Calliostomatidae, Colloniidae, Margaritidae, and Solariellidae (Gastropoda: Trochoidea) collected by the Marion Dufresne (MD55) expedition in southeastern Brazil, with description of a new species of Calliostoma.

The deep-water mollusks collected during the Marion Dufresne (MD55) expedition to the southeastern Brazilian coast in 1987 have been studied in several recent works. The present paper lists and diagnoses 19 species belonging to the vetigastropod families Calliostomatidae, Colloniidae, Margaritidae, and Solariellidae. A new species, Calliostoma valkuri sp. nov., is described. It is mainly characterized by a very short teleoconch I, with limits marked by conspicuous varices and sculpture consisting of 3 spiral threads; sculpture of the teleoconch II consisting of spiral cords with thorn-like projections; and the presence of two strongly marked cords on the median portion of the whorls. Based on the MD55 samples and complementary specimens from other expeditions, the following species have their geographical and/or bathymetrical range extended: Bathymophila euspira, Calliostoma gemmosum, Calliostoma rude, Callogaza watsoni, Gaza compta, Falsimargarita terespira, Homalopoma boffii, Lamellitrochus cancapae comb. nov., Lamellitrochus pourtalesi, Margarites imperialis, and Solariella quinni.