I'm not sure whether there's just one or in fact two species of Riccia in these photos. I'll be speaking to a Riccia expert next week and I'll see if it's possible to get an idea of the species from photos alone.
Yes, there is definitely two species in the photos. The species with the white margins is Riccia lamellosa and the one with black margins is Riccia inflexa. Both are common species of Riccia.
Hi guys. I have edited this sighting based on your advice, and added a new sighting:- http://canberranaturemap.org/Community/Sightings/Details/3343395 Please check my work. Cheers Michael