I photographed this flower in Grenada in November of last year. The flowers were small (roughly 1½in or 4cm in diameter), white, with 5 narrow petals. There was just one flower on a stem, and one stem per plant (at least on the ones I saw); the plants had toothed leaves. It was growing wild near the Grand Etang Lake.
I did numerous Google searches, but could never find a match. I eventually found one image that looked pretty much identical, but the original page no longer exists, and (according to the Wayback Machine) it apparently didn't provide an identification anyway. Would anyone be able to point me in the right direction?