Riccia sommieri Levier is reported for the first time in Corsica, France. The ecology of the species in Corsica is described. Several morphological characters are deeply examined and critically evaluated based on the analysis of the material collected in the new Corsican localities and 24 additional herbarium specimens from various origins. As a result, ventral strips called “bandelettes” in Jovet-Ast's publications are referred to remnants of ventral scales. The hypodermis of Riccia sommieri is unique in the genus Riccia. This might support a phylogenetically and taxonomically isolated position of the species.