Circulus
Shell of Circulus ryalli (paratype at MNHN, Paris)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Subclass:	Caenogastropoda
Order:	Littorinimorpha
Superfamily:	Truncatelloidea
Family:	Vitrinellidae
Genus:	Circulus Jeffreys, 1865
Type species
Delphinula duminyi Requien, 1848
Synonyms[1]
Circlotoma Laseron, 1958 Circulus (Circulus) Jeffreys, 1865 Cyclostrema (Lydiphnis) Melvill, 1906 junior subjective synonym (original combination) Elachorbis Iredale, 1915 Lydiphnis Melvill, 1906 junior subjective synonym Lydiphnis (Cymatopteryx) Pilsbry & Olssen, 1946 junior subjective synonym Lydiphnis (Mesopteryx) Pilsbry & Olssen, 1945 junior homonym (of Mesopteryx Saussure, 1870 (Orthoptera ) Pygmaeorota Kuroda & Habe, 1954 † Pygmaeorota (Lydiphnopsis) Shuto, 1969 junior subjective synonym Pygmaeorota (Pygmaeorota) Kuroda & Habe, 1954 Pygmaeorota (Soyorota) Habe, 1961 Pygmaerota Kuroda & Habe, 1952 (nude name) Soyorota Habe, 1961 Trochus (Circulus) Jeffreys, 1865 (original rank) Vitrinella (Lydiphnis) Melvill, 1906

Circulus is a genus of very small and minute sea snails with an operculum, marine gastropod mollusks in the family Vitrinellidae.^[2]

According to the World Register of Marine Species (WoRMS), the following species with valid names are included within the genus Circulus^[3]

The Indo-Pacific Molluscan Database also mentions the following species with names in current use :^[1]

• Circulus callusa (Laseron, 1958)
• Circulus pachyston (Verco, 1907)

Species brought into synonymy

• Circulus bailyi Hertlein & A. M. Strong, 1951: synonym of Cyclostremiscus bailyi (Hertlein & A. M. Strong, 1951)
• Circulus biporcata [sic]: synonym of Circulus biporcatus (A. Adams, 1863)
• Circulus carinulatus Locard, 1889: synonym of Circulus striatus (Philippi, 1836)
• Circulus cerrosensis Bartsch, 1907 accepted as Cyclostremiscus cerrosensis (Bartsch, 1907)
• Circulus cingulatus Bartrum, 1919 † accepted as Pterolabrella cingulata (Bartrum, 1919) †
• Circulus costulatus Locard, 1889: synonym of Circulus striatus (Philippi, 1836)
• Circulus cubanus Pilsbry & Aguayo, 1933: synonym of Cyclostremiscus cubanus (Pilsbry & Aguayo, 1933)
• Circulus dalli Bush, 1897: synonym of Cyclostremiscus dalli (Bush, 1897)
• Circulus delectabile (Tate, 1899) accepted as Circulus delectabilis (Tate, 1899) (unaccepted > incorrect grammatical agreement of specific epithet)
• Circulus diomedeae Bartsch, 1911 accepted as Cyclostremiscus diomedeae (Bartsch, 1911)
• Circulus formosissimus Brugnone, 1873: synonym of Skeneoides jeffreysii (Monterosato, 1872)
• Circulus hendersoni (Dall, 1927): synonym of Cyclostremiscus hendersoni (Dall, 1927)
• Circulus jeffreysii Monterosato, 1872: synonym of Skeneoides jeffreysii (Monterosato, 1872)
• Circulus madreensis F. Baker, Hanna & A. M. Strong, 1938 accepted as Cyclostremiscus madreensis (F. Baker, Hanna & A. M. Strong, 1938)
• Circulus margaritiformis (Dall, 1927): synonym of Cirsonella margaritiformis (Dall, 1927)
• Circulus modesta [sic]: synonym of Circulus modestus (Gould, 1859)
• Circulus nicholsoni A. M. Strong & Hertlein, 1939 accepted as Episcynia nicholsoni (A. M. Strong & Hertlein, 1939)
• Circulus perlatus Pelseneer, 1903 accepted as Orbitestella perlata (Pelseneer, 1903) (original combination)
• Circulus philippinensis Rubio & Rolán, 2022: synonym of Circulus pacomartinezi Rubio & Rolán, 2023 (junior homonym, invalid: secondary junior homonym of Circulus philippinensis (Shuto, 1969); C. pacomartinezi is a replacement name)
• Circulus sarsi (Bush, 1897) accepted as Orbitestella sarsi (Bush, 1897)
• Circulus stirophorus M. Smith, 1937: synonym of Cyclostremiscus beauii (P. Fischer, 1857)
• * Circulus taigai Hertlein & A. M. Strong, 1951 accepted as Cyclostremiscus taigai (Hertlein & A. M. Strong, 1951)
• Circulus tornata [sic]: synonym of Circulus tornatus (A. Adams, 1864)
• Circulus tornatus (A. Adams, 1864): synonym of Tuberes tornatus (A. Adams, 1864) (unaccepted > superseded combination)
• Circulus translucens (Dall, 1927): synonym of Xyloskenea translucens (Dall, 1927)
• Circulus tricarinatus (Wood S., 1848): synonym of accepted as Circulus striatus (Philippi, 1836)

• Kuroda T. & Habe T. 1952. Check list and bibliography of the Recent marine Mollusca of Japan. Leo W. Stach, Tokyo. 210 pp
• Habe, T. (1961). Descriptions of fifteen new species of Japanese shells. Venus. 21(4): 416–431.
• Oliver, J. & Rolan, E., 2011. The family Tornidae (Gsatropoda: Rissooidea) in the East Atlantic, 2. Circulinae. Iberus 29(1): 9–33
• Rubio, F. & Rolán, E. (2022). New species of Vitrinellidae (Gastropoda: Truncatelloidea) from the Indo-Pacific. The genus Circulus Jeffreys, 1865. Museo de Historia Natural, Universidad Santiago de Compostela. 422 pp.
• Rubio F & Rolán E. , 2023. Circulus pacomartinezi nomen novum for Circulus philippinensis Rubio & Rolán, 2022, pag. 359. Iberus 41(1): 151–152

Wikimedia Commons has media related to Circulus.

• Iredale, T. (1915). A commentary on Suter's Manual of the New Zealand Mollusca. Transactions and Proceedings of the New Zealand Institute. 47: 417–497
• Kuroda, T. & Habe, T. (1954). On some Japanese Mollusca described by A. Adams, whose specimens are deposited in the Redpath Museum of Canada (No. 1). Venus. 18(1): 1–16, pls 1–2.
• effreys J.G. (1862–1869). British conchology. Vol. 1: pp. cxiv + 341 (1862). Vol. 2: pp. 479 (1864). Vol. 3: pp. 394 (1865). Vol. 4: pp. 487 (1867). Vol. 5: pp. 259 (1869). London, van Voorst.
• Ponder, W.F. (1994).The anatomy relationships of three species of vitrinelliform gastropods (Caenogastropoda: Rissooidea) from Hong Kong. In: Proceedings of the Third International workshop on the malacofauna of Hong Kong and Southern China (Eds. Motrton, B.). The malacofauna of Hong Kong and southern China III, pp243-281. Hong Kong University Press, Hong Kong