Shell— The shell has 7-8.5 slightly to rather convex whorls which are separated by a shallow suture. Shells of male specimens are smaller and have less whorls than those of females. Near the aperture the last whorl rises slightly. The peristome is strongly reflected, in particular in male specimens. At the apertural side of the penultimate whorl the ribs are generally rather widely spaced (about 5/mm), but in some specimens or populations they are very close (8-9/mm). They are even closer on the last whorl, except near the aperture. The ribs are rather regular but the number of ribs is very variable. On the penultimate whorl their number varies from 51 to 151. In some populations there are thin riblets in between these ribs.
Height 8.1-15.5 mm; width 4.0-6.4 mm.
The shell has a yellow to pale corneous brown colour; the peristome and part of the last whorl are white. The ribs have a pale corneous colour. Below the suture and on the lower part of the whorls, respectively, there are generally one and two bands, which may be uniformly brown or consisting of irregular whitish and brown spots; sometimes there is a light coloured band in between the two lower bands. The bands may be so broad that the shell is brown with only two lighter bands. Some specimens have broad, irregular vertical spots. In male specimens the upper whorls are violet, except the uppermost, embryonic, whorls which both in male and female specimens are pale yellow. In general, the colours are more vivid in male specimens.
In this variable species two extreme forms can be distinguished, viz. a larger and broad type with flat whorls, rather widely spaced ribs and a large aperture , and a small and narrow type with convex whorls, closely spaced ribs and a small aperture . The first form is most common in the lower areas along the northern slope of the Pyrenees and the second form is most common in higher mountainous areas in the central Pyrenees and in Spain. Both forms, however, may occur within a single population, connected by intermediate forms.
The animal is light grey, rarely blackish specimens occur. The sole is white, sometimes with a darker band along the edge. The anterior part of the proboscis is occasionally darker or lighter than the body and often the tentacles are darker grey with a pale ring near the base.
The radula is much shorter than it is in the other species, viz. 4-5 mm instead of 7-10 mm. The teeth have a quadrangular shape and central, lateral and marginal (Ml) teeth are all 0.27-0.30 mm broad.