From the many similar counterstamped Akragas coins in various archives and per the auction catalogers the countermark is Herakles wearing a lion skin headdress. Images from CNG's archives. The third coin shown has an arrangement of value-mark dots similar to Doug's coin. Here's one with a different type of "head right" countermark. The listing description doesn't say anything about who it might be:
Great post TIF. Coins five and six seem to have the same issue on the side of the head as Doug's. Is that just countermark deterioration that shows the side of the head looking like a weird flat hat?
The c/m is supposed to be the young river god Akragas after whom the city was named. The coins date to a time around when the city was destroyed and few survivors relocated for years before others were brought back to resettle. They played rough in those days. Remember that Carthage eventually was destroyed by Rome to the point they added salt to the ground so no one could grow crops there for years. By ancient standards, the appropriate treatment for a defeated enemy did not include rebuilding them. When no one is alive, what is there to rebuild?
If you look a little more you will find others making fun of catalogers who mistake the head for Herakles. As with everything experts vary and differ in their degree of expertise. My coin shows Akragas; yours shows whoever you see. Surely nobody knows all the river gods listed on this link: http://www.theoi.com/Potamos/Potamoi.html