Medium-sized to large, depressed to high-spired cone-shaped shell with moderately wide umbilicus; whorls inflated, on upper side gemmate (with axial sculpture dominant); subsutural rib distinctly separated, midrib-area undivided or divided by 1-3 faint spiral grooves; upper point of whorl attachment on lower part of lower peripheral rib; proxumbical rib absent to distinctly-separated. Color pattern of distinct brown blotches on subsutural rib, upper peripheral rib and proxumbical-rib area (also on umbilical crenae in some specimens). Protoconch diameter 1.36-1.56 mm; dark brown.
Medium-sized to large, diameter of specimens in collections usually 17-24 at 5 1/8 to 6 1/8 whorls. Shape: specimens from sublittoral high-spired cone-shaped with inflated whorls and moderately wide umbilicus (UD ca. 23% of SD), specimens from upper bathyal depressed cone-shaped with weakly convex whorls and wider umbilicus (UD ca. 29% of SD). Sculpture: Upper side: SSR distinctly separated; dominant sculpture in midrib-area by oblique axial grooves; midrib-area undivided or divided by 1-3 ± faint spiral grooves; Periphery: PR strong, with UPR often almost as prominent as LPR; upper point of whorl attachment on lower part of LPR (upper part of LPR thereby forming part of upper-side sculpture); no distinct suture; Base: IPR strong BF often with 1-2 ± wide, weakly separated spiral ribs in front of PUR; PUR almost absent to distinctly separated; UC clearly separated, relatively small and usually regular; columellar wall forming almost straight inner lip with plications for support of the columellar muscle, with deepest groove in UC overhanging umbilicus; no spiral sculpture on umbilical side of wall Coloration: midrib-area and BF light brown, often marbled with slightly darker shades of brown; ground color of SSR, PR and UC distinctly lighter, SSR and UPR well-marked with pattern of brown blotches (about 16-22 on 4th Tw of UPR); LPR, IPR, PUR-area (rarely also UC) with faint brown pattern. - Protoconch : large to very large (1.36-1.56, x = 1.46); distinctly heterostrophic, with weak anal keel; dark brown. - Operculum: as described for genus. - Radula: "ptenoglossate," with 15 teeth per row (7-1-7). Rachidian stronger than marginals and tricuspid with the central cusp flanked by smaller lateral cusps. Marginal teeth strongly curved and forked with long tapering subequal cusps; the outermost marginal teeth shorter. - Anatomy, alimentary tract described by CLIMO, 1975: 281 ff., figs. 4H, 5B [but see corrections in HASZPRUNAR, 1985b].

New Zealand: Northland east coast to Bay of Plenty. Takau Bay, near Whangaroa; Great Barrier Island; Whangarei Heads; Mount Maunganui. Also New South Wales; type locality of reevei probably Sydney, that of offlexa, Sydney also.
Shell conoidal, solid, with an obtuse spire and a flat base; periphery triple keeled, one cord above, one at, and the other below the periphery; rest of the dorsal surface faintly spirally grooved, and crossed by dense linear incised radials. Base with two strongly crenate spiral ribs bordering the umbilicus, which is deep, per¬spective, and between a fourth and a fifth the maximum diameter. Colour pale yellowish-orange to greyish-lilac, with reddish-brown maculations on the sutural, peripheral and umbilical cords.
Height 13.5-18.0 mm., width 22.5-25.0 mm.

Adelphotectonica reevei is often confused with Architectonica perdix, which is similar in shell shape and coloration. Distinguishing characters for A. perdix are the much more prominent axial sculpture, an upper point of whorl attachment that is at the upper edge of the lower peripheral rib, and a much smaller (< 0.96), yellowish to light-brown protoconch. Adelphotectonica kuroharai, A. nomotoi and the Atlantic species A. uruguaya CARCELLES, 1953, are similar to this species .

Geographical distribution: Subtropical to temperate western Pacific and Australian coastline including Tasmania. Record from Ceylon (Sri Lanka) in need of verification.
Habitat: Sublittoral to upper bathyal (most depth records between 30 and 400 m), live records from 100-150 m, sandy substrates.