Jørgensen & James (1983) in their detailed study of the Leptogium azureum group in western Europe, pointed out that L. azureum (Swartz) Mont. was absent from Europe and that most of the European material so named belongs to L. cochleatum (Dicks.) P. M. Jørg. & P. James. Although both species show some morphological similarity, they also show a great number of differences. Leptogium cochleatum develops a darker and thicker thallus than L. azureum, with a finely striate upper surface, a different arrangement of the photobiont in the thallus, apothecia with persistent±wrinkled margins, proper euparaplectenchymatous exciples, the presence of paraplectenchymatous tissue at the base of apothecia and muriform ascospores which are larger than in L. azureum. For a summary of the most important characters distinguishing these two species see Jørgensen & James (1983). Leptogium valdivianum M. Lindström, a species from cool temperate South America, has also been confused with L. azureum, however, it can be distinguished by its distinctly thicker and dark leaden grey­blue thallus, apothecia with persistent thalline margins and its larger and broader distinctly muriform ascospores (Galloway & Jørgensen 1995; Lindström 1996).