Brasilennea arethusae is a fossil species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Cerionidae, from the Paleocene Itaboraí Basin, Brazil.[1] Brasilennea arethusae is the largest species in the genus Brasilennea.[1] It was one of the first fossils found in Itaboraí Basin and its name makes reference to the fact that it is a terrestrial species: the name is in honor of Arethusa, a sylvan nymph and one of the Hesperides from Greek mythology.