Left: 13.5mm high X 17mm wide. Young adult with white outer lip not yet much everted.
Centre: 11.5mm high X 16mm wide. Older adult with everted lip and pitted shell.
Right 11.5mm high X 14mm wide. Juvenile with thin fragile outer lip.
The nature of the outer lip is a better indicator of maturity than shell height.
1: shell height 13.5mm.
2: height of body whorl 83% of shell height. So spire 17%. Spire 15% on other adult, 11% on juvenile; juveniles of most gastropods have relatively smaller spires than adults of same species.
3: height of aperture 55% of shell height. Other adult 45% (may be diminished by angle of view having apex tilted slightly forwards), juvenile 69%; juveniles have rounder aperture than adults.
4: columellar lip very small on adults.
5: columellar lip distinct on juveniles.
6: thin, fragile outer lip lacking any thickening indicates juvenile shell.
7: thickened, white outer lip indicates adult shell, everts on older specimens.
8: faecal pellets expelled from pneuomostome (respiratory pore) while animal retracted into shell; white as had eaten white cardboard.
9: straight basal section of adult outer lip.
10: curved basal section of juvenile outer lip.