Opaque shell is white internally and externally, apart from thin external pale-pinkish/pale-brownish layer deposited by external mantle in grooves dorsally and laterally; ribs receive less pigment so paler than grooves.
No pitch-brown/black marks on shell.
Aperture a gently bowed slit along entire height of shell, positioned ventrally on living animal.
1: extension of aperture at posterior forms exhalent-siphonal canal.
2: wide extension of aperture at anterior forms inhalent- siphonal canal.
3: curved groove, and ribs protrude as teeth, but no lip on body-whorl on inner side of aperture.
4: outer (palatal) lip curved out of sight into interior of shell.

. Height (longest shell-dimension) 9.6 mm. Ardnamurchan, Scotland. April 1976.