lea, 1838) - Watercress Snail (NS, AFS)
Lyogyrus pilsbryi (Walker, 1906) - Lake Duskysnail (NS, AFS)
Marstonia lustrica (Pilsbry, 1890) - Boreal Marstonia (P, NS, AFS)
Marstonia scalariformis (Wolf, 1869) - Moss Pyrg (F)
Somatogyrus integra (Say, 1829) - Ohio Pebblesnail (NS, AFS)
Somatogyrus integra (Say, 1829) - Ohio Pebblesnail (F)
Elimia livescens (Menke, 1830) - Liver Elimia (P, NS, AFS, O, F)
Elimia semicarinata (Say, 1829) - Fine-ridged Elimia (, NS, AFS, F)
Leptoxis praerosa (Say, 1821) - Onyx Rocksnail (P, NS, AFS, O, F)
Leptoxis trilineata (Say, 1829) - Broad Mudalia (AFS, O)
Lithasia armigera (Say, 1821) - Armored Rocksnail (NS, AFS, F)
Lithasia obovata (Say, 1820) - Shawnee Rocksnail (P, NS, AFS, F)
Lithasia verrucosa (Rafinesque, 1820) - Varicose Rocksnail (, NS, AFS, F)
Pleurocera acuta (Rafinesque, 1831) - Sharp Hornsnail (P, NS, AFS, O, F)
Pleurocera alveare (Conrad, 1834) - Rugged Hornsnail (AFS)
Pleurocera canaliculata (Say, 1821) - Silty Hornsnail (P, NS, AFS, F)
Probythinella emarginata (Kuster, 1852) - Delta Hydrobe (NS, AFS, F)
Pomatiopsis cincinnatiensis (I. Lea, 1850) - Brown Walker (P, NS, AFS, F)
Pomatiopsis lapidaria (Say, 1817) - Slender Walker (, NS, AFS, O)
Valvata bicarinata (Lea, 1841) - Two-ridge Valvata (NS, AFS)
Valvata lewisi (Currier 1868) - Fringed Valvata (P, NS, AFS)
Valvata perdepressa Walker, 1906 - Purplecap Valvata (AFS, O)
Valvata sincera (Say, 1824) - Mossy Valvata (, NS, AFS, O)
Valvata tricarinata (Say, 1817) - Threeridge Valvata (P, NS, AFS, O)
Campeloma crassulum Rafinesque, 1819 - Ponderous Campeloma (AFS, F)
Campeloma decisum (Say, 1817) * - Pointed Campeloma (P, NS, AFS, O, F)
Campeloma rufum (Haldeman, 1841) - a freshwater snail (NS, AFS)
Cipangopaludina chinensis (J.E. Gray, 1834) - Chinese Mysterysnail (P, NS, OK, O, F)
Cipangopaludina japonica (von Martens, 1861) - Japanese Mysterysnail (C, NS, OK, O, F)
Lioplax subcarinata (Say, 1816) - Ridged Lioplax (F)
Lioplax sulculosa (Menke, 1827)- Furrowed Lioplax (AFS, O)
Viviparus georgianus (Lea, 1834) - Banded Mysterysnail (P, NS, AFS, F)
Viviparus intertextus (Say, 1829) - Rotund Mysterysnail (NS, F)
Viviparus subpurpureus (Say, 1829) - Olive Mysterysnail (NS, AFS, F)
Ferrissia fragilis (Tryon, 1863) - Fragile Ancylid (P, NS, AFS, O, F)
Ferrissia rivularis (Say, 1817) - Creeping Ancylid (P, NS, AFS, O, F)
Laevapex fuscus (C. B. Adams, 1841) - Dusky Ancylid (P, NS, AFS, F)
Rhodacmea hinkleyi (Walker, 1908) - Knobby Ancylid (NS, AFS)
Galba dalli (Baker, 1907) - Dusky Fossaria (AFS)
Galba exigua (Lea, 1841) - Graceful Fossaria (AFS)
Galba humilis Say 1822 - Marsh Fossaria (F)
Galba modicella (Say, 1825) - Rock Fossaria (P, NS, AFS, O)
Galba obrussa (Say, 1825) - Golden Fossaria (NS, AFS)
Galba parva (I. Lea, 1841) - Pygmy Fossaria (NS, AFS)
Galba rustica (Lea, 1841) - Rusty Fossaria (AFS )
Lymnaea stagnalis (Linnaeus, 1758) * - Swamp Lymnaea (P, NS, F)
Pseudosuccinea columella (Say, 1821) - Mimic Lymnaea Snail (P, NS, AFS, O, F)
Stagnicola caperata (Say, 1829) - Wrinkled Pondsnail (NS, AFS, O, F)
Stagnicola catascopium (Say, 1867) - Woodland Pondsnail (P, NS, AFS, O, F)
Stagnicola elodes (Say, 1821) - Marsh Pondsnail (P, NS, AFS, O, F)
Stagnicola exilis (I. Lea, 1838) - Flat-whorled Pondsnail (P, NS, AFS, O)
Stagnicola walkeriana F.C. Baker, 1926 - Calabash Pondsnail (NS, AFS)
Stagnicola woodruffi (F.C Baker, 1901) - Coldwater Pondsnail (NS, AFS)
Aplexa elongata (Say, 1821) - Lance Aplexa (P, NS, AFS, O)
Physella acuta (Draparnaud, 1805) - Wandering Physa (P, NS, AFS, O, F)
Physella gyrina (Say, 1821) - Tadpole Physa (P, NS, AFS, O, F)
Physella integra (Haldeman, 1841) - Ashy Physa (NS, AFS, O)
Gyraulus circumstriatus (Tryon, 1866) - Disc Gyro (NS, AFS, F)
Gyraulus deflectus (Say, 1824) - Flexed Gyro (P, NS, AFS, O, F)
Gyraulus parvus (Say, 1817) - Ash Gyro (P, NS, AFS, F)
Helisoma anceps (Menke, 1830) - Two-ridged Ramshorn (P, NS, AFS, O, F)
Micromenetus dilatatus (Gould, 1841) - Bugle Sprite (AFS, O)
Planorbella campanulata (Say, 1821) - Bell-mouthed Ramshorn (P, NS, AFS, O)
Planorbella trivolvis (Say, 1817) - Marsh Ramshorn (P, NS, AFS, O, F)
Planorbula armigera (Say, 1821) - Thicklip Ramshorn (P, NS, AFS, F)
Promenetus exacuous (Say, 1821) - Sharp Sprite (P, NS, AFS)
Promenetus umbilicatellus (Cockerell, 1887)- Umbilicate Sprite (AFS)