Williamia

Williamia is a genus of small sea snails or false limpets, marine pulmonate gastropod molluscs in the family Siphonariidae, the false (air-breathing) limpets.

Their development is similar to other Siphonariids.

Species
Species within the genus Williamia include:
 * Williamia eximia (Nevill in G. & H. Nevill, 1869)
 * Williamia gussoni Costa, 1829
 * Williamia krebsii (Mörch, 1877)
 * Williamia magellanica Dall, 1927
 * Williamia peltoides (Carpenter, 1864) - shield false limpet
 * Williamia radiata (Pease, 1860)
 * Williamia radiata nutata Headley, 1908
 * Williamia subspiralis (Carpenter, 1864)

Species brought into synonymy:
 * Williamia galapagana Dall : synonym of Williamia peltoides (Carpenter, 1864)
 * Williamia gussonii (O. G. Costa, 1829) : synonym of Williamia gussoni (Costa O. G., 1829)
 * Williamia japonica Habe, 1962 : synonym of Williamia radiata (Pease, 1860)
 * Williamia kermadecensis (Iredale, 1912) : synonym of Williamia radiata (Pease, 1860)
 * Williamia nutata (Headley, 1908) : synonym of Williamia radiata nutata (Headley, 1908)
 * Williamia oblongata (Yokoyama, 1926) : synonym of Siphonacmea oblongata (Yokoyama, 1926)
 * Williamia polynesica Rehder, 1980 : synonym of Williamia radiata (Pease, 1860)
 * Williamia radiata Kuroda & Habe, in Habe, 1961 : synonym of Williamia radiata (Pease, 1860)
 * Williamia tomlini (Robson, 1913) : synonym of Aporemodon tomlini Robson, 1913