Note that the FourCC codes used for chunk names and other identifiers, although they are often interpreted as 32-bit integers, are not reversed. They have the same order as in RIFF (left-to-right).
Evidently, there is also a little-endian variant of RIFX, whose files begin with "XFIR" ("RIFX" backwards). The difference between "XFIR" and RIFF is that in "XFIR", the FourCC codes are stored in reverse order (right-to-left).
RIFX files begin with ASCII "
Files that use the "XFIR" variant begin with "