In preparation for compiling a catalogue of the South Atlantic American malacofauna, this study addresses the taxonomy of selected species within less intricate groups to ensure accurate classification within the catalogue. The following nomenclatural acts are undertaken for this purpose: New species descriptions: 1, Tectura iguypis; 2, Nacella mirim; 3, Calliostoma soror; 4, Abyssochrysos quasilissus; 5, Caecum jonesae; 6, Sinum striotis; 7, Agaronia sterica; 8, Voluta melodica; 9, Phrontis rocas; 10, Goniofusus phoenix; 11, Dolicholatirus etherius; 12, Lightbournus rendatus; 13, Terebra joculosa; 14, Neoterebra potiguar; 15, Trimusculus pifius; 16, Brevinucula overa; 17, Ennucula ipepa; 18, Tindaria ruru; 19, Barbatia pehenguis; 20, Bathyarca arcadia; 21, Bentharca celeris; 22, Electroma electra; 23, Brachidontes ynous; 24, Pinna trindadis; 25, Pinna nembia; 26, Pinna pereria; 27, Servatrina amazonica; 28, Warrana culmen; 29, Lucinoma apocalyptica; 30, Cyrenoida implexa; 31, Hiatella marisqueira; 32, Cyrtopleura angelicalis; 33, Lyonsiella angulosa; 34, Graptacme obtura. Species revalidated: 1, Fissurella itapema; 2, Cranopsis watsoni; 3, Pedicularia tibia; 4, Semicassis iheringi; 5, Anachis veleda; 6, Terebra chilensis; 7, Iselica anomala; 8, Barbatia cancellaria; 9, Acar domingensis; 10, Limopsis paucidentata; 11, Paracratis borealis; 12, Crassostrea mangle; 13, Abra americana; 14, Choristodon typicum; 15, Pseudochama radians; 16, Polyschides quadridentatum. New synonyms: 1, Fissurella clenchi; 2, Natica castanea; 3, Cyphoma macumba; 4, Voluta thevenini; 5, Pleuroploca granulilabris; 6, Polyschides xavante; 7, Polyschides noronhensis. New combinations: 1, Falsilunatia limbata; 2, Goniofusus damasoi. Redescriptions/taxonomy commented: 1, Nacella mytilina; 2, Fissurella rosea; 3, Calliostoma depictum; 4, Depressiscala nautlae; 5, Depressiscala niditella; 6, Scala scipio; 7, Abyssochrysos brasilianus; 8, Caecum antillarum; 9, Cheilea equestris; 10, Sinum perspectivum; 11, Pseudocyphoma intermedium; 12, Cyphoma signatum; 13, Coronium; 14, Voluta ebraea; 15, Nassarius albus; 16, Goniofusus brasiliensis; 17, Goniofusus strigatus; 18, Leucozonia nassa; 19, Anachis lyrata; 20, Terebra gemmulata; 21, Turbonilla obsoleta; 22, Brevinucula verrillii; 23, Tindaria amabilis; 24, Bathyarca glomerula; 25, Bentharca asperula; 26, Crassostrea mangle; 27, Pinna carnea; 28, Kalolophus antillarum; 29, Warrana besnardi; 30, Chama cristella; 31, Hiatella solida; 32, Cyrtopleura costata; 33, Polyschides tetraschistus. Extension of distribution: 1, Amaea mitchelli; 2, Tindaria cytherea; 3, Lyratellina juttingae. Change of genus: 1, Naticarius cayennensis. New replacement name: 1, Turbonilla absalaoi. Validity of species discussed: 1, Cheilea atlantica; 2, Cheilea americana. Families revalidated: 1, Trichotropidae. Fossil species proposed to remain fossil-only: 1, Cranopsis granulata; 2, Iselica globosa; 3, Limopsis aurita; 4, Limopsis minuta; 5, Abra longicallus. All 104 nomenclatural acts are thoroughly justified, discussed, and mostly illustrated. Several of these acts have co-authors. https://zoobank.org/6DB1BC9F-A0E9-4C36-8BEF-EF8A375F0693.