This was described as a natural hybrid between C. nobilior and C. walkeriana that occurs in the State of Goias, Brazil. Opinions vary a little as to whether it would really be a hybrid or a separate species because it is common in the wild, in the sense that it was found a uniform population.
This guy in the photo has very good shape and besides these two flowers there are six other buds just about to open! In a week or so it is going to make quite a sight!