Size and shape comparison with similar species. B:: Barleeia unifasciata 2.9 mm high. One brown band on body whorl. C: C. trifasciata 3.8 mm high. Three bands on body whorl (occasionally white with no bands). Spire whorls only slightly rounded. Spiral striae on body-whorl (may be obscure). E: Eatonina fulgida 1.0 mm high (max.) Three bands on body whorl. Short spire, tumid whorls. L: Lacuna vincta 2.9 mm high summer juvenile. Four bands on body whorl (but can be fused or absent). Spire whorls well rounded. No spiral striae. In July L. vincta are rarely, if ever, higher than adult C. trifasciata; in winter they are larger than it. P: Peringia ulvae juvenile 2.5 mm high. No bands.   Most of these species also have unbanded forms.