A revision of 15 species of the lichen genus Calicium in the Indian Himalayas is presented. Six species-C. indicum, C. laevigatum, C. nobile, C pyriforme, C. tenuisporum and C. verrucosum-are described as new to science. Furthermore C. chlorosporum, C. hyperelloides and C. quercinum are new to India. Material from other parts of the Himalayas was also studied. Most Calicium species occur in the temperate mixed oak-conifer forest on the S face of the mountains, particularly at altitudes between 2500 and 3600m, where they inhabit bark of the lower parts of old trees and decorticated stumps, particularly in forests dominated by Quercus semecarpifolia or in mixed forests with Q. semecarpifolia and Abies pindrow, Tsuga dumosa and Picea. Descriptions of the species are supplied along with information on secondary product chemistry and habitat ecology. The ornamentation of the spores is described for the new species. An identification key to the species is provided. In a molecular phylogeny based on nuclear rDNA ITS1-5.8S-ITS2 sequences the new species appeared in different lineages in the paraphyletic Calicium, viz. C. pyriforme and C. verrucosum in the 'Caticium glaucellum-clade', C. indicum, C. laevigatum and C. tenuisporum in the 'Calicium viride-clade' and C. nobile in the 'Acolium-clade'. For each species 'Signature Sequences Stretches' ('SSS', usually 8-20 bp long), have been identified. They are-as far as known-unique to the species in relation to other Calicium species and species in related genera. They may hence serve as molecular markers for identifying the species. Forty new ITS sequences are reported.
