In the Mississippian (Early Carboniferous) of the Rocky Mountain and Great Basin regions of the United States, colonial Rugosa occur exclusively in shallow-water lithofacies. Tabulates occur in both deep- and shallow-water lithofacies. Among the solitary Rugosa, which occur in both deep- and shallow-water lithofacies, deep-water forms are predominantly nondissepimented. Most taxa that occur in both deep- and shallow-water lithofacies first appeared in deep water, then migrated to shallow water later in geologic time. Corals lived predominantly in deep water during Kinderhookian (early and middle Tournaisian) time, despite the existence of large areas of shallow-water deposition. A marked shift in coral occurrence to predominantly shallow-water environments took place in latest Kinderhookian (middle Tournaisian) time, and this trend toward shallow-water continued to the end of the Mississippian (early Namurian).