The deep-water Naticidae Guilding, 1834 collected in the expedition MD55 off SE Brazil are taxonomically studied; of the eleven species found, nine species and one genus are new. Microlinices n. gen., mainly characterized by its minute shell size (5-8 mm), thick unpigmented shell walls, weak callus, umbilicus wide lacking central fold, corneous operculum, absence of eyes, osphradium somewhat peduncular, penis at right of or ventral to right cephalic tentacle, nerve ring highly concentrated, and found in deepwater environment. The following taxa are studied here: Microlinices latiusculus n. gen., n. sp., the type species, off Rio de Janeiro (RJ), 430-450 m (anatomy included); M. ibitingus n. gen., n. sp., off Espírito Santo (ES) and RJ, 640-1575 m (anatomy included); M. benthovus n. gen., n. sp., same distribution, 607-1575 m (anatomy included); M. ombratus n. gen., n. sp., off ES, 1500-1575 m; M. apiculus n. gen., n. sp., off ES, 367 m; M. gaiophanis n. gen., n. sp., off RJ, 830 m; Natica jukyriuva n. sp., off ES, 295-620 m; N. pipoca n. sp., off ES, 15 m; N. juani Costa & Pastorino, 2012, off ES, 52-105 m, expanding the geographic distribution to north, to ES and Trindade Island; an operculum of Natica (ss) sp., off ES, 295 m; Eunaticina abyssalis n. sp., off ES, 1500-1575 m. The Natica Scopoli, 1777 ss and Eunaticina Fisher, 1885 are reported on the Brazilian coast for the first time. The three species with anatomical descriptions, representing the new genus Microlinices n. gen., had their phenotypic characters coded and inserted in a wider cladistic analysis (Simone 2011), with no inclusion of new characters. The three species resulted as a monophyletic taxon amongst the basal Naticoidea Guilding, 1834, supported by 20 synapomorphies.
Brazil, Anatomy, Naticidae, Caenogastropoda, Deep-water, new genus, new species.