This small plant-leaves <5mm across-grows in very boggy conditions at the Kuripapango lakes, Kaweka Ranges. I think it is a Schizielema but there is also a pic of a Hydrocotyle that has similar leaves but is without much written detail. I'm hoping that whichever it turns out to be it will be one for which there is not yet a pic.
As an aside, under Doodia milnei in the para headed Features the word 'industrious' has, I think, been substituted for indusia