Distribution. Known from Point Pinos, Monterey County, California (36° N), to Punta Rompiente, Baja California Sur (27° N), intertidal to 91 m, found in shallower water in the northern portion of the range, recorded deeper in southern localities.
Description. Shell small to extremely small, length 19.2 mm, width 10.2 mm (lectotype), spire moderately acute, ribs bladelike, overall sculpture somewhat variable, specimens from northern portion of range typically having more upward projecting spines. Spiral cords scabrous, more prominent in tertiary cords. Shape rhomboid ovate, some specimens slender, shell thick, color occasionally variable, primarily dark brown, occasionally tan, rarely with brown band on base of final whorl. Protoconch initially bulbous, slight keel rapidly developed, initial teleoconch whorls with two large cords, quickly countered by thin, scabrously bladed ribs, tightly set, transitioning to subtle clathrations. First, second whorl with P1, P2, third whorl with PI, P2, starting sl, s2, fourth whorl with P1, sl, P2, s2, starting IP, final whorl with adis, IP, abis, P1, t, sl, t, P2, s2, P3, s3, P4, s4, P5, s5, P6, ADP, MP, ABP. Spiral cords variable in strength and size. Denticle morphology Dl—D5. Aperture small, elongate ovate, lip extremely thick, scabrous, parietal wall very thick throughout, denticles moderate to wanting, siphonal canal very thick, somewhat short in length.
Remarks. This species is quite variable and has two forms along the coastline. The more typical, larger form ranges from Point Pinos, Monterey County, California, to Punta Rompiente, Baja California Sur, with specimens from Monterey to Santa Barbara tending to exhibit long projecting shoulder spines at rib intersections, specimens south of this range primarily with rounded shoulders. A miniature, primarily deeper water form, from cooler waters has been consistently recorded from Big Sur, Monterey County, California (36° N), to the outer California Channel Islands (Buck 1989), reappearing in the upwelling region of northern Baja California. These specimens are very similar in spiral morphology and are here considered conspecific. Due to the similarities in spiral morphology, Ocenebra keenae Bormann, 1946, is here regarded as a junior synonym. Until further samples of these forms are collected, and a molecular analysis is conducted, this interpretation remains speculative.
Dall’s (1921) illustration of what he considered P. harbarensis (Gabb, 1865) is here regarded as P. neobarharensis n. sp. , a circumstance, which resulted in a long-standing confusion about this species identity. The superficially similar species are separated by their size, shape, habitat and spiral morphology with P. harbarensis having adis, abis, the absence of t cord after P1, s6 and ms cord after MP in comparison to P. neobarharensis . Specimens of P. neobarharensis are found at greater depths, are thinner in composition, have projecting ribs on last whorl, commonly with no projections prior, are much more slender, the spire is more acute, is overall taller, and the siphonal canal is thinner and longer. Paciocinehrina foveolata (Hinds, 1844) is also comparable to P. barbarensis but is larger in size, has less exaggerated projections at ribs, spines absent, more denticles, less scabrous in sculpture, cords weaker , with additional t cord after IP, s4, s6 and abs after ABP , P. barbarensis with additional t cord after sl and s2, D6 absent. Paciocinehrina fraseri (Oldroyd, 1920) is comparable to P. barbarensis, but has s4 and ads, lacking abis, two t cords, one after PI and another after P6 compared to P. barbarensis (Fig. 10A). The shell of P fraseri is overall more slender, elongate in shape and has a narrower and longer siphonal canal. The species epithet barbarensis is especially appropriate as the species is most commonly found in the Santa Barbara area.