Genus Caribbonus, gen. nov. Type species: Caribbonus karudeux sp. nov. Diagnosis Shell fusiform to elongate-fusiform, thin-walled, white or lightly colored, with moderately long siphonal canal. Sculpture of fine densely set orthocline ribs overridden by regular, rounded or flattened cords, forming characteristic beaded sculptural pattem. Shell base convex, clearly demarcated from siphonal canal. Outer lip thin, lirate within; parietal callus forming low pad; inner lip with four columella folds. Radula with multicuspidate rachidian 43 Species included. Caribbonus fabergei sp. nov.; C. karudeux' sp. nov.; C. macrocephala' sp. nov.; C. styria (Dall, 1889)'. Tentatively, C. bairdii (Dall, 1889). Etymology The genus epithet refers to the known distribution of the genus in Caribbean, while “bonus", reference to the find of a new lineage in a generally well know Caribbean fauna. Distribution and habitat Caribbean, lower subtidal and bathyal depths.Remarks Analysis of our Cox l dataset revealed four SSHs that we place in Caribbonus based on shell features. We note that these SSHs do not form a clade in the Cox l based analysis, however, the paraphyly of Caribbonus as circumscribed herein is not supported either. Only SSH 149 has a name available ("Vecillum' styria), and three SSHs are described as new species. The genus Caribbonus n. gen. is easily recognizable among Caribbean costellariids by its uniformly white or light coloured shells , typically with characteristic beaded sculpture pattern and a multispiral protoconch. Another Caribbean genus, Bathythala n. gen., shows a combination of a lightly colored shell sculptured with both axial and spiral elements, and a multicuspidate rachidian. However, Caribbonus n. gen. possesses a columella with four folds (three in Bathythala n. gen.), and the outer lip is lirate inside (smooth in Bathythala). The Caribbean Costapex baldwinae has an elongated, thin- walled, lightly sculptured shell, but it is distinctive among Caribbean species by the prevalence of spiral elements in the sculpture and, like its congeners, possesses a tricuspidate rachidian. Among Indo-Pacific taxa, species of Tosapusia (e.g., T. diadema sp. nov.) and Vexillena (e.g., V. kurodai) show somewhat similar sculpture patterns, but both have radulae with tricuspidate rachidians. One specimen with a dried body of the enigmatic species Mitra bairdii Dall, 1889, previously placed in Volutomitra, was available for study (MNHN-IM-2023-8695 Gulf of Mexico, 970 m.). and its radula appears to closely match that of C. karudex sp. nov. . Such radular morphology clearly indicates that M. bairdii is a costellariid, and based on the sum of morphological and biogeographic characteristics, we tentatively allocate it to Caribbonus, even though this species possesses a notably more elongated shell, which lacks a characteristic beaded sculpture pattern. One further species that we tentatively place in Caribbonus based on shell morphology is Voiutomitra wandoensis Holmes, 1860.