English literature buffs: purpose of "---shire" in "Pride and Prejudice"?

In Austen's "Pride and Prejudice" she wrote in some sections "The regiment troops of the ---shire" or something along the lines of that. Does anyone know what the purpose is of doing "---shire"? I asked my English teacher and she said that she's never been sure as to why Austen did that, and that it was common for other English writers to do the same. That's not a good enough answer for me!