Type material: Holotype (93.2mm long x 66.0mm wide x 22.8mm high) deposited at Paris National Museum of Natural History, France with Registration No: MNHN-IM-2000-38116.
Other material: Paratype 1 (88.4mm); Paratype 2 (86.1mm), Paratype 3 (91.5mm), Paratype 4 (91.4mm) and Paratype 5 (76.5mm) in Dr Thach collection. All types from type locality.
Type locality: Nha Trang area, Khanh Hoa Province, Central Vietnam.
Habitat: Rocky shores at 3-5m.
Diagnosis: The new species is characterized by very large size, flat spire, principal ridges broad, conspicuous, extending transversely and wide area located between columella and outer edge.
Description: Shell very large, elongate-ovate in outline and longer than high with length range 76.5-93.2mm of collected specimens. Spire flat, sutures deep. Shell width 73.0% and shell height 20.8% of shell length. Outer surface ornamented with broad, indistinct, whitish radiating stripes. Sculpture consists of eight conspicuous, extending transversely ridges at anterior area of dorsal side while the remaining ridges at posterior area much weaker and turned to opposite direction; these ridges are crossed by very narrow, closely-spaced spiral ribs which are well visible along outer lip. Open holes large, strongly erected and six in number. Area between series of holes and outer edge very wide, up to 19.5mm and sculptured with six elevated spiral and riblets crossed by growth lines. Aperture very wide with external ridges visible within, outer lip slightly convex and moderately thick. Columella very broad, well separated from remaining shell by a groove wide up to 8.2mm and very concave, apex visible at interior side. Color externally greenish with whitish radiating stripes and whitish oblique lines near outer edge and internally iridesecent with pink and blue dazes.
Comparison: The new species is distinctive and differs from all other species of this genus as they have not the following characters: (1) large adult size, up to 93.2mm long, (2) very elongate shape, (3) rather depressed shell, especially at posterior area, (4) elevated and flat spire, (5) very flat apex, (6) radial ridges at dorsal side conspicuous, highly raised and zigzag, (7) columella well separated from remaining shell by a wide and pink groove, (8) area between series of holes and outer edge very wide, (9) greenish color.