Floristic affinity of bentonic vegetational types of Cala di Mitigliano (Massa Lubrense Napoli). — We have studied the bentonic plants community in the Cala di Mitigliano. It appears that some species compositions repeat themselves with a certain regularity. This fact lets us recognize and consequently classify them. In Cala di Mitigliano we took an interest and considered only such species compositions. We calculated, in them and between them, the coefficient of affinity by SÖRENSEN(1948). The cluster analysis by average linkage and the use of an index of «individualisation» (Feoli, ined.) based on floristic comparison showed that the species compositions, although we chose such ones to describe the vegetation, equally change gradually from place to place.