Having examined the material, and obtained a sequence, I think we can safely conclude this is Dermoloma hemisphaericum. It hasn't been recorded since the original collection, on which the name was based, 65 years ago from Otago. I've also examined that material (held by Royal Botanic Gardens Kew) and they are identical. I guess it's just been overlooked, being a bit drab, but 65 years is a long time in obscurity.
codfish
2016-11-00
2016/11/06 12:31 PM NZDT
New Zealand, Auckland, Howick, Mangemangeroa Valley Walkway
Cap dark brown, smooth and lighter around the margin. The gills are creamy-grey-tan with a sinuate attachment to the stipe. The stipe is light grey-tan and fibrous in appearance, 2.5 mm in diameter and tapering at the base to 1.5 mm. The cap was 1.6 cm in diameter and 1.3 cm in height. Remnant mature coastal broadleaf forest.