Parietal callus

The Parietalkallus is a part of the housing of different snail species. It involves a thickening of the parietal wall, which is next the wall of the penultimate turn of the spindle ( columella ) with other Kalkan bearings. The Parietalkallus is usually smooth and shiny, but can also be sculpted.

The function of the Parietalkallus is not yet clear, although a large part of the screw housing occupies particularly in many marine snails close to the mouth, and seems to be repeatedly developed independently of each other at different unspecified screw related families ( convergence).

A Parietalkallus is present in some families of marine snails such as the Ranellidae, Cassidae, Nassariidae, Ringiculidae, Olividae and Strombidae. But he also occurs in some families of terrestrial snails, for example, in the Mulmnadeln ( Aciculidae ) and the Polygyridae.