Modern ecologic models for conodonts were extrapolated principally from experience with North American shallow-water subequatorial faunas. Further evidence can be derived from the calcareous lower part of the Swedish Ordovician. This succession among other things offers uniformity of facies, as well as long-ranging conodont genera. Paleomagnetic data indicate deposition at 60°S, i.e., relatively cool climate and fluctuations in air and shallow-water temperatures. The succession might represent a subantarctic shallow-water carbonate platform. Another interpretation favors depth of 100 to 500 m. The relative frequencies of long-ranging conodont genera were plotted against facies data. All data indicate complexity of interaction of depth,...