Castaneobuccinum pagodaformis n. sp. Type locality: Amutka Pass, Aleutian Ids., Alaska (52°29.4 N, 171°), 469 m. (23-200001-52). Type material: Holotype, LACM 3593, 64.0 mm. (leg. K. Maslenikov, 31 May, 2000) Paratypes: Pt 1, LACM 3662, 37.5 mm (type locality); Pt 2, SBMNH 183015, 54.5 mm. (type locality); Pt 3, LACM 3661, 50.4 mm. S of Agattu Island, Near Ids. (52°19.15 N, 173°29.8 E), 93 m (RB 86-211); Pt 4, RNC 4231, 79.5 mm. Petrel Bank, Rat Ids. (52°05.67 N, 179°22.78 E), 312 m. (NMFS 94-200201-174). Referred material: 1, RNC 4671, S of Buldir Island (51°57.82 N, 176°01.82 E). (NMFS 147-200401-188) 72 m. 62.5mm
Description: Shell relatively large for genus (to 80 mm, RNC 4231), tall spired, strongly keeled; dark brown with lighter tone on spiral cords. Protoconch with two whorls; teleconch with six to seven whorls. Axial sculpture lacking. Spiral sculpture dominated by one strongly projecting shoulder cord beginning as a sharp carination on the first teleconch whorl, becoming T-shaped in cross-section on adult whorls; shoulder ramp convex. A second cord of lesser strength just above the suture; base with one weaker cord; entire surface with incised spiral striae. Aperture large, oval, about 1/3 of shell height; outer lip massively thickened, with indentation reflecting the cords, and broad, shallow sinus on shoulder; canal very short, narrow. Radula: Typical for genus, rachidian tooth sub-rectangular, posterior edge strongly indented; bearing five uniform. well-spaced cusps. Lateral teeth large tri-cuspid, Outer cusp long, slender, curved; middle cusp about half the length of the outer one, slender; inner cusp about 2/3 as long as outer one, very broad, curved. Remarks: This species shows strong similarities with Casteobuccinum triplostephanum (Dall, 1919), but differs in the much stronger ribs, the primary one (and sometimes the sutural one) of which is T-shaped in section, as well as in the details of the radular teeth. Etymology: Named for its pagoda-like form. Distribution: Central and western Aleutians, Seguam Pass, SE of Seguam Id. (170°30 W) to S of Agattu Id., Near Ids. (173°30 E). 72-469 m. Habitat: Sand, gravel and cobble bottoms with a bottom temperature of 3.7-3.8°C.