Natica millepunctata from Korytnica is as elongate as N. helicina sympatric with it, whereas N. millepunctata from Nawodzice (the only naticid species at this locality) is significantly more globose than both the Korytnica naticids. It is here postulated that this intraspecific morphological differentiation resulted from either a convergent character displacement, or a divergent character release. Character shift has also been detected in shell size of N. millepunctata. The shifts were related to interspecific competition for food.