Left: Mixed sizes/generations of C. trifasciata living together. Northern Ireland, January 2024. © D. Craig.

Right: 1: C. trifasciata H. 3.8 mm. Three bands on body whorl (see fig. 05) occasionally all white. Spire whorls slightly rounded. Spiral striae on body-whorl, may be obscure. 2: Lacuna vincta H. 2.9 mm summer juvenile; no adults in summer. Four bands on body whorl, but can be fused or absent. Spire whorls well rounded. No spiral striae. 3: Lacuna vincta H. 5.8 mm in February, winter adult. Max. H. 10 mm. In winter all L. vincta are bigger than C. trifasciata.