Australis has striations on the petals and sepals and the labellum is quite distinctive. It has quite unique patterning. Red/purple and yellow lines extending down its length from front to back to near where the spur is on the inside of the labellum. The labellum also usually does not overlap the column but some forms do. The leaves on australis are different as well i have noticed. They are not as broad, as rigid or as dark green as either wallichii or tankervilleae. Here is another flower pic, note the patterning on the inside of the labellum. Even the forms with the overlapping labellum that some confuse with tankervilleae have this patterning. In my opinion the labellum is definitely the most destinguishing feature with its colour and patterning which you will not see in either tankervilleae or wallichii. The other species don't have the intricate patterning.
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