An analysis of shell shape variation in the painted topshell Calliostoma zizyphinum (L.) (Prosobranchia:Trochidae)

Littoral and sublittoral Calliostoma zizyphinum (L.) from fourteen sites around Ireland are compared by a new method of shell shape analysis. The apparatus used is described and results show clear variation between populations. It is also used to show similarity between the variegated and white morphs found in Strangford Lough. Patterns of growth are shown to be largely in response to the habitat conditions encountered at each site. The mean apical angle of each population is shown to be of great importance in distinguishing populations of topshells, as it varies with the relative exposure of each site