Meerdere mondopeningen bij landslakken, polystomie of polystomatisme?

The occurrence of a ”double” aperture in a gastropod shell found by Kronenberg (1998) is not new to science. Taylor described this phenomenon in 1894 and invented a name for it: ”polystomatism” (although to me ”polystomy” is a preferable term). It is probably caused by shell damage of the outerwall of the bodywhorl. Butot (1976) mentions two possible kinds of damage as causes: A hole in the outer wall, through which the snail forms a new aperture, or obstruction of the aperture e.g. if the epiphragm could only be partly removed after the winter, necessitating Helix pomatias to form a second aperture within the old one. Partial obstruction of the aperture most probably caused polystomy in Kronenberg’s Fruticola fruticum.