Thanks for all these replies, Davemonkey, in particular. None of the species pictured on the US Gov. site you give are the one that I have collected. Mine is very fine and 'spidery'; fragile. I'm going to collect some more today and set it up in an old 10-gallon outside.
On the Ontario Provincial Government website there are NO riccia listed as native in the aquatic plants catagory, but I tend to think that this may simply be an under-researched area.
I fear it may be tricky to photograph my riccia well, but I'll try.
No responses on whether anyone has tried using native riccia in their tanks, so I'm taking this as a provisional 'no'.