Eight species of Herpothallon are recorded from the Andaman Islands, four of which are described as new: Herpothallon coralloides, H. globuliferum, H. lutescens and H. minutum. All these new species have a non-pigmented thallus, prothallus, hypothallus and pseudisidia. Herpothallon coralloides and H. lutescens possess cylindrical pseudisidia whereas H. globuliferum and H. minutum have granular to globose pseudisidia. Herpothallon globuliferum is foliicolous. Herpothallon echinatum, H. granulare, H. granulosum and H. philippinum are reported for the first time from the Andaman Islands. A key to the Indian species is provided. Heiomasia pallescens (Graphidaceae), a byssoid taxon with a disc-shaped isidioid structure, is also described as new to science.
