The Cystiscidae (Caenogastropoda) from upper reef formations of New Caledonia

The species of Cystiscidae from the New Caledonian upper reef formations are studied on the ground of recent intensive recolts managed by Paris Museum, mainly the ones from Noumea 1992-93, from the Expedition Montrouzier 1993 and from the Expedition Lifou 2000. The taxonomic analysis is focused on the morphs sampled off New Caledonia mainland (northern and southern areas). The marginellids collection of Bavay recently deposited in Paris Museum is used for the revision of several taxa.
 Twenty eight morphs are recognized, among which five are attributed to species previously described, namely Gibberula lifouana (Crosse, 1871), Cystiscus goubini (Bavay, 1922), C. montrouzieri (Bavay, 1922), C. bougei (Bavay, 1917) and Plesiocystiscus tomlini (Bavay, 1917), the last one with much reserve. The syntypes of Gibberula pulchella (Kiener, 1834) are pictured and the species is compared to a New Caledonian relative. Eighteen species are described as new: Gibberula squamosa sp. nov., G. cincta sp. nov., Crithe caledonica sp. nov., C. gofasi sp. nov., Cystiscus viridis sp. nov., C. punctatus sp. nov., C. aurantius sp. nov., C. marshalli sp. nov., C. boucheti sp. nov., C. camelopardalis sp. nov., C. minor sp. nov., C. pardus sp. nov., C. deltoides sp. nov., C. caeruleus sp. nov., C. tricinctus sp. nov., C. pseudoaurantius sp. nov., C. cooverti sp. nov., Plesiocystiscus bavayi sp. nov.
 Five morphs are recorded as potential new species and provisionally referred as Gibberula sp. aff. philippii (Monterosato, 1878) (morphs A, B and S), Cystiscus sp. 1 and Plesiocystiscus sp. aff. bavayi sp. nov.
 Despite the high diversity reported about the group Crithe/Cystiscus in shallow waters of New Caledonia mainland, this diversity is appreciated as remaining much underestimated. This diversity cannot be considered as restricted to the New Caledonian waters and equivalent intensive collecting efforts in other places from West Pacific might possibly yield equivalent results.
 The genera Crithe and Cystiscus show as belonging to a continuous complex of related forms, but the taxonomic unification of the group waits for a better knowledge of its total diversity, allowing to propose appropriate subdivisions.
 On the ground of the concrete limits met with the taxonomic interpretation, it is suggested that the managing of systematic observations in the field about micro-habitats and about the variability of the soft parts would highly increase the scientific profitability of intensive malacological samplings.