Caecum (gastropod)

This genus occurs worldwide in warm and temperate seas. Many species live in sponges, in sandy spots on reefs, or in grassy beds in shallow waters in bays and lagoons. Some species are very common and can be extremely numerous where they do occur, such as the "beautiful caecum"(Caecum pulchellum), but even they can be easily overlooked as they are so tiny. Many species are considered to be uncommon, but this assessment may be a result of lack of proper sampling.

The shells in this genus, like the others in the family, are very small with a length between 2 mm and 6 mm. Their colour is white to yellowish white and some are almost translucent. They are unusual in that the teleoconch of the adult shell is a curving tube for most of its length. In the first stage of the shell it is spiral-shaped but soon becomes cylindrical. The shell is sealed with a permanent calcareous plug at one end and (when the animal has withdrawn into the shell) with a circular, multispiral, horny operculum at the other end, the shell aperture. The sculpture is smooth or consists of a close-set, large number of annular ridges.

These snails feed on one-celled organisms on sand grains or pebbles.

Species in the genus Caecum include:[1][2]

Subgenera brought into synonymy

• Caecum (Defolinia) Weisbord, 1962: synonym of Caecum Fleming, 1813
• Caecum (Meioceras) Carpenter, 1859: synonym of Meioceras Carpenter, 1859

Species brought into synonymy

• Caecum abnormale Carpenter, 1857: synonym of Caecum subspirale Carpenter, 1857
• Caecum amaltheanum Hedley, 1899: synonym of Mauroceras legumen (Hedley, 1899)
• Caecum amamiense Habe, 1978: synonym of Mauroceras amamiense (Habe, 1978)
• Caecum arcuatum de Folin, 1867 : synonym of Caecum sepimentum de Folin, 1868
• Caecum bahiahondaense A. M. Strong & J. G. Hertlein, 1939 : synonym of Caecum clathratum Carpenter, 1857
• Caecum bakeri (Bartsch, 1920): synonym of Caecum dextroversum Carpenter, 1857
• Caecum berthae Lange de Morretes, 1954: synonym of Caecum plicatum Carpenter, 1858
• Caecum biminicola Pilsbry, 1951: synonym of Caecum plicatum Carpenter, 1858
• Caecum buccina de Folin, 1870: synonym of Caecum circumvolutum de Folin, 1867
• Caecum bucheri Parenzan, 1979: synonym of Filogranula annulata (O. G. Costa, 1861)
• Caecum butoti Jong & Coomans, 1988 : synonym of Caecum marmoratum de Folin, 1869
• Caecum capitanum de Folin, 1874: synonym of Caecum pulchellum Stimpson, 1851
• Caecum carmenense de Folin, 1870: synonym of Caecum circumvolutum de Folin, 1867
• Caecum carpenteri (Bartsch, 1920): synonym of Caecum adamsi Raines, 2020
• Caecum cayoense Rehder, 1943: synonym of Caecum floridanum Stimpson, 1851
• Caecum clenchi Olsson & McGinty, 1958: synonym of Caecum cycloferum de Folin, 1867
• Caecum compactum P. P. Carpenter, 1857 : synonym of Caecum quadratum Carpenter, 1857
• Caecum conjunctum de Folin, 1867: synonym of Caecum pulchellum Stimpson, 1851
• Caecum contractum de Folin, 1870: synonym of Caecum bipartitum de Folin, 1870
• Caecum corneum R. W. Dunker, 1875 : synonym of Caecum ryssotitum de Folin, 1867
• Caecum cornucopiae (Carpenter, 1858) - horn-of-plenty caecum : synonym of Meioceras cornucopiae Carpenter, 1859
• Caecum coronatum de Folin, 1867: synonym of Caecum imbricatum Carpenter, 1858
• Caecum coronellum Dall, 1892: synonym of Caecum cycloferum de Folin, 1867
• Caecum costatum A. E. Verrill, 1872: synonym of Caecum cooperi S. I. Smith, 1860
• Caecum crassicostum Gabb, 1881: synonym of Caecum floridanum Stimpson, 1851
• Caecum curtatum de Folin, 1867: synonym of Caecum pulchellum Stimpson, 1851
• Caecum decussatum de Folin, 1869: synonym of Caecum plicatum Carpenter, 1858
• Caecum dux de Folin, 1871: synonym of Caecum floridanum Stimpson, 1851
• Caecum eburneum de Folin, 1886: synonym of Caecum folini Kisch, 1959
• Caecum elagans Deregaslavtseva, 1891: synonym of Caecum trachea (Montagu, 1803)
• Caecum elegans Perejoslavitseva, 1831 : synonym of Caecum trachea (Montagu, 1803)
• Caecum fasciatum de Folin, 1876: synonym of Caecum trachea (Montagu, 1803)
• Caecum formulosum de Folin, 1869: synonym of Caecum imbricatum Carpenter, 1858
• Caecum fulvum Kisch, 1959: synonym of Caecum neocaledonicum de Folin, 1867
• Caecum heladum Olsson and Harbison, 1953 - fine-line caecum  : synonym of Caecum multicostatum de Folin, 1867
• Caecum heterapex T. Habe, 1963 : synonym of Caecum clarum Lamy, 1910
• Caecum hinoidei T. Habe, 1978 : synonym of Caecum neocaledonicum de Folin, 1867
• Caecum insigne de Folin, 1867: synonym of Caecum imbricatum Carpenter, 1858
• Caecum instructum de Folin, 1870: synonym of Caecum bipartitum de Folin, 1870
• Caecum irregulare de Folin, 1867: synonym of Caecum floridanum Stimpson, 1851
• Caecum legumen Hedley, 1904: synonym of Meioceras legumen (Hedley, 1904)
• Caecum leptoglyphos de Folin, 1881: synonym of Caecum textile de Folin, 1867
• Caecum lermondi Dall, 1924: synonym of Meioceras nitidum (Stimpson, 1851)
• Caecum lightfootae Pizzini, Nofroni, Oliverio, 1994 : synonym of Caecum atlantidis Watson, 1897
• Caecum lilianum Ch. Hedley, 1903 : synonym of Caecum sepimentum de Folin, 1867
• Caecum maculatum T. Habe, 1963 : synonym of Caecum sepimentum de Folin, 1867
• Caecum malleatum var. sublaevis de Folin, 1868: synonym of Caecum modestum de Folin, 1868
• Caecum microcyclus de Folin, 1879 : synonym of Caecum attenuatum de Folin, 1880 (subsequent spelling)
• Caecum nitidum Stimpson, 1851 - little horn caecum: synonym of Meioceras nitidum (Stimpson, 1851)
• Caecum obesum A. E. Verrill & Bush, 1900 : synonym of Caecum plicatum Carpenter, 1858
• Caecum orientale de Folin, 1868 : synonym of Caecum clarkii Carpenter, 1859
• Caecum phronimum de Folin, 1867 : synonym of Caecum floridanum Stimpson, 1851
• Caecum puntagordanum Weisbord, 1962: synonym of Caecum floridanum Stimpson, 1851
• Caecum putnamense Mansfield, 1924 : synonym of Caecum johnsoni Winkley, 1908
• Caecum rotundum de Folin, 1868 : synonym of Meioceras nitidum (Stimpson, 1851)
• Caecum saavedrae Beltran, 1965 : synonym of Caecum auriculatum de Folin, 1868
• Caecum sardinianum de Folin, 1869 : synonym of Caecum clarkii Carpenter, 1859
• Caecum sculptum de Folin, 1881: synonym of Caecum imbricatum Carpenter, 1858
• Caecum semitracheum S. Brusina, 1865 : synonym of Caecum clarkii Carpenter, 1859
• Caecum smithi Cooper, 1872: synonym of Caecum cooperi S. Smith, 1860
• Caecum solitarium Oliver, 1915 : synonym of Caecum maori Pizzini & Raines, 2006
• Caecum syriacum de Folin, 1869: synonym of Caecum auriculatum de Folin, 1868
• Caecum tenue A. E. Verrill & Bush, 1900: synonym of Caecum armoricum de Folin, 1869
• Caecum termes Heilprin, 1889: synonym of Caecum plicatum Carpenter, 1858
• Caecum tomaculum (Weisbord, 1962) : synonym of Caecum ryssotitum de Folin, 1867
• Caecum triornatum de Folin, 1870: synonym of Caecum bipartitum de Folin, 1870
• Caecum uvea Pizzini, Raines & Vannozzi, 2013: synonym of Caecum folini Kisch, 1959
• Caecum veracruzanum Collins, 1937 : synonym of Caecum circumvolutum de Folin, 1867
• Caecum vestitum de Folin, 1868 - Vera Cruz caecum: synonym of Caecum circumvolutum de Folin, 1867

Nomina dubia

• Caecum abreviatum de Folin, 1870
• Caecum bicinctum de Folin, 1870
• Caecum gracile Carpenter, 1858
• Caecum hemisphericum de Folin, 1867
• Caecum imperforatum (Kanmacher, 1798)

• Vaught, K.C. (1989). A classification of the living Mollusca. American Malacologists: Melbourne, FL (USA). ISBN 0-915826-22-4. XII, 195 pp
• Gofas, S.; Le Renard, J.; Bouchet, P. (2001). Mollusca, in: Costello, M.J. et al. (Ed.) (2001). European register of marine species: a check-list of the marine species in Europe and a bibliography of guides to their identification. Collection Patrimoines Naturels, 50: pp. 180–213
• Spencer, H.; Marshall. B. (2009). All Mollusca except Opisthobranchia. In: Gordon, D. (Ed.) (2009). New Zealand Inventory of Biodiversity. Volume One: Kingdom Animalia. 584 pp
• Aartsen, J. J. van (1977). Revision of the East Atlantic and Mediterranean Caecidae. - Basteria 41 (1/4): 7-19

• Moore, Donald R., The Systematic Position of the Family Caecidae (Mollusca: Gastropoda) , Bulletin of Marine Science, Volume 12, Number 4, 1962 ,pp. 695-701(7)
• Moore, Donald R., Ecological and Systematic Notes on Caecidae from St. Croix, U.S. Virgin Islands, Bulletin of Marine Science, Volume 22, Number 4, December 1972 , pp. 881-899(19)
• Powell A. W. B., New Zealand Mollusca, William Collins Publishers Ltd, Auckland, New Zealand 1979 ISBN 0-00-216906-1
• Shell-bearing Mollusca: : Caecidae
• Malacolog Version 4.1.0 : A Database of Western Atlantic Marine Mollusca
• The Paleobiology Database : Classification of the Caecidae
• Goedert J.L. & Raines B.K. (2016). First Paleogene Caecidae (Gastropoda: Truncatelloidea) from the northeastern Pacific Ocean and the earliest record for the genus Caecum Fleming, 1813. Proceedings of the Biological Society of Washington. 129: 38-47

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  Caecum auriculatum
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  Caecum subannulatum