These two species seemed to be destined for confusion, no doubt about it. Except that labiata is a fall bloomer and mossiae is a spring bloomer.
I just went though 82 AOS awards for Cattleya mossiae and found all of them to be blooming Essentially from March through May, one was very late February. As for Cattleya labiata, out of 68 AOS awards, I found one for late July, one for August and the vast majority were September through November. The only exception I can think of is Newly Imported Plants. I say that for this reason. If you purchased or acquired a Cattleya mossiae from a South American source, their spring IS our Fall. So that newly acquired plant make take a year or so until it conforms to our Spring here in the Northern Hemisphere.
The same would also be true for a Cattleya labiata. They can bloom 6 months out of sequence.
Now my research indicated that mossiae was the second described Cattleya species after labiata. They have been capturing awards from the RHS since the early 1800's! That's amazing!
Now from what I remember from blooming both species is the substance of the blooms. This is something that you really do not read about since it comes from direct observation. Mossiae in my experience does not have the best substance. They are a floppy flower. Dorsals flopping backwards are not rare. When you see mossiae after mossiae as a judge at shows for example, you notice the thinner, substance. Labiata on the other hand has better substance. I would not call it "heavy" or "waxy", but it is clearly more substantial then mossiae.
The other observation comment that I have, and your beautiful image shows this Ursula, is the tubular-like aspect to the mossiae lip. Labiata's lip is generally more open and broader. Mossiae's is more narrow or it appears 'elongated'! Plus, and this is something I notice all of the time, the golden and amethyst coloring in the Mossiae lip reminds me of the coloring of a lueddemanniana lip.
