The Answer

Two of you guessed right!  The skull (last week's post) was that of a squirrel.  I got my first clue when I found a muskrat skull online.  The teeth were the giveaway. Of course, the muskrat was a lot bigger. Obviously I needed to look at smaller rodents and zeroed in on either sciurus carolinensis (Grey Squirrel) or sciurus niger  Fox Squirrel.   But that's as far as I could go.  There might be a slight size difference between the Fox and the Grey, but I haven't the knowledge or the ability to distinguish further.

Thank you everyone for your responses!  What fun!!!