Not sure about this one. E. cucullatus is, supposedly, not found above 800m, so I am inclined to think that it is a pale or partial albino form of E. magenteus.
I take it that post flowering leaf characteristics are the most reliable way to differentiate between the species and in the absence of leaves altitude is a more reliable character than flower colour? I haven't been able to find the original description for E. magenteus online, since this is a Jones species do you know if he has published anything else beyond the original description on this species other than the ACT orchid book?
In both species the leaf is not completely developed at flowering time. Both are ovate to heart shaped. In the Canberra region, E. magenteus flowers in February while E. cucullatus does not usually commence flowering before March. Another reason for thinking its more likely to be E. magenteus. I'm reasonably certain the original description of E. magenteus was in The Orchadian, but I would have to look it up
Ken, the description is in The Orchadian (Vol 15, No 12, June 2008). Apart from colour, the main differences are in leaf and labellum detail. I have decided to confirm it as E. magenteus based on altitude and timing of flowering.