Never give a sucker a ....

These two fish look similar; however, the photographers tell me they are different species.
First, to what genus do they belong? Why?

If you had the fish in your hand, what characteristics would you look at?

Would it help if I told you that:
The lips of the top specimen are plicate. The lower lip of the bottom specimen issubplicate.
Lips of the top specimen are larger that lips of lower specimen.
If you dissected out the pharyngeal teeth, you would see molariform teeth on top specimen and comblike teeth on bottom specimen.