Molluscs living in shingle on the south shore of the lower Fleet, Dorset, are listed, and densities at various tidal levels are given for the commoner species. Two assemblages are described. The upper one was characterised by Truncatella subcylindrica and contained lower densities of Ovatella myosotis, Leucophytia bidnztata, and rarely Paludinella littorina. The lower one occurred in areas known as ‘springs’ where oxygenated sea water emerged continuously. The only species common in the springs was Lasaea rubra, which was extremely patchy. Other species were rare, but several usually subtidal species were found there, e.g. Emarginula conica and Leptochiton asellus. Factors affecting the distribution of these species, especially their patchiness, are discussed.