It looks quite a bit like the water wisteria (aka Hygrophila difformis) I used to have. Wisteria is a plant that has completely different appearances depending on what kind of light its grown under... low light looks a lot like your picture, higher light tends to look like most of the pictures that Google returns.
That's exactly what mine looked like when I brought it home from the LFS. After it started growing under high lights it was like a completely different plant. I have Bacopa too and it does have a much rounder leaf.
I though you meant the one at left... go figure. The green one is definitely Hygrophila difformis. I've kept bunch of them in mid to high light tanks. This plant may not do so well in low light as it will likely loose its lower leaves. It needs to be anchored until it develop strong roots capable of holding it in place (which takes some time).
Placed directly below the lamp might be a solution in low light tanks. If you attempt this route, try to place the lamp assembly as far back as possible since this plant will find its way to the surface (and change the morphology of the leaves, hence the name "difformis").
One last thing: consider dosing chelated iron (and other nutrients if possible) at least weekly since this plant seem to have an uncanny nutrient uptake from the water column. If you don't, this plant, and likely all others may turn yellow and perish.