In 1835 M. Charles Léveillé described a peculiar and extinct univalve shell under the name Porcellia, which he had discovered in the Carboniferous Limestone of Tournay in Belgium. Since that time the right of this name to stand has never been questioned, notwithstanding the fact of its pre-occupation by Latreille in 1804, for an Isopodous Crustacean genus, and which he rendered Porcellio. As the retaining of two names so nearly alike, differing only in their terminal letter, must constantly lead to confusion in Natural History nomenclature, it becomes necessary to suggest an alteration, and Léveillia is therefore proposed to take the place of Levéillé's genus Porcellia.