~UPDATE~ Millie Crosier H. wrote: "According to Frank Pulaski's website, Arthur Crosier's son, Alexander Crosier, had a daughter, Mary Crosier, born 1798. That's the closest I can come to the right date and age for a "Mary" Crosier in the census. She would have been James A. Crosier's aunt.
But based on the ages involved, and the fact that James Crosieris listed as living with Rufus Crosier in 1860, at the age of 77, with "Mary" Crosier listed right under his name, and aged 76, I have a feeling that she really was Polly Stowe. I have no idea why she was calling herself Mary."