Type species. Tritonium luridum Middendorff, 1848: 244. Recent, Sitka, Alaska [two syntypes, ZISP 62131.
Description. Shell highly variable, most species small for the genus, several groups possessing morphologically recognizable characteristics, including teleoconch clathration, projecting spines, grotesquely inflated, tightly set, low laying cord sequences, indented sutures, often with series of subsutural cords. Protoconch tabulate, mostly carinate, sometimes smoother, teleoconch sculpture heavily scabrous, microstructure mostly consisting of vaulted scales, crispate fimbriations, siphonal canal sealed in most species. Absence of labral tooth, apertural denticles strong to weak, rarely absent, often with series of infrasutural cords.
Habitat. Species inhabit intertidal and subtidal rocky reefs and are associated with drilling barnacles, limpets and other gastropods. They are known from the temperate zone, mostly inhabiting shallow depths (0-39 m), several species residing in deeper habitats (40-238 m).
Remarks. Very few studies (Spight et ai 1974, Talmadge 1975, Palmer 1988) address the ecology and physiology of this northeast Pacific group. As seen with other gastropods (Deas 1971, Vance 1978, Forester 1979), and members of Muricidae in particular (Deas 1971, Wicksten, 1981), sponge associations are particularly common in several abundant species, including Paciocinebrina foveolata (Hinds, 1844), P. lurida
(Middendorff, 1848) and P. munda (Carpenter, 1864). Morphologically, two genera, Ocenebra Gray, 1847 and Ocinebrina Jousseaume, 1880, have been confused and used for northeast Pacific members (Bormann 1946, Rice 1971, Abbott 1974, Fair 1976, Radwin & D'Attilio 1976, McLean 1978, 2007, Turgeon et al 1998, Marko & Vermeij 1999, Houart & Sirenko 2003, Houart 2011). In comparing Paciocinebrina protoconchs to illustrations by Myers & D'Attilio (1986), of the northeast Atlantic, Ocenebra erinaceus (Linnaeus, 1758). type species of the genus, was shown to possess, at least, one extra protoconch whorl. Crocetta et ai (2012) figured and described protoconchs of several species of Ocinebrina, specifically, O. corallinoides (Pallary, 1912), O. reinai Bonomolo & Crocetta, 2012 and the type species of the genus, O. aciculata (Lamarck, 1822). All species have a similar number of protoconch whorls compared to all Paciocinebrina spp. examined, except that Ocinebrina has a bulbous protoconch structure versus tabulate protoconch in all known Paciocinebrina spp. Phylogenetic analyses of mitochondrial and nuclear genes (COI + 16S + 28S) indicate the necessity to separate northeast Pacific members from the similar appearing northeast Atlantic clade, as northeast Pacific species are supported as more closely related to Nucella and Ocinebrellus Jousseaume, 1880 than to Atlantic groups (Barco et al. 2017).
Etymology. Named after the geographic affinity to the Pacific Ocean and the 'Ocinebrina’ like morphology. Gender feminine.