This is an old but commonly used name, there aren’t any formally recognized varieties or forms of this species. After some research, I believe this is what would have been called variety paraguay, however this is commonly distributed under the variety name ‘anceps’ and is sometimes referred to under the name ‘Hans Wiehler’ to denote whose collection it came from.
The branches are almost entirely flat, the blooms are white with marginal cream tipping and/or midstripe, and the branches have red margins that are enhanced with high light.