Justin is right, it is what most call Philo. micans. If you do some indepth research though, people have several other names that are also used. Great terrarium plant though, have it in a couple of my tanks, absolutely love the coloring on it.
If you are into taxonomy then look at the link on the bottom of the first page.
That being said, it is a great vivarium plant and has done really well for me. I keep it as a houseplant, in vivariums, and have even have some cuttings that have been kept in just tap water for about five months (and have started cuttings from these cuttings!).