Seen that critter in Ellsworth Oh.(just west of Canfield). Actually, there were two of them there with that same color combo, not to mention several other black ones.
I heard about Kent. From what i understand, blacks are simply a color phase of the gray squirrel, which pretty much says they are the same critter.
But a part black and a part fox squirrel make them basically a different phylum of said species, a new animal. Very cool, me thinks.