A number of taxa described as endemic to the Galapagos Islands are here treated as integral parts of two species aggregates. One is Roccella lirellina (Darb.) Follm. and the other is R. galapagoensis Follm. Roccella lirellina (Darb.) Follm. is considered the sorediate, sterile counterpart of the fertile R. galapagoensis Follm. Both aggregates present a considerable morphological and chemical plasticity and no clear discontinuities between specimens or populations within the aggregates can be distinguished on basis of morphology, anatomy and chemistry alone. Included under Roccella lirellina are the taxa and names: R. floreana, R. kappeniana, R. margaritifera, R. nigerrima, R. margaritifera f. octopodioides, R. stipitata and R. translucida. Included under Roccella galapagoensis are the taxa: R. capitata, R. colonii, R. geniculata, R. glebaria and R. obscurissima. The identity of Roccellodea nigerrima [Roccella nigerrima (Darb.) Follm.] and Reinkella lirellina Darb. [Roccella lirellina (Darb.) Follm.] is clarified