Shell consists of two roughly equal "valves" hinged together on one side; inside of shell usually dull and greyish; very small

SPHAERIIDAE (Fingernail Clams)
| Shell consists of two roughly equal "valves" hinged together on one side; inside of shell shiny, often colorful; often large (Not keyed here)
UNIONIDAE (Freshwater Mussels)UNIONIDAE (Freshwater Mussels)
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