Description: Medium size (height to 7 cm); Profile high, whorls rounded to angulate; spiral sculpture of fine lirae, axial sculpture absent; mature lip slightly flared; operculum sub-triangular with lateral nucleus. Remarks: Kantor & Harasewych (1998) Originally placed Aleutibuccinum clarki in the genus Bathybuccinum (Golikov & Sirenko, 1988) subgenus Ovulatibuccinum (Golikov & Sirenko, 1988) but it is clearly distinct from both of these groups. The unique operculum sets this genus apart from all other North Pacific Buccininae. At present, the Aleutibuccinum clarki is the only species assigned to this genus.

Genus Castaneobuccinum n. gen. Type species: Buccinum castaneum Dall, 1877 (n. comb.) Description: Profile tall, moderately broad, whorls rounded, suture deeply impressed, color light to dark chestnut brown (rarely white); shell surface devoid of periostracum, shell thick and heavy, the result of a calcitic exterior layer; with sharp- ly incised, spiral microsculpture, with or without initial carination in early teleconch; final lip inflated, heavily reinforced, with broad anal sinus on shoulder. Operculum with concentric growth, nearly filling aperture. Remarks: Three previously described varieties of Buccinum castaneum are herein regarded as distinct species Based on morphology and sympatric distribution, and placed in Castaneobuccinum. Buccinum castaneum , which lacks axial sculpture or has only weakly indicated axial folds near the suture, Buccinum castaneum var. triplostephanum Dall, 1919 lacks axial sculpture, but has three (rarely four) low, broad, strong spiral cords, and Buccinum castaneum var. fluctuatum Dall, 1919 which has 14-18 relatively strong, often prosocline axial folds. Buccinum castaneum var. incisulum Dall, 1919 is considered a synonym of this last species. These and four presently described species form a unique complex that is endemic to the Aleutian and Pribilof Islands. They are distinguished from all other Buccinum (s.L) by 1) thickly reinforced outer lip of the aperture, 2) lack of periostracum, and 3) typically dark brown coloration. Seven species are recognized, all in the Aleutians.