This is a species easily recognizable due to its very characteristic sculpture made by three considerable spiral cords divided by two deep grooves obliquely striated by numerous lamellae imbricated. The shell has whorls convex but sharp-cornered mainly on the periphery, base convex , umbilicus narrow and deep, aperture subround, pearly, with two folds in correspondence with the grooves. Columella straight with one considerable tooth on the lower part. Base adorned with numerous concentric little cords with thin lamellae in the interspaces. Operculum corneus, multispiral. Ground dirty white in colour pattern either with flammulae, streaks or stains brown-reddish in colour, present at the base too. The adult specimens average measures are around 8-10 mm in diametre.

It is recognizable from the juvenile forms of G. magus due to the different sculpture of the first whorls (more reticulated in magus) and to the lack of the considerable tooth on the lower part of columella. The juvenile forms of G. fanulum are slimmer in outline, they have one more prominent peripherical carina and a different sculpture.

Distribution: it can be found in the Western Mediterranean and in the Adriatic Sea but never common
Habitat: it lives between rocks and meadows of Posidonia oceanica, in the infralittoral zone.