lucobrium, corrected
heard as lucobrium
spelled leucobryum
Leucobryum. Two letters go back in: the e of leuco- and the y of bryum.
What the ear did
Both losses come from the same instinct, which is to write what the mouth does. Neither vowel is audible as a separate sound, and both are load-bearing in the spelling.
L-E-U-C-O-B-R-Y-U-M
The full entry for leucobryum covers the name itself.