This is a very variable species, both locally and geographically, which mainly differs from R. guerinii and R. similis in the larger dimensions of the apex, in the colour of part of the shells, and in the distribution. The lower limit of the apical dimensions of R. lia is about d = 0.09 mm. Slightly smaller apices do occur, but are quite rare. The upper limits of the apical dimensions are about d = 0.13 mm. In addition to the dimensions of the apex, R. lia is characterized by the protruding and inflated nucleus of the apex. The length of the shells varies, 2.0-5.4 mm. Punctate spiral striae are usually present in shells of R. I. lia. In some specimens, however, they may be absent. In others, they may appear only at the lowermost part of the shell. Most shells of R.lia are ribbed. Generally, there are 8-14, rarely 15 terminal ribs per whorl. Some shells, however, may be ribless. A labial rib is usually present, though it may be weak or absent in some shells or samples. As in R. guerinii, the labial rib is white. There usually are 1-4 ribbed whorls. The area between the last well-developed longitudinal rib and the labial rib may vary from about nil to as much as one whorl, occasionally even more.
As regards the colour, R. lia is very variable indeed. In a sample from Trapani, Sicily many colours and colour patterns can be discerned, among which the colour pattern conspersa, known in R. guerinii and R. decorata. Shells from S. France may be more or less similar to the normal colour variety of R. guerinii, though the colour lines between the ribs tend to be shorter. Among material from Getares, S. Spain, however, shells of R. similis, R. guerinii and R. lia could be separated in a very satisfactory way with the help of the colour and other characters, even before the dimensions of the apices of the last two species were measured. Shells of R. L lia from that locality are somewhat different, in particular as regards the presence of broken brownish colour lines which encircle the shells.

R. lia is washed ashore quite numerously at many localities in the western Mediterranean and in the Adriatic Sea. In my experience, it is somewhat more rare in the eastern Mediterranean, but I have seen fine specimens from Rodhos town (Vrd 0235) and Naxos (Cad). The Rijksmuseum van Geologie en Mineralogie, Leiden, contains a sample of fresh shells from the Canary Islands.