Click to enlarge, and take a look at the size of the claws. This is a Red-bellied Turtle (Pseudemys rubriventris). The males have elongate claws which they use to stroke the females during courtship.
Red-bellied Turtles are common here in the Potomac, but are threatened in Pennsylvania, and endangered in Massachusetts.
In comic book terms, this is what happens when you cross the Teenage Mutant Ninja Turtles with Wolverine.