Akragas, founded around 580 BC by Greek colonists from Gela, began striking silver coins about 520-510 BC, and from the start it paired an eagle with a crab. The crab was the city's parasemon or its civic badge, the same role the owl played for Athens or the turtle for Aegina.  Why a crab? The simple answer is a local river. The city took its name from the river Akragas beside it, and Greek cities often built coin imagery around their rivers.

Interestingly, the engraving is detailed enough to identify the species as Potamon fluviatile, a freshwater river crab native to Sicily and not a sea crab. This points firmly to the river rather than just the coast. Some examples even show a small human face on the crab's shell, usually read as the eponymous river god Akragas. A second, compatible theory sees the crab, at home on land and in water, as a boast of the wealthy city's mastery over both.