This is Masd. wagneriana var. pteroglossa. Its a miniature Masdevallia. Its growing in a 2 inch pot of sphagnum and I keep it in my basement under fluorescent light. The basement is cool and mildly humid, so the Masdevallias do OK down there, although admittedly they'd probably do better if I watered more often.
When this opened I was confused because I thought I'd never bloomed the plant before but it looked very familiar. After checking my images I find that I have a Masd. citrinella (second photo) that looks very similar, although the plant is slightly larger and it doesn't have the red racing stripe in the dorsal sepal.