Rissoa is a genus of minute sea snails, marine gastropod mollusks or micromollusks in the family Rissoidae. The genus was first introduced by M. de Freminville for some small shells observed by M. Antoine Risso, a distinguished naturalist of Nice, France. They were described by M. Demarest in 1814 in the "New Bulletin of the Philomatic Society". Description The soft body of the snail is elongated and spiral. The somewhat prolonged mouth has a proboscis. The tentacles are awl-shaped with the eyes on a small prominence near the base. The foot is oval or elliptical. The species is phytophagous. The conical shell has an elongated spire with its apex nipple-shaped. The size of the shell varies between 1 mm and 8 mm. The whorls are generally convex-shaped with a distinct suture. The aperture is ovate, roundish or pear-shaped with its anterior end rounded, the posterior end acute and with the peristome complete. The thin and horny operculum is spirally marked and equally ovate, roundish or pear-shaped. Habitat This species can be found on brown algae (genus Fucus), in clefts of rocks, on stones, on mud or sand. Most will be found on sandy beaches along the line of the last tide. Species Species within the genus Rissoa include: Rissoa aartseni Verduin, 1985 Rissoa acerosa Seguenza, 1903 Rissoa acutata Schauroth, 1857 † Rissoa acuticosta (Sacco, 1895) † (Homonymy junior secondary homonym of R. acuticosta Von Koenen, 1892, which seems to be a true Rissoa) Rissoa acuticosta Von Koenen, 1892 † Rissoa adela d'Orbigny, 1852 † Rissoa aethiopica Thiele, 1925 Rissoa albugo Watson, 1873 † Rissoa alienocurta Lozouet, 1998 Rissoa alleryi (Nordsieck, 1972) Rissoa alpina Gümbel, 1861 † Rissoa angusticostata Sandberger, 1860 † Rissoa angustior (Monterosato, 1917) (taxon inquirendum) Rissoa anomala Eichwald, 1830 † Rissoa arata Philippi, 1849 Rissoa athymorhyssa Dall, 1892 † Rissoa auriculata Seguenza, 1903 Rissoa auriformis Pallary, 1904 Rissoa auriscalpium (Linnaeus, 1758) Rissoa australis G. B. Sowerby II, 1877 Rissoa baldacconii Cantraine, 1842 † Rissoa balliae W. Thompson, 1840 Rissoa banatica Jekelius, 1944 † Rissoa basisulcata Etheridge & Bell in Bell, 1898 † Rissoa becki W. H. Turton, 1933 Rissoa bissulca Buvignier, 1843 † Rissoa boytonensis Harmer, 1925 † Rissoa buccinalis (Lamarck, 1804) † Rissoa callistrophia Dall, 1892 † Rissoa candidata W. H. Turton, 1932 Rissoa certa Svagrovský, 1971 † Rissoa clotho Hörnes, 1856 † Rissoa conica L. Périer, 1867 Rissoa conuloidea Etheridge & Bell in Bell, 1893 †