PROC. BIOL. SOC. WASH. 97(4), 1984, pp. 688-692 THE SYSTEMATIC POSITION OF THE NERITID PROSOBRANCH GASTROPOD NERITA POLITA AND RELATED SPECIES Geerat J. Vermeij Abstract.— A^mra polita Linnaeus, 1758, is the type of the new subgenus Lin-nerita of the genus Nerita Linnaeus, 1758. This species, like the three other members of the subgenus, is a common intertidal gastropod in the Indo-West-Pacific region. Nerita polita Linnaeus, 1 758, is an abundant intertidal gastropod which is widely distributed in the Indo-West-Pacific region from the mainland coast of East Africa to the Hawaiian Islands. It is the best known of a small group of distinctive Indo-West-Pacific species whose taxonomic unity has never been questioned but whose nomenclature and relationships to other members of the genus Nerita have re-mained unresolved. Baker (1923) exacerbated an already confusing situation when he synonymized several subgenerically distinct species under the single name Nerita polita. In this paper I review the relationships of A^. polita and its relatives to superficially similar species of the genus, and I formally erect a taxon for this group. Nomenclatorial Background Von Martens (1887-89) believed that A^. polita was the type of the genus Nerita Linnaeus, 1758, and therefore saw no need to coin a name for the group containing this and related species. Abbott (1958), however, confirmed the suspicion of other workers that the distinctive West Indian A^. peloronta Linnaeus, 1758, was the type of the genus. In his classification based on radular characters. Baker (1923) considered A^. polita to be a senior synonym of A^. umlaasiana Krauss, 1848, which von Martens (1887-89) established as the type of his subgenus Amphinerita. Nerita umlaasiana and its relatives are morphologically and ecologically distinct from A^. polita and its relatives, so that the name Amphinerita cannot be applied to the latter group. The only other name which has been proposed for the A^. polita group is Odontostoma Morch, 1852, but this name is preoccupied by Odon-tostoma Turton, 1829 (see Baker 1923). Accordingly, no valid name exists for the A^. polita group, even though most students of Nerita have recognized the distinctiveness of this group. Linnerita, new subgenus Type-species.— Nerita polita Linnaeus, 1758. Diagnosis. — Shell neritiform; spiral sculpture very weakly developed or absent; coUabral sculpture consists of closely spaced wrinkles slightly reflected away from outer lip; apex hardly protruding above rest of shell; outer lip with numerous weakly developed denticles; columellar edge with 3 to 5 teeth; parietal callus
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