Sub-adult L. crassior.
A) Dead shell has costal ridges of periostracum reduced by drying. Distinct spire (1) 46% of shell height; body whorl (2) 82% of shell height. Dots are boundary between spire and body whorl. Shell height 5.5 mm, Orkney, August 1976.
B & C) Fresh shells in water with thick periostracum raised in distinct transverse (costal) ridges (3). Wide white columellar shelf (4); groove/chink and umbilicus absent. Heights 3.7 mm and 5.3 mm, North Yorkshire, England, September 2014.

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