Molluscan assemblages on an intertidal sandflat in Princess Royal Harbour, Westren Austrailia

The molluscan fauna of an intertidal sand beach in Princess Royal Harbour, W.A.. is divided into two associations. The upper association, located between +0.10 and +0.59 m relative to tidal datum, is characterized by Hydrococcus graniformis and Batillariella estuarina. The lower assemblage, between +0.09 and -0.29 m is dominated numerically by Zeacumantus diemenensis and Katelysia scalarina. The assemblages are equivalent to the midlittoral- and sublittoral-fringe groupings described on both sandy and rocky shores by other authors. There is no supralittoral-fringe component in the molluscan fauna ofprincess Royal Harbour. The break between the two assemblages occurs at + 0.1 m, just below the minimum tide level in the area. Possible reasons for the zonation patterns are discussed and compared with other studies of intertidal zonation on sandy shores.