Mississippi Map Turtles seen sunning and swimming in Hickory Creek under the Old Alton Bridge.

This is what Wikipedia has to say about Mississippi Map Turtles:

It derives its common name not from the state of Mississippi, but rather from the Mississippi River. The specific name, kohni, is in honor of Gustave Kohn of New Orleans, Louisiana, who collected the type specimen.

Females are considerably larger than males, the adult male being 3.5 to 5 inches (about 9 to 13 cm) in carapace length, and the adult female from 6 to 10 inches (about 15 to 25 cm) in carapace length. Males have a leaner look, more like juveniles, but females have a larger, bulkier build.