A person could identify a Stagnicola emarginata snail by its compressed spires, which are the complete turns in the snail shell collectively.  They also have a subglobose body, which means that their body is not quite round or spherical (Mycology online 2011).  Their shells are broader in shape and light in color.  They are inhabitants of rivers and lakes.  These are a few of their broad defining features to distinguish them from other snail taxa (Burch 1982).  The shell itself is more than 15 mm in height.  Other things to distinguish the Stagnicola emarginata from other genera is by its aperture.  The aperture is the opening of the snail's shell.  The unique characteristics of its aperture is how strongly plaited it is when compared to other shells.  It is also not brownish or purplish in color like much of the mollusks do (G.L. Mackie 1980).  Throughout the site there is much more information on what makes the Stagnicola emarginata unique and such an interesting organism.