An emended circumscription of the genus Paulia Fée is given and the morphology and anatomy of the eight included species analysed in detail. Four new species are described, P. gibbosa Henssen and P. rhizophora Henssen from Bermuda, P. tessellata Henssen from Bermuda and Mexico and P. stipitata Henssen from Puerto Rico. The new combination P. cubana (Tuck.) Henssen is made. The genus is characterized by an umbilicate thallus composed of reticulately arranged hyphae; apothecia without an excipulum, with branched paraphyses and thickwalled ascospores; and a member of the Chroococcales as phycobiont with brown gelatinous algal sheaths in which characteristic particles are deposited. The species differ in the external morphology of the thallus and apothecia. The species all grow on limestone, and most of them are confined to islands; the distribution of the genus is world-wide.