Saskatchewan Snails, Limpets and Clams
(Gastropoda and Pelecypoda: Mollusca)
Below is a basic taxonomic key to the families of Mollusca found in SK.:
1a: Shell in two pieces
~~~.--(Clams: Pelycypoda)--Go to
2
1b: Shell with only one piece. May be coiled in a spire or flat like a rope or in the shape of a cone.--(Snails and Limpets: Gastropoda)--Go to 3
Clams:
2a: Shells greater than 25 mm. In mature specimens very much larger.--Unionidae (Pearly Mussels)
2b: Shells less than 25 mm.--Sphaeriidae (Pea Clams)
Snails and Limpets:
3a: Shell in the form of a cone
with no visible spiralling or coiling.-- Ancylidae (Freshwater Limpets)
3b: Shell coiled flat or in a spiral spire
~~.--4
4a: Shell coiled flat
~~ like a rope coil.--Planorbidae (Rams Horn Snails)
4b: Shell coiled in a spire
~~ although in some groups it may be relatively low.--5
5a: Spire low 
O indicates operculum. only about one whorl high. Shell has an operculum that closes the shell opening.-- Valvatidae (Valve Snails)
5b: Spire taller, more than one whorl high. Operculum can be present or absent.--6
6a: With the spire pointing to your left the shell opening will be downward
~~ when looking into the shell opening.-- Physidae (Tadpole Snails)
6b: With the spire pointing to your left the shell opening will be upward
~~ when looking into the shell opening.--7
7a: Mature snails larger than 6 mm tall. The tip of the shell spire very pointed. Operculum absent.-- Lymnaeidae (Pond Snails)~~~
7b: Mature snails are smaller than 6 mm and have. The shell is blunt at the tip and an operculum is present.-- Hydrobiidae (Spire Snails)
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Saskatchewan species list to snails, clams and limpets: The species list below is primarily based on Clarke 1981.
(Please note if you do not have a "wheeled" mouse and a list expands below the page bottom just left click on the first entry of the list in question and use the keyboard's down arrow button to scroll down the list.)
References
Clarke, A.H. 1981. The Freshwater Molluscs of Canada. National Museum of Natural Sciences, Ottawa, Canada.
Prescott, D.R.C. and M.M. Curteanu. 2004. Survey of Aquatic Gastropods in the Central Parkland Subregion of Alberta. Alberta Sustainable Resource Development, Fish and Wildlife Division, Alberta Species at Risk Report No. 92, Edmonton, AB.