Relatively delicate shell up to about 12mm high (though males are only half his size). It has about 3 or 4 whorls with the last whorl occupying nearly the whole height of the shell - there is virtually no spire. The aperure is very large making up about 80% of the shell height. The shell possesses a very large umbilicalis and associated grove leading into this. The shell is greenish in colour.
- Shell has very low spire with large, D-shaped, aperture
- Very broad groove along the columella
- Lacuna parva has a taller spire and usually bands on the last whorl
Occurs primarily on Fucus serratus on the lower shore. Breeding occurs mainly between February and May with individual eggs laid within individual capsules in oval or circular jelly masses (of up to about 100 eggs). Young snails emerge directly from the eggs (no plankton stage).
Occurs from the Barents Sea south to France.