Joe Connell's study of competition between two species of barnacles in the rocky intertidal zone showed that the lower limit of Chthamalus was determined by interactions with the snail Nucella the lower limit of Chthamalus was determined by dessication the upper limit of Chthamalus was determined by competition with Semibalanus the lower limit of Chthamalus was determined by competition with Semibalanus.