Planktonic microfossils in Proterozoic sedimentary rocks can be recognized on the basis of their facies distribution, morphology, independence of the distributions of benthic microbial associations, and, where observable, spatial distribution within a rock sample as seen in thin section. Like their Phanerozoic counterparts, late Precambrian plankters exhibit discernible inshore-offshore patterns of distribution. Inshore and, especially, lagoonal biotas are characteristically low diversity assemblages dominated by one or a few taxa, while contemporaneous plankton assemblages from open shelf environment contain a diverse heterogeneous array of morphologically complex forms. As the paleoecological ranges of Proterozoic plankters are discernible, so are their stratigraphic ranges,...