Polymorphism in fossil Velacumantus australis (Gastropoda : Potamididae)

Abstract

The snail Velacumantus australis occurs in banded and unbanded forms. An examination of fossil and living material from a shell spit at Wallaga Lake shows that the frequency of the white-banded form varied between 2.11 and 4.47% during the last 2500 yr. Such minor fluctuation is consistent with the hypothesis that these two forms are maintained as a selectively balanced polymorphism. Predatory gastropods may kill more unbanded than banded juvenile snails.