Is certainly not O. costatum
O. costatum. Rootstock cormlike, v. ∞ fibrous diard roots, Lamina w. broad rather pale median band - hence name costat [costatum].
M.A. Pocock
Supplementary remarks:
Spores type = O. pedunculosum
Slide no. 2898
W.F.H., 16/8/[19]51