[tahoe61]

Crocea and Derasa are actually the easiest to tell apart. The Derasa has more of a green tint and lined mantel and a smoother shell. The Crocea may or may not have any scutes and tend to be blue to purple in color and more squat in appearence. But these are just generalizations. Just take a look at a Derasa in pics and they pretty much look alike except for the rare exception.