Dusky Horkelia?

As a naturalist, I come back from almost every outing with more questions than answers. Also, as a naturalist, questions come easily - too many questions to research by doing straight science. If I were doing science research in a "publish or perish" environment, I'd have to narrow the scope of my curiosity. Maybe study one species of lizard for 30 years, that sort of thing. But since I have the luxury of letting my curiosity loose, I can afford to take pictures, draw and paint what I see, and comment on what I see without the obligation of having to know all the answers or to find answers by doing direct research. So, I consult field guides, experts on particular taxa, and any other promising source of information.
I hope the forgoing paragraph is sufficient justification for posting photos or drawings of species I haven't yet been able to identify. I welcome input from any readers who recognize what they are. Today's posting is three photos of a small white flower I saw on the Old Highway near Keddie, the same spot where i saw the season's first Shooting Stars a couple of weeks ago. They're a really interesting looking flower, 5 smallish petals and 5 prominent sepals arranged in such a way that at first there appear to be 10 petals. My first trip through my field guides and a couple of websites has me thinking it's Dusky Horkelia, Horkelia fusca, a member of the rose family, Rosaceae. Please help meout here, botanists. I love the way this flower looks, so I'll be going back to get better photos if I can. Also saw Shepherd's Purse today, blooming in the school district office lawn. Hope I get to photograph it before they mow.
THIS JUST IN: Sunday, May 1. A little more careful research and I see that I was "close, but no cigar" as they used to say in the circus. The new flower is Three-toothed Horkelia, Horkelia tridentata. Should have been obvious if I had paid more attention to the leaves.