The Eastern River Cooter looks similar to the Yellow-bellied Slider Terrapin (Turtle in America) and is also from the USA.
It is a different species of terrapin and has less yellow around the shoulders, no vertical yellow bar behind the eye, different webbing to its back feet and a vertical yellow line down its back legs. Its upper shell is darker and as it gets older the shell becomes almost smooth and black as shown above right. Its belly doesn't have the dark spots that the Yellow-bellied Slider has.
It is one of six subspecies of River Cooters in different geographical ranges of the USA living in rivers, lakes and brackish coastal waters
and is related to other American Cooters and Red-bellied "Turtles" (Terrapins).