Check out this link and scroll down half way to find out. http://www.thenatural-gardener.com/December2008.pdf
They're both called Christmas ferns. And they look really different. I bought a little Selaginella one today, after seeing a friend's. The tag says that, and the web page terrestrial_man pointed to shows it - but the article does say When I first queried the common name, I just got Polystichum hits.