Coenocorrelation is the correlation of positions in a stratigraphic sequence with corresponding positions along a paleoenvironmental gradient through gradient analysis of fossil communities. By ordination of community samples, the distribution and abundance of taxa along a depth gradient can be translated into a continuous scale that accurately measures the gradient and thus makes possible analysis of facies change on a continuum. The procedure is tested using data on marine benthic invertebrates along ten time-parallel transects down an Ordovician basin slope (Trenton Group, New York). Reversals between transgression and regression revealed in coenocorrelation curves served nearly as well as bentonite beds in time-correlation of sections. Ordinations gave estimates of depositional strike in close agreement with estimates from physical indicators. Walther's Law of Facies is evidently a more rigorous, quantifiable generalization than it has been revealed to be through classificatory approaches to communities and environments.