Lacuna is a genus of sea snails, marine gastropod mollusks in the family Littorinidae, the winkles or periwinkles.
The spiral animal body is elongated. The mouth has a proboscis with two thick lips and a spiral, filiform tongue. There are two slender, contractile tentacles with the eyes on small pedicels near their base. The foot is oval and somewhat broader behind.
The thin shell has an ovate-conical or subglobose shape and is covered with a delicate horny periostracum. It has a short spire with convex whorls that are rapidly expanding. The last whorl is ventricose, i.e. inflated in the middle. The apex is rather obtuse. The oval or roundish aperture is covered with a horny, spirally marked operculum. The peristome is incomplete behind. The columella is flattened and forms with the peristome an elongated groove continued from the umbilicus. This groove is bounded internally by the decurved margin of the pillar.
Species within the genus Lacuna include:
Lacuna carinifera A. Adams, 1851
Lacuna cleicecabrale Barros, 1994
Lacuna crassior (Montagu, 1803)
Lacuna decorata A. Adams, 1861
Lacuna latifasciata A. Adams, 1863
Lacuna lepidula A. Adams, 1863
Lacuna lukinii (Golikov & Gulbin, 1985)
Lacuna marmorata Dall, 1919
Lacuna minor (Dall, 1919)
Lacuna orientalis (Golikov & Gulbin, 1985)
Lacuna pallidula (da Costa, 1778)
Lacuna parva (da Costa, 1778)
Lacuna porrecta Carpenter, 1864
Lacuna pumilio E. A. Smith, 1890
Lacuna reflexa (Dall, 1884)
Lacuna setonaikaiensis (Habe, 1958)
Lacuna smithii Pilsbry, 1895
Lacuna succinea Berry, 1953
Lacuna turneri (Dall, 1886)
Lacuna turrita A. Adams, 1861
Lacuna uchidai (Habe, 1953)
Lacuna unifasciata Carpenter, 1856
Lacuna vaginata (Dall, 1918)
Lacuna variegata Carpenter, 1864
Lacuna vincta (Montagu, 1803)
Species brought into synonymy
Lacuna abyssicola Melvill & Standen, 1912: synonym of Moelleriopsis poppei Engl, 2012
Lacuna azonata Locard, 1886: synonym of Megalomphalus azoneus (Brusina, 1865)
Lacuna carinata Gould, 1848: synonym of Lacuna vincta (Montagu, 1803)
Lacuna cossmanni Locard, 1897 : synonym of Benthobia tryonii Dall, 1889
Lacuna macmurdensis Hedley, 1911 : synonym of Trilirata macmurdensis (Hedley, 1911)
Lacuna mediterranea Monterosato, 1869 : synonym of Ersilia mediterranea (Monterosato, 1869)
Lacuna neritoidea Gould, 1840 : synonym of Lacuna pallidula (da Costa, 1778)
Lacuna notorcadensis Melvill & Standen, 1907: synonym of Laevilitorina wandelensis (Lamy, 1905)
Lacuna pallidula var. patula Hanley in Thorpe, 1844: synonym of Lacuna pallidula (da Costa, 1778)
Lacuna puteolus (Turton, 1819) : synonym of Lacuna parva (da Costa, 1778)
