Shell of moderate size, up to 40 mm. ( 1,5inches) in length, lightly built, very depressed, apex between the anterior third and fourth, elongate-ovate, narrow, with flattened sides, and tapered to a narrowly rounded front margin; margins weakly crenulated. Sculpture variable, typically consisting of 30-40 moderately strong, narrow, sharply raised primary radial cords, and from 1-3 secondary cords in each interspace, the whole crossed by fine sharp growth lines, that weakly decussate the radial cords, especially the secondary ones. Colour extremely variable; externally, usually greenish or buff, boldly rayed, mottled and blotched with dark reddish brown; internally bluish silvery, the external pattern showing through strongly; spatula ill defined, usually diffused chestnut-brown, but white callused at the anterior end. Length: 36-40 mm; Width: 25-31 mm; Height: 5-9mm.

The predominant form of the species is long and narrow with subparallel sides, and internally, the spatula is long and narrow also. Certain shells from the Philippines are broadly ovate, but these are extreme individuals in populations that have narrow shells as well. Pilsbry’s Helcioniscus nigrolineatus var. divergens is still another viariant of toreuma, which is of large size, elongate-ovate, but with rounded rather than subparallel sides, and dense, fine, subgranose radial sculpture. Rugosely sculptured shells are, according to Ino, found towards low water, where rocks have rough surfaces, contrasted with rock surfaces from higher levels that have been smoothed by erosion.

Japan to Ryukyu Islands, Mariana Islands, Taiwan, Hongkong, China, and Philippines.