Abapertural/dorsal view. Growth sequence of post veliger shell.

Largest juveniles larger than many adults. May be because shell reabsorbed during change to adult (disputed by Forbes & Hanley, 1853), or because of individual size-variation.

As with most snails, the size of the spire relative to the body whorl increases with growth until over 6mm shell-height; then it reverses and becomes relatively smaller until enveloped entirely by the final whorl.

Heights in mm, top left to bottom right: juveniles 3.3 (N. Rona 2015), 6.3, 9.6, 11.7, adults 10.1, 11.2. Orkney 1975.