The Calyptraeidae are a family of small to medium-sized marine prosobranch gastropods. This family includes the slipper snails (Crepidula species), the Chinese hat snails, (Calyptraea species), and the cup-and-saucer snails (Crucibulum species) among others. The Calyptraeidae are the only family in the superfamily Calyptraeoidea. This family has no subfamilies according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005. Crepidula fornicata was brought to Europe on imported American oysters in the late 19th century and is now considered a significant pest in European oyster beds. Description Internally, the shell is distinguished by a shelf-like, cup-like, or half-cup-like structure used for muscle attachment. Some calyptraeids have shells that externally resemble those of limpets, so species in the genus Crepidula are often called slipper limpets. However, these snails are not closely related to true limpets and are more closely related to conches and cowries. The "slipper" in the name "slipper limpet" is based on the appearance of the inside of the shell, which with its half-shelf resembles a traditional western bedroom slipper. Reproduction Calyptraeids may form a tower of up to 25 animals, sometimes referred to as a mating chain. The bottom snail is always female. When she dies, the male above her will change from male to female, and the chain continues. Genera Genera within the family Calyptraeidae include: Bicatillus Swainson, 1840 Bostrycapulus Olsson & Harbison, 1953 Calyptraea Lamarck, 1799 Crepidula Lamarck, 1799 Crepipatella Lesson, 1831 Crucibulum Schumacher, 1817 Desmaulus Rehder, 1943 Ergaea H. Adams & A. Adams, 1854 Grandicrepidula McLean, 1995 Maoricrypta Finlay, 1926 Sigapatella Lesson, 1930 † Taimyroconus Guzhov, 2015 Trochita Schumacher, 1817 Genera brought into synonymy Cheila Modeer, 1793: synonym of Cheilea Modeer, 1793 – this is actually in the Hipponicidae, not the Calyptraeidae Clypeola Gray, 1868: synonym of Sigapatella Lesson, 1831 Crypta Gray, 1847: synonym of Crepidula Lamarck, 1799 Dispotaea Say, 1824: synonym of Crucibulum Schumacher, 1817 Galerus Gray, 1847 : synonym of Calyptraea Lamarck, 1799 Garnotia Gray, 1857: synonym of Crepidula Lamarck, 1799 Ianacus Mörch, 1852: synonym of Crepidula Lamarck, 1799 Siphopatella Lesson, 1831: synonym of Syphopatella Lesson, 1831; synonym ofCrepidula Lamarck, 1799 (unjustified emendation of Syphopatella) Spirogalerus Finlay & Marwick, 1937 †: synonym of Sigapatella Lesson, 1831 Syphopatella Lesson, 1831: synonym of Crepidula Lamarck, 1799 Trochatella Lesson, 1831: synonym of Trochita Schumacher, 1817 Trochilla Swainson, 1835: synonym of Trochita Schumacher, 1817 Verticumbo Berry, 1940 †: synonym of Crepipatella Lesson, 1831 Zeacrypta Finlay, 1926: