Callus (mollusc)


The shell of the sea snail Neverita josephinia has an umbilical callus which almost completely fills the umbilicus, leaving only a groove open.

A callus is an anatomical feature that exists in some mollusk shells, a thickened area of shell material that can partly or completely cover the umbilicus, or can be located as a coating on the body whorl near the aperture of the shell (i.e. a parietal callus or columellar callus).

A callus exists in the shells of various species of gastropods (snails) and also in the shells of several species of Nautilus, a cephalopod.

The shell of the sea snail Semicassis pyrum, has a large aperture and a pronounced parietal callus

A callum is an anatomical feature of some mature bivalve shells of species in the family Pholadidae, the piddocks.[1] The callum is an area of shell material that fills the gap between the two valves.[2]


  1. ^ "Corns and calluses: Symptoms, diagnosis and treatment". Retrieved 2017-08-15.
  2. ^ Definitions of terms for parts of gastropod shell