The intra-molluscan stages of three species of the Mesometridae Poche, 1926 are described. The corresponding adult stages are intestinal parasites of herbivorous sparid teleosts. The cercariae develop in prosobranch gastropods. The larvae of Elstia stossichianum occur in Vermetus triqueter, those of Wardula capitellata are parasites of Barleeia rubra and those of Centroderma spinosissima are found in three related rissoid hosts species: Rissoa ventricosa, R. auriscalpium and R. similis. The phylogenetic status of the Mesometridae in the Digenea is discussed in relation to larval and life-cycle characters.