The chief economic use of biostratigraphic data is short distance temporal correlation within or between petroleum bearing areas and is based primarily on subsurface sampling. Of greater overall importance, the stratigraphic distribution of countless fossil organisms has permitted widespread approximation of time equivalence and forms the basis for recognitiion of the fundamental subdivisions of the geologic time scale. Echinoderm remains are common constituents of marine sedimentary rocks, especially during much of the Paleozoic; they rarely have been studied in such a manner as to become a widely used tool in biostratigraphic zonation. The common problems associated with the detailed stratigraphic study of echinoderms involve many of the “classic” characteristics of biostratigraphically useful organisms: