Features 1, 2, 6 and 7 match those in ‘Key features’ and ‘Similar species’ section of main account.

1 When live, calcareous, white shell is covered by substantial periostracum that is smooth, apart from numerous growth lines; brown or olive-brown on adults.

2 When live, adult shell is opaque.

6 When live and active, mantle may protrude very slightly, but is not reflected onto the shell.

7 Flesh usually white, often with some yellow on snout, penis and parts of foot. Sometimes flesh is pink or whitish grey.

Left: 12 mm, Dorset, April 2016. Right: H 7.5 mm, W 9.5 mm, Anglesey, March 2014.