The deep-water molluscs collected during the expedition MD55 off SE Brazil have been gradually studied in some previous papers. The present one is focused on samples belonging to caenogastropod taxa Xenophoridae Troschel, 1852, Cypraeoidea Rafinesque, 1815, mitriforms and Terebridae Mörch, 1852. Regarding the Xenophoridae, Onustus aquitanus n. sp. is a new species, collected off the littoral of Espírito Santo and Rio de Janeiro, Brazil, 430–637 m depth (continental slope). The main characters of the species include the small size (c. 20 mm), the proportionally wide shell, the white colour, the short peripheral flange, the oblique riblets weakly developed and a brown multispiral protoconch. This appears to be the smallest living species of the family, resembling in this aspect fossil species. In respect to the Cypraeoidea, the following results were obtained: family Cypraeidae Rafinesque, 1815: Erosaria acicularis (Gmelin, 1791) and Luria cinerea (Gmelin, 1791) had the deepest record, respectively 607–620 m and 295–940 m, although the samples were all dead, eroded shells. Family Lamellariidae d'Orbigny, 1841 : a total of three lots were collected, provisionally identified as Lamellaria spp. as the samples consist of only vestigial shells; possibly each lot represents a different species. Family Pediculariidae Gray, 1853: a sample of Pedicularia tibia Simone, 2005 was found, expanding the range c. 1000 km southwards, from Ceará to Espírito Santo. Family Ovulidae Fleming, 1822: Pseudosimnia lacrima n. sp., collected off Espírito Santo, 607–620 m depth, is described here and is mainly characterised by its strong biconic outline, small size (c. 7 mm), and a thick peripheral callus. Family Triviidae Troschel, 1863: CLeotrivia antillarum (Schilder, 1922) is recorded for the first time as deep as 620 m, and its distribution expanded from Rio Grande do Norte to Espírito Santo; Dolichupis akangus n. sp. with rounded outline and c. 15 transverse ribs; D. pingius n. sp. with the outer lip expanded posteriorly and c. 10 ribs. In respect to the mitriform neogastropods, the following species are emphasised: family Costellariidae MacDonald, 1860: Vexillum sp., 607–620 m depth; Turricostellaria amphissa n. sp., 295 m depth; T. jukyry n. sp.; T. apyrahi n. sp., both 790–1575 m depth; T. ovir n. sp., 1200 m depth; Nodicostellaria crassa (Simone, 1995), 240–600 m depth, with extension northwards of the range up to Espírito Santo; Austromitra decresca n. sp., 60–105 m depth. Family Mitridae Swainson, 1829: Subcancilla joapyra n. sp., 295 m depth; S. cf. straminea (Adams, 1853), 607–620 m depth. Family Volutomitridae Gray, 1854: Microvoluta corona n. sp., 1500–1575 m depth. Family Mitromorphidae Casey, 1904: Mitromorpha sama n. sp., 607–940 m depth; M. mirim n. sp., 60– 105 m depth. Regarding the conoidean Terebridae, this paper is a complement of a previous study. It deals with a new species — Terebra assu Simone n. sp., from the Abrolhos Bank, 295 m depth, characterised by its narrow outline, yellowish colour, weak sculpture on the last whorls, and a proportionally broad, paucispiral protoconch. A second finding of Terebra alagoensis Lima, Tenório & Barros, 2007 expands the geographic range from Alagoas to north Espírito Santo. A discussion on the systematics of the “complex Terebra doellojuradoi” in South American coast is also provided, highlighting the improbability of synonymy between T. leptapsis
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