Calliostoma

The name of this genus is derived from the Greek words kallos (beautiful) and stoma (mouth), referring to the pearly aperture of the shell. The genus Calliostoma is known in fossil records from the Upper Cretaceous onwards.^[2]

The thin, acute, coeloconoid (=approaching conical shape but with concave sides) shell is imperforate or rarely umbilicate. The whorls are smooth, often polished and spirally ridged or granular. The body whorl is angulated at the periphery. The aperture is quadrangular, sinuated at the base and slightly oblique. The columella is simple, usually ending anteriorly in a slight tooth.^[3] The nucleus appears to be either dextral or sinistral indifferently.^[4][5]

As of 2022, Calliostoma is treated as a very broad genus of about 300 accepted species.^[6] While current information is too fragmentary to assign all species in a revised genus, it is expected to be broken up and (some) subgenera will be elevated to the status of genus.^{[citation needed]}

The distribution of this genus is worldwide, found mainly on hard substrates, although Japanese species have been found on sandy bottoms. These snails occur from shallow waters to bathyal depths.

The species in this genus are mainly herbivorous or feed on detritus,^[7] although a few have been observed to be omnivorous (Keen, 1975) or even carnivorous, feeding on a wide range of algae and on animals belonging to various other invertebrate phyla.^[8] The North Atlantic topshell Calliostoma occidentale has been reported to feed on coelenterates.^[9]

Contrary to what is the case in most other top shells, species of the genus Calliostoma deposits their eggs in gelatinous ribbons that are only fertilized after being deposited. The young emerge as small snails (Lebour, 1936) without passing through a free-living planktonic stage as a veliger larva.

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  Drawing of a dorsal view of a living animal of Calliostoma bairdii dredged in the Atlantic Ocean at a depth of from 100 m to 1170 m
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  Rare purple beaded specimen of Calliostoma supragranosum found subtidally in Southern California

• Vilvens C. (2012) New species and new records of Seguenzioidea and Trochoidea (Gastropoda) from French Polynesia. Novapex 13(1): 1–23. [10 March 2012] page(s): 18

• Marshall, B.A. (1995). "A revision of the recent Calliostoma species of New Zealand". The Nautilus. 108: 83–127.
• Quinn, J.F. Jr. (1992). "New species of Calliostoma and notes on some poorly known species from the Western Atlantic". The Nautilus. 106: 77–114.
• Rosenberg G. (2005). "Malacolog 4.1.0: : A database of Western Atlantic Marine Mollusca". Archived from the original on 24 September 2015. Retrieved 18 March 2009.
• Williams, S.T.; K.M. Donald; H.G. Spencer; T. Nakano (March 2010). "Molecular systematics of the marine gastropod families Trochidae and Calliostomatidae (Mollusca: Superfamily Trochoidea)". Molecular Phylogenetics and Evolution. 3. 54 (3): 783–809. doi:10.1016/j.ympev.2009.11.008. PMID 19919851.
• Vilvens C. (2009). New species and new records of Calliostomatidae (Gastropoda: Trochoidea) from New Caledonia and Solomon Islands. Novapex 10(4): 125-163