All have more than one denticle on the palatal (outer) lip; M. myosotis has none or a single one.
1: Caker Point, Cloghan, S. Kerry, Ireland. Leg. A.W. Stelfox 4th June 1948. 10mm high; unusually large for the species.
2 & 6: Menai Strait, Wales. Under stones at EHWS, sheltered, full salinity, no vascular saltmarsh plants or Puccinellia maritima sward.
All others from by tidal River Dee under stones or driftwood at EHWS, low salinity, on Puccinellia maritima sward close to sandstone cliff.
5: abapertural view of live specimen in water (more translucent than when dry). Lines indicate palatal protrusions visible through shell from exterior; double row of 4 near rim and single row of 4 far back in the aperture marking a previous lip position.

marinvert.senckenberg.science/image-browse/